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
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+   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)
 ==========
 

cmd/litestream/databases.go

@@ -15,7 +15,7 @@ type DatabasesCommand struct{}
 // Run executes the command.
 func (c *DatabasesCommand) Run(ctx context.Context, args []string) (err error) {
 	fs := flag.NewFlagSet("litestream-databases", flag.ContinueOnError)
-	configPath := registerConfigFlag(fs)
+	configPath, noExpandEnv := registerConfigFlag(fs)
 	fs.Usage = c.Usage
 	if err := fs.Parse(args); err != nil {
 		return err
@@ -27,7 +27,7 @@ func (c *DatabasesCommand) Run(ctx context.Context, args []string) (err error) {
 	if *configPath == "" {
 		*configPath = DefaultConfigPath()
 	}
-	config, err := ReadConfigFile(*configPath)
+	config, err := ReadConfigFile(*configPath, !*noExpandEnv)
 	if err != nil {
 		return err
 	}
@@ -72,6 +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

@@ -18,7 +18,7 @@ type GenerationsCommand struct{}
 // Run executes the command.
 func (c *GenerationsCommand) Run(ctx context.Context, args []string) (err error) {
 	fs := flag.NewFlagSet("litestream-generations", flag.ContinueOnError)
-	configPath := registerConfigFlag(fs)
+	configPath, noExpandEnv := registerConfigFlag(fs)
 	replicaName := fs.String("replica", "", "replica name")
 	fs.Usage = c.Usage
 	if err := fs.Parse(args); err != nil {
@@ -45,7 +45,7 @@ func (c *GenerationsCommand) Run(ctx context.Context, args []string) (err error)
 		}
 
 		// Load configuration.
-		config, err := ReadConfigFile(*configPath)
+		config, err := ReadConfigFile(*configPath, !*noExpandEnv)
 		if err != nil {
 			return err
 		}
@@ -131,6 +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

@@ -14,6 +14,7 @@ import (
 	"path"
 	"path/filepath"
 	"regexp"
+	"strconv"
 	"strings"
 	"time"
 
@@ -60,6 +61,9 @@ func (m *Main) Run(ctx context.Context, args []string) (err error) {
 		return runWindowsService(ctx)
 	}
 
+	// Copy "LITESTEAM" environment credentials.
+	applyLitestreamEnv()
+
 	// Extract command name.
 	var cmd string
 	if len(args) > 0 {
@@ -79,8 +83,7 @@ func (m *Main) Run(ctx context.Context, args []string) (err error) {
 
 		// Setup signal handler.
 		ctx, cancel := context.WithCancel(ctx)
-		ch := make(chan os.Signal, 1)
-		signal.Notify(ch, os.Interrupt)
+		ch := signalChan()
 		go func() { <-ch; cancel() }()
 
 		if err := c.Run(ctx); err != nil {
@@ -90,9 +93,14 @@ func (m *Main) Run(ctx context.Context, args []string) (err error) {
 		// Wait for signal to stop program.
 		<-ctx.Done()
 		signal.Reset()
+		fmt.Println("signal received, litestream shutting down")
 
 		// Gracefully close.
-		return c.Close()
+		if err := c.Close(); err != nil {
+			return err
+		}
+		fmt.Println("litestream shut down")
+		return nil
 
 	case "restore":
 		return (&RestoreCommand{}).Run(ctx, args)
@@ -175,7 +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.
@@ -184,12 +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
 	}
 
@@ -272,6 +289,7 @@ type ReplicaConfig struct {
 	Bucket          string `yaml:"bucket"`
 	Endpoint        string `yaml:"endpoint"`
 	ForcePathStyle  *bool  `yaml:"force-path-style"`
+	SkipVerify      bool   `yaml:"skip-verify"`
 }
 
 // NewReplicaFromConfig instantiates a replica for a DB based on a config.
@@ -343,7 +361,7 @@ func newS3ReplicaFromConfig(c *ReplicaConfig, db *litestream.DB) (_ *s3.Replica,
 	}
 
 	bucket, path := c.Bucket, c.Path
-	region, endpoint := c.Region, c.Endpoint
+	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.
@@ -392,6 +410,7 @@ func newS3ReplicaFromConfig(c *ReplicaConfig, db *litestream.DB) (_ *s3.Replica,
 	r.Region = region
 	r.Endpoint = endpoint
 	r.ForcePathStyle = forcePathStyle
+	r.SkipVerify = skipVerify
 
 	if v := c.Retention; v > 0 {
 		r.Retention = v
@@ -411,6 +430,22 @@ func newS3ReplicaFromConfig(c *ReplicaConfig, db *litestream.DB) (_ *s3.Replica,
 	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)
+		}
+	}
+}
+
 // ParseReplicaURL parses a replica URL.
 func ParseReplicaURL(s string) (scheme, host, urlpath string, err error) {
 	u, err := url.Parse(s)
@@ -455,8 +490,9 @@ func DefaultConfigPath() string {
 	return defaultConfigPath
 }
 
-func registerConfigFlag(fs *flag.FlagSet) *string {
-	return fs.String("config", "", "config path")
+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.
@@ -481,3 +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

@@ -4,6 +4,9 @@ package main
 
 import (
 	"context"
+	"os"
+	"os/signal"
+	"syscall"
 )
 
 const defaultConfigPath = "/etc/litestream.yml"
@@ -15,3 +18,9 @@ func isWindowsService() (bool, error) {
 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

@@ -2,6 +2,7 @@ package main_test
 
 import (
 	"io/ioutil"
+	"os"
 	"path/filepath"
 	"testing"
 
@@ -26,7 +27,7 @@ dbs:
 			t.Fatal(err)
 		}
 
-		config, err := main.ReadConfigFile(filename)
+		config, err := main.ReadConfigFile(filename, true)
 		if err != nil {
 			t.Fatal(err)
 		} else if got, want := config.AccessKeyID, `XXX`; got != want {
@@ -39,6 +40,56 @@ dbs:
 			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) {

cmd/litestream/main_windows.go

@@ -7,6 +7,7 @@ import (
 	"io"
 	"log"
 	"os"
+	"os/signal"
 
 	"golang.org/x/sys/windows"
 	"golang.org/x/sys/windows/svc"
@@ -103,3 +104,9 @@ 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

@@ -32,7 +32,7 @@ func NewReplicateCommand() *ReplicateCommand {
 func (c *ReplicateCommand) ParseFlags(ctx context.Context, args []string) (err error) {
 	fs := flag.NewFlagSet("litestream-replicate", flag.ContinueOnError)
 	tracePath := fs.String("trace", "", "trace path")
-	configPath := registerConfigFlag(fs)
+	configPath, noExpandEnv := registerConfigFlag(fs)
 	fs.Usage = c.Usage
 	if err := fs.Parse(args); err != nil {
 		return err
@@ -58,7 +58,7 @@ func (c *ReplicateCommand) ParseFlags(ctx context.Context, args []string) (err e
 		if *configPath == "" {
 			*configPath = DefaultConfigPath()
 		}
-		if c.Config, err = ReadConfigFile(*configPath); err != nil {
+		if c.Config, err = ReadConfigFile(*configPath, !*noExpandEnv); err != nil {
 			return err
 		}
 	}
@@ -70,7 +70,7 @@ func (c *ReplicateCommand) ParseFlags(ctx context.Context, args []string) (err e
 			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
 	}
 
 	return nil
@@ -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"
@@ -21,12 +22,13 @@ func (c *RestoreCommand) Run(ctx context.Context, args []string) (err error) {
 	opt.Verbose = true
 
 	fs := flag.NewFlagSet("litestream-restore", flag.ContinueOnError)
-	configPath := registerConfigFlag(fs)
+	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
@@ -45,14 +47,9 @@ 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.
@@ -68,13 +65,18 @@ func (c *RestoreCommand) Run(ctx context.Context, args []string) (err error) {
 		if *configPath == "" {
 			*configPath = DefaultConfigPath()
 		}
-		if r, err = c.loadFromConfig(ctx, fs.Arg(0), *configPath, &opt); err != nil {
+		if r, err = c.loadFromConfig(ctx, fs.Arg(0), *configPath, !*noExpandEnv, &opt); err != nil {
 			return err
 		}
 	}
 
 	// 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")
 	}
 
@@ -92,9 +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
 	}
@@ -144,6 +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.
@@ -153,7 +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
@@ -164,9 +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

@@ -17,7 +17,7 @@ type SnapshotsCommand struct{}
 // Run executes the command.
 func (c *SnapshotsCommand) Run(ctx context.Context, args []string) (err error) {
 	fs := flag.NewFlagSet("litestream-snapshots", flag.ContinueOnError)
-	configPath := registerConfigFlag(fs)
+	configPath, noExpandEnv := registerConfigFlag(fs)
 	replicaName := fs.String("replica", "", "replica name")
 	fs.Usage = c.Usage
 	if err := fs.Parse(args); err != nil {
@@ -43,7 +43,7 @@ func (c *SnapshotsCommand) Run(ctx context.Context, args []string) (err error) {
 		}
 
 		// Load configuration.
-		config, err := ReadConfigFile(*configPath)
+		config, err := ReadConfigFile(*configPath, !*noExpandEnv)
 		if err != nil {
 			return err
 		}
@@ -112,6 +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

@@ -17,7 +17,7 @@ type WALCommand struct{}
 // Run executes the command.
 func (c *WALCommand) Run(ctx context.Context, args []string) (err error) {
 	fs := flag.NewFlagSet("litestream-wal", flag.ContinueOnError)
-	configPath := registerConfigFlag(fs)
+	configPath, noExpandEnv := registerConfigFlag(fs)
 	replicaName := fs.String("replica", "", "replica name")
 	generation := fs.String("generation", "", "generation name")
 	fs.Usage = c.Usage
@@ -44,7 +44,7 @@ func (c *WALCommand) Run(ctx context.Context, args []string) (err error) {
 		}
 
 		// Load configuration.
-		config, err := ReadConfigFile(*configPath)
+		config, err := ReadConfigFile(*configPath, !*noExpandEnv)
 		if err != nil {
 			return err
 		}
@@ -118,6 +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.
@@ -291,18 +292,50 @@ 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) {
-	// Ensure replicas all stop replicating.
-	for _, r := range db.Replicas {
-		r.Stop(true)
+	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
 		}
 	}
 
-	if db.db != nil {
+	// 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
 		}
@@ -420,7 +453,7 @@ func (db *DB) init() (err error) {
 	// 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 fmt.Errorf("enable wal: %w", err)
+		return err
 	} else if mode != "wal" {
 		return fmt.Errorf("enable wal failed, mode=%q", mode)
 	}
@@ -597,26 +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(false)
-	}
-
-	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 {
@@ -711,7 +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()
 
@@ -738,27 +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.
@@ -805,16 +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)
 		}
 	}
@@ -1325,7 +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
@@ -1368,7 +1355,7 @@ func (db *DB) checkpointAndInit(generation, mode string) error {
 	// 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 {
+	if _, err := tx.ExecContext(ctx, `INSERT INTO _litestream_lock (id) VALUES (1);`); err != nil {
 		return fmt.Errorf("_litestream_lock: %w", err)
 	}
 
@@ -1410,7 +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)
 		}
 	}
@@ -1422,13 +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")
 	}
 
@@ -1443,19 +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 {
-		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
-		}
+	// 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.
@@ -1463,7 +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}
@@ -1471,39 +1462,124 @@ 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 err := restoreSnapshot(ctx, r, pos.Generation, pos.Index, tmpPath); err != nil {
+		return fmt.Errorf("cannot restore snapshot: %w", err)
 	}
 
-	// Restore each WAL file until we reach our maximum index.
-	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)
-			}
-		}
+	// 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)
+	}
 
-		if opt.Verbose {
-			logger.Printf("%s: restored wal %s/%08x", logPrefix, opt.Generation, 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++ {
+		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
+	}
+
+	// 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
-		}
+	if err := os.Rename(tmpPath, opt.OutputPath); err != nil {
+		return err
 	}
 
 	return nil
 }
 
+type walRestoreState struct {
+	ready bool
+	err   error
+}
+
 // CalcRestoreTarget returns a replica & generation to restore from based on opt criteria.
 func (db *DB) CalcRestoreTarget(ctx context.Context, opt RestoreOptions) (Replica, string, error) {
 	var target struct {
@@ -1613,8 +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 {
@@ -1629,7 +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
 	}
@@ -1641,6 +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)
@@ -1655,7 +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()
 }
 
@@ -1666,7 +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()
 
@@ -1684,7 +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
 	}
 
@@ -1706,6 +1792,9 @@ func (db *DB) CRC64() (uint64, Pos, error) {
 	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.
@@ -1721,16 +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
@@ -1740,7 +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,
 	}
 }
 

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/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

@@ -8,6 +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=

replica.go

@@ -37,6 +37,9 @@ type Replica interface {
 	// Stops all replication processing. Blocks until processing stopped.
 	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
 
@@ -604,6 +607,11 @@ func (r *FileReplica) snapshot(ctx context.Context, generation string, index int
 	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 {
@@ -1061,34 +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
@@ -1106,7 +1145,7 @@ 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
@@ -1164,7 +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.
-	chksum0, pos, err := db.CRC64()
+	chksum0, pos, err := db.CRC64(ctx)
 	if err != nil {
 		return fmt.Errorf("cannot compute checksum: %w", err)
 	}

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

@@ -3,11 +3,13 @@ package s3
 import (
 	"bytes"
 	"context"
+	"crypto/tls"
 	"fmt"
 	"io"
 	"io/ioutil"
 	"log"
 	"net"
+	"net/http"
 	"os"
 	"path"
 	"regexp"
@@ -79,6 +81,7 @@ type Replica struct {
 	Path           string
 	Endpoint       string
 	ForcePathStyle bool
+	SkipVerify     bool
 
 	// Time between syncs with the shadow WAL.
 	SyncInterval time.Duration
@@ -646,6 +649,11 @@ func (r *Replica) snapshot(ctx context.Context, generation string, index int) er
 	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 {
@@ -769,6 +777,12 @@ func (r *Replica) config() *aws.Config {
 	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
 }