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Remove streaming replication implementation

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This commit is contained in:
Ben Johnson
2022-08-08 15:44:44 -06:00
parent a8ab14cca2
commit 868d564988
7 changed files with 9 additions and 1067 deletions
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17
cmd/litestream/main.go
View File

@@ -23,7 +23,6 @@ import (
"github.com/benbjohnson/litestream"
"github.com/benbjohnson/litestream/abs"
"github.com/benbjohnson/litestream/gs"
"github.com/benbjohnson/litestream/http"
"github.com/benbjohnson/litestream/s3"
"github.com/benbjohnson/litestream/sftp"
_ "github.com/mattn/go-sqlite3"
@@ -284,7 +283,6 @@ func readConfigFile(filename string, expandEnv bool) (_ Config, err error) {
// DBConfig represents the configuration for a single database.
type DBConfig struct {
Path string `yaml:"path"`
Upstream UpstreamConfig `yaml:"upstream"`
MonitorDelayInterval *time.Duration `yaml:"monitor-delay-interval"`
CheckpointInterval *time.Duration `yaml:"checkpoint-interval"`
MinCheckpointPageN *int `yaml:"min-checkpoint-page-count"`
@@ -308,16 +306,6 @@ func NewDBFromConfigWithPath(dbc *DBConfig, path string) (*litestream.DB, error)
// Initialize database with given path.
db := litestream.NewDB(path)
// Attach upstream HTTP client if specified.
if upstreamURL := dbc.Upstream.URL; upstreamURL != "" {
// Use local database path if upstream path is not specified.
upstreamPath := dbc.Upstream.Path
if upstreamPath == "" {
upstreamPath = db.Path()
}
db.StreamClient = http.NewClient(upstreamURL, upstreamPath)
}
// Override default database settings if specified in configuration.
if dbc.MonitorDelayInterval != nil {
db.MonitorDelayInterval = *dbc.MonitorDelayInterval
@@ -347,11 +335,6 @@ func NewDBFromConfigWithPath(dbc *DBConfig, path string) (*litestream.DB, error)
return db, nil
}
type UpstreamConfig struct {
URL string `yaml:"url"`
Path string `yaml:"path"`
}
// ReplicaConfig represents the configuration for a single replica in a database.
type ReplicaConfig struct {
Type string `yaml:"type"` // "file", "s3"

404
db.go
View File

@@ -54,9 +54,6 @@ type DB struct {
pageSize int // page size, in bytes
notifyCh chan struct{} // notifies DB of changes
// Iterators used to stream new WAL changes to replicas
itrs map[*FileWALSegmentIterator]struct{}
// Cached salt & checksum from current shadow header.
hdr []byte
frame []byte
@@ -85,11 +82,6 @@ type DB struct {
checkpointErrorNCounterVec *prometheus.CounterVec
checkpointSecondsCounterVec *prometheus.CounterVec
// Client used to receive live, upstream changes. If specified, then
// DB should be used as read-only as local changes will conflict with
// upstream changes.
StreamClient StreamClient
// Minimum threshold of WAL size, in pages, before a passive checkpoint.
// A passive checkpoint will attempt a checkpoint but fail if there are
// active transactions occurring at the same time.
@@ -130,8 +122,6 @@ func NewDB(path string) *DB {
path: path,
notifyCh: make(chan struct{}, 1),
itrs: make(map[*FileWALSegmentIterator]struct{}),
MinCheckpointPageN: DefaultMinCheckpointPageN,
MaxCheckpointPageN: DefaultMaxCheckpointPageN,
ShadowRetentionN: DefaultShadowRetentionN,
@@ -275,7 +265,7 @@ func (db *DB) invalidatePos(ctx context.Context) error {
}
// Iterate over all segments to find the last one.
itr, err := db.walSegments(context.Background(), generation, false)
itr, err := db.walSegments(context.Background(), generation)
if err != nil {
return err
}
@@ -422,9 +412,7 @@ func (db *DB) Open() (err error) {
return fmt.Errorf("cannot remove tmp files: %w", err)
}
// If an upstream client is specified, then we should simply stream changes
// into the database. If it is not specified, then we should monitor the
// database for local changes and replicate them out.
// Continually monitor local changes in a separate goroutine.
db.g.Go(func() error { return db.monitor(db.ctx) })
return nil
@@ -466,14 +454,6 @@ func (db *DB) Close() (err error) {
}
}
// Remove all iterators.
db.mu.Lock()
for itr := range db.itrs {
itr.SetErr(ErrDBClosed)
delete(db.itrs, itr)
}
db.mu.Unlock()
// Release the read lock to allow other applications to handle checkpointing.
if db.rtx != nil {
if e := db.releaseReadLock(); e != nil && err == nil {
@@ -645,74 +625,6 @@ func (db *DB) init() (err error) {
return nil
}
// initReplica initializes a new database file as a replica of an upstream database.
func (db *DB) initReplica(pageSize int) (err error) {
// Exit if already initialized.
if db.db != nil {
return nil
}
// Obtain permissions for parent directory.
fi, err := os.Stat(filepath.Dir(db.path))
if err != nil {
return err
}
db.dirMode = fi.Mode()
dsn := db.path
dsn += fmt.Sprintf("?_busy_timeout=%d", BusyTimeout.Milliseconds())
// Connect to SQLite database. Use the driver registered with a hook to
// prevent WAL files from being removed.
if db.db, err = sql.Open("litestream-sqlite3", dsn); err != nil {
return err
}
// Initialize database file if it doesn't exist. It doesn't matter what we
// store in it as it will be erased by the replication. We just need to
// ensure a WAL file is created and there is at least a page in the database.
if _, err := os.Stat(db.path); os.IsNotExist(err) {
if _, err := db.db.ExecContext(db.ctx, fmt.Sprintf(`PRAGMA page_size = %d`, pageSize)); err != nil {
return fmt.Errorf("set page size: %w", err)
}
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)
}
if _, err := db.db.ExecContext(db.ctx, `CREATE TABLE IF NOT EXISTS _litestream (id INTEGER)`); err != nil {
return fmt.Errorf("create _litestream table: %w", err)
} else if _, err := db.db.ExecContext(db.ctx, `PRAGMA wal_checkpoint(TRUNCATE)`); err != nil {
return fmt.Errorf("create _litestream table: %w", err)
}
}
// Obtain file info once we know the database exists.
fi, err = os.Stat(db.path)
if err != nil {
return fmt.Errorf("init file stat: %w", err)
}
db.fileMode = fi.Mode()
db.uid, db.gid = internal.Fileinfo(fi)
// Verify page size matches.
if err := db.db.QueryRowContext(db.ctx, `PRAGMA page_size;`).Scan(&db.pageSize); err != nil {
return fmt.Errorf("read page size: %w", err)
} else if db.pageSize != pageSize {
return fmt.Errorf("page size mismatch: %d <> %d", db.pageSize, pageSize)
}
// Ensure meta directory structure exists.
if err := internal.MkdirAll(db.MetaPath(), db.dirMode, db.uid, db.gid); err != nil {
return err
}
return nil
}
func (db *DB) clearGeneration(ctx context.Context) error {
if err := os.Remove(db.GenerationNamePath()); err != nil && !os.IsNotExist(err) {
return err
@@ -927,11 +839,6 @@ func (db *DB) createGeneration(ctx context.Context) (string, error) {
// Sync copies pending data from the WAL to the shadow WAL.
func (db *DB) Sync(ctx context.Context) error {
if db.StreamClient != nil {
db.Logger.Printf("using upstream client, skipping sync")
return nil
}
const retryN = 5
for i := 0; i < retryN; i++ {
@@ -1386,8 +1293,7 @@ func (db *DB) writeWALSegment(ctx context.Context, pos Pos, rd io.Reader) error
}
defer f.Close()
n, err := io.Copy(f, rd)
if err != nil {
if _, err := io.Copy(f, rd); err != nil {
return err
} else if err := f.Sync(); err != nil {
return err
@@ -1405,50 +1311,9 @@ func (db *DB) writeWALSegment(ctx context.Context, pos Pos, rd io.Reader) error
return fmt.Errorf("write position file: %w", err)
}
// Generate
info := WALSegmentInfo{
Generation: pos.Generation,
Index: pos.Index,
Offset: pos.Offset,
Size: n,
CreatedAt: time.Now(),
}
// Notify all managed segment iterators.
for itr := range db.itrs {
// Notify iterators of generation change.
if itr.Generation() != pos.Generation {
itr.SetErr(ErrGenerationChanged)
delete(db.itrs, itr)
continue
}
// Attempt to append segment to end of iterator.
// On error, mark it on the iterator and remove from future notifications.
if err := itr.Append(info); err != nil {
itr.SetErr(fmt.Errorf("cannot append wal segment: %w", err))
delete(db.itrs, itr)
continue
}
}
return nil
}
// readPositionFile reads the position from the position file.
func (db *DB) readPositionFile() (Pos, error) {
buf, err := os.ReadFile(db.PositionPath())
if os.IsNotExist(err) {
return Pos{}, nil
} else if err != nil {
return Pos{}, err
}
// Treat invalid format as a non-existent file so we return an empty position.
pos, _ := ParsePos(strings.TrimSpace(string(buf)))
return pos, nil
}
// writePositionFile writes pos as the current position.
func (db *DB) writePositionFile(pos Pos) error {
return internal.WriteFile(db.PositionPath(), []byte(pos.String()+"\n"), db.fileMode, db.uid, db.gid)
@@ -1458,10 +1323,10 @@ func (db *DB) writePositionFile(pos Pos) error {
func (db *DB) WALSegments(ctx context.Context, generation string) (*FileWALSegmentIterator, error) {
db.mu.Lock()
defer db.mu.Unlock()
return db.walSegments(ctx, generation, true)
return db.walSegments(ctx, generation)
}
func (db *DB) walSegments(ctx context.Context, generation string, managed bool) (*FileWALSegmentIterator, error) {
func (db *DB) walSegments(ctx context.Context, generation string) (*FileWALSegmentIterator, error) {
ents, err := os.ReadDir(db.ShadowWALDir(generation))
if os.IsNotExist(err) {
return NewFileWALSegmentIterator(db.ShadowWALDir(generation), generation, nil), nil
@@ -1481,27 +1346,7 @@ func (db *DB) walSegments(ctx context.Context, generation string, managed bool)
sort.Ints(indexes)
itr := NewFileWALSegmentIterator(db.ShadowWALDir(generation), generation, indexes)
// Managed iterators will have new segments pushed to them.
if managed {
itr.closeFunc = func() error {
return db.CloseWALSegmentIterator(itr)
}
db.itrs[itr] = struct{}{}
}
return itr, nil
}
// CloseWALSegmentIterator removes itr from the list of managed iterators.
func (db *DB) CloseWALSegmentIterator(itr *FileWALSegmentIterator) error {
db.mu.Lock()
defer db.mu.Unlock()
delete(db.itrs, itr)
return nil
return NewFileWALSegmentIterator(db.ShadowWALDir(generation), generation, indexes), nil
}
// SQLite WAL constants
@@ -1645,15 +1490,8 @@ func (db *DB) execCheckpoint(mode string) (err error) {
return nil
}
func (db *DB) monitor(ctx context.Context) error {
if db.StreamClient != nil {
return db.monitorUpstream(ctx)
}
return db.monitorLocal(ctx)
}
// monitor runs in a separate goroutine and monitors the local database & WAL.
func (db *DB) monitorLocal(ctx context.Context) error {
func (db *DB) monitor(ctx context.Context) error {
var timer *time.Timer
if db.MonitorDelayInterval > 0 {
timer = time.NewTimer(db.MonitorDelayInterval)
@@ -1686,189 +1524,6 @@ func (db *DB) monitorLocal(ctx context.Context) error {
}
}
// monitorUpstream runs in a separate goroutine and streams data into the local DB.
func (db *DB) monitorUpstream(ctx context.Context) error {
for {
if err := db.stream(ctx); err != nil {
if ctx.Err() != nil {
return nil
}
db.Logger.Printf("stream error, retrying: %s", err)
}
// Delay before retrying stream.
select {
case <-ctx.Done():
return nil
case <-time.After(1 * time.Second):
}
}
}
// stream initializes the local database and continuously streams new upstream data.
func (db *DB) stream(ctx context.Context) error {
pos, err := db.readPositionFile()
if err != nil {
return fmt.Errorf("read position file: %w", err)
}
// Continuously stream and apply records from client.
sr, err := db.StreamClient.Stream(ctx, pos)
if err != nil {
return fmt.Errorf("stream connect: %w", err)
}
defer sr.Close()
// Initialize the database and create it if it doesn't exist.
if err := db.initReplica(sr.PageSize()); err != nil {
return fmt.Errorf("init replica: %w", err)
}
for {
hdr, err := sr.Next()
if err != nil {
return err
}
switch hdr.Type {
case StreamRecordTypeSnapshot:
if err := db.streamSnapshot(ctx, hdr, sr); err != nil {
return fmt.Errorf("snapshot: %w", err)
}
case StreamRecordTypeWALSegment:
if err := db.streamWALSegment(ctx, hdr, sr); err != nil {
return fmt.Errorf("wal segment: %w", err)
}
default:
return fmt.Errorf("invalid stream record type: 0x%02x", hdr.Type)
}
}
}
// streamSnapshot reads the snapshot into the WAL and applies it to the main database.
func (db *DB) streamSnapshot(ctx context.Context, hdr *StreamRecordHeader, r io.Reader) error {
// Truncate WAL file.
if _, err := db.db.ExecContext(ctx, `PRAGMA wal_checkpoint(TRUNCATE)`); err != nil {
return fmt.Errorf("truncate: %w", err)
}
// Determine total page count.
pageN := int(hdr.Size / int64(db.pageSize))
ww := NewWALWriter(db.WALPath(), db.fileMode, db.pageSize)
if err := ww.Open(); err != nil {
return fmt.Errorf("open wal writer: %w", err)
}
defer func() { _ = ww.Close() }()
if err := ww.WriteHeader(); err != nil {
return fmt.Errorf("write wal header: %w", err)
}
// Iterate over pages
buf := make([]byte, db.pageSize)
for pgno := uint32(1); ; pgno++ {
// Read snapshot page into a buffer.
if _, err := io.ReadFull(r, buf); err == io.EOF {
break
} else if err != nil {
return fmt.Errorf("read snapshot page %d: %w", pgno, err)
}
// Issue a commit flag when the last page is reached.
var commit uint32
if pgno == uint32(pageN) {
commit = uint32(pageN)
}
// Write page into WAL frame.
if err := ww.WriteFrame(pgno, commit, buf); err != nil {
return fmt.Errorf("write wal frame: %w", err)
}
}
// Close WAL file writer.
if err := ww.Close(); err != nil {
return fmt.Errorf("close wal writer: %w", err)
}
// Invalidate WAL index.
if err := invalidateSHMFile(db.path); err != nil {
return fmt.Errorf("invalidate shm file: %w", err)
}
// Write position to file so other processes can read it.
if err := db.writePositionFile(hdr.Pos()); err != nil {
return fmt.Errorf("write position file: %w", err)
}
db.Logger.Printf("snapshot applied")
return nil
}
// streamWALSegment rewrites a WAL segment into the local WAL and applies it to the main database.
func (db *DB) streamWALSegment(ctx context.Context, hdr *StreamRecordHeader, r io.Reader) error {
// Decompress incoming segment
zr := lz4.NewReader(r)
// Drop WAL header if starting from offset zero.
if hdr.Offset == 0 {
if _, err := io.CopyN(io.Discard, zr, WALHeaderSize); err != nil {
return fmt.Errorf("read wal header: %w", err)
}
}
ww := NewWALWriter(db.WALPath(), db.fileMode, db.pageSize)
if err := ww.Open(); err != nil {
return fmt.Errorf("open wal writer: %w", err)
}
defer func() { _ = ww.Close() }()
if err := ww.WriteHeader(); err != nil {
return fmt.Errorf("write wal header: %w", err)
}
// Iterate over incoming WAL pages.
buf := make([]byte, WALFrameHeaderSize+db.pageSize)
for i := 0; ; i++ {
// Read snapshot page into a buffer.
if _, err := io.ReadFull(zr, buf); err == io.EOF {
break
} else if err != nil {
return fmt.Errorf("read wal frame %d: %w", i, err)
}
// Read page number & commit field.
pgno := binary.BigEndian.Uint32(buf[0:])
commit := binary.BigEndian.Uint32(buf[4:])
// Write page into WAL frame.
if err := ww.WriteFrame(pgno, commit, buf[WALFrameHeaderSize:]); err != nil {
return fmt.Errorf("write wal frame: %w", err)
}
}
// Close WAL file writer.
if err := ww.Close(); err != nil {
return fmt.Errorf("close wal writer: %w", err)
}
// Invalidate WAL index.
if err := invalidateSHMFile(db.path); err != nil {
return fmt.Errorf("invalidate shm file: %w", err)
}
// Write position to file so other processes can read it.
if err := db.writePositionFile(hdr.Pos()); err != nil {
return fmt.Errorf("write position file: %w", err)
}
db.Logger.Printf("wal segment applied: %s", hdr.Pos().String())
return nil
}
// ApplyWAL performs a truncating checkpoint on the given database.
func ApplyWAL(ctx context.Context, dbPath, walPath string) error {
// Copy WAL file from it's staging path to the correct "-wal" location.
@@ -2016,51 +1671,6 @@ func logPrefixPath(path string) string {
return path
}
// invalidateSHMFile clears the iVersion field of the -shm file in order that
// the next transaction will rebuild it.
func invalidateSHMFile(dbPath string) error {
db, err := sql.Open("sqlite3", dbPath)
if err != nil {
return fmt.Errorf("reopen db: %w", err)
}
defer func() { _ = db.Close() }()
if _, err := db.Exec(`PRAGMA wal_checkpoint(PASSIVE)`); err != nil {
return fmt.Errorf("passive checkpoint: %w", err)
}
f, err := os.OpenFile(dbPath+"-shm", os.O_RDWR, 0666)
if err != nil {
return fmt.Errorf("open shm index: %w", err)
}
defer f.Close()
buf := make([]byte, WALIndexHeaderSize)
if _, err := io.ReadFull(f, buf); err != nil {
return fmt.Errorf("read shm index: %w", err)
}
// Invalidate "isInit" fields.
buf[12], buf[60] = 0, 0
// Rewrite header.
if _, err := f.Seek(0, io.SeekStart); err != nil {
return fmt.Errorf("seek shm index: %w", err)
} else if _, err := f.Write(buf); err != nil {
return fmt.Errorf("overwrite shm index: %w", err)
} else if err := f.Close(); err != nil {
return fmt.Errorf("close shm index: %w", err)
}
// Truncate WAL file again.
var row [3]int
if err := db.QueryRow(`PRAGMA wal_checkpoint(TRUNCATE)`).Scan(&row[0], &row[1], &row[2]); err != nil {
return fmt.Errorf("truncate: %w", err)
}
return nil
}
// A marker error to indicate that a restart checkpoint could not verify
// continuity between WAL indices and a new generation should be started.
var errRestartGeneration = errors.New("restart generation")

7
file_replica_client.go
View File

@@ -364,7 +364,6 @@ func (c *FileReplicaClient) DeleteWALSegments(ctx context.Context, a []Pos) erro
type FileWALSegmentIterator struct {
mu sync.Mutex
notifyCh chan struct{}
closeFunc func() error
dir string
generation string
@@ -386,12 +385,6 @@ func NewFileWALSegmentIterator(dir, generation string, indexes []int) *FileWALSe
}
func (itr *FileWALSegmentIterator) Close() (err error) {
if itr.closeFunc != nil {
if e := itr.closeFunc(); e != nil && err == nil {
err = e
}
}
if e := itr.Err(); e != nil && err == nil {
err = e
}

140
http/client.go
View File

@@ -1,140 +0,0 @@
package http
import (
"context"
"fmt"
"io"
"net/http"
"net/url"
"strconv"
"github.com/benbjohnson/litestream"
)
// Client represents an client for a streaming Litestream HTTP server.
type Client struct {
// Upstream endpoint
URL string
// Path of database on upstream server.
Path string
// Underlying HTTP client
HTTPClient *http.Client
}
// NewClient returns an instance of Client.
func NewClient(rawurl, path string) *Client {
return &Client{
URL: rawurl,
Path: path,
HTTPClient: http.DefaultClient,
}
}
// Stream returns a snapshot and continuous stream of WAL updates.
func (c *Client) Stream(ctx context.Context, pos litestream.Pos) (litestream.StreamReader, error) {
u, err := url.Parse(c.URL)
if err != nil {
return nil, fmt.Errorf("invalid client URL: %w", err)
} else if u.Scheme != "http" && u.Scheme != "https" {
return nil, fmt.Errorf("invalid URL scheme")
} else if u.Host == "" {
return nil, fmt.Errorf("URL host required")
}
// Add path & position to query path.
q := url.Values{"path": []string{c.Path}}
if !pos.IsZero() {
q.Set("generation", pos.Generation)
q.Set("index", litestream.FormatIndex(pos.Index))
}
// Strip off everything but the scheme & host.
*u = url.URL{
Scheme: u.Scheme,
Host: u.Host,
Path: "/stream",
RawQuery: q.Encode(),
}
req, err := http.NewRequest("GET", u.String(), nil)
if err != nil {
return nil, err
}
req = req.WithContext(ctx)
resp, err := c.HTTPClient.Do(req)
if err != nil {
return nil, err
} else if resp.StatusCode != http.StatusOK {
resp.Body.Close()
return nil, fmt.Errorf("invalid response: code=%d", resp.StatusCode)
}
pageSize, _ := strconv.Atoi(resp.Header.Get("Litestream-page-size"))
if pageSize <= 0 {
resp.Body.Close()
return nil, fmt.Errorf("stream page size unavailable")
}
return &StreamReader{
pageSize: pageSize,
rc: resp.Body,
lr: io.LimitedReader{R: resp.Body},
}, nil
}
// StreamReader represents an optional snapshot followed by a continuous stream
// of WAL updates. It is used to implement live read replication from a single
// primary Litestream server to one or more remote Litestream replicas.
type StreamReader struct {
pageSize int
rc io.ReadCloser
lr io.LimitedReader
}
// Close closes the underlying reader.
func (r *StreamReader) Close() (err error) {
if e := r.rc.Close(); err == nil {
err = e
}
return err
}
// PageSize returns the page size on the remote database.
func (r *StreamReader) PageSize() int { return r.pageSize }
// Read reads bytes of the current payload into p. Only valid after a successful
// call to Next(). On io.EOF, call Next() again to begin reading next record.
func (r *StreamReader) Read(p []byte) (n int, err error) {
return r.lr.Read(p)
}
// Next returns the next available record. This call will block until a record
// is available. After calling Next(), read the payload from the reader using
// Read() until io.EOF is reached.
func (r *StreamReader) Next() (*litestream.StreamRecordHeader, error) {
// If bytes remain on the current file, discard.
if r.lr.N > 0 {
if _, err := io.Copy(io.Discard, &r.lr); err != nil {
return nil, err
}
}
// Read record header.
buf := make([]byte, litestream.StreamRecordHeaderSize)
if _, err := io.ReadFull(r.rc, buf); err != nil {
return nil, fmt.Errorf("http.StreamReader.Next(): %w", err)
}
var hdr litestream.StreamRecordHeader
if err := hdr.UnmarshalBinary(buf); err != nil {
return nil, err
}
// Update remaining bytes on file reader.
r.lr.N = hdr.Size
return &hdr, nil
}

185
http/server.go
View File

@@ -2,13 +2,11 @@ package http
import (
"fmt"
"io"
"log"
"net"
"net/http"
httppprof "net/http/pprof"
"os"
"strconv"
"strings"
"github.com/benbjohnson/litestream"
@@ -113,190 +111,7 @@ func (s *Server) serveHTTP(w http.ResponseWriter, r *http.Request) {
switch r.URL.Path {
case "/metrics":
s.promHandler.ServeHTTP(w, r)
case "/stream":
switch r.Method {
case http.MethodGet:
s.handleGetStream(w, r)
default:
s.writeError(w, r, "Method not allowed", http.StatusMethodNotAllowed)
}
default:
http.NotFound(w, r)
}
}
func (s *Server) handleGetStream(w http.ResponseWriter, r *http.Request) {
q := r.URL.Query()
path := q.Get("path")
if path == "" {
s.writeError(w, r, "Database name required", http.StatusBadRequest)
return
}
// Parse current client position, if available.
var pos litestream.Pos
if generation, index := q.Get("generation"), q.Get("index"); generation != "" && index != "" {
pos.Generation = generation
var err error
if pos.Index, err = litestream.ParseIndex(index); err != nil {
s.writeError(w, r, "Invalid index query parameter", http.StatusBadRequest)
return
}
}
// Fetch database instance from the primary server.
db := s.server.DB(path)
if db == nil {
s.writeError(w, r, "Database not found", http.StatusNotFound)
return
}
// Set the page size in the header.
w.Header().Set("Litestream-page-size", strconv.Itoa(db.PageSize()))
// Determine starting position.
dbPos := db.Pos()
if dbPos.Generation == "" {
s.writeError(w, r, "No generation available", http.StatusServiceUnavailable)
return
}
dbPos.Offset = 0
// Use database position if generation has changed.
var snapshotRequired bool
if pos.Generation != dbPos.Generation {
s.Logger.Printf("stream generation mismatch, using primary position: client.pos=%s", pos)
pos, snapshotRequired = dbPos, true
}
// Obtain iterator before snapshot so we don't miss any WAL segments.
fitr, err := db.WALSegments(r.Context(), pos.Generation)
if err != nil {
s.writeError(w, r, fmt.Sprintf("Cannot obtain WAL iterator: %s", err), http.StatusInternalServerError)
return
}
defer fitr.Close()
bitr := litestream.NewBufferedWALSegmentIterator(fitr)
// Peek at first position to see if client is too old.
if info, ok := bitr.Peek(); !ok {
s.writeError(w, r, "cannot peek WAL iterator, no segments available", http.StatusInternalServerError)
return
} else if cmp, err := litestream.ComparePos(pos, info.Pos()); err != nil {
s.writeError(w, r, fmt.Sprintf("cannot compare pos: %s", err), http.StatusInternalServerError)
return
} else if cmp == -1 {
s.Logger.Printf("stream position no longer available, using using primary position: client.pos=%s", pos)
pos, snapshotRequired = dbPos, true
}
s.Logger.Printf("stream connected: pos=%s snapshot=%v", pos, snapshotRequired)
defer s.Logger.Printf("stream disconnected")
// Write snapshot to response body.
if snapshotRequired {
if err := db.WithFile(func(f *os.File) error {
fi, err := f.Stat()
if err != nil {
return err
}
// Write snapshot header with current position & size.
hdr := litestream.StreamRecordHeader{
Type: litestream.StreamRecordTypeSnapshot,
Generation: pos.Generation,
Index: pos.Index,
Size: fi.Size(),
}
if buf, err := hdr.MarshalBinary(); err != nil {
return fmt.Errorf("marshal snapshot stream record header: %w", err)
} else if _, err := w.Write(buf); err != nil {
return fmt.Errorf("write snapshot stream record header: %w", err)
}
if _, err := io.CopyN(w, f, fi.Size()); err != nil {
return fmt.Errorf("copy snapshot: %w", err)
}
return nil
}); err != nil {
s.writeError(w, r, err.Error(), http.StatusInternalServerError)
return
}
// Flush after snapshot has been written.
w.(http.Flusher).Flush()
}
for {
// Wait for notification of new entries.
select {
case <-r.Context().Done():
return
case <-fitr.NotifyCh():
}
for bitr.Next() {
info := bitr.WALSegment()
// Skip any segments before our initial position.
if cmp, err := litestream.ComparePos(info.Pos(), pos); err != nil {
s.Logger.Printf("pos compare: %s", err)
return
} else if cmp == -1 {
continue
}
hdr := litestream.StreamRecordHeader{
Type: litestream.StreamRecordTypeWALSegment,
Flags: 0,
Generation: info.Generation,
Index: info.Index,
Offset: info.Offset,
Size: info.Size,
}
// Write record header.
data, err := hdr.MarshalBinary()
if err != nil {
s.Logger.Printf("marshal WAL segment stream record header: %s", err)
return
} else if _, err := w.Write(data); err != nil {
s.Logger.Printf("write WAL segment stream record header: %s", err)
return
}
// Copy WAL segment data to writer.
if err := func() error {
rd, err := db.WALSegmentReader(r.Context(), info.Pos())
if err != nil {
return fmt.Errorf("cannot fetch wal segment reader: %w", err)
}
defer rd.Close()
if _, err := io.CopyN(w, rd, hdr.Size); err != nil {
return fmt.Errorf("cannot copy wal segment: %w", err)
}
return nil
}(); err != nil {
log.Print(err)
return
}
// Flush after WAL segment has been written.
w.(http.Flusher).Flush()
}
if err := bitr.Err(); err != nil {
s.Logger.Printf("wal iterator error: %s", err)
return
}
}
}
func (s *Server) writeError(w http.ResponseWriter, r *http.Request, err string, code int) {
s.Logger.Printf("error: %s", err)
http.Error(w, err, code)
}

248
integration/cmd_test.go
View File

@@ -391,254 +391,6 @@ LOOP:
restoreAndVerify(t, ctx, env, filepath.Join(testDir, "litestream.yml"), filepath.Join(tempDir, "db"))
}
// Ensure a database can be replicated over HTTP.
func TestCmd_Replicate_HTTP(t *testing.T) {
ctx := context.Background()
testDir, tempDir := filepath.Join("testdata", "replicate", "http"), t.TempDir()
if err := os.Mkdir(filepath.Join(tempDir, "0"), 0777); err != nil {
t.Fatal(err)
} else if err := os.Mkdir(filepath.Join(tempDir, "1"), 0777); err != nil {
t.Fatal(err)
}
env0 := []string{"LITESTREAM_TEMPDIR=" + tempDir}
env1 := []string{"LITESTREAM_TEMPDIR=" + tempDir, "LITESTREAM_UPSTREAM_URL=http://localhost:10001"}
cmd0, stdout0, _ := commandContext(ctx, env0, "replicate", "-config", filepath.Join(testDir, "litestream.0.yml"))
if err := cmd0.Start(); err != nil {
t.Fatal(err)
}
cmd1, stdout1, _ := commandContext(ctx, env1, "replicate", "-config", filepath.Join(testDir, "litestream.1.yml"))
if err := cmd1.Start(); err != nil {
t.Fatal(err)
}
db0, err := sql.Open("sqlite3", filepath.Join(tempDir, "0", "db"))
if err != nil {
t.Fatal(err)
} else if _, err := db0.ExecContext(ctx, `PRAGMA journal_mode = wal`); err != nil {
t.Fatal(err)
} else if _, err := db0.ExecContext(ctx, `CREATE TABLE t (id INTEGER PRIMARY KEY)`); err != nil {
t.Fatal(err)
}
defer db0.Close()
// Execute writes periodically.
for i := 0; i < 100; i++ {
t.Logf("[exec] INSERT INTO t (id) VALUES (%d)", i)
if _, err := db0.ExecContext(ctx, `INSERT INTO t (id) VALUES (?)`, i); err != nil {
t.Fatal(err)
}
time.Sleep(100 * time.Millisecond)
}
// Wait for replica to catch up.
time.Sleep(1 * time.Second)
// Verify count in replica table.
db1, err := sql.Open("sqlite3", filepath.Join(tempDir, "1", "db"))
if err != nil {
t.Fatal(err)
}
defer db1.Close()
var n int
if err := db1.QueryRowContext(ctx, `SELECT COUNT(*) FROM t`).Scan(&n); err != nil {
t.Fatal(err)
} else if got, want := n, 100; got != want {
t.Fatalf("replica count=%d, want %d", got, want)
}
// Stop & wait for Litestream command.
killLitestreamCmd(t, cmd1, stdout1) // kill
killLitestreamCmd(t, cmd0, stdout0)
}
// Ensure a database can recover when disconnected from HTTP.
func TestCmd_Replicate_HTTP_PartialRecovery(t *testing.T) {
ctx := context.Background()
testDir, tempDir := filepath.Join("testdata", "replicate", "http-partial-recovery"), t.TempDir()
if err := os.Mkdir(filepath.Join(tempDir, "0"), 0777); err != nil {
t.Fatal(err)
} else if err := os.Mkdir(filepath.Join(tempDir, "1"), 0777); err != nil {
t.Fatal(err)
}
env0 := []string{"LITESTREAM_TEMPDIR=" + tempDir}
env1 := []string{"LITESTREAM_TEMPDIR=" + tempDir, "LITESTREAM_UPSTREAM_URL=http://localhost:10002"}
cmd0, stdout0, _ := commandContext(ctx, env0, "replicate", "-config", filepath.Join(testDir, "litestream.0.yml"))
if err := cmd0.Start(); err != nil {
t.Fatal(err)
}
cmd1, stdout1, _ := commandContext(ctx, env1, "replicate", "-config", filepath.Join(testDir, "litestream.1.yml"))
if err := cmd1.Start(); err != nil {
t.Fatal(err)
}
db0, err := sql.Open("sqlite3", filepath.Join(tempDir, "0", "db"))
if err != nil {
t.Fatal(err)
} else if _, err := db0.ExecContext(ctx, `PRAGMA journal_mode = wal`); err != nil {
t.Fatal(err)
} else if _, err := db0.ExecContext(ctx, `CREATE TABLE t (id INTEGER PRIMARY KEY)`); err != nil {
t.Fatal(err)
}
defer db0.Close()
var index int
insertAndWait := func() {
index++
t.Logf("[exec] INSERT INTO t (id) VALUES (%d)", index)
if _, err := db0.ExecContext(ctx, `INSERT INTO t (id) VALUES (?)`, index); err != nil {
t.Fatal(err)
}
time.Sleep(100 * time.Millisecond)
}
// Execute writes periodically.
for i := 0; i < 50; i++ {
insertAndWait()
}
// Kill the replica.
t.Logf("Killing replica...")
killLitestreamCmd(t, cmd1, stdout1)
t.Logf("Replica killed")
// Keep writing.
for i := 0; i < 25; i++ {
insertAndWait()
}
// Restart replica.
t.Logf("Restarting replica...")
cmd1, stdout1, _ = commandContext(ctx, env1, "replicate", "-config", filepath.Join(testDir, "litestream.1.yml"))
if err := cmd1.Start(); err != nil {
t.Fatal(err)
}
t.Logf("Replica restarted")
// Continue writing...
for i := 0; i < 25; i++ {
insertAndWait()
}
// Wait for replica to catch up.
time.Sleep(1 * time.Second)
// Verify count in replica table.
db1, err := sql.Open("sqlite3", filepath.Join(tempDir, "1", "db"))
if err != nil {
t.Fatal(err)
}
defer db1.Close()
var n int
if err := db1.QueryRowContext(ctx, `SELECT COUNT(*) FROM t`).Scan(&n); err != nil {
t.Fatal(err)
} else if got, want := n, 100; got != want {
t.Fatalf("replica count=%d, want %d", got, want)
}
// Stop & wait for Litestream command.
killLitestreamCmd(t, cmd1, stdout1) // kill
killLitestreamCmd(t, cmd0, stdout0)
}
// Ensure a database can recover when disconnected from HTTP but when last index
// is no longer available.
func TestCmd_Replicate_HTTP_FullRecovery(t *testing.T) {
ctx := context.Background()
testDir, tempDir := filepath.Join("testdata", "replicate", "http-full-recovery"), t.TempDir()
if err := os.Mkdir(filepath.Join(tempDir, "0"), 0777); err != nil {
t.Fatal(err)
} else if err := os.Mkdir(filepath.Join(tempDir, "1"), 0777); err != nil {
t.Fatal(err)
}
env0 := []string{"LITESTREAM_TEMPDIR=" + tempDir}
env1 := []string{"LITESTREAM_TEMPDIR=" + tempDir, "LITESTREAM_UPSTREAM_URL=http://localhost:10002"}
cmd0, stdout0, _ := commandContext(ctx, env0, "replicate", "-config", filepath.Join(testDir, "litestream.0.yml"))
if err := cmd0.Start(); err != nil {
t.Fatal(err)
}
cmd1, stdout1, _ := commandContext(ctx, env1, "replicate", "-config", filepath.Join(testDir, "litestream.1.yml"))
if err := cmd1.Start(); err != nil {
t.Fatal(err)
}
db0, err := sql.Open("sqlite3", filepath.Join(tempDir, "0", "db"))
if err != nil {
t.Fatal(err)
} else if _, err := db0.ExecContext(ctx, `PRAGMA journal_mode = wal`); err != nil {
t.Fatal(err)
} else if _, err := db0.ExecContext(ctx, `CREATE TABLE t (id INTEGER PRIMARY KEY)`); err != nil {
t.Fatal(err)
}
defer db0.Close()
var index int
insertAndWait := func() {
index++
t.Logf("[exec] INSERT INTO t (id) VALUES (%d)", index)
if _, err := db0.ExecContext(ctx, `INSERT INTO t (id) VALUES (?)`, index); err != nil {
t.Fatal(err)
}
time.Sleep(100 * time.Millisecond)
}
// Execute writes periodically.
for i := 0; i < 50; i++ {
insertAndWait()
}
// Kill the replica.
t.Logf("Killing replica...")
killLitestreamCmd(t, cmd1, stdout1)
t.Logf("Replica killed")
// Keep writing.
for i := 0; i < 25; i++ {
insertAndWait()
}
// Restart replica.
t.Logf("Restarting replica...")
cmd1, stdout1, _ = commandContext(ctx, env1, "replicate", "-config", filepath.Join(testDir, "litestream.1.yml"))
if err := cmd1.Start(); err != nil {
t.Fatal(err)
}
t.Logf("Replica restarted")
// Continue writing...
for i := 0; i < 25; i++ {
insertAndWait()
}
// Wait for replica to catch up.
time.Sleep(1 * time.Second)
// Verify count in replica table.
db1, err := sql.Open("sqlite3", filepath.Join(tempDir, "1", "db"))
if err != nil {
t.Fatal(err)
}
defer db1.Close()
var n int
if err := db1.QueryRowContext(ctx, `SELECT COUNT(*) FROM t`).Scan(&n); err != nil {
t.Fatal(err)
} else if got, want := n, 100; got != want {
t.Fatalf("replica count=%d, want %d", got, want)
}
// Stop & wait for Litestream command.
killLitestreamCmd(t, cmd1, stdout1) // kill
killLitestreamCmd(t, cmd0, stdout0)
}
// commandContext returns a "litestream" command with stdout/stderr buffers.
func commandContext(ctx context.Context, env []string, arg ...string) (cmd *exec.Cmd, stdout, stderr *internal.LockingBuffer) {
cmd = exec.CommandContext(ctx, "litestream", arg...)

71
litestream.go
View File

@@ -1,7 +1,6 @@
package litestream
import (
"context"
"database/sql"
"encoding/binary"
"errors"
@@ -536,76 +535,6 @@ func ParseOffset(s string) (int64, error) {
return int64(v), nil
}
const (
StreamRecordTypeSnapshot = 1
StreamRecordTypeWALSegment = 2
)
const StreamRecordHeaderSize = 0 +
4 + 4 + // type, flags
8 + 8 + 8 + 8 // generation, index, offset, size
type StreamRecordHeader struct {
Type int
Flags int
Generation string
Index int
Offset int64
Size int64
}
func (hdr *StreamRecordHeader) Pos() Pos {
return Pos{
Generation: hdr.Generation,
Index: hdr.Index,
Offset: hdr.Offset,
}
}
func (hdr *StreamRecordHeader) MarshalBinary() ([]byte, error) {
generation, err := strconv.ParseUint(hdr.Generation, 16, 64)
if err != nil {
return nil, fmt.Errorf("invalid generation: %q", generation)
}
data := make([]byte, StreamRecordHeaderSize)
binary.BigEndian.PutUint32(data[0:4], uint32(hdr.Type))
binary.BigEndian.PutUint32(data[4:8], uint32(hdr.Flags))
binary.BigEndian.PutUint64(data[8:16], generation)
binary.BigEndian.PutUint64(data[16:24], uint64(hdr.Index))
binary.BigEndian.PutUint64(data[24:32], uint64(hdr.Offset))
binary.BigEndian.PutUint64(data[32:40], uint64(hdr.Size))
return data, nil
}
// UnmarshalBinary from data into hdr.
func (hdr *StreamRecordHeader) UnmarshalBinary(data []byte) error {
if len(data) < StreamRecordHeaderSize {
return io.ErrUnexpectedEOF
}
hdr.Type = int(binary.BigEndian.Uint32(data[0:4]))
hdr.Flags = int(binary.BigEndian.Uint32(data[4:8]))
hdr.Generation = fmt.Sprintf("%016x", binary.BigEndian.Uint64(data[8:16]))
hdr.Index = int(binary.BigEndian.Uint64(data[16:24]))
hdr.Offset = int64(binary.BigEndian.Uint64(data[24:32]))
hdr.Size = int64(binary.BigEndian.Uint64(data[32:40]))
return nil
}
// StreamClient represents a client for streaming changes to a replica DB.
type StreamClient interface {
// Stream returns a reader which contains and optional snapshot followed
// by a series of WAL segments. This stream begins from the given position.
Stream(ctx context.Context, pos Pos) (StreamReader, error)
}
// StreamReader represents a reader that streams snapshot and WAL records.
type StreamReader interface {
io.ReadCloser
PageSize() int
Next() (*StreamRecordHeader, error)
}
// removeDBFiles deletes the database and related files (journal, shm, wal).
func removeDBFiles(filename string) error {
if err := os.Remove(filename); err != nil && !os.IsNotExist(err) {