Merge pull request #174 from benbjohnson/fix-snapshot-only-restore

Fix snapshot-only restore

.github/pull_request_template.md

@@ -0,0 +1,7 @@
+Litestream is not accepting code contributions at this time. You can find a summary of why on the project's GitHub README:
+
+https://github.com/benbjohnson/litestream#open-source-not-open-contribution
+
+Web site & Documentation changes, however, are welcome. You can find that repository here:
+
+https://github.com/benbjohnson/litestream.io

.github/workflows/release.linux.yml

@@ -3,10 +3,30 @@ on:
     types:
       - created
 
-name: release
+name: release (linux)
 jobs:
-  linux:
+  build:
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        include:
+          - arch: amd64
+            cc:   gcc
+          - arch: arm64
+            cc:   aarch64-linux-gnu-gcc
+          - arch: arm
+            arm:  6
+            cc:   arm-linux-gnueabi-gcc
+          - arch: arm
+            arm:  7
+            cc:   arm-linux-gnueabihf-gcc
+
+    env:
+      GOOS:   linux
+      GOARCH: ${{ matrix.arch }}
+      GOARM:  ${{ matrix.arm }}
+      CC:     ${{ matrix.cc }}
+
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-go@v2
@@ -16,6 +36,11 @@ jobs:
         env:
           GITHUB_TOKEN: ${{ github.token }}
 
+      - name: Install cross-compilers
+        run: |
+          sudo apt-get update 
+          sudo apt-get install -y gcc-aarch64-linux-gnu gcc-arm-linux-gnueabihf gcc-arm-linux-gnueabi
+
       - name: Install nfpm
         run: |
           wget https://github.com/goreleaser/nfpm/releases/download/v2.2.3/nfpm_2.2.3_Linux_x86_64.tar.gz
@@ -23,23 +48,24 @@ jobs:
 
       - name: Build litestream
         run: |
+          rm -rf dist
           mkdir -p dist
           cp etc/litestream.yml etc/litestream.service dist
           cat etc/nfpm.yml | LITESTREAM_VERSION=${{ steps.release.outputs.tag_name }} envsubst > dist/nfpm.yml
-          go build -ldflags "-X 'main.Version=${{ steps.release.outputs.tag_name }}'" -o dist/litestream ./cmd/litestream
+          CGO_ENABLED=1 go build -ldflags "-s -w -X 'main.Version=${{ steps.release.outputs.tag_name }}'" -o dist/litestream ./cmd/litestream
           
           cd dist
-          tar -czvf litestream-${{ steps.release.outputs.tag_name }}-linux-amd64.tar.gz litestream
-          ../nfpm pkg --config nfpm.yml --packager deb --target litestream-${{ steps.release.outputs.tag_name }}-linux-amd64.deb 
+          tar -czvf litestream-${{ steps.release.outputs.tag_name }}-${{ env.GOOS }}-${{ env.GOARCH }}${{ env.GOARM }}.tar.gz litestream
+          ../nfpm pkg --config nfpm.yml --packager deb --target litestream-${{ steps.release.outputs.tag_name }}-${{ env.GOOS }}-${{ env.GOARCH }}${{ env.GOARM }}.deb 
 
-      - name: Upload release binary
+      - name: Upload release tarball
         uses: actions/upload-release-asset@v1.0.2
         env:
           GITHUB_TOKEN: ${{ github.token }}
         with:
           upload_url: ${{ steps.release.outputs.upload_url }}
-          asset_path: ./dist/litestream-${{ steps.release.outputs.tag_name }}-linux-amd64.tar.gz
-          asset_name: litestream-${{ steps.release.outputs.tag_name }}-linux-amd64.tar.gz
+          asset_path: ./dist/litestream-${{ steps.release.outputs.tag_name }}-${{ env.GOOS }}-${{ env.GOARCH }}${{ env.GOARM }}.tar.gz
+          asset_name: litestream-${{ steps.release.outputs.tag_name }}-${{ env.GOOS }}-${{ env.GOARCH }}${{ env.GOARM }}.tar.gz
           asset_content_type: application/gzip
 
       - name: Upload debian package
@@ -48,6 +74,6 @@ jobs:
           GITHUB_TOKEN: ${{ github.token }}
         with:
           upload_url: ${{ steps.release.outputs.upload_url }}
-          asset_path: ./dist/litestream-${{ steps.release.outputs.tag_name }}-linux-amd64.deb
-          asset_name: litestream-${{ steps.release.outputs.tag_name }}-linux-amd64.deb
+          asset_path: ./dist/litestream-${{ steps.release.outputs.tag_name }}-${{ env.GOOS }}-${{ env.GOARCH }}${{ env.GOARM }}.deb
+          asset_name: litestream-${{ steps.release.outputs.tag_name }}-${{ env.GOOS }}-${{ env.GOARCH }}${{ env.GOARM }}.deb
           asset_content_type: application/octet-stream

.github/workflows/release.linux_static.yml

@@ -0,0 +1,60 @@
+on:
+  release:
+    types:
+      - created
+
+name: release (linux/static)
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        include:
+          - arch: amd64
+            cc:   gcc
+          - arch: arm64
+            cc:   aarch64-linux-gnu-gcc
+          - arch: arm
+            arm:  6
+            cc:   arm-linux-gnueabi-gcc
+          - arch: arm
+            arm:  7
+            cc:   arm-linux-gnueabihf-gcc
+
+    env:
+      GOOS:   linux
+      GOARCH: ${{ matrix.arch }}
+      GOARM:  ${{ matrix.arm }}
+      CC:     ${{ matrix.cc }}
+
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-go@v2
+
+      - id: release
+        uses: bruceadams/get-release@v1.2.2
+        env:
+          GITHUB_TOKEN: ${{ github.token }}
+
+      - name: Install cross-compilers
+        run: |
+          sudo apt-get update 
+          sudo apt-get install -y gcc-aarch64-linux-gnu gcc-arm-linux-gnueabihf gcc-arm-linux-gnueabi
+
+      - name: Build litestream
+        run: |
+          rm -rf dist
+          mkdir -p dist
+          CGO_ENABLED=1 go build -ldflags "-s -w -extldflags "-static" -X 'main.Version=${{ steps.release.outputs.tag_name }}'" -tags osusergo,netgo,sqlite_omit_load_extension -o dist/litestream ./cmd/litestream
+          cd dist
+          tar -czvf litestream-${{ steps.release.outputs.tag_name }}-${{ env.GOOS }}-${{ env.GOARCH }}${{ env.GOARM }}-static.tar.gz litestream
+
+      - name: Upload release tarball
+        uses: actions/upload-release-asset@v1.0.2
+        env:
+          GITHUB_TOKEN: ${{ github.token }}
+        with:
+          upload_url: ${{ steps.release.outputs.upload_url }}
+          asset_path: ./dist/litestream-${{ steps.release.outputs.tag_name }}-${{ env.GOOS }}-${{ env.GOARCH }}${{ env.GOARM }}-static.tar.gz
+          asset_name: litestream-${{ steps.release.outputs.tag_name }}-${{ env.GOOS }}-${{ env.GOARCH }}${{ env.GOARM }}-static.tar.gz
+          asset_content_type: application/gzip

Dockerfile

@@ -0,0 +1,11 @@
+FROM golang:1.16 as builder
+WORKDIR /src/litestream
+COPY . .
+RUN --mount=type=cache,target=/root/.cache/go-build \
+	--mount=type=cache,target=/go/pkg \
+	go build -ldflags '-s -w -extldflags "-static"' -tags osusergo,netgo,sqlite_omit_load_extension -o /usr/local/bin/litestream ./cmd/litestream
+
+FROM alpine
+COPY --from=builder /usr/local/bin/litestream /usr/local/bin/litestream
+ENTRYPOINT ["/usr/local/bin/litestream"]
+CMD []

LICENSE

@@ -1,674 +1,202 @@
-                    GNU GENERAL PUBLIC LICENSE
-                       Version 3, 29 June 2007
 
- Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
- Everyone is permitted to copy and distribute verbatim copies
- of this license document, but changing it is not allowed.
-
-                            Preamble
-
-  The GNU General Public License is a free, copyleft license for
-software and other kinds of works.
-
-  The licenses for most software and other practical works are designed
-to take away your freedom to share and change the works.  By contrast,
-the GNU General Public License is intended to guarantee your freedom to
-share and change all versions of a program--to make sure it remains free
-software for all its users.  We, the Free Software Foundation, use the
-GNU General Public License for most of our software; it applies also to
-any other work released this way by its authors.  You can apply it to
-your programs, too.
-
-  When we speak of free software, we are referring to freedom, not
-price.  Our General Public Licenses are designed to make sure that you
-have the freedom to distribute copies of free software (and charge for
-them if you wish), that you receive source code or can get it if you
-want it, that you can change the software or use pieces of it in new
-free programs, and that you know you can do these things.
-
-  To protect your rights, we need to prevent others from denying you
-these rights or asking you to surrender the rights.  Therefore, you have
-certain responsibilities if you distribute copies of the software, or if
-you modify it: responsibilities to respect the freedom of others.
-
-  For example, if you distribute copies of such a program, whether
-gratis or for a fee, you must pass on to the recipients the same
-freedoms that you received.  You must make sure that they, too, receive
-or can get the source code.  And you must show them these terms so they
-know their rights.
-
-  Developers that use the GNU GPL protect your rights with two steps:
-(1) assert copyright on the software, and (2) offer you this License
-giving you legal permission to copy, distribute and/or modify it.
-
-  For the developers' and authors' protection, the GPL clearly explains
-that there is no warranty for this free software.  For both users' and
-authors' sake, the GPL requires that modified versions be marked as
-changed, so that their problems will not be attributed erroneously to
-authors of previous versions.
-
-  Some devices are designed to deny users access to install or run
-modified versions of the software inside them, although the manufacturer
-can do so.  This is fundamentally incompatible with the aim of
-protecting users' freedom to change the software.  The systematic
-pattern of such abuse occurs in the area of products for individuals to
-use, which is precisely where it is most unacceptable.  Therefore, we
-have designed this version of the GPL to prohibit the practice for those
-products.  If such problems arise substantially in other domains, we
-stand ready to extend this provision to those domains in future versions
-of the GPL, as needed to protect the freedom of users.
-
-  Finally, every program is threatened constantly by software patents.
-States should not allow patents to restrict development and use of
-software on general-purpose computers, but in those that do, we wish to
-avoid the special danger that patents applied to a free program could
-make it effectively proprietary.  To prevent this, the GPL assures that
-patents cannot be used to render the program non-free.
-
-  The precise terms and conditions for copying, distribution and
-modification follow.
-
-                       TERMS AND CONDITIONS
-
-  0. Definitions.
-
-  "This License" refers to version 3 of the GNU General Public License.
-
-  "Copyright" also means copyright-like laws that apply to other kinds of
-works, such as semiconductor masks.
-
-  "The Program" refers to any copyrightable work licensed under this
-License.  Each licensee is addressed as "you".  "Licensees" and
-"recipients" may be individuals or organizations.
-
-  To "modify" a work means to copy from or adapt all or part of the work
-in a fashion requiring copyright permission, other than the making of an
-exact copy.  The resulting work is called a "modified version" of the
-earlier work or a work "based on" the earlier work.
-
-  A "covered work" means either the unmodified Program or a work based
-on the Program.
-
-  To "propagate" a work means to do anything with it that, without
-permission, would make you directly or secondarily liable for
-infringement under applicable copyright law, except executing it on a
-computer or modifying a private copy.  Propagation includes copying,
-distribution (with or without modification), making available to the
-public, and in some countries other activities as well.
-
-  To "convey" a work means any kind of propagation that enables other
-parties to make or receive copies.  Mere interaction with a user through
-a computer network, with no transfer of a copy, is not conveying.
-
-  An interactive user interface displays "Appropriate Legal Notices"
-to the extent that it includes a convenient and prominently visible
-feature that (1) displays an appropriate copyright notice, and (2)
-tells the user that there is no warranty for the work (except to the
-extent that warranties are provided), that licensees may convey the
-work under this License, and how to view a copy of this License.  If
-the interface presents a list of user commands or options, such as a
-menu, a prominent item in the list meets this criterion.
-
-  1. Source Code.
-
-  The "source code" for a work means the preferred form of the work
-for making modifications to it.  "Object code" means any non-source
-form of a work.
-
-  A "Standard Interface" means an interface that either is an official
-standard defined by a recognized standards body, or, in the case of
-interfaces specified for a particular programming language, one that
-is widely used among developers working in that language.
-
-  The "System Libraries" of an executable work include anything, other
-than the work as a whole, that (a) is included in the normal form of
-packaging a Major Component, but which is not part of that Major
-Component, and (b) serves only to enable use of the work with that
-Major Component, or to implement a Standard Interface for which an
-implementation is available to the public in source code form.  A
-"Major Component", in this context, means a major essential component
-(kernel, window system, and so on) of the specific operating system
-(if any) on which the executable work runs, or a compiler used to
-produce the work, or an object code interpreter used to run it.
-
-  The "Corresponding Source" for a work in object code form means all
-the source code needed to generate, install, and (for an executable
-work) run the object code and to modify the work, including scripts to
-control those activities.  However, it does not include the work's
-System Libraries, or general-purpose tools or generally available free
-programs which are used unmodified in performing those activities but
-which are not part of the work.  For example, Corresponding Source
-includes interface definition files associated with source files for
-the work, and the source code for shared libraries and dynamically
-linked subprograms that the work is specifically designed to require,
-such as by intimate data communication or control flow between those
-subprograms and other parts of the work.
-
-  The Corresponding Source need not include anything that users
-can regenerate automatically from other parts of the Corresponding
-Source.
-
-  The Corresponding Source for a work in source code form is that
-same work.
-
-  2. Basic Permissions.
-
-  All rights granted under this License are granted for the term of
-copyright on the Program, and are irrevocable provided the stated
-conditions are met.  This License explicitly affirms your unlimited
-permission to run the unmodified Program.  The output from running a
-covered work is covered by this License only if the output, given its
-content, constitutes a covered work.  This License acknowledges your
-rights of fair use or other equivalent, as provided by copyright law.
-
-  You may make, run and propagate covered works that you do not
-convey, without conditions so long as your license otherwise remains
-in force.  You may convey covered works to others for the sole purpose
-of having them make modifications exclusively for you, or provide you
-with facilities for running those works, provided that you comply with
-the terms of this License in conveying all material for which you do
-not control copyright.  Those thus making or running the covered works
-for you must do so exclusively on your behalf, under your direction
-and control, on terms that prohibit them from making any copies of
-your copyrighted material outside their relationship with you.
-
-  Conveying under any other circumstances is permitted solely under
-the conditions stated below.  Sublicensing is not allowed; section 10
-makes it unnecessary.
-
-  3. Protecting Users' Legal Rights From Anti-Circumvention Law.
-
-  No covered work shall be deemed part of an effective technological
-measure under any applicable law fulfilling obligations under article
-11 of the WIPO copyright treaty adopted on 20 December 1996, or
-similar laws prohibiting or restricting circumvention of such
-measures.
-
-  When you convey a covered work, you waive any legal power to forbid
-circumvention of technological measures to the extent such circumvention
-is effected by exercising rights under this License with respect to
-the covered work, and you disclaim any intention to limit operation or
-modification of the work as a means of enforcing, against the work's
-users, your or third parties' legal rights to forbid circumvention of
-technological measures.
-
-  4. Conveying Verbatim Copies.
-
-  You may convey verbatim copies of the Program's source code as you
-receive it, in any medium, provided that you conspicuously and
-appropriately publish on each copy an appropriate copyright notice;
-keep intact all notices stating that this License and any
-non-permissive terms added in accord with section 7 apply to the code;
-keep intact all notices of the absence of any warranty; and give all
-recipients a copy of this License along with the Program.
-
-  You may charge any price or no price for each copy that you convey,
-and you may offer support or warranty protection for a fee.
-
-  5. Conveying Modified Source Versions.
-
-  You may convey a work based on the Program, or the modifications to
-produce it from the Program, in the form of source code under the
-terms of section 4, provided that you also meet all of these conditions:
-
-    a) The work must carry prominent notices stating that you modified
-    it, and giving a relevant date.
-
-    b) The work must carry prominent notices stating that it is
-    released under this License and any conditions added under section
-    7.  This requirement modifies the requirement in section 4 to
-    "keep intact all notices".
-
-    c) You must license the entire work, as a whole, under this
-    License to anyone who comes into possession of a copy.  This
-    License will therefore apply, along with any applicable section 7
-    additional terms, to the whole of the work, and all its parts,
-    regardless of how they are packaged.  This License gives no
-    permission to license the work in any other way, but it does not
-    invalidate such permission if you have separately received it.
-
-    d) If the work has interactive user interfaces, each must display
-    Appropriate Legal Notices; however, if the Program has interactive
-    interfaces that do not display Appropriate Legal Notices, your
-    work need not make them do so.
-
-  A compilation of a covered work with other separate and independent
-works, which are not by their nature extensions of the covered work,
-and which are not combined with it such as to form a larger program,
-in or on a volume of a storage or distribution medium, is called an
-"aggregate" if the compilation and its resulting copyright are not
-used to limit the access or legal rights of the compilation's users
-beyond what the individual works permit.  Inclusion of a covered work
-in an aggregate does not cause this License to apply to the other
-parts of the aggregate.
-
-  6. Conveying Non-Source Forms.
-
-  You may convey a covered work in object code form under the terms
-of sections 4 and 5, provided that you also convey the
-machine-readable Corresponding Source under the terms of this License,
-in one of these ways:
-
-    a) Convey the object code in, or embodied in, a physical product
-    (including a physical distribution medium), accompanied by the
-    Corresponding Source fixed on a durable physical medium
-    customarily used for software interchange.
-
-    b) Convey the object code in, or embodied in, a physical product
-    (including a physical distribution medium), accompanied by a
-    written offer, valid for at least three years and valid for as
-    long as you offer spare parts or customer support for that product
-    model, to give anyone who possesses the object code either (1) a
-    copy of the Corresponding Source for all the software in the
-    product that is covered by this License, on a durable physical
-    medium customarily used for software interchange, for a price no
-    more than your reasonable cost of physically performing this
-    conveying of source, or (2) access to copy the
-    Corresponding Source from a network server at no charge.
-
-    c) Convey individual copies of the object code with a copy of the
-    written offer to provide the Corresponding Source.  This
-    alternative is allowed only occasionally and noncommercially, and
-    only if you received the object code with such an offer, in accord
-    with subsection 6b.
-
-    d) Convey the object code by offering access from a designated
-    place (gratis or for a charge), and offer equivalent access to the
-    Corresponding Source in the same way through the same place at no
-    further charge.  You need not require recipients to copy the
-    Corresponding Source along with the object code.  If the place to
-    copy the object code is a network server, the Corresponding Source
-    may be on a different server (operated by you or a third party)
-    that supports equivalent copying facilities, provided you maintain
-    clear directions next to the object code saying where to find the
-    Corresponding Source.  Regardless of what server hosts the
-    Corresponding Source, you remain obligated to ensure that it is
-    available for as long as needed to satisfy these requirements.
-
-    e) Convey the object code using peer-to-peer transmission, provided
-    you inform other peers where the object code and Corresponding
-    Source of the work are being offered to the general public at no
-    charge under subsection 6d.
-
-  A separable portion of the object code, whose source code is excluded
-from the Corresponding Source as a System Library, need not be
-included in conveying the object code work.
-
-  A "User Product" is either (1) a "consumer product", which means any
-tangible personal property which is normally used for personal, family,
-or household purposes, or (2) anything designed or sold for incorporation
-into a dwelling.  In determining whether a product is a consumer product,
-doubtful cases shall be resolved in favor of coverage.  For a particular
-product received by a particular user, "normally used" refers to a
-typical or common use of that class of product, regardless of the status
-of the particular user or of the way in which the particular user
-actually uses, or expects or is expected to use, the product.  A product
-is a consumer product regardless of whether the product has substantial
-commercial, industrial or non-consumer uses, unless such uses represent
-the only significant mode of use of the product.
-
-  "Installation Information" for a User Product means any methods,
-procedures, authorization keys, or other information required to install
-and execute modified versions of a covered work in that User Product from
-a modified version of its Corresponding Source.  The information must
-suffice to ensure that the continued functioning of the modified object
-code is in no case prevented or interfered with solely because
-modification has been made.
-
-  If you convey an object code work under this section in, or with, or
-specifically for use in, a User Product, and the conveying occurs as
-part of a transaction in which the right of possession and use of the
-User Product is transferred to the recipient in perpetuity or for a
-fixed term (regardless of how the transaction is characterized), the
-Corresponding Source conveyed under this section must be accompanied
-by the Installation Information.  But this requirement does not apply
-if neither you nor any third party retains the ability to install
-modified object code on the User Product (for example, the work has
-been installed in ROM).
-
-  The requirement to provide Installation Information does not include a
-requirement to continue to provide support service, warranty, or updates
-for a work that has been modified or installed by the recipient, or for
-the User Product in which it has been modified or installed.  Access to a
-network may be denied when the modification itself materially and
-adversely affects the operation of the network or violates the rules and
-protocols for communication across the network.
-
-  Corresponding Source conveyed, and Installation Information provided,
-in accord with this section must be in a format that is publicly
-documented (and with an implementation available to the public in
-source code form), and must require no special password or key for
-unpacking, reading or copying.
-
-  7. Additional Terms.
-
-  "Additional permissions" are terms that supplement the terms of this
-License by making exceptions from one or more of its conditions.
-Additional permissions that are applicable to the entire Program shall
-be treated as though they were included in this License, to the extent
-that they are valid under applicable law.  If additional permissions
-apply only to part of the Program, that part may be used separately
-under those permissions, but the entire Program remains governed by
-this License without regard to the additional permissions.
-
-  When you convey a copy of a covered work, you may at your option
-remove any additional permissions from that copy, or from any part of
-it.  (Additional permissions may be written to require their own
-removal in certain cases when you modify the work.)  You may place
-additional permissions on material, added by you to a covered work,
-for which you have or can give appropriate copyright permission.
-
-  Notwithstanding any other provision of this License, for material you
-add to a covered work, you may (if authorized by the copyright holders of
-that material) supplement the terms of this License with terms:
-
-    a) Disclaiming warranty or limiting liability differently from the
-    terms of sections 15 and 16 of this License; or
-
-    b) Requiring preservation of specified reasonable legal notices or
-    author attributions in that material or in the Appropriate Legal
-    Notices displayed by works containing it; or
-
-    c) Prohibiting misrepresentation of the origin of that material, or
-    requiring that modified versions of such material be marked in
-    reasonable ways as different from the original version; or
-
-    d) Limiting the use for publicity purposes of names of licensors or
-    authors of the material; or
-
-    e) Declining to grant rights under trademark law for use of some
-    trade names, trademarks, or service marks; or
-
-    f) Requiring indemnification of licensors and authors of that
-    material by anyone who conveys the material (or modified versions of
-    it) with contractual assumptions of liability to the recipient, for
-    any liability that these contractual assumptions directly impose on
-    those licensors and authors.
-
-  All other non-permissive additional terms are considered "further
-restrictions" within the meaning of section 10.  If the Program as you
-received it, or any part of it, contains a notice stating that it is
-governed by this License along with a term that is a further
-restriction, you may remove that term.  If a license document contains
-a further restriction but permits relicensing or conveying under this
-License, you may add to a covered work material governed by the terms
-of that license document, provided that the further restriction does
-not survive such relicensing or conveying.
-
-  If you add terms to a covered work in accord with this section, you
-must place, in the relevant source files, a statement of the
-additional terms that apply to those files, or a notice indicating
-where to find the applicable terms.
-
-  Additional terms, permissive or non-permissive, may be stated in the
-form of a separately written license, or stated as exceptions;
-the above requirements apply either way.
-
-  8. Termination.
-
-  You may not propagate or modify a covered work except as expressly
-provided under this License.  Any attempt otherwise to propagate or
-modify it is void, and will automatically terminate your rights under
-this License (including any patent licenses granted under the third
-paragraph of section 11).
-
-  However, if you cease all violation of this License, then your
-license from a particular copyright holder is reinstated (a)
-provisionally, unless and until the copyright holder explicitly and
-finally terminates your license, and (b) permanently, if the copyright
-holder fails to notify you of the violation by some reasonable means
-prior to 60 days after the cessation.
-
-  Moreover, your license from a particular copyright holder is
-reinstated permanently if the copyright holder notifies you of the
-violation by some reasonable means, this is the first time you have
-received notice of violation of this License (for any work) from that
-copyright holder, and you cure the violation prior to 30 days after
-your receipt of the notice.
-
-  Termination of your rights under this section does not terminate the
-licenses of parties who have received copies or rights from you under
-this License.  If your rights have been terminated and not permanently
-reinstated, you do not qualify to receive new licenses for the same
-material under section 10.
-
-  9. Acceptance Not Required for Having Copies.
-
-  You are not required to accept this License in order to receive or
-run a copy of the Program.  Ancillary propagation of a covered work
-occurring solely as a consequence of using peer-to-peer transmission
-to receive a copy likewise does not require acceptance.  However,
-nothing other than this License grants you permission to propagate or
-modify any covered work.  These actions infringe copyright if you do
-not accept this License.  Therefore, by modifying or propagating a
-covered work, you indicate your acceptance of this License to do so.
-
-  10. Automatic Licensing of Downstream Recipients.
-
-  Each time you convey a covered work, the recipient automatically
-receives a license from the original licensors, to run, modify and
-propagate that work, subject to this License.  You are not responsible
-for enforcing compliance by third parties with this License.
-
-  An "entity transaction" is a transaction transferring control of an
-organization, or substantially all assets of one, or subdividing an
-organization, or merging organizations.  If propagation of a covered
-work results from an entity transaction, each party to that
-transaction who receives a copy of the work also receives whatever
-licenses to the work the party's predecessor in interest had or could
-give under the previous paragraph, plus a right to possession of the
-Corresponding Source of the work from the predecessor in interest, if
-the predecessor has it or can get it with reasonable efforts.
-
-  You may not impose any further restrictions on the exercise of the
-rights granted or affirmed under this License.  For example, you may
-not impose a license fee, royalty, or other charge for exercise of
-rights granted under this License, and you may not initiate litigation
-(including a cross-claim or counterclaim in a lawsuit) alleging that
-any patent claim is infringed by making, using, selling, offering for
-sale, or importing the Program or any portion of it.
-
-  11. Patents.
-
-  A "contributor" is a copyright holder who authorizes use under this
-License of the Program or a work on which the Program is based.  The
-work thus licensed is called the contributor's "contributor version".
-
-  A contributor's "essential patent claims" are all patent claims
-owned or controlled by the contributor, whether already acquired or
-hereafter acquired, that would be infringed by some manner, permitted
-by this License, of making, using, or selling its contributor version,
-but do not include claims that would be infringed only as a
-consequence of further modification of the contributor version.  For
-purposes of this definition, "control" includes the right to grant
-patent sublicenses in a manner consistent with the requirements of
-this License.
-
-  Each contributor grants you a non-exclusive, worldwide, royalty-free
-patent license under the contributor's essential patent claims, to
-make, use, sell, offer for sale, import and otherwise run, modify and
-propagate the contents of its contributor version.
-
-  In the following three paragraphs, a "patent license" is any express
-agreement or commitment, however denominated, not to enforce a patent
-(such as an express permission to practice a patent or covenant not to
-sue for patent infringement).  To "grant" such a patent license to a
-party means to make such an agreement or commitment not to enforce a
-patent against the party.
-
-  If you convey a covered work, knowingly relying on a patent license,
-and the Corresponding Source of the work is not available for anyone
-to copy, free of charge and under the terms of this License, through a
-publicly available network server or other readily accessible means,
-then you must either (1) cause the Corresponding Source to be so
-available, or (2) arrange to deprive yourself of the benefit of the
-patent license for this particular work, or (3) arrange, in a manner
-consistent with the requirements of this License, to extend the patent
-license to downstream recipients.  "Knowingly relying" means you have
-actual knowledge that, but for the patent license, your conveying the
-covered work in a country, or your recipient's use of the covered work
-in a country, would infringe one or more identifiable patents in that
-country that you have reason to believe are valid.
-
-  If, pursuant to or in connection with a single transaction or
-arrangement, you convey, or propagate by procuring conveyance of, a
-covered work, and grant a patent license to some of the parties
-receiving the covered work authorizing them to use, propagate, modify
-or convey a specific copy of the covered work, then the patent license
-you grant is automatically extended to all recipients of the covered
-work and works based on it.
-
-  A patent license is "discriminatory" if it does not include within
-the scope of its coverage, prohibits the exercise of, or is
-conditioned on the non-exercise of one or more of the rights that are
-specifically granted under this License.  You may not convey a covered
-work if you are a party to an arrangement with a third party that is
-in the business of distributing software, under which you make payment
-to the third party based on the extent of your activity of conveying
-the work, and under which the third party grants, to any of the
-parties who would receive the covered work from you, a discriminatory
-patent license (a) in connection with copies of the covered work
-conveyed by you (or copies made from those copies), or (b) primarily
-for and in connection with specific products or compilations that
-contain the covered work, unless you entered into that arrangement,
-or that patent license was granted, prior to 28 March 2007.
-
-  Nothing in this License shall be construed as excluding or limiting
-any implied license or other defenses to infringement that may
-otherwise be available to you under applicable patent law.
-
-  12. No Surrender of Others' Freedom.
-
-  If conditions are imposed on you (whether by court order, agreement or
-otherwise) that contradict the conditions of this License, they do not
-excuse you from the conditions of this License.  If you cannot convey a
-covered work so as to satisfy simultaneously your obligations under this
-License and any other pertinent obligations, then as a consequence you may
-not convey it at all.  For example, if you agree to terms that obligate you
-to collect a royalty for further conveying from those to whom you convey
-the Program, the only way you could satisfy both those terms and this
-License would be to refrain entirely from conveying the Program.
-
-  13. Use with the GNU Affero General Public License.
-
-  Notwithstanding any other provision of this License, you have
-permission to link or combine any covered work with a work licensed
-under version 3 of the GNU Affero General Public License into a single
-combined work, and to convey the resulting work.  The terms of this
-License will continue to apply to the part which is the covered work,
-but the special requirements of the GNU Affero General Public License,
-section 13, concerning interaction through a network will apply to the
-combination as such.
-
-  14. Revised Versions of this License.
-
-  The Free Software Foundation may publish revised and/or new versions of
-the GNU General Public License from time to time.  Such new versions will
-be similar in spirit to the present version, but may differ in detail to
-address new problems or concerns.
-
-  Each version is given a distinguishing version number.  If the
-Program specifies that a certain numbered version of the GNU General
-Public License "or any later version" applies to it, you have the
-option of following the terms and conditions either of that numbered
-version or of any later version published by the Free Software
-Foundation.  If the Program does not specify a version number of the
-GNU General Public License, you may choose any version ever published
-by the Free Software Foundation.
-
-  If the Program specifies that a proxy can decide which future
-versions of the GNU General Public License can be used, that proxy's
-public statement of acceptance of a version permanently authorizes you
-to choose that version for the Program.
-
-  Later license versions may give you additional or different
-permissions.  However, no additional obligations are imposed on any
-author or copyright holder as a result of your choosing to follow a
-later version.
-
-  15. Disclaimer of Warranty.
-
-  THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
-APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
-HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
-OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
-THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
-PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
-IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
-ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
-
-  16. Limitation of Liability.
-
-  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
-WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
-THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
-GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
-USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
-DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
-PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
-EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
-SUCH DAMAGES.
-
-  17. Interpretation of Sections 15 and 16.
-
-  If the disclaimer of warranty and limitation of liability provided
-above cannot be given local legal effect according to their terms,
-reviewing courts shall apply local law that most closely approximates
-an absolute waiver of all civil liability in connection with the
-Program, unless a warranty or assumption of liability accompanies a
-copy of the Program in return for a fee.
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
+      the Work and Derivative Works thereof.
+
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to Licensor for inclusion in the Work by the copyright owner
+      or by an individual or Legal Entity authorized to submit on behalf of
+      the copyright owner. For the purposes of this definition, "submitted"
+      means any form of electronic, verbal, or written communication sent
+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
+      excluding communication that is conspicuously marked or otherwise
+      designated in writing by the copyright owner as "Not a Contribution."
+
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
+      publicly display, publicly perform, sublicense, and distribute the
+      Work and such Derivative Works in Source or Object form.
+
+   3. Grant of Patent License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      (except as stated in this section) patent license to make, have made,
+      use, offer to sell, sell, import, and otherwise transfer the Work,
+      where such license applies only to those patent claims licensable
+      by such Contributor that are necessarily infringed by their
+      Contribution(s) alone or by combination of their Contribution(s)
+      with the Work to which such Contribution(s) was submitted. If You
+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
+      or contributory patent infringement, then any patent licenses
+      granted to You under this License for that Work shall terminate
+      as of the date such litigation is filed.
+
+   4. Redistribution. You may reproduce and distribute copies of the
+      Work or Derivative Works thereof in any medium, with or without
+      modifications, and in Source or Object form, provided that You
+      meet the following conditions:
+
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
+          that You distribute, all copyright, patent, trademark, and
+          attribution notices from the Source form of the Work,
+          excluding those notices that do not pertain to any part of
+          the Derivative Works; and
+
+      (d) If the Work includes a "NOTICE" text file as part of its
+          distribution, then any Derivative Works that You distribute must
+          include a readable copy of the attribution notices contained
+          within such NOTICE file, excluding those notices that do not
+          pertain to any part of the Derivative Works, in at least one
+          of the following places: within a NOTICE text file distributed
+          as part of the Derivative Works; within the Source form or
+          documentation, if provided along with the Derivative Works; or,
+          within a display generated by the Derivative Works, if and
+          wherever such third-party notices normally appear. The contents
+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
+          or as an addendum to the NOTICE text from the Work, provided
+          that such additional attribution notices cannot be construed
+          as modifying the License.
+
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+      implied, including, without limitation, any warranties or conditions
+      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
 
    END OF TERMS AND CONDITIONS
 
-            How to Apply These Terms to Your New Programs
+   APPENDIX: How to apply the Apache License to your work.
 
-  If you develop a new program, and you want it to be of the greatest
-possible use to the public, the best way to achieve this is to make it
-free software which everyone can redistribute and change under these terms.
+      To apply the Apache License to your work, attach the following
+      boilerplate notice, with the fields enclosed by brackets "[]"
+      replaced with your own identifying information. (Don't include
+      the brackets!)  The text should be enclosed in the appropriate
+      comment syntax for the file format. We also recommend that a
+      file or class name and description of purpose be included on the
+      same "printed page" as the copyright notice for easier
+      identification within third-party archives.
 
-  To do so, attach the following notices to the program.  It is safest
-to attach them to the start of each source file to most effectively
-state the exclusion of warranty; and each file should have at least
-the "copyright" line and a pointer to where the full notice is found.
+   Copyright [yyyy] [name of copyright owner]
 
-    <one line to give the program's name and a brief idea of what it does.>
-    Copyright (C) <year>  <name of author>
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
 
-    This program is free software: you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 3 of the License, or
-    (at your option) any later version.
+       http://www.apache.org/licenses/LICENSE-2.0
 
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
-
-    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <https://www.gnu.org/licenses/>.
-
-Also add information on how to contact you by electronic and paper mail.
-
-  If the program does terminal interaction, make it output a short
-notice like this when it starts in an interactive mode:
-
-    <program>  Copyright (C) <year>  <name of author>
-    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
-    This is free software, and you are welcome to redistribute it
-    under certain conditions; type `show c' for details.
-
-The hypothetical commands `show w' and `show c' should show the appropriate
-parts of the General Public License.  Of course, your program's commands
-might be different; for a GUI interface, you would use an "about box".
-
-  You should also get your employer (if you work as a programmer) or school,
-if any, to sign a "copyright disclaimer" for the program, if necessary.
-For more information on this, and how to apply and follow the GNU GPL, see
-<https://www.gnu.org/licenses/>.
-
-  The GNU General Public License does not permit incorporating your program
-into proprietary programs.  If your program is a subroutine library, you
-may consider it more useful to permit linking proprietary applications with
-the library.  If this is what you want to do, use the GNU Lesser General
-Public License instead of this License.  But first, please read
-<https://www.gnu.org/licenses/why-not-lgpl.html>.
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.

Makefile

@@ -1,17 +1,26 @@
 default:
 
+docker:
+	docker build -t litestream .
+
 dist-linux:
 	mkdir -p dist
 	cp etc/litestream.yml dist/litestream.yml
-	docker run --rm -v "${PWD}":/usr/src/litestream -w /usr/src/litestream -e GOOS=linux -e GOARCH=amd64 golang:1.15 go build -v -o dist/litestream ./cmd/litestream
+	docker run --rm -v "${PWD}":/usr/src/litestream -w /usr/src/litestream -e GOOS=linux -e GOARCH=amd64 golang:1.16 go build -v -ldflags "-s -w" -o dist/litestream ./cmd/litestream
 	tar -cz -f dist/litestream-linux-amd64.tar.gz -C dist litestream
 
+dist-linux-arm:
+	docker run --rm -v "${PWD}":/usr/src/litestream -w /usr/src/litestream -e CGO_ENABLED=1 -e CC=arm-linux-gnueabihf-gcc -e GOOS=linux -e GOARCH=arm golang-xc:1.16 go build -v -o dist/litestream-linux-arm ./cmd/litestream
+
+dist-linux-arm64:
+	docker run --rm -v "${PWD}":/usr/src/litestream -w /usr/src/litestream -e CGO_ENABLED=1 -e CC=aarch64-linux-gnu-gcc -e GOOS=linux -e GOARCH=arm64 golang-xc:1.16 go build -v -o dist/litestream-linux-arm64 ./cmd/litestream
+
 dist-macos:
 ifndef LITESTREAM_VERSION
 	$(error LITESTREAM_VERSION is undefined)
 endif
 	mkdir -p dist
-	go build -v -ldflags "-X 'main.Version=${LITESTREAM_VERSION}'"  -o dist/litestream ./cmd/litestream
+	go build -v -ldflags "-s -w -X 'main.Version=${LITESTREAM_VERSION}'"  -o dist/litestream ./cmd/litestream
 	gon etc/gon.hcl
 	mv dist/litestream.zip dist/litestream-${LITESTREAM_VERSION}-darwin-amd64.zip
 	openssl dgst -sha256 dist/litestream-${LITESTREAM_VERSION}-darwin-amd64.zip

README.md

@@ -2,6 +2,7 @@ Litestream
 ![GitHub release (latest by date)](https://img.shields.io/github/v/release/benbjohnson/litestream)
 ![Status](https://img.shields.io/badge/status-beta-blue)
 ![GitHub](https://img.shields.io/github/license/benbjohnson/litestream)
+[![Docker Pulls](https://img.shields.io/docker/pulls/litestream/litestream.svg?maxAge=604800)](https://hub.docker.com/r/litestream/litestream/)
 ![test](https://github.com/benbjohnson/litestream/workflows/test/badge.svg)
 ==========
 
@@ -10,275 +11,35 @@ background process and safely replicates changes incrementally to another file
 or S3. Litestream only communicates with SQLite through the SQLite API so it
 will not corrupt your database.
 
-If you need support or have ideas for improving Litestream, please visit the
-[GitHub Discussions](https://github.com/benbjohnson/litestream/discussions) to
-chat. 
+If you need support or have ideas for improving Litestream, please join the
+[Litestream Slack][slack] or visit the [GitHub Discussions](https://github.com/benbjohnson/litestream/discussions).
+Please visit the [Litestream web site](https://litestream.io) for installation
+instructions and documentation.
 
 If you find this project interesting, please consider starring the project on
 GitHub.
 
+[slack]: https://join.slack.com/t/litestream/shared_invite/zt-n0j4s3ci-lx1JziR3bV6L2NMF723H3Q
 
-## Installation
 
-### Mac OS (Homebrew)
+## Acknowledgements
 
-To install from homebrew, run the following command:
-
-```sh
-$ brew install benbjohnson/litestream/litestream
-```
-
-
-### Linux (Debian)
-
-You can download the `.deb` file from the [Releases page][releases] page and
-then run the following:
-
-```sh
-$ sudo dpkg -i litestream-v0.3.0-linux-amd64.deb
-```
-
-Once installed, you'll need to enable & start the service:
-
-```sh
-$ sudo systemctl enable litestream
-$ sudo systemctl start litestream
-```
-
-
-### Release binaries
-
-You can also download the release binary for your system from the
-[releases page][releases] and run it as a standalone application.
-
-
-### Building from source
-
-Download and install the [Go toolchain](https://golang.org/) and then run:
-
-```sh
-$ go install ./cmd/litestream
-```
-
-The `litestream` binary should be in your `$GOPATH/bin` folder.
-
-
-## Quick Start
-
-Litestream provides a configuration file that can be used for production
-deployments but you can also specify a single database and replica on the
-command line when trying it out.
-
-First, you'll need to create an S3 bucket that we'll call `"mybkt"` in this
-example. You'll also need to set your AWS credentials:
-
-```sh
-$ export AWS_ACCESS_KEY_ID=AKIAxxxxxxxxxxxxxxxx
-$ export AWS_SECRET_ACCESS_KEY=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/xxxxxxxxx
-```
-
-Next, you can run the `litestream replicate` command with the path to the
-database you want to backup and the URL of your replica destination:
-
-```sh
-$ litestream replicate /path/to/db s3://mybkt/db
-```
-
-If you make changes to your local database, those changes will be replicated
-to S3 every 10 seconds. From another terminal window, you can restore your
-database from your S3 replica:
-
-```
-$ litestream restore -o /path/to/restored/db s3://mybkt/db
-```
-
-Voila! 🎉
-
-Your database should be restored to the last replicated state that
-was sent to S3. You can adjust your replication frequency and other options by
-using a configuration-based approach specified below.
-
-
-## Configuration
-
-A configuration-based install gives you more replication options. By default,
-the config file lives at `/etc/litestream.yml` but you can pass in a different
-path to any `litestream` command using the `-config PATH` flag. You can also 
-set the `LITESTREAM_CONFIG` environment variable to specify a new path.
-
-The configuration specifies one or more `dbs` and a list of one or more replica
-locations for each db. Below are some common configurations:
-
-### Replicate to S3
-
-This will replicate the database at `/path/to/db` to the `"/db"` path inside
-the S3 bucket named `"mybkt"`.
-
-```yaml
-access-key-id:     AKIAxxxxxxxxxxxxxxxx
-secret-access-key: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/xxxxxxxxx
-
-dbs:
-  - path: /path/to/db
-    replicas:
-      - url: s3://mybkt/db
-```
-
-### Replicate to another file path
-
-This will replicate the database at `/path/to/db` to a directory named
-`/path/to/replica`.
-
-```yaml
-dbs:
-  - path: /path/to/db
-    replicas:
-      - path: /path/to/replica
-```
-
-### Retention period
-
-By default, replicas will retain a snapshot & subsequent WAL changes for 24
-hours. When the snapshot age exceeds the retention threshold, a new snapshot
-is taken and uploaded and the previous snapshot and WAL files are removed.
-
-You can configure this setting per-replica. Times are parsed using [Go's
-duration](https://golang.org/pkg/time/#ParseDuration) so time units of hours
-(`h`), minutes (`m`), and seconds (`s`) are allowed but days, weeks, months, and
-years are not.
-
-
-```yaml
-db:
-  - path: /path/to/db
-    replicas:
-      - url: s3://mybkt/db
-        retention: 1h          # 1 hour retention
-```
-
-
-### Monitoring replication
-
-You can also enable a Prometheus metrics endpoint to monitor replication by
-specifying a bind address with the `addr` field:
-
-```yml
-addr: ":9090"
-```
-
-This will make metrics available at: http://localhost:9090/metrics
-
-
-### Other configuration options
-
-These are some additional configuration options available on replicas:
-
-- `type`—Specify the type of replica (`"file"` or `"s3"`). Derived from `"path"`.
-- `name`—Specify an optional name for the replica if you are using multiple replicas.
-- `path`—File path to the replica location.
-- `url`—URL to the replica location.
-- `retention-check-interval`—Time between retention enforcement checks. Defaults to `1h`.
-- `validation-interval`—Interval between periodic checks to ensure restored backup matches current database. Disabled by default.
-
-These replica options are only available for S3 replicas:
-
-- `bucket`—S3 bucket name. Derived from `"path"`.
-- `region`—S3 bucket region. Looked up on startup if unspecified.
-- `sync-interval`—Replication sync frequency.
-
-
-
-## Usage
-
-### Replication
-
-Once your configuration is saved, you'll need to begin replication. If you
-installed the `.deb` file then run:
-
-```sh
-$ sudo systemctl restart litestream
-```
-
-To run litestream on its own, run:
-
-```sh
-# Replicate using the /etc/litestream.yml configuration.
-$ litestream replicate
-
-# Replicate using a different configuration path.
-$ litestream replicate -config /path/to/litestream.yml
-```
-
-The `litestream` command will initialize and then wait indefinitely for changes.
-You should see your destination replica path is now populated with a
-`generations` directory. Inside there should be a 16-character hex generation
-directory and inside there should be snapshots & WAL files. As you make changes
-to your source database, changes will be copied over to your replica incrementally.
-
-
-### Restoring a backup
-
-Litestream can restore a previous snapshot and replay all replicated WAL files.
-By default, it will restore up to the latest WAL file but you can also perform
-point-in-time restores.
-
-A database can only be restored to a path that does not exist so you don't need
-to worry about accidentally overwriting your current database.
-
-```sh
-# Restore database to original path.
-$ litestream restore /path/to/db
-
-# Restore database to a new location.
-$ litestream restore -o /path/to/restored/db /path/to/db
-
-# Restore from a replica URL.
-$ litestream restore -o /path/to/restored/db s3://mybkt/db
-
-# Restore database to a specific point-in-time.
-$ litestream restore -timestamp 2020-01-01T00:00:00Z /path/to/db
-```
-
-Point-in-time restores only have the resolution of the timestamp of the WAL file
-itself. By default, Litestream will start a new WAL file every minute so
-point-in-time restores are only accurate to the minute.
-
-
-
-## How it works
-
-SQLite provides a WAL (write-ahead log) journaling mode which writes pages to
-a `-wal` file before eventually being copied over to the original database file.
-This copying process is known as checkpointing. The WAL file works as a circular
-buffer so when the WAL reaches a certain size then it restarts from the beginning.
-
-Litestream works by taking over the checkpointing process and controlling when
-it is restarted to ensure that it copies every new page. Checkpointing is only
-allowed when there are no read transactions so Litestream maintains a
-long-running read transaction against each database until it is ready to
-checkpoint.
-
-The SQLite WAL file is copied to a separate location called the shadow WAL which
-ensures that it will not be overwritten by SQLite. This shadow WAL acts as a
-temporary buffer so that replicas can replicate to their destination (e.g.
-another file path or to S3). The shadow WAL files are removed once they have
-been fully replicated. You can find the shadow directory as a hidden directory
-next to your database file. If you database file is named `/var/lib/my.db` then
-the shadow directory will be `/var/lib/.my.db-litestream`.
-
-Litestream groups a snapshot and all subsequent WAL changes into "generations".
-A generation is started on initial replication of a database and a new
-generation will be started if litestream detects that the WAL replication is
-no longer contiguous. This can occur if the `litestream` process is stopped and
-another process is allowed to checkpoint the WAL.
+While the Litestream project does not accept external code patches, many
+of the most valuable contributions are in the forms of testing, feedback, and
+documentation. These help harden software and streamline usage for other users.
 
+I want to give special thanks to individuals who invest much of their time and 
+energy into the project to help make it better. Shout out to [Michael
+Lynch](https://github.com/mtlynch) for digging into issues and contributing to
+the documentation.
 
 
 ## Open-source, not open-contribution
 
 [Similar to SQLite](https://www.sqlite.org/copyright.html), Litestream is open
-source but closed to contributions. This keeps the code base free of proprietary
-or licensed code but it also helps me continue to maintain and build Litestream.
+source but closed to code contributions. This keeps the code base free of
+proprietary or licensed code but it also helps me continue to maintain and build
+Litestream.
 
 As the author of [BoltDB](https://github.com/boltdb/bolt), I found that
 accepting and maintaining third party patches contributed to my burn out and
@@ -292,5 +53,8 @@ not wish to come off as anything but welcoming, however, I've
 made the decision to keep this project closed to contributions for my own
 mental health and long term viability of the project.
 
+The [documentation repository][docs] is MIT licensed and pull requests are welcome there.
 
 [releases]: https://github.com/benbjohnson/litestream/releases
+[docs]: https://github.com/benbjohnson/litestream.io
+

cmd/litestream/databases.go

@@ -2,7 +2,6 @@ package main
 
 import (
 	"context"
-	"errors"
 	"flag"
 	"fmt"
 	"os"
@@ -15,21 +14,20 @@ type DatabasesCommand struct{}
 
 // Run executes the command.
 func (c *DatabasesCommand) Run(ctx context.Context, args []string) (err error) {
-	var configPath string
 	fs := flag.NewFlagSet("litestream-databases", flag.ContinueOnError)
-	registerConfigFlag(fs, &configPath)
+	configPath, noExpandEnv := registerConfigFlag(fs)
 	fs.Usage = c.Usage
 	if err := fs.Parse(args); err != nil {
 		return err
 	} else if fs.NArg() != 0 {
-		return fmt.Errorf("too many argument")
+		return fmt.Errorf("too many arguments")
 	}
 
 	// Load configuration.
-	if configPath == "" {
-		return errors.New("-config required")
+	if *configPath == "" {
+		*configPath = DefaultConfigPath()
 	}
-	config, err := ReadConfigFile(configPath)
+	config, err := ReadConfigFile(*configPath, !*noExpandEnv)
 	if err != nil {
 		return err
 	}
@@ -40,7 +38,7 @@ func (c *DatabasesCommand) Run(ctx context.Context, args []string) (err error) {
 
 	fmt.Fprintln(w, "path\treplicas")
 	for _, dbConfig := range config.DBs {
-		db, err := newDBFromConfig(&config, dbConfig)
+		db, err := NewDBFromConfig(dbConfig)
 		if err != nil {
 			return err
 		}
@@ -74,6 +72,9 @@ Arguments:
 	    Specifies the configuration file.
 	    Defaults to %s
 
+	-no-expand-env
+	    Disables environment variable expansion in configuration file.
+
 `[1:],
 		DefaultConfigPath(),
 	)

cmd/litestream/generations.go

@@ -2,7 +2,6 @@ package main
 
 import (
 	"context"
-	"errors"
 	"flag"
 	"fmt"
 	"log"
@@ -18,9 +17,8 @@ type GenerationsCommand struct{}
 
 // Run executes the command.
 func (c *GenerationsCommand) Run(ctx context.Context, args []string) (err error) {
-	var configPath string
 	fs := flag.NewFlagSet("litestream-generations", flag.ContinueOnError)
-	registerConfigFlag(fs, &configPath)
+	configPath, noExpandEnv := registerConfigFlag(fs)
 	replicaName := fs.String("replica", "", "replica name")
 	fs.Usage = c.Usage
 	if err := fs.Parse(args); err != nil {
@@ -35,12 +33,19 @@ func (c *GenerationsCommand) Run(ctx context.Context, args []string) (err error)
 	var r litestream.Replica
 	updatedAt := time.Now()
 	if isURL(fs.Arg(0)) {
-		if r, err = NewReplicaFromURL(fs.Arg(0)); err != nil {
+		if *configPath != "" {
+			return fmt.Errorf("cannot specify a replica URL and the -config flag")
+		}
+		if r, err = NewReplicaFromConfig(&ReplicaConfig{URL: fs.Arg(0)}, nil); err != nil {
 			return err
 		}
-	} else if configPath != "" {
+	} else {
+		if *configPath == "" {
+			*configPath = DefaultConfigPath()
+		}
+
 		// Load configuration.
-		config, err := ReadConfigFile(configPath)
+		config, err := ReadConfigFile(*configPath, !*noExpandEnv)
 		if err != nil {
 			return err
 		}
@@ -50,7 +55,7 @@ func (c *GenerationsCommand) Run(ctx context.Context, args []string) (err error)
 			return err
 		} else if dbc := config.DBConfig(path); dbc == nil {
 			return fmt.Errorf("database not found in config: %s", path)
-		} else if db, err = newDBFromConfig(&config, dbc); err != nil {
+		} else if db, err = NewDBFromConfig(dbc); err != nil {
 			return err
 		}
 
@@ -65,8 +70,6 @@ func (c *GenerationsCommand) Run(ctx context.Context, args []string) (err error)
 		if updatedAt, err = db.UpdatedAt(); err != nil {
 			return err
 		}
-	} else {
-		return errors.New("config path or replica URL required")
 	}
 
 	var replicas []litestream.Replica
@@ -128,6 +131,9 @@ Arguments:
 	    Specifies the configuration file.
 	    Defaults to %s
 
+	-no-expand-env
+	    Disables environment variable expansion in configuration file.
+
 	-replica NAME
 	    Optional, filters by replica.
 

cmd/litestream/main.go

@@ -2,15 +2,19 @@ package main
 
 import (
 	"context"
+	"errors"
 	"flag"
 	"fmt"
 	"io/ioutil"
 	"log"
 	"net/url"
 	"os"
+	"os/signal"
 	"os/user"
 	"path"
 	"path/filepath"
+	"regexp"
+	"strconv"
 	"strings"
 	"time"
 
@@ -25,14 +29,17 @@ var (
 	Version = "(development build)"
 )
 
+// errStop is a terminal error for indicating program should quit.
+var errStop = errors.New("stop")
+
 func main() {
 	log.SetFlags(0)
 
 	m := NewMain()
-	if err := m.Run(context.Background(), os.Args[1:]); err == flag.ErrHelp {
+	if err := m.Run(context.Background(), os.Args[1:]); err == flag.ErrHelp || err == errStop {
 		os.Exit(1)
 	} else if err != nil {
-		fmt.Fprintln(os.Stderr, err)
+		log.Println(err)
 		os.Exit(1)
 	}
 }
@@ -47,6 +54,17 @@ func NewMain() *Main {
 
 // Run executes the program.
 func (m *Main) Run(ctx context.Context, args []string) (err error) {
+	// Execute replication command if running as a Windows service.
+	if isService, err := isWindowsService(); err != nil {
+		return err
+	} else if isService {
+		return runWindowsService(ctx)
+	}
+
+	// Copy "LITESTEAM" environment credentials.
+	applyLitestreamEnv()
+
+	// Extract command name.
 	var cmd string
 	if len(args) > 0 {
 		cmd, args = args[0], args[1:]
@@ -58,7 +76,32 @@ func (m *Main) Run(ctx context.Context, args []string) (err error) {
 	case "generations":
 		return (&GenerationsCommand{}).Run(ctx, args)
 	case "replicate":
-		return (&ReplicateCommand{}).Run(ctx, args)
+		c := NewReplicateCommand()
+		if err := c.ParseFlags(ctx, args); err != nil {
+			return err
+		}
+
+		// Setup signal handler.
+		ctx, cancel := context.WithCancel(ctx)
+		ch := signalChan()
+		go func() { <-ch; cancel() }()
+
+		if err := c.Run(ctx); err != nil {
+			return err
+		}
+
+		// Wait for signal to stop program.
+		<-ctx.Done()
+		signal.Reset()
+		fmt.Println("signal received, litestream shutting down")
+
+		// Gracefully close.
+		if err := c.Close(); err != nil {
+			return err
+		}
+		fmt.Println("litestream shut down")
+		return nil
+
 	case "restore":
 		return (&RestoreCommand{}).Run(ctx, args)
 	case "snapshots":
@@ -108,8 +151,20 @@ type Config struct {
 	// Global S3 settings
 	AccessKeyID     string `yaml:"access-key-id"`
 	SecretAccessKey string `yaml:"secret-access-key"`
-	Region          string `yaml:"region"`
-	Bucket          string `yaml:"bucket"`
+}
+
+// propagateGlobalSettings copies global S3 settings to replica configs.
+func (c *Config) propagateGlobalSettings() {
+	for _, dbc := range c.DBs {
+		for _, rc := range dbc.Replicas {
+			if rc.AccessKeyID == "" {
+				rc.AccessKeyID = c.AccessKeyID
+			}
+			if rc.SecretAccessKey == "" {
+				rc.SecretAccessKey = c.SecretAccessKey
+			}
+		}
+	}
 }
 
 // DefaultConfig returns a new instance of Config with defaults set.
@@ -128,7 +183,8 @@ func (c *Config) DBConfig(path string) *DBConfig {
 }
 
 // ReadConfigFile unmarshals config from filename. Expands path if needed.
-func ReadConfigFile(filename string) (_ Config, err error) {
+// If expandEnv is true then environment variables are expanded in the config.
+func ReadConfigFile(filename string, expandEnv bool) (_ Config, err error) {
 	config := DefaultConfig()
 
 	// Expand filename, if necessary.
@@ -137,12 +193,20 @@ func ReadConfigFile(filename string) (_ Config, err error) {
 		return config, err
 	}
 
-	// Read & deserialize configuration.
-	if buf, err := ioutil.ReadFile(filename); os.IsNotExist(err) {
+	// Read configuration.
+	buf, err := ioutil.ReadFile(filename)
+	if os.IsNotExist(err) {
 		return config, fmt.Errorf("config file not found: %s", filename)
 	} else if err != nil {
 		return config, err
-	} else if err := yaml.Unmarshal(buf, &config); err != nil {
+	}
+
+	// Expand environment variables, if enabled.
+	if expandEnv {
+		buf = []byte(os.ExpandEnv(string(buf)))
+	}
+
+	if err := yaml.Unmarshal(buf, &config); err != nil {
 		return config, err
 	}
 
@@ -153,15 +217,59 @@ func ReadConfigFile(filename string) (_ Config, err error) {
 		}
 	}
 
+	// Propage settings from global config to replica configs.
+	config.propagateGlobalSettings()
+
 	return config, nil
 }
 
 // DBConfig represents the configuration for a single database.
 type DBConfig struct {
 	Path               string         `yaml:"path"`
+	MonitorInterval    *time.Duration `yaml:"monitor-interval"`
+	CheckpointInterval *time.Duration `yaml:"checkpoint-interval"`
+	MinCheckpointPageN *int           `yaml:"min-checkpoint-page-count"`
+	MaxCheckpointPageN *int           `yaml:"max-checkpoint-page-count"`
+
 	Replicas []*ReplicaConfig `yaml:"replicas"`
 }
 
+// NewDBFromConfig instantiates a DB based on a configuration.
+func NewDBFromConfig(dbc *DBConfig) (*litestream.DB, error) {
+	path, err := expand(dbc.Path)
+	if err != nil {
+		return nil, err
+	}
+
+	// Initialize database with given path.
+	db := litestream.NewDB(path)
+
+	// Override default database settings if specified in configuration.
+	if dbc.MonitorInterval != nil {
+		db.MonitorInterval = *dbc.MonitorInterval
+	}
+	if dbc.CheckpointInterval != nil {
+		db.CheckpointInterval = *dbc.CheckpointInterval
+	}
+	if dbc.MinCheckpointPageN != nil {
+		db.MinCheckpointPageN = *dbc.MinCheckpointPageN
+	}
+	if dbc.MaxCheckpointPageN != nil {
+		db.MaxCheckpointPageN = *dbc.MaxCheckpointPageN
+	}
+
+	// Instantiate and attach replicas.
+	for _, rc := range dbc.Replicas {
+		r, err := NewReplicaFromConfig(rc, db)
+		if err != nil {
+			return nil, err
+		}
+		db.Replicas = append(db.Replicas, r)
+	}
+
+	return db, nil
+}
+
 // ReplicaConfig represents the configuration for a single replica in a database.
 type ReplicaConfig struct {
 	Type                   string        `yaml:"type"` // "file", "s3"
@@ -171,6 +279,7 @@ type ReplicaConfig struct {
 	Retention              time.Duration `yaml:"retention"`
 	RetentionCheckInterval time.Duration `yaml:"retention-check-interval"`
 	SyncInterval           time.Duration `yaml:"sync-interval"` // s3 only
+	SnapshotInterval       time.Duration `yaml:"snapshot-interval"`
 	ValidationInterval     time.Duration `yaml:"validation-interval"`
 
 	// S3 settings
@@ -178,25 +287,162 @@ type ReplicaConfig struct {
 	SecretAccessKey string `yaml:"secret-access-key"`
 	Region          string `yaml:"region"`
 	Bucket          string `yaml:"bucket"`
+	Endpoint        string `yaml:"endpoint"`
+	ForcePathStyle  *bool  `yaml:"force-path-style"`
+	SkipVerify      bool   `yaml:"skip-verify"`
 }
 
-// NewReplicaFromURL returns a new Replica instance configured from a URL.
-// The replica's database is not set.
-func NewReplicaFromURL(s string) (litestream.Replica, error) {
-	scheme, host, path, err := ParseReplicaURL(s)
-	if err != nil {
+// NewReplicaFromConfig instantiates a replica for a DB based on a config.
+func NewReplicaFromConfig(c *ReplicaConfig, db *litestream.DB) (litestream.Replica, error) {
+	// Ensure user did not specify URL in path.
+	if isURL(c.Path) {
+		return nil, fmt.Errorf("replica path cannot be a url, please use the 'url' field instead: %s", c.Path)
+	}
+
+	switch c.ReplicaType() {
+	case "file":
+		return newFileReplicaFromConfig(c, db)
+	case "s3":
+		return newS3ReplicaFromConfig(c, db)
+	default:
+		return nil, fmt.Errorf("unknown replica type in config: %q", c.Type)
+	}
+}
+
+// newFileReplicaFromConfig returns a new instance of FileReplica build from config.
+func newFileReplicaFromConfig(c *ReplicaConfig, db *litestream.DB) (_ *litestream.FileReplica, err error) {
+	// Ensure URL & path are not both specified.
+	if c.URL != "" && c.Path != "" {
+		return nil, fmt.Errorf("cannot specify url & path for file replica")
+	}
+
+	// Parse path from URL, if specified.
+	path := c.Path
+	if c.URL != "" {
+		if _, _, path, err = ParseReplicaURL(c.URL); err != nil {
+			return nil, err
+		}
+	}
+
+	// Ensure path is set explicitly or derived from URL field.
+	if path == "" {
+		return nil, fmt.Errorf("file replica path required")
+	}
+
+	// Expand home prefix and return absolute path.
+	if path, err = expand(path); err != nil {
 		return nil, err
 	}
 
-	switch scheme {
-	case "file":
-		return litestream.NewFileReplica(nil, "", path), nil
-	case "s3":
-		r := s3.NewReplica(nil, "")
-		r.Bucket, r.Path = host, path
+	// Instantiate replica and apply time fields, if set.
+	r := litestream.NewFileReplica(db, c.Name, path)
+	if v := c.Retention; v > 0 {
+		r.Retention = v
+	}
+	if v := c.RetentionCheckInterval; v > 0 {
+		r.RetentionCheckInterval = v
+	}
+	if v := c.SnapshotInterval; v > 0 {
+		r.SnapshotInterval = v
+	}
+	if v := c.ValidationInterval; v > 0 {
+		r.ValidationInterval = v
+	}
 	return r, nil
-	default:
-		return nil, fmt.Errorf("invalid replica url type: %s", s)
+}
+
+// newS3ReplicaFromConfig returns a new instance of S3Replica build from config.
+func newS3ReplicaFromConfig(c *ReplicaConfig, db *litestream.DB) (_ *s3.Replica, err error) {
+	// Ensure URL & constituent parts are not both specified.
+	if c.URL != "" && c.Path != "" {
+		return nil, fmt.Errorf("cannot specify url & path for s3 replica")
+	} else if c.URL != "" && c.Bucket != "" {
+		return nil, fmt.Errorf("cannot specify url & bucket for s3 replica")
+	}
+
+	bucket, path := c.Bucket, c.Path
+	region, endpoint, skipVerify := c.Region, c.Endpoint, c.SkipVerify
+
+	// Use path style if an endpoint is explicitly set. This works because the
+	// only service to not use path style is AWS which does not use an endpoint.
+	forcePathStyle := (endpoint != "")
+	if v := c.ForcePathStyle; v != nil {
+		forcePathStyle = *v
+	}
+
+	// Apply settings from URL, if specified.
+	if c.URL != "" {
+		_, host, upath, err := ParseReplicaURL(c.URL)
+		if err != nil {
+			return nil, err
+		}
+		ubucket, uregion, uendpoint, uforcePathStyle := s3.ParseHost(host)
+
+		// Only apply URL parts to field that have not been overridden.
+		if path == "" {
+			path = upath
+		}
+		if bucket == "" {
+			bucket = ubucket
+		}
+		if region == "" {
+			region = uregion
+		}
+		if endpoint == "" {
+			endpoint = uendpoint
+		}
+		if !forcePathStyle {
+			forcePathStyle = uforcePathStyle
+		}
+	}
+
+	// Ensure required settings are set.
+	if bucket == "" {
+		return nil, fmt.Errorf("bucket required for s3 replica")
+	}
+
+	// Build replica.
+	r := s3.NewReplica(db, c.Name)
+	r.AccessKeyID = c.AccessKeyID
+	r.SecretAccessKey = c.SecretAccessKey
+	r.Bucket = bucket
+	r.Path = path
+	r.Region = region
+	r.Endpoint = endpoint
+	r.ForcePathStyle = forcePathStyle
+	r.SkipVerify = skipVerify
+
+	if v := c.Retention; v > 0 {
+		r.Retention = v
+	}
+	if v := c.RetentionCheckInterval; v > 0 {
+		r.RetentionCheckInterval = v
+	}
+	if v := c.SyncInterval; v > 0 {
+		r.SyncInterval = v
+	}
+	if v := c.SnapshotInterval; v > 0 {
+		r.SnapshotInterval = v
+	}
+	if v := c.ValidationInterval; v > 0 {
+		r.ValidationInterval = v
+	}
+	return r, nil
+}
+
+// applyLitestreamEnv copies "LITESTREAM" prefixed environment variables to
+// their AWS counterparts as the "AWS" prefix can be confusing when using a
+// non-AWS S3-compatible service.
+func applyLitestreamEnv() {
+	if v, ok := os.LookupEnv("LITESTREAM_ACCESS_KEY_ID"); ok {
+		if _, ok := os.LookupEnv("AWS_ACCESS_KEY_ID"); !ok {
+			os.Setenv("AWS_ACCESS_KEY_ID", v)
+		}
+	}
+	if v, ok := os.LookupEnv("LITESTREAM_SECRET_ACCESS_KEY"); ok {
+		if _, ok := os.LookupEnv("AWS_SECRET_ACCESS_KEY"); !ok {
+			os.Setenv("AWS_SECRET_ACCESS_KEY", v)
+		}
 	}
 }
 
@@ -222,15 +468,14 @@ func ParseReplicaURL(s string) (scheme, host, urlpath string, err error) {
 
 // isURL returns true if s can be parsed and has a scheme.
 func isURL(s string) bool {
-	u, err := url.Parse(s)
-	return err == nil && u.Scheme != ""
+	return regexp.MustCompile(`^\w+:\/\/`).MatchString(s)
 }
 
 // ReplicaType returns the type based on the type field or extracted from the URL.
 func (c *ReplicaConfig) ReplicaType() string {
-	typ, _, _, _ := ParseReplicaURL(c.URL)
-	if typ != "" {
-		return typ
+	scheme, _, _, _ := ParseReplicaURL(c.URL)
+	if scheme != "" {
+		return scheme
 	} else if c.Type != "" {
 		return c.Type
 	}
@@ -242,138 +487,12 @@ func DefaultConfigPath() string {
 	if v := os.Getenv("LITESTREAM_CONFIG"); v != "" {
 		return v
 	}
-	return "/etc/litestream.yml"
+	return defaultConfigPath
 }
 
-func registerConfigFlag(fs *flag.FlagSet, p *string) {
-	fs.StringVar(p, "config", DefaultConfigPath(), "config path")
-}
-
-// newDBFromConfig instantiates a DB based on a configuration.
-func newDBFromConfig(c *Config, dbc *DBConfig) (*litestream.DB, error) {
-	path, err := expand(dbc.Path)
-	if err != nil {
-		return nil, err
-	}
-
-	// Initialize database with given path.
-	db := litestream.NewDB(path)
-
-	// Instantiate and attach replicas.
-	for _, rc := range dbc.Replicas {
-		r, err := newReplicaFromConfig(db, c, dbc, rc)
-		if err != nil {
-			return nil, err
-		}
-		db.Replicas = append(db.Replicas, r)
-	}
-
-	return db, nil
-}
-
-// newReplicaFromConfig instantiates a replica for a DB based on a config.
-func newReplicaFromConfig(db *litestream.DB, c *Config, dbc *DBConfig, rc *ReplicaConfig) (litestream.Replica, error) {
-	// Ensure user did not specify URL in path.
-	if isURL(rc.Path) {
-		return nil, fmt.Errorf("replica path cannot be a url, please use the 'url' field instead: %s", rc.Path)
-	}
-
-	switch rc.ReplicaType() {
-	case "file":
-		return newFileReplicaFromConfig(db, c, dbc, rc)
-	case "s3":
-		return newS3ReplicaFromConfig(db, c, dbc, rc)
-	default:
-		return nil, fmt.Errorf("unknown replica type in config: %q", rc.Type)
-	}
-}
-
-// newFileReplicaFromConfig returns a new instance of FileReplica build from config.
-func newFileReplicaFromConfig(db *litestream.DB, c *Config, dbc *DBConfig, rc *ReplicaConfig) (_ *litestream.FileReplica, err error) {
-	path := rc.Path
-	if rc.URL != "" {
-		_, _, path, err = ParseReplicaURL(rc.URL)
-		if err != nil {
-			return nil, err
-		}
-	}
-
-	if path == "" {
-		return nil, fmt.Errorf("%s: file replica path required", db.Path())
-	}
-
-	if path, err = expand(path); err != nil {
-		return nil, err
-	}
-
-	r := litestream.NewFileReplica(db, rc.Name, path)
-	if v := rc.Retention; v > 0 {
-		r.Retention = v
-	}
-	if v := rc.RetentionCheckInterval; v > 0 {
-		r.RetentionCheckInterval = v
-	}
-	if v := rc.ValidationInterval; v > 0 {
-		r.ValidationInterval = v
-	}
-	return r, nil
-}
-
-// newS3ReplicaFromConfig returns a new instance of S3Replica build from config.
-func newS3ReplicaFromConfig(db *litestream.DB, c *Config, dbc *DBConfig, rc *ReplicaConfig) (_ *s3.Replica, err error) {
-	bucket := c.Bucket
-	if v := rc.Bucket; v != "" {
-		bucket = v
-	}
-
-	path := rc.Path
-	if rc.URL != "" {
-		_, bucket, path, err = ParseReplicaURL(rc.URL)
-		if err != nil {
-			return nil, err
-		}
-	}
-
-	// Use global or replica-specific S3 settings.
-	accessKeyID := c.AccessKeyID
-	if v := rc.AccessKeyID; v != "" {
-		accessKeyID = v
-	}
-	secretAccessKey := c.SecretAccessKey
-	if v := rc.SecretAccessKey; v != "" {
-		secretAccessKey = v
-	}
-	region := c.Region
-	if v := rc.Region; v != "" {
-		region = v
-	}
-
-	// Ensure required settings are set.
-	if bucket == "" {
-		return nil, fmt.Errorf("%s: s3 bucket required", db.Path())
-	}
-
-	// Build replica.
-	r := s3.NewReplica(db, rc.Name)
-	r.AccessKeyID = accessKeyID
-	r.SecretAccessKey = secretAccessKey
-	r.Region = region
-	r.Bucket = bucket
-	r.Path = path
-
-	if v := rc.Retention; v > 0 {
-		r.Retention = v
-	}
-	if v := rc.RetentionCheckInterval; v > 0 {
-		r.RetentionCheckInterval = v
-	}
-	if v := rc.SyncInterval; v > 0 {
-		r.SyncInterval = v
-	}
-	if v := rc.ValidationInterval; v > 0 {
-		r.ValidationInterval = v
-	}
-	return r, nil
+func registerConfigFlag(fs *flag.FlagSet) (configPath *string, noExpandEnv *bool) {
+	return fs.String("config", "", "config path"),
+		fs.Bool("no-expand-env", false, "do not expand env vars in config")
 }
 
 // expand returns an absolute path for s.
@@ -398,3 +517,24 @@ func expand(s string) (string, error) {
 	}
 	return filepath.Join(u.HomeDir, strings.TrimPrefix(s, prefix)), nil
 }
+
+// indexVar allows the flag package to parse index flags as 4-byte hexadecimal values.
+type indexVar int
+
+// Ensure type implements interface.
+var _ flag.Value = (*indexVar)(nil)
+
+// String returns an 8-character hexadecimal value.
+func (v *indexVar) String() string {
+	return fmt.Sprintf("%08x", int(*v))
+}
+
+// Set parses s into an integer from a hexadecimal value.
+func (v *indexVar) Set(s string) error {
+	i, err := strconv.ParseInt(s, 16, 32)
+	if err != nil {
+		return fmt.Errorf("invalid hexadecimal format")
+	}
+	*v = indexVar(i)
+	return nil
+}

cmd/litestream/main_notwindows.go

@@ -0,0 +1,26 @@
+// +build !windows
+
+package main
+
+import (
+	"context"
+	"os"
+	"os/signal"
+	"syscall"
+)
+
+const defaultConfigPath = "/etc/litestream.yml"
+
+func isWindowsService() (bool, error) {
+	return false, nil
+}
+
+func runWindowsService(ctx context.Context) error {
+	panic("cannot run windows service as unix process")
+}
+
+func signalChan() <-chan os.Signal {
+	ch := make(chan os.Signal, 1)
+	signal.Notify(ch, syscall.SIGINT, syscall.SIGTERM)
+	return ch
+}

cmd/litestream/main_test.go

@@ -0,0 +1,182 @@
+package main_test
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/benbjohnson/litestream"
+	main "github.com/benbjohnson/litestream/cmd/litestream"
+	"github.com/benbjohnson/litestream/s3"
+)
+
+func TestReadConfigFile(t *testing.T) {
+	// Ensure global AWS settings are propagated down to replica configurations.
+	t.Run("PropagateGlobalSettings", func(t *testing.T) {
+		filename := filepath.Join(t.TempDir(), "litestream.yml")
+		if err := ioutil.WriteFile(filename, []byte(`
+access-key-id: XXX
+secret-access-key: YYY
+
+dbs:
+  - path: /path/to/db
+    replicas:
+      - url: s3://foo/bar
+`[1:]), 0666); err != nil {
+			t.Fatal(err)
+		}
+
+		config, err := main.ReadConfigFile(filename, true)
+		if err != nil {
+			t.Fatal(err)
+		} else if got, want := config.AccessKeyID, `XXX`; got != want {
+			t.Fatalf("AccessKeyID=%v, want %v", got, want)
+		} else if got, want := config.SecretAccessKey, `YYY`; got != want {
+			t.Fatalf("SecretAccessKey=%v, want %v", got, want)
+		} else if got, want := config.DBs[0].Replicas[0].AccessKeyID, `XXX`; got != want {
+			t.Fatalf("Replica.AccessKeyID=%v, want %v", got, want)
+		} else if got, want := config.DBs[0].Replicas[0].SecretAccessKey, `YYY`; got != want {
+			t.Fatalf("Replica.SecretAccessKey=%v, want %v", got, want)
+		}
+	})
+
+	// Ensure environment variables are expanded.
+	t.Run("ExpandEnv", func(t *testing.T) {
+		os.Setenv("LITESTREAM_TEST_0129380", "/path/to/db")
+		os.Setenv("LITESTREAM_TEST_1872363", "s3://foo/bar")
+
+		filename := filepath.Join(t.TempDir(), "litestream.yml")
+		if err := ioutil.WriteFile(filename, []byte(`
+dbs:
+  - path: $LITESTREAM_TEST_0129380
+    replicas:
+      - url: ${LITESTREAM_TEST_1872363}
+      - url: ${LITESTREAM_TEST_NO_SUCH_ENV}
+`[1:]), 0666); err != nil {
+			t.Fatal(err)
+		}
+
+		config, err := main.ReadConfigFile(filename, true)
+		if err != nil {
+			t.Fatal(err)
+		} else if got, want := config.DBs[0].Path, `/path/to/db`; got != want {
+			t.Fatalf("DB.Path=%v, want %v", got, want)
+		} else if got, want := config.DBs[0].Replicas[0].URL, `s3://foo/bar`; got != want {
+			t.Fatalf("Replica[0].URL=%v, want %v", got, want)
+		} else if got, want := config.DBs[0].Replicas[1].URL, ``; got != want {
+			t.Fatalf("Replica[1].URL=%v, want %v", got, want)
+		}
+	})
+
+	// Ensure environment variables are not expanded.
+	t.Run("NoExpandEnv", func(t *testing.T) {
+		os.Setenv("LITESTREAM_TEST_9847533", "s3://foo/bar")
+
+		filename := filepath.Join(t.TempDir(), "litestream.yml")
+		if err := ioutil.WriteFile(filename, []byte(`
+dbs:
+  - path: /path/to/db
+    replicas:
+      - url: ${LITESTREAM_TEST_9847533}
+`[1:]), 0666); err != nil {
+			t.Fatal(err)
+		}
+
+		config, err := main.ReadConfigFile(filename, false)
+		if err != nil {
+			t.Fatal(err)
+		} else if got, want := config.DBs[0].Replicas[0].URL, `${LITESTREAM_TEST_9847533}`; got != want {
+			t.Fatalf("Replica.URL=%v, want %v", got, want)
+		}
+	})
+}
+
+func TestNewFileReplicaFromConfig(t *testing.T) {
+	r, err := main.NewReplicaFromConfig(&main.ReplicaConfig{Path: "/foo"}, nil)
+	if err != nil {
+		t.Fatal(err)
+	} else if r, ok := r.(*litestream.FileReplica); !ok {
+		t.Fatal("unexpected replica type")
+	} else if got, want := r.Path(), "/foo"; got != want {
+		t.Fatalf("Path=%s, want %s", got, want)
+	}
+}
+
+func TestNewS3ReplicaFromConfig(t *testing.T) {
+	t.Run("URL", func(t *testing.T) {
+		r, err := main.NewReplicaFromConfig(&main.ReplicaConfig{URL: "s3://foo/bar"}, nil)
+		if err != nil {
+			t.Fatal(err)
+		} else if r, ok := r.(*s3.Replica); !ok {
+			t.Fatal("unexpected replica type")
+		} else if got, want := r.Bucket, "foo"; got != want {
+			t.Fatalf("Bucket=%s, want %s", got, want)
+		} else if got, want := r.Path, "bar"; got != want {
+			t.Fatalf("Path=%s, want %s", got, want)
+		} else if got, want := r.Region, ""; got != want {
+			t.Fatalf("Region=%s, want %s", got, want)
+		} else if got, want := r.Endpoint, ""; got != want {
+			t.Fatalf("Endpoint=%s, want %s", got, want)
+		} else if got, want := r.ForcePathStyle, false; got != want {
+			t.Fatalf("ForcePathStyle=%v, want %v", got, want)
+		}
+	})
+
+	t.Run("MinIO", func(t *testing.T) {
+		r, err := main.NewReplicaFromConfig(&main.ReplicaConfig{URL: "s3://foo.localhost:9000/bar"}, nil)
+		if err != nil {
+			t.Fatal(err)
+		} else if r, ok := r.(*s3.Replica); !ok {
+			t.Fatal("unexpected replica type")
+		} else if got, want := r.Bucket, "foo"; got != want {
+			t.Fatalf("Bucket=%s, want %s", got, want)
+		} else if got, want := r.Path, "bar"; got != want {
+			t.Fatalf("Path=%s, want %s", got, want)
+		} else if got, want := r.Region, "us-east-1"; got != want {
+			t.Fatalf("Region=%s, want %s", got, want)
+		} else if got, want := r.Endpoint, "http://localhost:9000"; got != want {
+			t.Fatalf("Endpoint=%s, want %s", got, want)
+		} else if got, want := r.ForcePathStyle, true; got != want {
+			t.Fatalf("ForcePathStyle=%v, want %v", got, want)
+		}
+	})
+
+	t.Run("Backblaze", func(t *testing.T) {
+		r, err := main.NewReplicaFromConfig(&main.ReplicaConfig{URL: "s3://foo.s3.us-west-000.backblazeb2.com/bar"}, nil)
+		if err != nil {
+			t.Fatal(err)
+		} else if r, ok := r.(*s3.Replica); !ok {
+			t.Fatal("unexpected replica type")
+		} else if got, want := r.Bucket, "foo"; got != want {
+			t.Fatalf("Bucket=%s, want %s", got, want)
+		} else if got, want := r.Path, "bar"; got != want {
+			t.Fatalf("Path=%s, want %s", got, want)
+		} else if got, want := r.Region, "us-west-000"; got != want {
+			t.Fatalf("Region=%s, want %s", got, want)
+		} else if got, want := r.Endpoint, "https://s3.us-west-000.backblazeb2.com"; got != want {
+			t.Fatalf("Endpoint=%s, want %s", got, want)
+		} else if got, want := r.ForcePathStyle, true; got != want {
+			t.Fatalf("ForcePathStyle=%v, want %v", got, want)
+		}
+	})
+
+	t.Run("GCS", func(t *testing.T) {
+		r, err := main.NewReplicaFromConfig(&main.ReplicaConfig{URL: "s3://foo.storage.googleapis.com/bar"}, nil)
+		if err != nil {
+			t.Fatal(err)
+		} else if r, ok := r.(*s3.Replica); !ok {
+			t.Fatal("unexpected replica type")
+		} else if got, want := r.Bucket, "foo"; got != want {
+			t.Fatalf("Bucket=%s, want %s", got, want)
+		} else if got, want := r.Path, "bar"; got != want {
+			t.Fatalf("Path=%s, want %s", got, want)
+		} else if got, want := r.Region, "us-east-1"; got != want {
+			t.Fatalf("Region=%s, want %s", got, want)
+		} else if got, want := r.Endpoint, "https://storage.googleapis.com"; got != want {
+			t.Fatalf("Endpoint=%s, want %s", got, want)
+		} else if got, want := r.ForcePathStyle, true; got != want {
+			t.Fatalf("ForcePathStyle=%v, want %v", got, want)
+		}
+	})
+}

cmd/litestream/main_windows.go

@@ -0,0 +1,112 @@
+// +build windows
+
+package main
+
+import (
+	"context"
+	"io"
+	"log"
+	"os"
+	"os/signal"
+
+	"golang.org/x/sys/windows"
+	"golang.org/x/sys/windows/svc"
+	"golang.org/x/sys/windows/svc/eventlog"
+)
+
+const defaultConfigPath = `C:\Litestream\litestream.yml`
+
+// serviceName is the Windows Service name.
+const serviceName = "Litestream"
+
+// isWindowsService returns true if currently executing within a Windows service.
+func isWindowsService() (bool, error) {
+	return svc.IsWindowsService()
+}
+
+func runWindowsService(ctx context.Context) error {
+	// Attempt to install new log service. This will fail if already installed.
+	// We don't log the error because we don't have anywhere to log until we open the log.
+	_ = eventlog.InstallAsEventCreate(serviceName, eventlog.Error|eventlog.Warning|eventlog.Info)
+
+	elog, err := eventlog.Open(serviceName)
+	if err != nil {
+		return err
+	}
+	defer elog.Close()
+
+	// Set eventlog as log writer while running.
+	log.SetOutput((*eventlogWriter)(elog))
+	defer log.SetOutput(os.Stderr)
+
+	log.Print("Litestream service starting")
+
+	if err := svc.Run(serviceName, &windowsService{ctx: ctx}); err != nil {
+		return errStop
+	}
+
+	log.Print("Litestream service stopped")
+	return nil
+}
+
+// windowsService is an interface adapter for svc.Handler.
+type windowsService struct {
+	ctx context.Context
+}
+
+func (s *windowsService) Execute(args []string, r <-chan svc.ChangeRequest, statusCh chan<- svc.Status) (svcSpecificEC bool, exitCode uint32) {
+	var err error
+
+	// Notify Windows that the service is starting up.
+	statusCh <- svc.Status{State: svc.StartPending}
+
+	// Instantiate replication command and load configuration.
+	c := NewReplicateCommand()
+	if c.Config, err = ReadConfigFile(DefaultConfigPath()); err != nil {
+		log.Printf("cannot load configuration: %s", err)
+		return true, 1
+	}
+
+	// Execute replication command.
+	if err := c.Run(s.ctx); err != nil {
+		log.Printf("cannot replicate: %s", err)
+		statusCh <- svc.Status{State: svc.StopPending}
+		return true, 2
+	}
+
+	// Notify Windows that the service is now running.
+	statusCh <- svc.Status{State: svc.Running, Accepts: svc.AcceptStop}
+
+	for {
+		select {
+		case req := <-r:
+			switch req.Cmd {
+			case svc.Stop:
+				c.Close()
+				statusCh <- svc.Status{State: svc.StopPending}
+				return false, windows.NO_ERROR
+			case svc.Interrogate:
+				statusCh <- req.CurrentStatus
+			default:
+				log.Printf("Litestream service received unexpected change request cmd: %d", req.Cmd)
+			}
+		}
+	}
+}
+
+// Ensure implementation implements io.Writer interface.
+var _ io.Writer = (*eventlogWriter)(nil)
+
+// eventlogWriter is an adapter for using eventlog.Log as an io.Writer.
+type eventlogWriter eventlog.Log
+
+func (w *eventlogWriter) Write(p []byte) (n int, err error) {
+	elog := (*eventlog.Log)(w)
+	return 0, elog.Info(1, string(p))
+}
+
+func signalChan() <-chan os.Signal {
+	ch := make(chan os.Signal, 1)
+	signal.Notify(ch, os.Interrupt)
+	return ch
+}

cmd/litestream/replicate.go

@@ -2,7 +2,6 @@ package main
 
 import (
 	"context"
-	"errors"
 	"flag"
 	"fmt"
 	"log"
@@ -10,7 +9,6 @@ import (
 	"net/http"
 	_ "net/http/pprof"
 	"os"
-	"os/signal"
 	"time"
 
 	"github.com/benbjohnson/litestream"
@@ -20,28 +18,34 @@ import (
 
 // ReplicateCommand represents a command that continuously replicates SQLite databases.
 type ReplicateCommand struct {
-	ConfigPath string
 	Config Config
 
 	// List of managed databases specified in the config.
 	DBs []*litestream.DB
 }
 
-// Run loads all databases specified in the configuration.
-func (c *ReplicateCommand) Run(ctx context.Context, args []string) (err error) {
+func NewReplicateCommand() *ReplicateCommand {
+	return &ReplicateCommand{}
+}
+
+// ParseFlags parses the CLI flags and loads the configuration file.
+func (c *ReplicateCommand) ParseFlags(ctx context.Context, args []string) (err error) {
 	fs := flag.NewFlagSet("litestream-replicate", flag.ContinueOnError)
 	tracePath := fs.String("trace", "", "trace path")
-	registerConfigFlag(fs, &c.ConfigPath)
+	configPath, noExpandEnv := registerConfigFlag(fs)
 	fs.Usage = c.Usage
 	if err := fs.Parse(args); err != nil {
 		return err
 	}
 
 	// Load configuration or use CLI args to build db/replica.
-	var config Config
 	if fs.NArg() == 1 {
 		return fmt.Errorf("must specify at least one replica URL for %s", fs.Arg(0))
 	} else if fs.NArg() > 1 {
+		if *configPath != "" {
+			return fmt.Errorf("cannot specify a replica URL and the -config flag")
+		}
+
 		dbConfig := &DBConfig{Path: fs.Arg(0)}
 		for _, u := range fs.Args()[1:] {
 			dbConfig.Replicas = append(dbConfig.Replicas, &ReplicaConfig{
@@ -49,14 +53,14 @@ func (c *ReplicateCommand) Run(ctx context.Context, args []string) (err error) {
 				SyncInterval: 1 * time.Second,
 			})
 		}
-		config.DBs = []*DBConfig{dbConfig}
-	} else if c.ConfigPath != "" {
-		config, err = ReadConfigFile(c.ConfigPath)
-		if err != nil {
+		c.Config.DBs = []*DBConfig{dbConfig}
+	} else {
+		if *configPath == "" {
+			*configPath = DefaultConfigPath()
+		}
+		if c.Config, err = ReadConfigFile(*configPath, !*noExpandEnv); err != nil {
 			return err
 		}
-	} else {
-		return errors.New("-config flag or database/replica arguments required")
 	}
 
 	// Enable trace logging.
@@ -66,24 +70,23 @@ func (c *ReplicateCommand) Run(ctx context.Context, args []string) (err error) {
 			return err
 		}
 		defer f.Close()
-		litestream.Tracef = log.New(f, "", log.LstdFlags|log.LUTC|log.Lshortfile).Printf
+		litestream.Tracef = log.New(f, "", log.LstdFlags|log.Lmicroseconds|log.LUTC|log.Lshortfile).Printf
 	}
 
-	// Setup signal handler.
-	ctx, cancel := context.WithCancel(ctx)
-	ch := make(chan os.Signal, 1)
-	signal.Notify(ch, os.Interrupt)
-	go func() { <-ch; cancel() }()
+	return nil
+}
 
+// Run loads all databases specified in the configuration.
+func (c *ReplicateCommand) Run(ctx context.Context) (err error) {
 	// Display version information.
-	fmt.Printf("litestream %s\n", Version)
+	log.Printf("litestream %s", Version)
 
-	if len(config.DBs) == 0 {
-		fmt.Println("no databases specified in configuration")
+	if len(c.Config.DBs) == 0 {
+		log.Println("no databases specified in configuration")
 	}
 
-	for _, dbConfig := range config.DBs {
-		db, err := newDBFromConfig(&config, dbConfig)
+	for _, dbConfig := range c.Config.DBs {
+		db, err := NewDBFromConfig(dbConfig)
 		if err != nil {
 			return err
 		}
@@ -97,41 +100,37 @@ func (c *ReplicateCommand) Run(ctx context.Context, args []string) (err error) {
 
 	// Notify user that initialization is done.
 	for _, db := range c.DBs {
-		fmt.Printf("initialized db: %s\n", db.Path())
+		log.Printf("initialized db: %s", db.Path())
 		for _, r := range db.Replicas {
 			switch r := r.(type) {
 			case *litestream.FileReplica:
-				fmt.Printf("replicating to: name=%q type=%q path=%q\n", r.Name(), r.Type(), r.Path())
+				log.Printf("replicating to: name=%q type=%q path=%q", r.Name(), r.Type(), r.Path())
 			case *s3.Replica:
-				fmt.Printf("replicating to: name=%q type=%q bucket=%q path=%q region=%q\n", r.Name(), r.Type(), r.Bucket, r.Path, r.Region)
+				log.Printf("replicating to: name=%q type=%q bucket=%q path=%q region=%q endpoint=%q sync-interval=%s", r.Name(), r.Type(), r.Bucket, r.Path, r.Region, r.Endpoint, r.SyncInterval)
 			default:
-				fmt.Printf("replicating to: name=%q type=%q\n", r.Name(), r.Type())
+				log.Printf("replicating to: name=%q type=%q", r.Name(), r.Type())
 			}
 		}
 	}
 
 	// Serve metrics over HTTP if enabled.
-	if config.Addr != "" {
-		_, port, _ := net.SplitHostPort(config.Addr)
-		fmt.Printf("serving metrics on http://localhost:%s/metrics\n", port)
+	if c.Config.Addr != "" {
+		hostport := c.Config.Addr
+		if host, port, _ := net.SplitHostPort(c.Config.Addr); port == "" {
+			return fmt.Errorf("must specify port for bind address: %q", c.Config.Addr)
+		} else if host == "" {
+			hostport = net.JoinHostPort("localhost", port)
+		}
+
+		log.Printf("serving metrics on http://%s/metrics", hostport)
 		go func() {
 			http.Handle("/metrics", promhttp.Handler())
-			if err := http.ListenAndServe(config.Addr, nil); err != nil {
+			if err := http.ListenAndServe(c.Config.Addr, nil); err != nil {
 				log.Printf("cannot start metrics server: %s", err)
 			}
 		}()
 	}
 
-	// Wait for signal to stop program.
-	<-ctx.Done()
-	signal.Reset()
-
-	// Gracefully close
-	if err := c.Close(); err != nil {
-		fmt.Fprintln(os.Stderr, err)
-		os.Exit(1)
-	}
-
 	return nil
 }
 
@@ -139,12 +138,13 @@ func (c *ReplicateCommand) Run(ctx context.Context, args []string) (err error) {
 func (c *ReplicateCommand) Close() (err error) {
 	for _, db := range c.DBs {
 		if e := db.SoftClose(); e != nil {
-			fmt.Printf("error closing db: path=%s err=%s\n", db.Path(), e)
+			log.Printf("error closing db: path=%s err=%s", db.Path(), e)
 			if err == nil {
 				err = e
 			}
 		}
 	}
+	// TODO(windows): Clear DBs
 	return err
 }
 
@@ -168,6 +168,9 @@ Arguments:
 	    Specifies the configuration file.
 	    Defaults to %s
 
+	-no-expand-env
+	    Disables environment variable expansion in configuration file.
+
 	-trace PATH
 	    Write verbose trace logging to PATH.
 

cmd/litestream/restore.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"log"
 	"os"
+	"strconv"
 	"time"
 
 	"github.com/benbjohnson/litestream"
@@ -17,17 +18,17 @@ type RestoreCommand struct{}
 
 // Run executes the command.
 func (c *RestoreCommand) Run(ctx context.Context, args []string) (err error) {
-	var configPath string
 	opt := litestream.NewRestoreOptions()
 	opt.Verbose = true
 
 	fs := flag.NewFlagSet("litestream-restore", flag.ContinueOnError)
-	registerConfigFlag(fs, &configPath)
+	configPath, noExpandEnv := registerConfigFlag(fs)
 	fs.StringVar(&opt.OutputPath, "o", "", "output path")
 	fs.StringVar(&opt.ReplicaName, "replica", "", "replica name")
 	fs.StringVar(&opt.Generation, "generation", "", "generation name")
-	fs.IntVar(&opt.Index, "index", opt.Index, "wal index")
-	fs.BoolVar(&opt.DryRun, "dry-run", false, "dry run")
+	fs.Var((*indexVar)(&opt.Index), "index", "wal index")
+	fs.IntVar(&opt.Parallelism, "parallelism", opt.Parallelism, "parallelism")
+	ifReplicaExists := fs.Bool("if-replica-exists", false, "")
 	timestampStr := fs.String("timestamp", "", "timestamp")
 	verbose := fs.Bool("v", false, "verbose output")
 	fs.Usage = c.Usage
@@ -46,32 +47,36 @@ func (c *RestoreCommand) Run(ctx context.Context, args []string) (err error) {
 		}
 	}
 
-	// Verbose output is automatically enabled if dry run is specified.
-	if opt.DryRun {
-		*verbose = true
-	}
-
 	// Instantiate logger if verbose output is enabled.
 	if *verbose {
-		opt.Logger = log.New(os.Stderr, "", log.LstdFlags)
+		opt.Logger = log.New(os.Stderr, "", log.LstdFlags|log.Lmicroseconds)
 	}
 
 	// Determine replica & generation to restore from.
 	var r litestream.Replica
 	if isURL(fs.Arg(0)) {
+		if *configPath != "" {
+			return fmt.Errorf("cannot specify a replica URL and the -config flag")
+		}
 		if r, err = c.loadFromURL(ctx, fs.Arg(0), &opt); err != nil {
 			return err
 		}
-	} else if configPath != "" {
-		if r, err = c.loadFromConfig(ctx, fs.Arg(0), configPath, &opt); err != nil {
+	} else {
+		if *configPath == "" {
+			*configPath = DefaultConfigPath()
+		}
+		if r, err = c.loadFromConfig(ctx, fs.Arg(0), *configPath, !*noExpandEnv, &opt); err != nil {
 			return err
 		}
-	} else {
-		return errors.New("config path or replica URL required")
 	}
 
 	// Return an error if no matching targets found.
+	// If optional flag set, return success. Useful for automated recovery.
 	if opt.Generation == "" {
+		if *ifReplicaExists {
+			fmt.Println("no matching backups found")
+			return nil
+		}
 		return fmt.Errorf("no matching backups found")
 	}
 
@@ -80,7 +85,7 @@ func (c *RestoreCommand) Run(ctx context.Context, args []string) (err error) {
 
 // loadFromURL creates a replica & updates the restore options from a replica URL.
 func (c *RestoreCommand) loadFromURL(ctx context.Context, replicaURL string, opt *litestream.RestoreOptions) (litestream.Replica, error) {
-	r, err := NewReplicaFromURL(replicaURL)
+	r, err := NewReplicaFromConfig(&ReplicaConfig{URL: replicaURL}, nil)
 	if err != nil {
 		return nil, err
 	}
@@ -89,9 +94,9 @@ func (c *RestoreCommand) loadFromURL(ctx context.Context, replicaURL string, opt
 }
 
 // loadFromConfig returns a replica & updates the restore options from a DB reference.
-func (c *RestoreCommand) loadFromConfig(ctx context.Context, dbPath, configPath string, opt *litestream.RestoreOptions) (litestream.Replica, error) {
+func (c *RestoreCommand) loadFromConfig(ctx context.Context, dbPath, configPath string, expandEnv bool, opt *litestream.RestoreOptions) (litestream.Replica, error) {
 	// Load configuration.
-	config, err := ReadConfigFile(configPath)
+	config, err := ReadConfigFile(configPath, expandEnv)
 	if err != nil {
 		return nil, err
 	}
@@ -104,7 +109,7 @@ func (c *RestoreCommand) loadFromConfig(ctx context.Context, dbPath, configPath
 	if dbConfig == nil {
 		return nil, fmt.Errorf("database not found in config: %s", dbPath)
 	}
-	db, err := newDBFromConfig(&config, dbConfig)
+	db, err := NewDBFromConfig(dbConfig)
 	if err != nil {
 		return nil, err
 	}
@@ -141,6 +146,9 @@ Arguments:
 	    Specifies the configuration file.
 	    Defaults to %s
 
+	-no-expand-env
+	    Disables environment variable expansion in configuration file.
+
 	-replica NAME
 	    Restore from a specific replica.
 	    Defaults to replica with latest data.
@@ -150,7 +158,7 @@ Arguments:
 	    Defaults to generation with latest data.
 
 	-index NUM
-	    Restore up to a specific WAL index (inclusive).
+	    Restore up to a specific hex-encoded WAL index (inclusive).
 	    Defaults to use the highest available index.
 
 	-timestamp TIMESTAMP
@@ -161,9 +169,12 @@ Arguments:
 	    Output path of the restored database.
 	    Defaults to original DB path.
 
-	-dry-run
-	    Prints all log output as if it were running but does
-	    not perform actual restore.
+	-if-replica-exists
+	    Returns exit code of 0 if no backups found.
+
+	-parallelism NUM
+	    Determines the number of WAL files downloaded in parallel.
+	    Defaults to `+strconv.Itoa(litestream.DefaultRestoreParallelism)+`.
 
 	-v
 	    Verbose output.

cmd/litestream/snapshots.go

@@ -2,7 +2,6 @@ package main
 
 import (
 	"context"
-	"errors"
 	"flag"
 	"fmt"
 	"os"
@@ -17,9 +16,8 @@ type SnapshotsCommand struct{}
 
 // Run executes the command.
 func (c *SnapshotsCommand) Run(ctx context.Context, args []string) (err error) {
-	var configPath string
 	fs := flag.NewFlagSet("litestream-snapshots", flag.ContinueOnError)
-	registerConfigFlag(fs, &configPath)
+	configPath, noExpandEnv := registerConfigFlag(fs)
 	replicaName := fs.String("replica", "", "replica name")
 	fs.Usage = c.Usage
 	if err := fs.Parse(args); err != nil {
@@ -33,12 +31,19 @@ func (c *SnapshotsCommand) Run(ctx context.Context, args []string) (err error) {
 	var db *litestream.DB
 	var r litestream.Replica
 	if isURL(fs.Arg(0)) {
-		if r, err = NewReplicaFromURL(fs.Arg(0)); err != nil {
+		if *configPath != "" {
+			return fmt.Errorf("cannot specify a replica URL and the -config flag")
+		}
+		if r, err = NewReplicaFromConfig(&ReplicaConfig{URL: fs.Arg(0)}, nil); err != nil {
 			return err
 		}
-	} else if configPath != "" {
+	} else {
+		if *configPath == "" {
+			*configPath = DefaultConfigPath()
+		}
+
 		// Load configuration.
-		config, err := ReadConfigFile(configPath)
+		config, err := ReadConfigFile(*configPath, !*noExpandEnv)
 		if err != nil {
 			return err
 		}
@@ -48,7 +53,7 @@ func (c *SnapshotsCommand) Run(ctx context.Context, args []string) (err error) {
 			return err
 		} else if dbc := config.DBConfig(path); dbc == nil {
 			return fmt.Errorf("database not found in config: %s", path)
-		} else if db, err = newDBFromConfig(&config, dbc); err != nil {
+		} else if db, err = NewDBFromConfig(dbc); err != nil {
 			return err
 		}
 
@@ -58,8 +63,6 @@ func (c *SnapshotsCommand) Run(ctx context.Context, args []string) (err error) {
 				return fmt.Errorf("replica %q not found for database %q", *replicaName, db.Path())
 			}
 		}
-	} else {
-		return errors.New("config path or replica URL required")
 	}
 
 	// Find snapshots by db or replica.
@@ -109,6 +112,9 @@ Arguments:
 	    Specifies the configuration file.
 	    Defaults to %s
 
+	-no-expand-env
+	    Disables environment variable expansion in configuration file.
+
 	-replica NAME
 	    Optional, filter by a specific replica.
 

cmd/litestream/wal.go

@@ -2,7 +2,6 @@ package main
 
 import (
 	"context"
-	"errors"
 	"flag"
 	"fmt"
 	"os"
@@ -17,9 +16,8 @@ type WALCommand struct{}
 
 // Run executes the command.
 func (c *WALCommand) Run(ctx context.Context, args []string) (err error) {
-	var configPath string
 	fs := flag.NewFlagSet("litestream-wal", flag.ContinueOnError)
-	registerConfigFlag(fs, &configPath)
+	configPath, noExpandEnv := registerConfigFlag(fs)
 	replicaName := fs.String("replica", "", "replica name")
 	generation := fs.String("generation", "", "generation name")
 	fs.Usage = c.Usage
@@ -34,12 +32,19 @@ func (c *WALCommand) Run(ctx context.Context, args []string) (err error) {
 	var db *litestream.DB
 	var r litestream.Replica
 	if isURL(fs.Arg(0)) {
-		if r, err = NewReplicaFromURL(fs.Arg(0)); err != nil {
+		if *configPath != "" {
+			return fmt.Errorf("cannot specify a replica URL and the -config flag")
+		}
+		if r, err = NewReplicaFromConfig(&ReplicaConfig{URL: fs.Arg(0)}, nil); err != nil {
 			return err
 		}
-	} else if configPath != "" {
+	} else {
+		if *configPath == "" {
+			*configPath = DefaultConfigPath()
+		}
+
 		// Load configuration.
-		config, err := ReadConfigFile(configPath)
+		config, err := ReadConfigFile(*configPath, !*noExpandEnv)
 		if err != nil {
 			return err
 		}
@@ -49,7 +54,7 @@ func (c *WALCommand) Run(ctx context.Context, args []string) (err error) {
 			return err
 		} else if dbc := config.DBConfig(path); dbc == nil {
 			return fmt.Errorf("database not found in config: %s", path)
-		} else if db, err = newDBFromConfig(&config, dbc); err != nil {
+		} else if db, err = NewDBFromConfig(dbc); err != nil {
 			return err
 		}
 
@@ -59,8 +64,6 @@ func (c *WALCommand) Run(ctx context.Context, args []string) (err error) {
 				return fmt.Errorf("replica %q not found for database %q", *replicaName, db.Path())
 			}
 		}
-	} else {
-		return errors.New("config path or replica URL required")
 	}
 
 	// Find WAL files by db or replica.
@@ -115,6 +118,9 @@ Arguments:
 	    Specifies the configuration file.
 	    Defaults to %s
 
+	-no-expand-env
+	    Disables environment variable expansion in configuration file.
+
 	-replica NAME
 	    Optional, filter by a specific replica.
 

db.go

@@ -23,6 +23,7 @@ import (
 
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
+	"golang.org/x/sync/errgroup"
 )
 
 // Default DB settings.
@@ -45,6 +46,7 @@ type DB struct {
 	mu       sync.RWMutex
 	path     string        // part to database
 	db       *sql.DB       // target database
+	f        *os.File      // long-running db file descriptor
 	rtx      *sql.Tx       // long running read transaction
 	pageSize int           // page size, in bytes
 	notify   chan struct{} // closes on WAL change
@@ -259,6 +261,11 @@ func (db *DB) PageSize() int {
 
 // Open initializes the background monitoring goroutine.
 func (db *DB) Open() (err error) {
+	// Validate fields on database.
+	if db.MinCheckpointPageN <= 0 {
+		return fmt.Errorf("minimum checkpoint page count required")
+	}
+
 	// Validate that all replica names are unique.
 	m := make(map[string]struct{})
 	for _, r := range db.Replicas {
@@ -285,15 +292,55 @@ func (db *DB) Open() (err error) {
 // Close releases the read lock & closes the database. This method should only
 // be called by tests as it causes the underlying database to be checkpointed.
 func (db *DB) Close() (err error) {
-	if e := db.SoftClose(); e != nil && err == nil {
-		err = e
+	return db.close(false)
 }
 
+// SoftClose closes everything but the underlying db connection. This method
+// is available because the binary needs to avoid closing the database on exit
+// to prevent autocheckpointing.
+func (db *DB) SoftClose() (err error) {
+	return db.close(true)
+}
+
+func (db *DB) close(soft bool) (err error) {
+	db.cancel()
+	db.wg.Wait()
+
+	// Start a new context for shutdown since we canceled the DB context.
+	ctx := context.Background()
+
+	// Perform a final db sync, if initialized.
 	if db.db != nil {
+		if e := db.Sync(ctx); e != nil && err == nil {
+			err = e
+		}
+	}
+
+	// Ensure replicas perform a final sync and stop replicating.
+	for _, r := range db.Replicas {
+		if db.db != nil {
+			if e := r.Sync(ctx); e != nil && err == nil {
+				err = e
+			}
+		}
+		r.Stop(!soft)
+	}
+
+	// Release the read lock to allow other applications to handle checkpointing.
+	if db.rtx != nil {
+		if e := db.releaseReadLock(); e != nil && err == nil {
+			err = e
+		}
+	}
+
+	// Only perform full close if this is not a soft close.
+	// This closes the underlying database connection which can clean up the WAL.
+	if !soft && db.db != nil {
 		if e := db.db.Close(); e != nil && err == nil {
 			err = e
 		}
 	}
+
 	return err
 }
 
@@ -381,11 +428,34 @@ func (db *DB) init() (err error) {
 	dsn := db.path
 	dsn += fmt.Sprintf("?_busy_timeout=%d", BusyTimeout.Milliseconds())
 
-	// Connect to SQLite database & enable WAL.
+	// Connect to SQLite database.
 	if db.db, err = sql.Open("sqlite3", dsn); err != nil {
 		return err
-	} else if _, err := db.db.Exec(`PRAGMA journal_mode = wal;`); err != nil {
-		return fmt.Errorf("enable wal: %w", err)
+	}
+
+	// Open long-running database file descriptor. Required for non-OFD locks.
+	if db.f, err = os.Open(db.path); err != nil {
+		return fmt.Errorf("open db file descriptor: %w", err)
+	}
+
+	// Ensure database is closed if init fails.
+	// Initialization can retry on next sync.
+	defer func() {
+		if err != nil {
+			_ = db.releaseReadLock()
+			db.db.Close()
+			db.f.Close()
+			db.db, db.f = nil, nil
+		}
+	}()
+
+	// Enable WAL and ensure it is set. New mode should be returned on success:
+	// https://www.sqlite.org/pragma.html#pragma_journal_mode
+	var mode string
+	if err := db.db.QueryRow(`PRAGMA journal_mode = wal;`).Scan(&mode); err != nil {
+		return err
+	} else if mode != "wal" {
+		return fmt.Errorf("enable wal failed, mode=%q", mode)
 	}
 
 	// Disable autocheckpoint for litestream's connection.
@@ -425,7 +495,7 @@ func (db *DB) init() (err error) {
 
 	// If we have an existing shadow WAL, ensure the headers match.
 	if err := db.verifyHeadersMatch(); err != nil {
-		log.Printf("%s: init: cannot determine last wal position, clearing generation (%s)", db.path, err)
+		log.Printf("%s: init: cannot determine last wal position, clearing generation; %s", db.path, err)
 		if err := os.Remove(db.GenerationNamePath()); err != nil && !os.IsNotExist(err) {
 			return fmt.Errorf("remove generation name: %w", err)
 		}
@@ -475,7 +545,7 @@ func (db *DB) verifyHeadersMatch() error {
 	}
 
 	if !bytes.Equal(hdr0, hdr1) {
-		return fmt.Errorf("wal header mismatch")
+		return fmt.Errorf("wal header mismatch %x <> %x on %s", hdr0, hdr1, shadowWALPath)
 	}
 	return nil
 }
@@ -560,26 +630,6 @@ func (db *DB) cleanWAL() error {
 	return nil
 }
 
-// SoftClose closes everything but the underlying db connection. This method
-// is available because the binary needs to avoid closing the database on exit
-// to prevent autocheckpointing.
-func (db *DB) SoftClose() (err error) {
-	db.cancel()
-	db.wg.Wait()
-
-	// Ensure replicas all stop replicating.
-	for _, r := range db.Replicas {
-		r.Stop()
-	}
-
-	if db.rtx != nil {
-		if e := db.releaseReadLock(); e != nil && err == nil {
-			err = e
-		}
-	}
-	return err
-}
-
 // acquireReadLock begins a read transaction on the database to prevent checkpointing.
 func (db *DB) acquireReadLock() error {
 	if db.rtx != nil {
@@ -674,7 +724,7 @@ func (db *DB) createGeneration() (string, error) {
 }
 
 // Sync copies pending data from the WAL to the shadow WAL.
-func (db *DB) Sync() (err error) {
+func (db *DB) Sync(ctx context.Context) (err error) {
 	db.mu.Lock()
 	defer db.mu.Unlock()
 
@@ -701,27 +751,6 @@ func (db *DB) Sync() (err error) {
 		return fmt.Errorf("ensure wal exists: %w", err)
 	}
 
-	// Start a transaction. This will be promoted immediately after.
-	tx, err := db.db.Begin()
-	if err != nil {
-		return fmt.Errorf("begin: %w", err)
-	}
-
-	// Ensure write transaction rolls back before returning.
-	defer func() {
-		if e := rollback(tx); e != nil && err == nil {
-			err = e
-		}
-	}()
-
-	// Insert into the lock table to promote to a write tx. The lock table
-	// insert will never actually occur because our tx will be rolled back,
-	// however, it will ensure our tx grabs the write lock. Unfortunately,
-	// we can't call "BEGIN IMMEDIATE" as we are already in a transaction.
-	if _, err := tx.ExecContext(db.ctx, `INSERT INTO _litestream_lock (id) VALUES (1);`); err != nil {
-		return fmt.Errorf("_litestream_lock: %w", err)
-	}
-
 	// Verify our last sync matches the current state of the WAL.
 	// This ensures that we have an existing generation & that the last sync
 	// position of the real WAL hasn't been overwritten by another process.
@@ -768,16 +797,11 @@ func (db *DB) Sync() (err error) {
 		checkpoint = true
 	}
 
-	// Release write lock before checkpointing & exiting.
-	if err := tx.Rollback(); err != nil {
-		return fmt.Errorf("rollback write tx: %w", err)
-	}
-
 	// Issue the checkpoint.
 	if checkpoint {
 		changed = true
 
-		if err := db.checkpointAndInit(info.generation, checkpointMode); err != nil {
+		if err := db.checkpointAndInit(ctx, info.generation, checkpointMode); err != nil {
 			return fmt.Errorf("checkpoint: mode=%v err=%w", checkpointMode, err)
 		}
 	}
@@ -843,7 +867,7 @@ func (db *DB) verify() (info syncInfo, err error) {
 	if err != nil {
 		return info, err
 	}
-	info.walSize = fi.Size()
+	info.walSize = frameAlign(fi.Size(), db.pageSize)
 	info.walModTime = fi.ModTime()
 	db.walSizeGauge.Set(float64(fi.Size()))
 
@@ -867,7 +891,6 @@ func (db *DB) verify() (info syncInfo, err error) {
 	}
 	info.shadowWALSize = frameAlign(fi.Size(), db.pageSize)
 
-	// Truncate shadow WAL if there is a partial page.
 	// Exit if shadow WAL does not contain a full header.
 	if info.shadowWALSize < WALHeaderSize {
 		info.reason = "short shadow wal"
@@ -900,9 +923,9 @@ func (db *DB) verify() (info syncInfo, err error) {
 	// Verify last page synced still matches.
 	if info.shadowWALSize > WALHeaderSize {
 		offset := info.shadowWALSize - int64(db.pageSize+WALFrameHeaderSize)
-		if buf0, err := readFileAt(db.WALPath(), offset, int64(db.pageSize+WALFrameHeaderSize)); err != nil {
+		if buf0, err := readWALFileAt(db.WALPath(), offset, int64(db.pageSize+WALFrameHeaderSize)); err != nil {
 			return info, fmt.Errorf("cannot read last synced wal page: %w", err)
-		} else if buf1, err := readFileAt(info.shadowWALPath, offset, int64(db.pageSize+WALFrameHeaderSize)); err != nil {
+		} else if buf1, err := readWALFileAt(info.shadowWALPath, offset, int64(db.pageSize+WALFrameHeaderSize)); err != nil {
 			return info, fmt.Errorf("cannot read last synced shadow wal page: %w", err)
 		} else if !bytes.Equal(buf0, buf1) {
 			info.reason = "wal overwritten by another process"
@@ -1289,7 +1312,7 @@ func (db *DB) checkpoint(mode string) (err error) {
 
 // checkpointAndInit performs a checkpoint on the WAL file and initializes a
 // new shadow WAL file.
-func (db *DB) checkpointAndInit(generation, mode string) error {
+func (db *DB) checkpointAndInit(ctx context.Context, generation, mode string) error {
 	shadowWALPath, err := db.CurrentShadowWALPath(generation)
 	if err != nil {
 		return err
@@ -1321,6 +1344,21 @@ func (db *DB) checkpointAndInit(generation, mode string) error {
 		return nil
 	}
 
+	// Start a transaction. This will be promoted immediately after.
+	tx, err := db.db.Begin()
+	if err != nil {
+		return fmt.Errorf("begin: %w", err)
+	}
+	defer func() { _ = rollback(tx) }()
+
+	// Insert into the lock table to promote to a write tx. The lock table
+	// insert will never actually occur because our tx will be rolled back,
+	// however, it will ensure our tx grabs the write lock. Unfortunately,
+	// we can't call "BEGIN IMMEDIATE" as we are already in a transaction.
+	if _, err := tx.ExecContext(ctx, `INSERT INTO _litestream_lock (id) VALUES (1);`); err != nil {
+		return fmt.Errorf("_litestream_lock: %w", err)
+	}
+
 	// Copy the end of the previous WAL before starting a new shadow WAL.
 	if _, err := db.copyToShadowWAL(shadowWALPath); err != nil {
 		return fmt.Errorf("cannot copy to end of shadow wal: %w", err)
@@ -1338,6 +1376,10 @@ func (db *DB) checkpointAndInit(generation, mode string) error {
 		return fmt.Errorf("cannot init shadow wal file: name=%s err=%w", newShadowWALPath, err)
 	}
 
+	// Release write lock before checkpointing & exiting.
+	if err := tx.Rollback(); err != nil {
+		return fmt.Errorf("rollback post-checkpoint tx: %w", err)
+	}
 	return nil
 }
 
@@ -1355,7 +1397,7 @@ func (db *DB) monitor() {
 		}
 
 		// Sync the database to the shadow WAL.
-		if err := db.Sync(); err != nil && !errors.Is(err, context.Canceled) {
+		if err := db.Sync(db.ctx); err != nil && !errors.Is(err, context.Canceled) {
 			log.Printf("%s: sync error: %s", db.path, err)
 		}
 	}
@@ -1367,13 +1409,13 @@ func (db *DB) monitor() {
 // replica or generation or it will automatically choose the best one. Finally,
 // a timestamp can be specified to restore the database to a specific
 // point-in-time.
-func RestoreReplica(ctx context.Context, r Replica, opt RestoreOptions) error {
+func RestoreReplica(ctx context.Context, r Replica, opt RestoreOptions) (err error) {
 	// Validate options.
 	if opt.OutputPath == "" {
 		return fmt.Errorf("output path required")
-	} else if opt.Generation == "" && opt.Index != math.MaxInt64 {
+	} else if opt.Generation == "" && opt.Index != math.MaxInt32 {
 		return fmt.Errorf("must specify generation when restoring to index")
-	} else if opt.Index != math.MaxInt64 && !opt.Timestamp.IsZero() {
+	} else if opt.Index != math.MaxInt32 && !opt.Timestamp.IsZero() {
 		return fmt.Errorf("cannot specify index & timestamp to restore")
 	}
 
@@ -1388,19 +1430,23 @@ func RestoreReplica(ctx context.Context, r Replica, opt RestoreOptions) error {
 		logPrefix = fmt.Sprintf("%s(%s)", db.Path(), r.Name())
 	}
 
-	// Ensure output path does not already exist (unless this is a dry run).
-	if !opt.DryRun {
+	// Ensure output path does not already exist.
 	if _, err := os.Stat(opt.OutputPath); err == nil {
 		return fmt.Errorf("cannot restore, output path already exists: %s", opt.OutputPath)
 	} else if err != nil && !os.IsNotExist(err) {
 		return err
 	}
-	}
 
-	// Find lastest snapshot that occurs before timestamp.
-	minWALIndex, err := SnapshotIndexAt(ctx, r, opt.Generation, opt.Timestamp)
-	if err != nil {
-		return fmt.Errorf("cannot find snapshot index for restore: %w", err)
+	// Find lastest snapshot that occurs before timestamp or index.
+	var minWALIndex int
+	if opt.Index < math.MaxInt32 {
+		if minWALIndex, err = SnapshotIndexByIndex(ctx, r, opt.Generation, opt.Index); err != nil {
+			return fmt.Errorf("cannot find snapshot index: %w", err)
+		}
+	} else {
+		if minWALIndex, err = SnapshotIndexAt(ctx, r, opt.Generation, opt.Timestamp); err != nil {
+			return fmt.Errorf("cannot find snapshot index by timestamp: %w", err)
+		}
 	}
 
 	// Find the maximum WAL index that occurs before timestamp.
@@ -1408,7 +1454,7 @@ func RestoreReplica(ctx context.Context, r Replica, opt RestoreOptions) error {
 	if err != nil {
 		return fmt.Errorf("cannot find max wal index for restore: %w", err)
 	}
-	logger.Printf("%s: starting restore: generation %s, index %08x-%08x", logPrefix, opt.Generation, minWALIndex, maxWALIndex)
+	snapshotOnly := maxWALIndex == -1
 
 	// Initialize starting position.
 	pos := Pos{Generation: opt.Generation, Index: minWALIndex}
@@ -1416,51 +1462,122 @@ func RestoreReplica(ctx context.Context, r Replica, opt RestoreOptions) error {
 
 	// Copy snapshot to output path.
 	logger.Printf("%s: restoring snapshot %s/%08x to %s", logPrefix, opt.Generation, minWALIndex, tmpPath)
-	if !opt.DryRun {
 	if err := restoreSnapshot(ctx, r, pos.Generation, pos.Index, tmpPath); err != nil {
 		return fmt.Errorf("cannot restore snapshot: %w", err)
 	}
+
+	// If no WAL files available, move snapshot to final path & exit early.
+	if snapshotOnly {
+		logger.Printf("%s: snapshot only, finalizing database", logPrefix)
+		return os.Rename(tmpPath, opt.OutputPath)
 	}
 
-	// Restore each WAL file until we reach our maximum index.
+	// Begin processing WAL files.
+	logger.Printf("%s: restoring wal files: generation=%s index=[%08x,%08x]", logPrefix, opt.Generation, minWALIndex, maxWALIndex)
+
+	// Fill input channel with all WAL indexes to be loaded in order.
+	ch := make(chan int, maxWALIndex-minWALIndex+1)
 	for index := minWALIndex; index <= maxWALIndex; index++ {
-		if !opt.DryRun {
-			if err = restoreWAL(ctx, r, opt.Generation, index, tmpPath); os.IsNotExist(err) && index == minWALIndex && index == maxWALIndex {
-				logger.Printf("%s: no wal available, snapshot only", logPrefix)
-				break // snapshot file only, ignore error
-			} else if err != nil {
-				return fmt.Errorf("cannot restore wal: %w", err)
+		ch <- index
 	}
+	close(ch)
+
+	// Track load state for each WAL.
+	var mu sync.Mutex
+	cond := sync.NewCond(&mu)
+	walStates := make([]walRestoreState, maxWALIndex-minWALIndex+1)
+
+	parallelism := opt.Parallelism
+	if parallelism < 1 {
+		parallelism = 1
 	}
 
-		if opt.Verbose {
-			logger.Printf("%s: restored wal %s/%08x", logPrefix, opt.Generation, index)
+	// Download WAL files to disk in parallel.
+	g, ctx := errgroup.WithContext(ctx)
+	for i := 0; i < parallelism; i++ {
+		g.Go(func() error {
+			for {
+				select {
+				case <-ctx.Done():
+					cond.Broadcast()
+					return err
+				case index, ok := <-ch:
+					if !ok {
+						cond.Broadcast()
+						return nil
 					}
+
+					startTime := time.Now()
+
+					err := downloadWAL(ctx, r, opt.Generation, index, tmpPath)
+					if err != nil {
+						err = fmt.Errorf("cannot download wal %s/%08x: %w", opt.Generation, index, err)
+					}
+
+					// Mark index as ready-to-apply and notify applying code.
+					mu.Lock()
+					walStates[index-minWALIndex] = walRestoreState{ready: true, err: err}
+					mu.Unlock()
+					cond.Broadcast()
+
+					// Returning the error here will cancel the other goroutines.
+					if err != nil {
+						return err
+					}
+
+					logger.Printf("%s: downloaded wal %s/%08x elapsed=%s",
+						logPrefix, opt.Generation, index,
+						time.Since(startTime).String(),
+					)
+				}
+			}
+		})
+	}
+
+	// Apply WAL files in order as they are ready.
+	for index := minWALIndex; index <= maxWALIndex; index++ {
+		// Wait until next WAL file is ready to apply.
+		mu.Lock()
+		for !walStates[index-minWALIndex].ready {
+			if err := ctx.Err(); err != nil {
+				return err
+			}
+			cond.Wait()
+		}
+		if err := walStates[index-minWALIndex].err; err != nil {
+			return err
+		}
+		mu.Unlock()
+
+		// Apply WAL to database file.
+		startTime := time.Now()
+		if err = applyWAL(ctx, index, tmpPath); err != nil {
+			return fmt.Errorf("cannot apply wal: %w", err)
+		}
+		logger.Printf("%s: applied wal %s/%08x elapsed=%s",
+			logPrefix, opt.Generation, index,
+			time.Since(startTime).String(),
+		)
+	}
+
+	// Ensure all goroutines finish. All errors should have been handled during
+	// the processing of WAL files but this ensures that all processing is done.
+	if err := g.Wait(); err != nil {
+		return err
 	}
 
 	// Copy file to final location.
 	logger.Printf("%s: renaming database from temporary location", logPrefix)
-	if !opt.DryRun {
 	if err := os.Rename(tmpPath, opt.OutputPath); err != nil {
 		return err
 	}
-	}
 
 	return nil
 }
 
-func checksumFile(filename string) (uint64, error) {
-	f, err := os.Open(filename)
-	if err != nil {
-		return 0, err
-	}
-	defer f.Close()
-
-	h := crc64.New(crc64.MakeTable(crc64.ISO))
-	if _, err := io.Copy(h, f); err != nil {
-		return 0, err
-	}
-	return h.Sum64(), nil
+type walRestoreState struct {
+	ready bool
+	err   error
 }
 
 // CalcRestoreTarget returns a replica & generation to restore from based on opt criteria.
@@ -1572,8 +1689,10 @@ func restoreSnapshot(ctx context.Context, r Replica, generation string, index in
 	return f.Close()
 }
 
-// restoreWAL copies a WAL file from the replica to the local WAL and forces checkpoint.
-func restoreWAL(ctx context.Context, r Replica, generation string, index int, dbPath string) error {
+// downloadWAL copies a WAL file from the replica to a local copy next to the DB.
+// The WAL is later applied by applyWAL(). This function can be run in parallel
+// to download multiple WAL files simultaneously.
+func downloadWAL(ctx context.Context, r Replica, generation string, index int, dbPath string) error {
 	// Determine the user/group & mode based on the DB, if available.
 	uid, gid, mode := -1, -1, os.FileMode(0600)
 	if db := r.DB(); db != nil {
@@ -1588,7 +1707,7 @@ func restoreWAL(ctx context.Context, r Replica, generation string, index int, db
 	defer rd.Close()
 
 	// Open handle to destination WAL path.
-	f, err := createFile(dbPath+"-wal", mode, uid, gid)
+	f, err := createFile(fmt.Sprintf("%s-%08x-wal", dbPath, index), mode, uid, gid)
 	if err != nil {
 		return err
 	}
@@ -1600,6 +1719,15 @@ func restoreWAL(ctx context.Context, r Replica, generation string, index int, db
 	} else if err := f.Close(); err != nil {
 		return err
 	}
+	return nil
+}
+
+// applyWAL performs a truncating checkpoint on the given database.
+func applyWAL(ctx context.Context, index int, dbPath string) error {
+	// Copy WAL file from it's staging path to the correct "-wal" location.
+	if err := os.Rename(fmt.Sprintf("%s-%08x-wal", dbPath, index), dbPath+"-wal"); err != nil {
+		return err
+	}
 
 	// Open SQLite database and force a truncating checkpoint.
 	d, err := sql.Open("sqlite3", dbPath)
@@ -1614,7 +1742,6 @@ func restoreWAL(ctx context.Context, r Replica, generation string, index int, db
 	} else if row[0] != 0 {
 		return fmt.Errorf("truncation checkpoint failed during restore (%d,%d,%d)", row[0], row[1], row[2])
 	}
-
 	return d.Close()
 }
 
@@ -1625,7 +1752,7 @@ func restoreWAL(ctx context.Context, r Replica, generation string, index int, db
 // unable to checkpoint during this time.
 //
 // If dst is set, the database file is copied to that location before checksum.
-func (db *DB) CRC64() (uint64, Pos, error) {
+func (db *DB) CRC64(ctx context.Context) (uint64, Pos, error) {
 	db.mu.Lock()
 	defer db.mu.Unlock()
 
@@ -1643,7 +1770,7 @@ func (db *DB) CRC64() (uint64, Pos, error) {
 	}
 
 	// Force a RESTART checkpoint to ensure the database is at the start of the WAL.
-	if err := db.checkpointAndInit(generation, CheckpointModeRestart); err != nil {
+	if err := db.checkpointAndInit(ctx, generation, CheckpointModeRestart); err != nil {
 		return 0, Pos{}, err
 	}
 
@@ -1655,13 +1782,19 @@ func (db *DB) CRC64() (uint64, Pos, error) {
 	}
 	pos.Offset = 0
 
-	chksum, err := checksumFile(db.Path())
-	if err != nil {
+	// Seek to the beginning of the db file descriptor and checksum whole file.
+	h := crc64.New(crc64.MakeTable(crc64.ISO))
+	if _, err := db.f.Seek(0, io.SeekStart); err != nil {
+		return 0, pos, err
+	} else if _, err := io.Copy(h, db.f); err != nil {
 		return 0, pos, err
 	}
-	return chksum, pos, nil
+	return h.Sum64(), pos, nil
 }
 
+// DefaultRestoreParallelism is the default parallelism when downloading WAL files.
+const DefaultRestoreParallelism = 8
+
 // RestoreOptions represents options for DB.Restore().
 type RestoreOptions struct {
 	// Target path to restore into.
@@ -1677,16 +1810,15 @@ type RestoreOptions struct {
 	Generation string
 
 	// Specific index to restore from.
-	// Set to math.MaxInt64 to ignore index.
+	// Set to math.MaxInt32 to ignore index.
 	Index int
 
 	// Point-in-time to restore database.
 	// If zero, database restore to most recent state available.
 	Timestamp time.Time
 
-	// If true, no actual restore is performed.
-	// Only equivalent log output for a regular restore.
-	DryRun bool
+	// Specifies how many WAL files are downloaded in parallel during restore.
+	Parallelism int
 
 	// Logging settings.
 	Logger  *log.Logger
@@ -1696,7 +1828,8 @@ type RestoreOptions struct {
 // NewRestoreOptions returns a new instance of RestoreOptions with defaults.
 func NewRestoreOptions() RestoreOptions {
 	return RestoreOptions{
-		Index: math.MaxInt64,
+		Index:       math.MaxInt32,
+		Parallelism: DefaultRestoreParallelism,
 	}
 }
 
@@ -1791,24 +1924,3 @@ func headerByteOrder(hdr []byte) (binary.ByteOrder, error) {
 		return nil, fmt.Errorf("invalid wal header magic: %x", magic)
 	}
 }
-
-func copyFile(dst, src string) error {
-	r, err := os.Open(src)
-	if err != nil {
-		return err
-	}
-	defer r.Close()
-
-	w, err := os.Create(dst)
-	if err != nil {
-		return err
-	}
-	defer w.Close()
-
-	if _, err := io.Copy(w, r); err != nil {
-		return err
-	} else if err := w.Sync(); err != nil {
-		return err
-	}
-	return nil
-}

db_test.go

@@ -1,10 +1,12 @@
 package litestream_test
 
 import (
+	"context"
 	"database/sql"
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 	"time"
 
@@ -98,9 +100,12 @@ func TestDB_UpdatedAt(t *testing.T) {
 			t.Fatal(err)
 		}
 
+		sleepTime := 100 * time.Millisecond
 		if os.Getenv("CI") != "" {
-			time.Sleep(1 * time.Second)
+			sleepTime = 1 * time.Second
 		}
+		time.Sleep(sleepTime)
+
 		if _, err := sqldb.Exec(`CREATE TABLE t (id INT);`); err != nil {
 			t.Fatal(err)
 		}
@@ -118,7 +123,7 @@ func TestDB_CRC64(t *testing.T) {
 	t.Run("ErrNotExist", func(t *testing.T) {
 		db := MustOpenDB(t)
 		defer MustCloseDB(t, db)
-		if _, _, err := db.CRC64(); !os.IsNotExist(err) {
+		if _, _, err := db.CRC64(context.Background()); !os.IsNotExist(err) {
 			t.Fatalf("unexpected error: %#v", err)
 		}
 	})
@@ -127,11 +132,11 @@ func TestDB_CRC64(t *testing.T) {
 		db, sqldb := MustOpenDBs(t)
 		defer MustCloseDBs(t, db, sqldb)
 
-		if err := db.Sync(); err != nil {
+		if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		}
 
-		chksum0, _, err := db.CRC64()
+		chksum0, _, err := db.CRC64(context.Background())
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -139,7 +144,7 @@ func TestDB_CRC64(t *testing.T) {
 		// Issue change that is applied to the WAL. Checksum should not change.
 		if _, err := sqldb.Exec(`CREATE TABLE t (id INT);`); err != nil {
 			t.Fatal(err)
-		} else if chksum1, _, err := db.CRC64(); err != nil {
+		} else if chksum1, _, err := db.CRC64(context.Background()); err != nil {
 			t.Fatal(err)
 		} else if chksum0 == chksum1 {
 			t.Fatal("expected different checksum event after WAL change")
@@ -150,7 +155,7 @@ func TestDB_CRC64(t *testing.T) {
 			t.Fatal(err)
 		}
 
-		if chksum2, _, err := db.CRC64(); err != nil {
+		if chksum2, _, err := db.CRC64(context.Background()); err != nil {
 			t.Fatal(err)
 		} else if chksum0 == chksum2 {
 			t.Fatal("expected different checksums after checkpoint")
@@ -164,7 +169,7 @@ func TestDB_Sync(t *testing.T) {
 	t.Run("NoDB", func(t *testing.T) {
 		db := MustOpenDB(t)
 		defer MustCloseDB(t, db)
-		if err := db.Sync(); err != nil {
+		if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		}
 	})
@@ -174,7 +179,7 @@ func TestDB_Sync(t *testing.T) {
 		db, sqldb := MustOpenDBs(t)
 		defer MustCloseDBs(t, db, sqldb)
 
-		if err := db.Sync(); err != nil {
+		if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		}
 
@@ -212,7 +217,7 @@ func TestDB_Sync(t *testing.T) {
 		}
 
 		// Perform initial sync & grab initial position.
-		if err := db.Sync(); err != nil {
+		if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		}
 
@@ -227,7 +232,7 @@ func TestDB_Sync(t *testing.T) {
 		}
 
 		// Sync to ensure position moves forward one page.
-		if err := db.Sync(); err != nil {
+		if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		} else if pos1, err := db.Pos(); err != nil {
 			t.Fatal(err)
@@ -246,7 +251,7 @@ func TestDB_Sync(t *testing.T) {
 		defer MustCloseDBs(t, db, sqldb)
 
 		// Issue initial sync and truncate WAL.
-		if err := db.Sync(); err != nil {
+		if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		}
 
@@ -275,7 +280,7 @@ func TestDB_Sync(t *testing.T) {
 		defer MustCloseDB(t, db)
 
 		// Re-sync and ensure new generation has been created.
-		if err := db.Sync(); err != nil {
+		if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		}
 
@@ -298,7 +303,7 @@ func TestDB_Sync(t *testing.T) {
 		}
 
 		// Issue initial sync and truncate WAL.
-		if err := db.Sync(); err != nil {
+		if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		}
 
@@ -334,7 +339,7 @@ func TestDB_Sync(t *testing.T) {
 		defer MustCloseDB(t, db)
 
 		// Re-sync and ensure new generation has been created.
-		if err := db.Sync(); err != nil {
+		if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		}
 
@@ -354,7 +359,7 @@ func TestDB_Sync(t *testing.T) {
 		// Execute a query to force a write to the WAL and then sync.
 		if _, err := sqldb.Exec(`CREATE TABLE foo (bar TEXT);`); err != nil {
 			t.Fatal(err)
-		} else if err := db.Sync(); err != nil {
+		} else if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		}
 
@@ -378,7 +383,7 @@ func TestDB_Sync(t *testing.T) {
 		// Reopen managed database & ensure sync will still work.
 		db = MustOpenDBAt(t, db.Path())
 		defer MustCloseDB(t, db)
-		if err := db.Sync(); err != nil {
+		if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		}
 
@@ -398,7 +403,7 @@ func TestDB_Sync(t *testing.T) {
 		// Execute a query to force a write to the WAL and then sync.
 		if _, err := sqldb.Exec(`CREATE TABLE foo (bar TEXT);`); err != nil {
 			t.Fatal(err)
-		} else if err := db.Sync(); err != nil {
+		} else if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		}
 
@@ -417,7 +422,7 @@ func TestDB_Sync(t *testing.T) {
 		// Reopen managed database & ensure sync will still work.
 		db = MustOpenDBAt(t, db.Path())
 		defer MustCloseDB(t, db)
-		if err := db.Sync(); err != nil {
+		if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		}
 
@@ -437,7 +442,7 @@ func TestDB_Sync(t *testing.T) {
 		// Execute a query to force a write to the WAL and then sync.
 		if _, err := sqldb.Exec(`CREATE TABLE foo (bar TEXT);`); err != nil {
 			t.Fatal(err)
-		} else if err := db.Sync(); err != nil {
+		} else if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		}
 
@@ -462,7 +467,7 @@ func TestDB_Sync(t *testing.T) {
 		// Reopen managed database & ensure sync will still work.
 		db = MustOpenDBAt(t, db.Path())
 		defer MustCloseDB(t, db)
-		if err := db.Sync(); err != nil {
+		if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		}
 
@@ -489,7 +494,7 @@ func TestDB_Sync(t *testing.T) {
 		// Execute a query to force a write to the WAL and then sync.
 		if _, err := sqldb.Exec(`CREATE TABLE foo (bar TEXT);`); err != nil {
 			t.Fatal(err)
-		} else if err := db.Sync(); err != nil {
+		} else if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		}
 
@@ -508,7 +513,7 @@ func TestDB_Sync(t *testing.T) {
 		// Reopen managed database & ensure sync will still work.
 		db = MustOpenDBAt(t, db.Path())
 		defer MustCloseDB(t, db)
-		if err := db.Sync(); err != nil {
+		if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		}
 
@@ -532,7 +537,7 @@ func TestDB_Sync(t *testing.T) {
 		// Execute a query to force a write to the WAL and then sync.
 		if _, err := sqldb.Exec(`CREATE TABLE foo (bar TEXT);`); err != nil {
 			t.Fatal(err)
-		} else if err := db.Sync(); err != nil {
+		} else if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		}
 
@@ -544,7 +549,7 @@ func TestDB_Sync(t *testing.T) {
 		}
 
 		// Sync to shadow WAL.
-		if err := db.Sync(); err != nil {
+		if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		}
 
@@ -564,7 +569,7 @@ func TestDB_Sync(t *testing.T) {
 		// Execute a query to force a write to the WAL and then sync.
 		if _, err := sqldb.Exec(`CREATE TABLE foo (bar TEXT);`); err != nil {
 			t.Fatal(err)
-		} else if err := db.Sync(); err != nil {
+		} else if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		}
 
@@ -574,7 +579,7 @@ func TestDB_Sync(t *testing.T) {
 		// Write to WAL & sync.
 		if _, err := sqldb.Exec(`INSERT INTO foo (bar) VALUES ('baz');`); err != nil {
 			t.Fatal(err)
-		} else if err := db.Sync(); err != nil {
+		} else if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		}
 
@@ -589,12 +594,14 @@ func TestDB_Sync(t *testing.T) {
 
 // MustOpenDBs returns a new instance of a DB & associated SQL DB.
 func MustOpenDBs(tb testing.TB) (*litestream.DB, *sql.DB) {
+	tb.Helper()
 	db := MustOpenDB(tb)
 	return db, MustOpenSQLDB(tb, db.Path())
 }
 
 // MustCloseDBs closes db & sqldb and removes the parent directory.
 func MustCloseDBs(tb testing.TB, db *litestream.DB, sqldb *sql.DB) {
+	tb.Helper()
 	MustCloseDB(tb, db)
 	MustCloseSQLDB(tb, sqldb)
 }
@@ -619,7 +626,7 @@ func MustOpenDBAt(tb testing.TB, path string) *litestream.DB {
 // MustCloseDB closes db and removes its parent directory.
 func MustCloseDB(tb testing.TB, db *litestream.DB) {
 	tb.Helper()
-	if err := db.Close(); err != nil {
+	if err := db.Close(); err != nil && !strings.Contains(err.Error(), `database is closed`) {
 		tb.Fatal(err)
 	} else if err := os.RemoveAll(filepath.Dir(db.Path())); err != nil {
 		tb.Fatal(err)

etc/build.ps1

@@ -0,0 +1,17 @@
+[CmdletBinding()]
+Param (
+    [Parameter(Mandatory = $true)]
+    [String] $Version
+)
+$ErrorActionPreference = "Stop"
+
+# Update working directory.
+Push-Location $PSScriptRoot
+Trap {
+    Pop-Location
+}
+
+Invoke-Expression "candle.exe -nologo -arch x64 -ext WixUtilExtension -out litestream.wixobj -dVersion=`"$Version`" litestream.wxs"
+Invoke-Expression "light.exe  -nologo -spdb -ext WixUtilExtension -out `"litestream-${Version}.msi`" litestream.wixobj"
+
+Pop-Location

etc/litestream.wxs

@@ -0,0 +1,89 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Wix
+	xmlns="http://schemas.microsoft.com/wix/2006/wi"
+	xmlns:util="http://schemas.microsoft.com/wix/UtilExtension"
+>
+	<?if $(sys.BUILDARCH)=x64 ?>
+		<?define PlatformProgramFiles = "ProgramFiles64Folder" ?>
+	<?else ?>
+		<?define PlatformProgramFiles = "ProgramFilesFolder" ?>
+	<?endif ?>
+
+	<Product
+		Id="*"
+		UpgradeCode="5371367e-58b3-4e52-be0d-46945eb71ce6"
+		Name="Litestream"
+		Version="$(var.Version)"
+		Manufacturer="Litestream"
+		Language="1033"
+		Codepage="1252"
+	>
+		<Package
+			Id="*"
+			Manufacturer="Litestream"
+			InstallScope="perMachine"
+			InstallerVersion="500"
+			Description="Litestream $(var.Version) installer"
+			Compressed="yes"
+		/>
+		
+		<Media Id="1" Cabinet="litestream.cab" EmbedCab="yes"/>
+		
+		<MajorUpgrade
+			Schedule="afterInstallInitialize"
+			DowngradeErrorMessage="A later version of [ProductName] is already installed. Setup will now exit."
+		/>
+
+		<Directory Id="TARGETDIR" Name="SourceDir">
+			<Directory Id="$(var.PlatformProgramFiles)">
+				<Directory Id="APPLICATIONROOTDIRECTORY" Name="Litestream"/>
+			</Directory>
+		</Directory>
+
+		<ComponentGroup Id="Files">
+			<Component Directory="APPLICATIONROOTDIRECTORY">
+				<File
+					Id="litestream.exe"
+					Name="litestream.exe"
+					Source="litestream.exe"
+					KeyPath="yes"
+				/>
+
+				<ServiceInstall
+					Id="InstallService"
+					Name="Litestream"
+					DisplayName="Litestream"
+					Description="Replicates SQLite databases"
+					ErrorControl="normal"
+					Start="auto"
+					Type="ownProcess"
+				>
+					<util:ServiceConfig
+						FirstFailureActionType="restart"
+						SecondFailureActionType="restart"
+						ThirdFailureActionType="restart"
+						RestartServiceDelayInSeconds="60"
+					/>
+					<ServiceDependency Id="wmiApSrv" />
+				</ServiceInstall>
+
+				<ServiceControl
+					Id="ServiceStateControl"
+					Name="Litestream"
+					Remove="uninstall"
+					Start="install"
+					Stop="both"
+				/>
+				<util:EventSource
+					Log="Application"
+					Name="Litestream"
+					EventMessageFile="%SystemRoot%\System32\EventCreate.exe"
+				/>
+			</Component>
+		</ComponentGroup>
+
+		<Feature Id="DefaultFeature" Level="1">
+			<ComponentGroupRef Id="Files" />
+		</Feature>
+	</Product>
+</Wix>

etc/litestream.yml

@@ -6,5 +6,5 @@
 #  - path: /path/to/primary/db            # Database to replicate from
 #    replicas:
 #      - path: /path/to/replica           # File-based replication
-#      - path: s3://my.bucket.com/db      # S3-based replication
+#      - url:  s3://my.bucket.com/db      # S3-based replication
 

etc/nfpm.yml

@@ -1,13 +1,13 @@
 name: litestream
-arch: amd64
-platform: linux
+arch: "${GOARCH}"
+platform: "${GOOS}"
 version: "${LITESTREAM_VERSION}"
 section: "default"
 priority: "extra"
 maintainer: "Ben Johnson <benbjohnson@yahoo.com>"
 description: Litestream is a tool for real-time replication of SQLite databases.
 homepage: "https://github.com/benbjohnson/litestream"
-license: "GPLv3"
+license: "Apache 2"
 contents:
 - src: ./litestream
   dst: /usr/bin/litestream

go.mod

@@ -8,5 +8,7 @@ require (
 	github.com/mattn/go-sqlite3 v1.14.5
 	github.com/pierrec/lz4/v4 v4.1.3
 	github.com/prometheus/client_golang v1.9.0
+	golang.org/x/sync v0.0.0-20210220032951-036812b2e83c // indirect
+	golang.org/x/sys v0.0.0-20201214210602-f9fddec55a1e
 	gopkg.in/yaml.v2 v2.4.0
 )

go.sum

@@ -316,6 +316,8 @@ golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4/go.mod h1:RxMgew5VJxzue5/jJ
 golang.org/x/sync v0.0.0-20190227155943-e225da77a7e6/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.0.0-20210220032951-036812b2e83c h1:5KslGYwFpkhGh+Q16bwMP3cOontH8FOep7tGV86Y7SQ=
+golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20180823144017-11551d06cbcc/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180905080454-ebe1bf3edb33/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=

litestream.go

@@ -36,6 +36,7 @@ const (
 
 // Litestream errors.
 var (
+	ErrNoGeneration     = errors.New("no generation available")
 	ErrNoSnapshots      = errors.New("no snapshots available")
 	ErrChecksumMismatch = errors.New("invalid replica, checksum mismatch")
 )
@@ -151,8 +152,9 @@ func readWALHeader(filename string) ([]byte, error) {
 	return buf[:n], err
 }
 
-// readFileAt reads a slice from a file.
-func readFileAt(filename string, offset, n int64) ([]byte, error) {
+// readWALFileAt reads a slice from a file. Do not use this with database files
+// as it causes problems with non-OFD locks.
+func readWALFileAt(filename string, offset, n int64) ([]byte, error) {
 	f, err := os.Open(filename)
 	if err != nil {
 		return nil, err

replica.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/binary"
 	"fmt"
+	"hash/crc64"
 	"io"
 	"io/ioutil"
 	"log"
@@ -31,10 +32,13 @@ type Replica interface {
 	DB() *DB
 
 	// Starts replicating in a background goroutine.
-	Start(ctx context.Context)
+	Start(ctx context.Context) error
 
 	// Stops all replication processing. Blocks until processing stopped.
-	Stop()
+	Stop(hard bool) error
+
+	// Performs a backup of outstanding WAL frames to the replica.
+	Sync(ctx context.Context) error
 
 	// Returns the last replication position.
 	LastPos() Pos
@@ -90,6 +94,9 @@ type FileReplica struct {
 	mu  sync.RWMutex
 	pos Pos // last position
 
+	muf sync.Mutex
+	f   *os.File // long-running file descriptor to avoid non-OFD lock issues
+
 	wg     sync.WaitGroup
 	cancel func()
 
@@ -98,8 +105,11 @@ type FileReplica struct {
 	walIndexGauge      prometheus.Gauge
 	walOffsetGauge     prometheus.Gauge
 
+	// Frequency to create new snapshots.
+	SnapshotInterval time.Duration
+
 	// Time to keep snapshots and related WAL files.
-	// Database is snapshotted after interval and older WAL files are discarded.
+	// Database is snapshotted after interval, if needed, and older WAL files are discarded.
 	Retention time.Duration
 
 	// Time between checks for retention.
@@ -389,29 +399,45 @@ func (r *FileReplica) WALs(ctx context.Context) ([]*WALInfo, error) {
 }
 
 // Start starts replication for a given generation.
-func (r *FileReplica) Start(ctx context.Context) {
+func (r *FileReplica) Start(ctx context.Context) (err error) {
 	// Ignore if replica is being used sychronously.
 	if !r.MonitorEnabled {
-		return
+		return nil
 	}
 
 	// Stop previous replication.
-	r.Stop()
+	r.Stop(false)
 
 	// Wrap context with cancelation.
 	ctx, r.cancel = context.WithCancel(ctx)
 
 	// Start goroutine to replicate data.
-	r.wg.Add(3)
+	r.wg.Add(4)
 	go func() { defer r.wg.Done(); r.monitor(ctx) }()
 	go func() { defer r.wg.Done(); r.retainer(ctx) }()
+	go func() { defer r.wg.Done(); r.snapshotter(ctx) }()
 	go func() { defer r.wg.Done(); r.validator(ctx) }()
+
+	return nil
 }
 
 // Stop cancels any outstanding replication and blocks until finished.
-func (r *FileReplica) Stop() {
+//
+// Performing a hard stop will close the DB file descriptor which could release
+// locks on per-process locks. Hard stops should only be performed when
+// stopping the entire process.
+func (r *FileReplica) Stop(hard bool) (err error) {
 	r.cancel()
 	r.wg.Wait()
+
+	r.muf.Lock()
+	defer r.muf.Unlock()
+	if hard && r.f != nil {
+		if e := r.f.Close(); e != nil && err == nil {
+			err = e
+		}
+	}
+	return err
 }
 
 // monitor runs in a separate goroutine and continuously replicates the DB.
@@ -446,7 +472,18 @@ func (r *FileReplica) monitor(ctx context.Context) {
 
 // retainer runs in a separate goroutine and handles retention.
 func (r *FileReplica) retainer(ctx context.Context) {
-	ticker := time.NewTicker(r.RetentionCheckInterval)
+	// Disable retention enforcement if retention period is non-positive.
+	if r.Retention <= 0 {
+		return
+	}
+
+	// Ensure check interval is not longer than retention period.
+	checkInterval := r.RetentionCheckInterval
+	if checkInterval > r.Retention {
+		checkInterval = r.Retention
+	}
+
+	ticker := time.NewTicker(checkInterval)
 	defer ticker.Stop()
 
 	for {
@@ -462,6 +499,28 @@ func (r *FileReplica) retainer(ctx context.Context) {
 	}
 }
 
+// snapshotter runs in a separate goroutine and handles snapshotting.
+func (r *FileReplica) snapshotter(ctx context.Context) {
+	if r.SnapshotInterval <= 0 {
+		return
+	}
+
+	ticker := time.NewTicker(r.SnapshotInterval)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-ticker.C:
+			if err := r.Snapshot(ctx); err != nil && err != ErrNoGeneration {
+				log.Printf("%s(%s): snapshotter error: %s", r.db.Path(), r.Name(), err)
+				continue
+			}
+		}
+	}
+}
+
 // validator runs in a separate goroutine and handles periodic validation.
 func (r *FileReplica) validator(ctx context.Context) {
 	// Initialize counters since validation occurs infrequently.
@@ -531,8 +590,28 @@ func (r *FileReplica) CalcPos(ctx context.Context, generation string) (pos Pos,
 	return pos, nil
 }
 
+// Snapshot copies the entire database to the replica path.
+func (r *FileReplica) Snapshot(ctx context.Context) error {
+	// Find current position of database.
+	pos, err := r.db.Pos()
+	if err != nil {
+		return fmt.Errorf("cannot determine current db generation: %w", err)
+	} else if pos.IsZero() {
+		return ErrNoGeneration
+	}
+	return r.snapshot(ctx, pos.Generation, pos.Index)
+}
+
 // snapshot copies the entire database to the replica path.
 func (r *FileReplica) snapshot(ctx context.Context, generation string, index int) error {
+	r.muf.Lock()
+	defer r.muf.Unlock()
+
+	// Issue a passive checkpoint to flush any pages to disk before snapshotting.
+	if _, err := r.db.db.ExecContext(ctx, `PRAGMA wal_checkpoint(PASSIVE);`); err != nil {
+		return fmt.Errorf("pre-snapshot checkpoint: %w", err)
+	}
+
 	// Acquire a read lock on the database during snapshot to prevent checkpoints.
 	tx, err := r.db.db.Begin()
 	if err != nil {
@@ -553,11 +632,50 @@ func (r *FileReplica) snapshot(ctx context.Context, generation string, index int
 
 	if err := mkdirAll(filepath.Dir(snapshotPath), r.db.dirmode, r.db.diruid, r.db.dirgid); err != nil {
 		return err
-	} else if err := compressFile(r.db.Path(), snapshotPath, r.db.uid, r.db.gid); err != nil {
+	}
+
+	// Open db file descriptor, if not already open.
+	if r.f == nil {
+		if r.f, err = os.Open(r.db.Path()); err != nil {
+			return err
+		}
+	}
+
+	if _, err := r.f.Seek(0, io.SeekStart); err != nil {
 		return err
 	}
 
-	log.Printf("%s(%s): snapshot: creating %s/%08x t=%s", r.db.Path(), r.Name(), generation, index, time.Since(startTime))
+	fi, err := r.f.Stat()
+	if err != nil {
+		return err
+	}
+
+	w, err := createFile(snapshotPath+".tmp", fi.Mode(), r.db.uid, r.db.gid)
+	if err != nil {
+		return err
+	}
+	defer w.Close()
+
+	zr := lz4.NewWriter(w)
+	defer zr.Close()
+
+	// Copy & compress file contents to temporary file.
+	if _, err := io.Copy(zr, r.f); err != nil {
+		return err
+	} else if err := zr.Close(); err != nil {
+		return err
+	} else if err := w.Sync(); err != nil {
+		return err
+	} else if err := w.Close(); err != nil {
+		return err
+	}
+
+	// Move compressed file to final location.
+	if err := os.Rename(snapshotPath+".tmp", snapshotPath); err != nil {
+		return err
+	}
+
+	log.Printf("%s(%s): snapshot: creating %s/%08x t=%s", r.db.Path(), r.Name(), generation, index, time.Since(startTime).Truncate(time.Millisecond))
 	return nil
 }
 
@@ -756,7 +874,7 @@ func (r *FileReplica) compress(ctx context.Context, generation string) error {
 		}
 
 		dst := filename + ".lz4"
-		if err := compressFile(filename, dst, r.db.uid, r.db.gid); err != nil {
+		if err := compressWALFile(filename, dst, r.db.uid, r.db.gid); err != nil {
 			return err
 		} else if err := os.Remove(filename); err != nil {
 			return err
@@ -951,34 +1069,65 @@ func SnapshotIndexAt(ctx context.Context, r Replica, generation string, timestam
 		return 0, ErrNoSnapshots
 	}
 
-	index := -1
+	snapshotIndex := -1
 	var max time.Time
 	for _, snapshot := range snapshots {
-		if !timestamp.IsZero() && snapshot.CreatedAt.After(timestamp) {
+		if snapshot.Generation != generation {
+			continue // generation mismatch, skip
+		} else if !timestamp.IsZero() && snapshot.CreatedAt.After(timestamp) {
 			continue // after timestamp, skip
 		}
 
 		// Use snapshot if it newer.
 		if max.IsZero() || snapshot.CreatedAt.After(max) {
-			index, max = snapshot.Index, snapshot.CreatedAt
+			snapshotIndex, max = snapshot.Index, snapshot.CreatedAt
 		}
 	}
 
-	if index == -1 {
+	if snapshotIndex == -1 {
 		return 0, ErrNoSnapshots
 	}
-	return index, nil
+	return snapshotIndex, nil
 }
 
-// WALIndexAt returns the highest index for a WAL file that occurs before maxIndex & timestamp.
-// If timestamp is zero, returns the highest WAL index.
+// SnapshotIndexbyIndex returns the highest index for a snapshot within a generation
+// that occurs before a given index. If index is MaxInt32, returns the latest snapshot.
+func SnapshotIndexByIndex(ctx context.Context, r Replica, generation string, index int) (int, error) {
+	snapshots, err := r.Snapshots(ctx)
+	if err != nil {
+		return 0, err
+	} else if len(snapshots) == 0 {
+		return 0, ErrNoSnapshots
+	}
+
+	snapshotIndex := -1
+	for _, snapshot := range snapshots {
+		if index < math.MaxInt32 && snapshot.Index > index {
+			continue // after index, skip
+		}
+
+		// Use snapshot if it newer.
+		if snapshotIndex == -1 || snapshotIndex >= snapshotIndex {
+			snapshotIndex = snapshot.Index
+		}
+	}
+
+	if snapshotIndex == -1 {
+		return 0, ErrNoSnapshots
+	}
+	return snapshotIndex, nil
+}
+
+// WALIndexAt returns the highest index for a WAL file that occurs before
+// maxIndex & timestamp. If timestamp is zero, returns the highest WAL index.
+// Returns -1 if no WAL found and MaxInt32 specified.
 func WALIndexAt(ctx context.Context, r Replica, generation string, maxIndex int, timestamp time.Time) (int, error) {
 	wals, err := r.WALs(ctx)
 	if err != nil {
 		return 0, err
 	}
 
-	var index int
+	index := -1
 	for _, wal := range wals {
 		if wal.Generation != generation {
 			continue
@@ -996,14 +1145,15 @@ func WALIndexAt(ctx context.Context, r Replica, generation string, maxIndex int,
 	}
 
 	// If max index is specified but not found, return an error.
-	if maxIndex != math.MaxInt64 && index != maxIndex {
+	if maxIndex != math.MaxInt32 && index != maxIndex {
 		return index, fmt.Errorf("unable to locate index %d in generation %q, highest index was %d", maxIndex, generation, index)
 	}
 	return index, nil
 }
 
-// compressFile compresses a file and replaces it with a new file with a .lz4 extension.
-func compressFile(src, dst string, uid, gid int) error {
+// compressWALFile compresses a file and replaces it with a new file with a .lz4 extension.
+// Do not use this on database files because of issues with non-OFD locks.
+func compressWALFile(src, dst string, uid, gid int) error {
 	r, err := os.Open(src)
 	if err != nil {
 		return err
@@ -1053,8 +1203,7 @@ func ValidateReplica(ctx context.Context, r Replica) error {
 
 	// Compute checksum of primary database under lock. This prevents a
 	// sync from occurring and the database will not be written.
-	primaryPath := filepath.Join(tmpdir, "primary")
-	chksum0, pos, err := db.CRC64()
+	chksum0, pos, err := db.CRC64(ctx)
 	if err != nil {
 		return fmt.Errorf("cannot compute checksum: %w", err)
 	}
@@ -1076,10 +1225,19 @@ func ValidateReplica(ctx context.Context, r Replica) error {
 	}
 
 	// Open file handle for restored database.
-	chksum1, err := checksumFile(restorePath)
+	// NOTE: This open is ok as the restored database is not managed by litestream.
+	f, err := os.Open(restorePath)
 	if err != nil {
 		return err
 	}
+	defer f.Close()
+
+	// Read entire file into checksum.
+	h := crc64.New(crc64.MakeTable(crc64.ISO))
+	if _, err := io.Copy(h, f); err != nil {
+		return err
+	}
+	chksum1 := h.Sum64()
 
 	status := "ok"
 	mismatch := chksum0 != chksum1
@@ -1091,15 +1249,6 @@ func ValidateReplica(ctx context.Context, r Replica) error {
 	// Validate checksums match.
 	if mismatch {
 		internal.ReplicaValidationTotalCounterVec.WithLabelValues(db.Path(), r.Name(), "error").Inc()
-
-		// Compress mismatched databases and report temporary path for investigation.
-		if err := compressFile(primaryPath, primaryPath+".lz4", db.uid, db.gid); err != nil {
-			return fmt.Errorf("cannot compress primary db: %w", err)
-		} else if err := compressFile(restorePath, restorePath+".lz4", db.uid, db.gid); err != nil {
-			return fmt.Errorf("cannot compress replica db: %w", err)
-		}
-		log.Printf("%s(%s): validator: mismatch files @ %s", db.Path(), r.Name(), tmpdir)
-
 		return ErrChecksumMismatch
 	}
 

replica_test.go

@@ -15,7 +15,7 @@ func TestFileReplica_Sync(t *testing.T) {
 		r := NewTestFileReplica(t, db)
 
 		// Sync database & then sync replica.
-		if err := db.Sync(); err != nil {
+		if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		} else if err := r.Sync(context.Background()); err != nil {
 			t.Fatal(err)
@@ -47,7 +47,7 @@ func TestFileReplica_Sync(t *testing.T) {
 
 			// Sync periodically.
 			if i%100 == 0 || i == n-1 {
-				if err := db.Sync(); err != nil {
+				if err := db.Sync(context.Background()); err != nil {
 					t.Fatal(err)
 				} else if err := r.Sync(context.Background()); err != nil {
 					t.Fatal(err)

s3/s3.go

@@ -3,12 +3,16 @@ package s3
 import (
 	"bytes"
 	"context"
+	"crypto/tls"
 	"fmt"
 	"io"
 	"io/ioutil"
 	"log"
+	"net"
+	"net/http"
 	"os"
 	"path"
+	"regexp"
 	"sync"
 	"time"
 
@@ -50,6 +54,9 @@ type Replica struct {
 	snapshotMu sync.Mutex
 	pos        litestream.Pos // last position
 
+	muf sync.Mutex
+	f   *os.File // long-lived read-only db file descriptor
+
 	wg     sync.WaitGroup
 	cancel func()
 
@@ -72,10 +79,16 @@ type Replica struct {
 	Region         string
 	Bucket         string
 	Path           string
+	Endpoint       string
+	ForcePathStyle bool
+	SkipVerify     bool
 
 	// Time between syncs with the shadow WAL.
 	SyncInterval time.Duration
 
+	// Frequency to create new snapshots.
+	SnapshotInterval time.Duration
+
 	// Time to keep snapshots and related WAL files.
 	// Database is snapshotted after interval and older WAL files are discarded.
 	Retention time.Duration
@@ -410,29 +423,47 @@ func (r *Replica) WALs(ctx context.Context) ([]*litestream.WALInfo, error) {
 }
 
 // Start starts replication for a given generation.
-func (r *Replica) Start(ctx context.Context) {
+func (r *Replica) Start(ctx context.Context) (err error) {
 	// Ignore if replica is being used sychronously.
 	if !r.MonitorEnabled {
-		return
+		return nil
 	}
 
 	// Stop previous replication.
-	r.Stop()
+	r.Stop(false)
 
 	// Wrap context with cancelation.
 	ctx, r.cancel = context.WithCancel(ctx)
 
 	// Start goroutines to manage replica data.
-	r.wg.Add(3)
+	r.wg.Add(4)
 	go func() { defer r.wg.Done(); r.monitor(ctx) }()
 	go func() { defer r.wg.Done(); r.retainer(ctx) }()
+	go func() { defer r.wg.Done(); r.snapshotter(ctx) }()
 	go func() { defer r.wg.Done(); r.validator(ctx) }()
+
+	return nil
 }
 
 // Stop cancels any outstanding replication and blocks until finished.
-func (r *Replica) Stop() {
+//
+// Performing a hard stop will close the DB file descriptor which could release
+// locks on per-process locks. Hard stops should only be performed when
+// stopping the entire process.
+func (r *Replica) Stop(hard bool) (err error) {
 	r.cancel()
 	r.wg.Wait()
+
+	r.muf.Lock()
+	defer r.muf.Unlock()
+
+	if hard && r.f != nil {
+		if e := r.f.Close(); e != nil && err == nil {
+			err = e
+		}
+	}
+
+	return err
 }
 
 // monitor runs in a separate goroutine and continuously replicates the DB.
@@ -475,7 +506,18 @@ func (r *Replica) monitor(ctx context.Context) {
 
 // retainer runs in a separate goroutine and handles retention.
 func (r *Replica) retainer(ctx context.Context) {
-	ticker := time.NewTicker(r.RetentionCheckInterval)
+	// Disable retention enforcement if retention period is non-positive.
+	if r.Retention <= 0 {
+		return
+	}
+
+	// Ensure check interval is not longer than retention period.
+	checkInterval := r.RetentionCheckInterval
+	if checkInterval > r.Retention {
+		checkInterval = r.Retention
+	}
+
+	ticker := time.NewTicker(checkInterval)
 	defer ticker.Stop()
 
 	for {
@@ -491,6 +533,28 @@ func (r *Replica) retainer(ctx context.Context) {
 	}
 }
 
+// snapshotter runs in a separate goroutine and handles snapshotting.
+func (r *Replica) snapshotter(ctx context.Context) {
+	if r.SnapshotInterval <= 0 {
+		return
+	}
+
+	ticker := time.NewTicker(r.SnapshotInterval)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-ticker.C:
+			if err := r.Snapshot(ctx); err != nil && err != litestream.ErrNoGeneration {
+				log.Printf("%s(%s): snapshotter error: %s", r.db.Path(), r.Name(), err)
+				continue
+			}
+		}
+	}
+}
+
 // validator runs in a separate goroutine and handles periodic validation.
 func (r *Replica) validator(ctx context.Context) {
 	// Initialize counters since validation occurs infrequently.
@@ -568,8 +632,28 @@ func (r *Replica) CalcPos(ctx context.Context, generation string) (pos litestrea
 	return pos, nil
 }
 
+// Snapshot copies the entire database to the replica path.
+func (r *Replica) Snapshot(ctx context.Context) error {
+	// Find current position of database.
+	pos, err := r.db.Pos()
+	if err != nil {
+		return fmt.Errorf("cannot determine current db generation: %w", err)
+	} else if pos.IsZero() {
+		return litestream.ErrNoGeneration
+	}
+	return r.snapshot(ctx, pos.Generation, pos.Index)
+}
+
 // snapshot copies the entire database to the replica path.
 func (r *Replica) snapshot(ctx context.Context, generation string, index int) error {
+	r.muf.Lock()
+	defer r.muf.Unlock()
+
+	// Issue a passive checkpoint to flush any pages to disk before snapshotting.
+	if _, err := r.db.SQLDB().ExecContext(ctx, `PRAGMA wal_checkpoint(PASSIVE);`); err != nil {
+		return fmt.Errorf("pre-snapshot checkpoint: %w", err)
+	}
+
 	// Acquire a read lock on the database during snapshot to prevent checkpoints.
 	tx, err := r.db.SQLDB().Begin()
 	if err != nil {
@@ -580,14 +664,21 @@ func (r *Replica) snapshot(ctx context.Context, generation string, index int) er
 	}
 	defer func() { _ = tx.Rollback() }()
 
-	// Open database file handle.
-	f, err := os.Open(r.db.Path())
-	if err != nil {
+	// Open long-lived file descriptor on database.
+	if r.f == nil {
+		if r.f, err = os.Open(r.db.Path()); err != nil {
 			return err
 		}
-	defer f.Close()
+	}
 
-	fi, err := f.Stat()
+	// Move the file descriptor to the beginning. We only use one long lived
+	// file descriptor because some operating systems will remove the database
+	// lock when closing a separate file descriptor on the DB.
+	if _, err := r.f.Seek(0, io.SeekStart); err != nil {
+		return err
+	}
+
+	fi, err := r.f.Stat()
 	if err != nil {
 		return err
 	}
@@ -595,7 +686,7 @@ func (r *Replica) snapshot(ctx context.Context, generation string, index int) er
 	pr, pw := io.Pipe()
 	zw := lz4.NewWriter(pw)
 	go func() {
-		if _, err := io.Copy(zw, f); err != nil {
+		if _, err := io.Copy(zw, r.f); err != nil {
 			_ = pw.CloseWithError(err)
 			return
 		}
@@ -616,8 +707,7 @@ func (r *Replica) snapshot(ctx context.Context, generation string, index int) er
 	r.putOperationTotalCounter.Inc()
 	r.putOperationBytesCounter.Add(float64(fi.Size()))
 
-	log.Printf("%s(%s): snapshot: creating %s/%08x t=%s", r.db.Path(), r.Name(), generation, index, time.Since(startTime))
-
+	log.Printf("%s(%s): snapshot: creating %s/%08x t=%s", r.db.Path(), r.Name(), generation, index, time.Since(startTime).Truncate(time.Millisecond))
 	return nil
 }
 
@@ -646,17 +736,25 @@ func (r *Replica) Init(ctx context.Context) (err error) {
 		return nil
 	}
 
-	// Look up region if not specified.
+	// Look up region if not specified and no endpoint is used.
+	// Endpoints are typically used for non-S3 object stores and do not
+	// necessarily require a region.
 	region := r.Region
 	if region == "" {
+		if r.Endpoint == "" {
 			if region, err = r.findBucketRegion(ctx, r.Bucket); err != nil {
 				return fmt.Errorf("cannot lookup bucket region: %w", err)
 			}
+		} else {
+			region = "us-east-1" // default for non-S3 object stores
+		}
 	}
 
 	// Create new AWS session.
 	config := r.config()
+	if region != "" {
 		config.Region = aws.String(region)
+	}
 	sess, err := session.NewSession(config)
 	if err != nil {
 		return fmt.Errorf("cannot create aws session: %w", err)
@@ -673,6 +771,18 @@ func (r *Replica) config() *aws.Config {
 	if r.AccessKeyID != "" || r.SecretAccessKey != "" {
 		config.Credentials = credentials.NewStaticCredentials(r.AccessKeyID, r.SecretAccessKey, "")
 	}
+	if r.Endpoint != "" {
+		config.Endpoint = aws.String(r.Endpoint)
+	}
+	if r.ForcePathStyle {
+		config.S3ForcePathStyle = aws.Bool(r.ForcePathStyle)
+	}
+	if r.SkipVerify {
+		config.HTTPClient = &http.Client{Transport: &http.Transport{
+			TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
+		}}
+	}
+
 	return config
 }
 
@@ -1027,6 +1137,60 @@ func (r *Replica) deleteGenerationBefore(ctx context.Context, generation string,
 	return nil
 }
 
+// ParseHost extracts data from a hostname depending on the service provider.
+func ParseHost(s string) (bucket, region, endpoint string, forcePathStyle bool) {
+	// Extract port if one is specified.
+	host, port, err := net.SplitHostPort(s)
+	if err != nil {
+		host = s
+	}
+
+	// Default to path-based URLs, except for with AWS S3 itself.
+	forcePathStyle = true
+
+	// Extract fields from provider-specific host formats.
+	scheme := "https"
+	if a := localhostRegex.FindStringSubmatch(host); a != nil {
+		bucket, region = a[1], "us-east-1"
+		scheme, endpoint = "http", "localhost"
+	} else if a := gcsRegex.FindStringSubmatch(host); a != nil {
+		bucket, region = a[1], "us-east-1"
+		endpoint = "storage.googleapis.com"
+	} else if a := digitalOceanRegex.FindStringSubmatch(host); a != nil {
+		bucket, region = a[1], a[2]
+		endpoint = fmt.Sprintf("%s.digitaloceanspaces.com", region)
+	} else if a := linodeRegex.FindStringSubmatch(host); a != nil {
+		bucket, region = a[1], a[2]
+		endpoint = fmt.Sprintf("%s.linodeobjects.com", region)
+	} else if a := backblazeRegex.FindStringSubmatch(host); a != nil {
+		bucket, region = a[1], a[2]
+		endpoint = fmt.Sprintf("s3.%s.backblazeb2.com", region)
+	} else {
+		bucket = host
+		forcePathStyle = false
+	}
+
+	// Add port back to endpoint, if available.
+	if endpoint != "" && port != "" {
+		endpoint = net.JoinHostPort(endpoint, port)
+	}
+
+	// Prepend scheme to endpoint.
+	if endpoint != "" {
+		endpoint = scheme + "://" + endpoint
+	}
+
+	return bucket, region, endpoint, forcePathStyle
+}
+
+var (
+	localhostRegex    = regexp.MustCompile(`^(?:(.+)\.)?localhost$`)
+	digitalOceanRegex = regexp.MustCompile(`^(?:(.+)\.)?([^.]+)\.digitaloceanspaces.com$`)
+	linodeRegex       = regexp.MustCompile(`^(?:(.+)\.)?([^.]+)\.linodeobjects.com$`)
+	backblazeRegex    = regexp.MustCompile(`^(?:(.+)\.)?s3.([^.]+)\.backblazeb2.com$`)
+	gcsRegex          = regexp.MustCompile(`^(?:(.+)\.)?storage.googleapis.com$`)
+)
+
 // S3 metrics.
 var (
 	operationTotalCounterVec = promauto.NewCounterVec(prometheus.CounterOpts{

s3/s3_test.go

@@ -0,0 +1,80 @@
+package s3_test
+
+import (
+	"testing"
+
+	"github.com/benbjohnson/litestream/s3"
+)
+
+func TestParseHost(t *testing.T) {
+	// Ensure non-specific hosts return as buckets.
+	t.Run("S3", func(t *testing.T) {
+		bucket, region, endpoint, forcePathStyle := s3.ParseHost(`test.litestream.io`)
+		if got, want := bucket, `test.litestream.io`; got != want {
+			t.Fatalf("bucket=%q, want %q", got, want)
+		} else if got, want := region, ``; got != want {
+			t.Fatalf("region=%q, want %q", got, want)
+		} else if got, want := endpoint, ``; got != want {
+			t.Fatalf("endpoint=%q, want %q", got, want)
+		} else if got, want := forcePathStyle, false; got != want {
+			t.Fatalf("forcePathStyle=%v, want %v", got, want)
+		}
+	})
+
+	// Ensure localhosts use an HTTP endpoint and extract the bucket name.
+	t.Run("Localhost", func(t *testing.T) {
+		t.Run("WithPort", func(t *testing.T) {
+			bucket, region, endpoint, forcePathStyle := s3.ParseHost(`test.localhost:9000`)
+			if got, want := bucket, `test`; got != want {
+				t.Fatalf("bucket=%q, want %q", got, want)
+			} else if got, want := region, `us-east-1`; got != want {
+				t.Fatalf("region=%q, want %q", got, want)
+			} else if got, want := endpoint, `http://localhost:9000`; got != want {
+				t.Fatalf("endpoint=%q, want %q", got, want)
+			} else if got, want := forcePathStyle, true; got != want {
+				t.Fatalf("forcePathStyle=%v, want %v", got, want)
+			}
+		})
+
+		t.Run("WithoutPort", func(t *testing.T) {
+			bucket, region, endpoint, forcePathStyle := s3.ParseHost(`test.localhost`)
+			if got, want := bucket, `test`; got != want {
+				t.Fatalf("bucket=%q, want %q", got, want)
+			} else if got, want := region, `us-east-1`; got != want {
+				t.Fatalf("region=%q, want %q", got, want)
+			} else if got, want := endpoint, `http://localhost`; got != want {
+				t.Fatalf("endpoint=%q, want %q", got, want)
+			} else if got, want := forcePathStyle, true; got != want {
+				t.Fatalf("forcePathStyle=%v, want %v", got, want)
+			}
+		})
+	})
+
+	// Ensure backblaze B2 URLs extract bucket, region, & endpoint from host.
+	t.Run("Backblaze", func(t *testing.T) {
+		bucket, region, endpoint, forcePathStyle := s3.ParseHost(`test-123.s3.us-west-000.backblazeb2.com`)
+		if got, want := bucket, `test-123`; got != want {
+			t.Fatalf("bucket=%q, want %q", got, want)
+		} else if got, want := region, `us-west-000`; got != want {
+			t.Fatalf("region=%q, want %q", got, want)
+		} else if got, want := endpoint, `https://s3.us-west-000.backblazeb2.com`; got != want {
+			t.Fatalf("endpoint=%q, want %q", got, want)
+		} else if got, want := forcePathStyle, true; got != want {
+			t.Fatalf("forcePathStyle=%v, want %v", got, want)
+		}
+	})
+
+	// Ensure GCS URLs extract bucket & endpoint from host.
+	t.Run("GCS", func(t *testing.T) {
+		bucket, region, endpoint, forcePathStyle := s3.ParseHost(`litestream.io.storage.googleapis.com`)
+		if got, want := bucket, `litestream.io`; got != want {
+			t.Fatalf("bucket=%q, want %q", got, want)
+		} else if got, want := region, `us-east-1`; got != want {
+			t.Fatalf("region=%q, want %q", got, want)
+		} else if got, want := endpoint, `https://storage.googleapis.com`; got != want {
+			t.Fatalf("endpoint=%q, want %q", got, want)
+		} else if got, want := forcePathStyle, true; got != want {
+			t.Fatalf("forcePathStyle=%v, want %v", got, want)
+		}
+	})
+}