litestream

package module
v0.0.0-...-a056490 Latest Latest
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 Go to latest Published: Aug 15, 2024 License: Apache-2.0 Imports: 27 Imported by: 0

README

litestream-lib

Forked from litestream(web | github)

Trying to make it as a lib to init sqlite db client, that can automatically restore and replicate sqlite db to remote, but user can just treat it as golang *sql.DB.

Usage:

import (
    ...

	"github.com/supersupersimple/litestream-lib/lslib"
	_ "modernc.org/sqlite"
)
  • Setup env to set url and access key and secret
export LITESTREAM_URL="s3://mybkt.localhost:9000/fruits.db"
export LITESTREAM_ACCESS_KEY_ID=minioadmin
export LITESTREAM_SECRET_ACCESS_KEY=minioadmin
  • Init and open db.
lsdb := lslib.NewDB(lslib.NewConfig("test.db").WithDriverName("sqlite"))
db, err := lsdb.Open(ctx) // db is *sql.DB
if err != nil {
	panic(err)
}

defer lsdb.Close(ctx)
db.SetMaxOpenConns(1)

pingErr := db.Ping()
if pingErr != nil {
	log.Fatal(pingErr)
}
fmt.Println("Connected!")

Documentation

Index

Constants

View Source 
const (
	DefaultMonitorInterval    = 1 * time.Second
	DefaultCheckpointInterval = 1 * time.Minute
	DefaultMinCheckpointPageN = 1000
	DefaultMaxCheckpointPageN = 10000
	DefaultTruncatePageN      = 500000
)

Default DB settings.

View Source 
const (
	WALHeaderChecksumOffset      = 24
	WALFrameHeaderChecksumOffset = 16
)

SQLite WAL constants

View Source 
const (
	MetaDirSuffix = "-litestream"

	WALDirName    = "wal"
	WALExt        = ".wal"
	WALSegmentExt = ".wal.lz4"
	SnapshotExt   = ".snapshot.lz4"

	GenerationNameLen = 16
)

Naming constants.

View Source 
const (
	CheckpointModePassive  = "PASSIVE"
	CheckpointModeFull     = "FULL"
	CheckpointModeRestart  = "RESTART"
	CheckpointModeTruncate = "TRUNCATE"
)

SQLite checkpoint modes.

View Source 
const (
	// WALHeaderSize is the size of the WAL header, in bytes.
	WALHeaderSize = 32

	// WALFrameHeaderSize is the size of the WAL frame header, in bytes.
	WALFrameHeaderSize = 24
)
View Source 
const (
	DefaultSyncInterval           = 1 * time.Second
	DefaultRetention              = 24 * time.Hour
	DefaultRetentionCheckInterval = 1 * time.Hour
)

Default replica settings.

View Source 
const BusyTimeout = 1 * time.Second

BusyTimeout is the timeout to wait for EBUSY from SQLite.

View Source 
const DefaultRestoreParallelism = 8

DefaultRestoreParallelism is the default parallelism when downloading WAL files.

View Source 
const MaxIndex = 0x7FFFFFFF

MaxIndex is the maximum possible WAL index. If this index is reached then a new generation will be started.

Variables

View Source 
var (
	ErrNoGeneration     = errors.New("no generation available")
	ErrNoSnapshots      = errors.New("no snapshots available")
	ErrChecksumMismatch = errors.New("invalid replica, checksum mismatch")
)

Litestream errors.

Functions

func Checksum 

func Checksum(bo binary.ByteOrder, s0, s1 uint32, b []byte) (uint32, uint32)

Checksum computes a running SQLite checksum over a byte slice.

func FormatSnapshotPath 

func FormatSnapshotPath(index int) string

FormatSnapshotPath formats a snapshot filename with a given index.

func FormatWALPath 

func FormatWALPath(index int) string

FormatWALPath formats a WAL filename with a given index.

func FormatWALSegmentPath 

func FormatWALSegmentPath(index int, offset int64) string

FormatWALSegmentPath formats a WAL segment filename with a given index & offset.

func GenerationPath 

func GenerationPath(root, generation string) (string, error)

GenerationPath returns the path to a generation's root directory.

func GenerationsPath 

func GenerationsPath(root string) string

GenerationsPath returns the path to a generation root directory.

func IsGenerationName 

func IsGenerationName(s string) bool

IsGenerationName returns true if s is the correct length and is only lowercase hex characters.

func IsSnapshotPath 

func IsSnapshotPath(s string) bool

IsSnapshotPath returns true if s is a path to a snapshot file.

func IsWALPath 

func IsWALPath(s string) bool

IsWALPath returns true if s is a path to a WAL file.

func ParseSnapshotPath 

func ParseSnapshotPath(s string) (index int, err error)

ParseSnapshotPath returns the index for the snapshot. Returns an error if the path is not a valid snapshot path.

func ParseWALPath 

func ParseWALPath(s string) (index int, err error)

ParseWALPath returns the index for the WAL file. Returns an error if the path is not a valid WAL path.

func ParseWALSegmentPath 

func ParseWALSegmentPath(s string) (index int, offset int64, err error)

ParseWALSegmentPath returns the index & offset for the WAL segment file. Returns an error if the path is not a valid wal segment path.

func SnapshotPath 

func SnapshotPath(root, generation string, index int) (string, error)

SnapshotPath returns the path to an uncompressed snapshot file.

func SnapshotsPath 

func SnapshotsPath(root, generation string) (string, error)

SnapshotsPath returns the path to a generation's snapshot directory.

func WALPath 

func WALPath(root, generation string) (string, error)

WALPath returns the path to a generation's WAL directory

func WALSegmentPath 

func WALSegmentPath(root, generation string, index int, offset int64) (string, error)

WALSegmentPath returns the path to a WAL segment file.

Types

type DB 

type DB struct {

	// 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.
	MinCheckpointPageN int

	// Maximum threshold of WAL size, in pages, before a forced checkpoint.
	// A forced checkpoint will block new transactions and wait for existing
	// transactions to finish before issuing a checkpoint and resetting the WAL.
	//
	// If zero, no checkpoints are forced. This can cause the WAL to grow
	// unbounded if there are always read transactions occurring.
	MaxCheckpointPageN int

	// Threshold of WAL size, in pages, before a forced truncation checkpoint.
	// A forced truncation checkpoint will block new transactions and wait for
	// existing transactions to finish before issuing a checkpoint and
	// truncating the WAL.
	//
	// If zero, no truncates are forced. This can cause the WAL to grow
	// unbounded if there's a sudden spike of changes between other
	// checkpoints.
	TruncatePageN int

	// Time between automatic checkpoints in the WAL. This is done to allow
	// more fine-grained WAL files so that restores can be performed with
	// better precision.
	CheckpointInterval time.Duration

	// Frequency at which to perform db sync.
	MonitorInterval time.Duration

	// List of replicas for the database.
	// Must be set before calling Open().
	Replicas []*Replica

	// Where to send log messages, defaults to global slog with databas epath.
	Logger *slog.Logger
	// contains filtered or unexported fields
}

DB represents a managed instance of a SQLite database in the file system.

func NewDB 

func NewDB(path string) *DB

NewDB returns a new instance of DB for a given path.

func (*DB) BeginSnapshot 

func (db *DB) BeginSnapshot()

BeginSnapshot takes an internal snapshot lock preventing checkpoints.

When calling this the caller must also call EndSnapshot() once the snapshot is finished.

func (*DB) CRC64 

func (db *DB) CRC64(ctx context.Context) (uint64, Pos, error)

CRC64 returns a CRC-64 ISO checksum of the database and its current position.

This function obtains a read lock so it prevents syncs from occurring until the operation is complete. The database will still be usable but it will be unable to checkpoint during this time.

If dst is set, the database file is copied to that location before checksum.

func (*DB) CalcRestoreTarget 

func (db *DB) CalcRestoreTarget(ctx context.Context, opt RestoreOptions) (*Replica, string, error)

CalcRestoreTarget returns a replica & generation to restore from based on opt criteria.

func (*DB) Checkpoint 

func (db *DB) Checkpoint(ctx context.Context, mode string) (err error)

Checkpoint performs a checkpoint on the WAL file.

func (*DB) Close 

func (db *DB) Close(ctx context.Context) (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. Takes a context for final sync.

func (*DB) CurrentGeneration 

func (db *DB) CurrentGeneration() (string, error)

CurrentGeneration returns the name of the generation saved to the "generation" file in the meta data directory. Returns empty string if none exists.

func (*DB) CurrentShadowWALIndex 

func (db *DB) CurrentShadowWALIndex(generation string) (index int, size int64, err error)

CurrentShadowWALIndex returns the current WAL index & total size.

func (*DB) CurrentShadowWALPath 

func (db *DB) CurrentShadowWALPath(generation string) (string, error)

CurrentShadowWALPath returns the path to the last shadow WAL in a generation.

func (*DB) DirInfo 

func (db *DB) DirInfo() os.FileInfo

DirInfo returns the cached file stats for the parent directory of the database file when it was initialized.

func (*DB) EndSnapshot 

func (db *DB) EndSnapshot()

EndSnapshot releases the internal snapshot lock that prevents checkpoints.

func (*DB) FileInfo 

func (db *DB) FileInfo() os.FileInfo

FileInfo returns the cached file stats for the database file when it was initialized.

func (*DB) GenerationNamePath 

func (db *DB) GenerationNamePath() string

GenerationNamePath returns the path of the name of the current generation.

func (*DB) GenerationPath 

func (db *DB) GenerationPath(generation string) string

GenerationPath returns the path of a single generation. Panics if generation is blank.

func (*DB) MetaPath 

func (db *DB) MetaPath() string

MetaPath returns the path to the database metadata.

func (*DB) Notify 

func (db *DB) Notify() <-chan struct{}

Notify returns a channel that closes when the shadow WAL changes.

func (*DB) Open 

func (db *DB) Open() (err error)

Open initializes the background monitoring goroutine.

func (*DB) PageSize 

func (db *DB) PageSize() int

PageSize returns the page size of the underlying database. Only valid after database exists & Init() has successfully run.

func (*DB) Path 

func (db *DB) Path() string

Path returns the path to the database.

func (*DB) Pos 

func (db *DB) Pos() (Pos, error)

Pos returns the current position of the database.

func (*DB) Replica 

func (db *DB) Replica(name string) *Replica

Replica returns a replica by name.

func (*DB) SQLDB 

func (db *DB) SQLDB() *sql.DB

SQLDB returns a reference to the underlying sql.DB connection.

func (*DB) SetDriverName 

func (db *DB) SetDriverName(dn string)

func (*DB) SetMetaPath 

func (db *DB) SetMetaPath(mp string)

SetMetaPath sets the path to database metadata.

func (*DB) ShadowWALDir 

func (db *DB) ShadowWALDir(generation string) string

ShadowWALDir returns the path of the shadow wal directory. Panics if generation is blank.

func (*DB) ShadowWALPath 

func (db *DB) ShadowWALPath(generation string, index int) string

ShadowWALPath returns the path of a single shadow WAL file. Panics if generation is blank or index is negative.

func (*DB) ShadowWALReader 

func (db *DB) ShadowWALReader(pos Pos) (r *ShadowWALReader, err error)

ShadowWALReader opens a reader for a shadow WAL file at a given position. If the reader is at the end of the file, it attempts to return the next file.

The caller should check Pos() & Size() on the returned reader to check offset.

func (*DB) SoftClose 

func (db *DB) SoftClose(ctx context.Context) (err error)

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) Sync 

func (db *DB) Sync(ctx context.Context) (err error)

Sync copies pending data from the WAL to the shadow WAL.

func (*DB) UpdatedAt 

func (db *DB) UpdatedAt() (time.Time, error)

UpdatedAt returns the last modified time of the database or WAL file.

func (*DB) WALPath 

func (db *DB) WALPath() string

WALPath returns the path to the database's WAL file.

type Pos 

type Pos struct {
	Generation string // generation name
	Index      int    // wal file index
	Offset     int64  // offset within wal file
}

Pos is a position in the WAL for a generation.

func (Pos) IsZero 

func (p Pos) IsZero() bool

IsZero returns true if p is the zero value.

func (Pos) String 

func (p Pos) String() string

String returns a string representation.

func (Pos) Truncate 

func (p Pos) Truncate() Pos

Truncate returns p with the offset truncated to zero.

type Replica 

type Replica struct {

	// Client used to connect to the remote replica.
	Client ReplicaClient

	// Time between syncs with the shadow WAL.
	SyncInterval time.Duration

	// Frequency to create new snapshots.
	SnapshotInterval time.Duration

	// Time to keep snapshots and related WAL files.
	// Database is snapshotted after interval, if needed, and older WAL files are discarded.
	Retention time.Duration

	// Time between checks for retention.
	RetentionCheckInterval time.Duration

	// Time between validation checks.
	ValidationInterval time.Duration

	// If true, replica monitors database for changes automatically.
	// Set to false if replica is being used synchronously (such as in tests).
	MonitorEnabled bool

	// Encryption identities and recipients
	AgeIdentities []age.Identity
	AgeRecipients []age.Recipient
	// contains filtered or unexported fields
}

Replica connects a database to a replication destination via a ReplicaClient. The replica manages periodic synchronization and maintaining the current replica position.

func NewReplica 

func NewReplica(db *DB, name string) *Replica

func (*Replica) CalcRestoreTarget 

func (r *Replica) CalcRestoreTarget(ctx context.Context, opt RestoreOptions) (generation string, updatedAt time.Time, err error)

CalcRestoreTarget returns a generation to restore from.

func (*Replica) DB 

func (r *Replica) DB() *DB

DB returns a reference to the database the replica is attached to, if any.

func (*Replica) EnforceRetention 

func (r *Replica) EnforceRetention(ctx context.Context) (err error)

EnforceRetention forces a new snapshot once the retention interval has passed. Older snapshots and WAL files are then removed.

func (*Replica) GenerationCreatedAt 

func (r *Replica) GenerationCreatedAt(ctx context.Context, generation string) (time.Time, error)

GenerationCreatedAt returns the earliest creation time of any snapshot. Returns zero time if no snapshots exist.

func (*Replica) GenerationTimeBounds 

func (r *Replica) GenerationTimeBounds(ctx context.Context, generation string) (createdAt, updatedAt time.Time, err error)

GenerationTimeBounds returns the creation time & last updated time of a generation. Returns zero time if no snapshots or WAL segments exist.

func (*Replica) Logger 

func (r *Replica) Logger() *slog.Logger

Logger returns the DB sub-logger for this replica.

func (*Replica) Name 

func (r *Replica) Name() string

Name returns the name of the replica.

func (*Replica) Pos 

func (r *Replica) Pos() Pos

Pos returns the current replicated position. Returns a zero value if the current position cannot be determined.

func (*Replica) Restore 

func (r *Replica) Restore(ctx context.Context, opt RestoreOptions) (err error)

Replica restores the database from a replica based on the options given. This method will restore into opt.OutputPath, if specified, or into the DB's original database path. It can optionally restore from a specific 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 (*Replica) Snapshot 

func (r *Replica) Snapshot(ctx context.Context) (info SnapshotInfo, err error)

Snapshot copies the entire database to the replica path.

func (*Replica) SnapshotIndexAt 

func (r *Replica) SnapshotIndexAt(ctx context.Context, generation string, timestamp time.Time) (int, error)

SnapshotIndexAt returns the highest index for a snapshot within a generation that occurs before timestamp. If timestamp is zero, returns the latest snapshot.

func (*Replica) SnapshotIndexByIndex 

func (r *Replica) SnapshotIndexByIndex(ctx context.Context, generation string, index int) (int, error)

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 (*Replica) Snapshots 

func (r *Replica) Snapshots(ctx context.Context) ([]SnapshotInfo, error)

Snapshots returns a list of all snapshots across all generations.

func (*Replica) Start 

func (r *Replica) Start(ctx context.Context) error

Starts replicating in a background goroutine.

func (*Replica) Stop 

func (r *Replica) Stop(hard bool) (err error)

Stop cancels any outstanding replication and blocks until finished.

Performing a hard stop will close the DB file descriptor which could release locks on per-process locks. Hard stops should only be performed when stopping the entire process.

func (*Replica) Sync 

func (r *Replica) Sync(ctx context.Context) (err error)

Sync copies new WAL frames from the shadow WAL to the replica client.

func (*Replica) Validate 

func (r *Replica) Validate(ctx context.Context) error

Validate restores the most recent data from a replica and validates that the resulting database matches the current database.

type ReplicaClient 

type ReplicaClient interface {
	// Returns the type of client.
	Type() string

	// Returns a list of available generations. Order is undefined.
	Generations(ctx context.Context) ([]string, error)

	// Deletes all snapshots & WAL segments within a generation.
	DeleteGeneration(ctx context.Context, generation string) error

	// Returns an iterator of all snapshots within a generation on the replica. Order is undefined.
	Snapshots(ctx context.Context, generation string) (SnapshotIterator, error)

	// Writes LZ4 compressed snapshot data to the replica at a given index
	// within a generation. Returns metadata for the snapshot.
	WriteSnapshot(ctx context.Context, generation string, index int, r io.Reader) (SnapshotInfo, error)

	// Deletes a snapshot with the given generation & index.
	DeleteSnapshot(ctx context.Context, generation string, index int) error

	// Returns a reader that contains LZ4 compressed snapshot data for a
	// given index within a generation. Returns an os.ErrNotFound error if
	// the snapshot does not exist.
	SnapshotReader(ctx context.Context, generation string, index int) (io.ReadCloser, error)

	// Returns an iterator of all WAL segments within a generation on the replica. Order is undefined.
	WALSegments(ctx context.Context, generation string) (WALSegmentIterator, error)

	// Writes an LZ4 compressed WAL segment at a given position.
	// Returns metadata for the written segment.
	WriteWALSegment(ctx context.Context, pos Pos, r io.Reader) (WALSegmentInfo, error)

	// Deletes one or more WAL segments at the given positions.
	DeleteWALSegments(ctx context.Context, a []Pos) error

	// Returns a reader that contains an LZ4 compressed WAL segment at a given
	// index/offset within a generation. Returns an os.ErrNotFound error if the
	// WAL segment does not exist.
	WALSegmentReader(ctx context.Context, pos Pos) (io.ReadCloser, error)
}

ReplicaClient represents client to connect to a Replica.

type RestoreOptions 

type RestoreOptions struct {
	// Target path to restore into.
	// If blank, the original DB path is used.
	OutputPath string

	// Specific replica to restore from.
	// If blank, all replicas are considered.
	ReplicaName string

	// Specific generation to restore from.
	// If blank, all generations considered.
	Generation string

	// Specific index to restore from.
	// 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

	// Specifies how many WAL files are downloaded in parallel during restore.
	Parallelism int

	DriverName string
}

RestoreOptions represents options for DB.Restore().

func NewRestoreOptions 

func NewRestoreOptions() RestoreOptions

NewRestoreOptions returns a new instance of RestoreOptions with defaults.

type ShadowWALReader 

type ShadowWALReader struct {
	// contains filtered or unexported fields
}

ShadowWALReader represents a reader for a shadow WAL file that tracks WAL position.

func (*ShadowWALReader) Close 

func (r *ShadowWALReader) Close() error

Close closes the underlying WAL file handle.

func (*ShadowWALReader) N 

func (r *ShadowWALReader) N() int64

N returns the remaining bytes in the reader.

func (*ShadowWALReader) Name 

func (r *ShadowWALReader) Name() string

Name returns the filename of the underlying file.

func (*ShadowWALReader) Pos 

func (r *ShadowWALReader) Pos() Pos

Pos returns the current WAL position.

func (*ShadowWALReader) Read 

func (r *ShadowWALReader) Read(p []byte) (n int, err error)

Read reads bytes into p, updates the position, and returns the bytes read. Returns io.EOF at the end of the available section of the WAL.

type SnapshotInfo 

type SnapshotInfo struct {
	Generation string
	Index      int
	Size       int64
	CreatedAt  time.Time
}

SnapshotInfo represents file information about a snapshot.

func FilterSnapshotsAfter 

func FilterSnapshotsAfter(a []SnapshotInfo, t time.Time) []SnapshotInfo

FilterSnapshotsAfter returns all snapshots that were created on or after t.

func FindMinSnapshotByGeneration 

func FindMinSnapshotByGeneration(a []SnapshotInfo, generation string) *SnapshotInfo

FindMinSnapshotByGeneration finds the snapshot with the lowest index in a generation.

func SliceSnapshotIterator 

func SliceSnapshotIterator(itr SnapshotIterator) ([]SnapshotInfo, error)

SliceSnapshotIterator returns all snapshots from an iterator as a slice.

func (*SnapshotInfo) Pos 

func (info *SnapshotInfo) Pos() Pos

Pos returns the WAL position when the snapshot was made.

type SnapshotInfoSlice 

type SnapshotInfoSlice []SnapshotInfo

SnapshotInfoSlice represents a slice of snapshot metadata.

func (SnapshotInfoSlice) Len 

func (a SnapshotInfoSlice) Len() int

func (SnapshotInfoSlice) Less 

func (a SnapshotInfoSlice) Less(i, j int) bool

func (SnapshotInfoSlice) Swap 

func (a SnapshotInfoSlice) Swap(i, j int)

type SnapshotInfoSliceIterator 

type SnapshotInfoSliceIterator struct {
	// contains filtered or unexported fields
}

SnapshotInfoSliceIterator represents an iterator for iterating over a slice of snapshots.

func NewSnapshotInfoSliceIterator 

func NewSnapshotInfoSliceIterator(a []SnapshotInfo) *SnapshotInfoSliceIterator

NewSnapshotInfoSliceIterator returns a new instance of SnapshotInfoSliceIterator.

func (*SnapshotInfoSliceIterator) Close 

func (itr *SnapshotInfoSliceIterator) Close() error

Close always returns nil.

func (*SnapshotInfoSliceIterator) Err 

func (itr *SnapshotInfoSliceIterator) Err() error

Err always returns nil.

func (*SnapshotInfoSliceIterator) Next 

func (itr *SnapshotInfoSliceIterator) Next() bool

Next moves to the next snapshot. Returns true if another snapshot is available.

func (*SnapshotInfoSliceIterator) Snapshot 

func (itr *SnapshotInfoSliceIterator) Snapshot() SnapshotInfo

Snapshot returns the metadata from the currently positioned snapshot.

type SnapshotIterator 

type SnapshotIterator interface {
	io.Closer

	// Prepares the the next snapshot for reading with the Snapshot() method.
	// Returns true if another snapshot is available. Returns false if no more
	// snapshots are available or if an error occured.
	Next() bool

	// Returns an error that occurred during iteration.
	Err() error

	// Returns metadata for the currently positioned snapshot.
	Snapshot() SnapshotInfo
}

SnapshotIterator represents an iterator over a collection of snapshot metadata.

type WALInfo 

type WALInfo struct {
	Generation string
	Index      int
	CreatedAt  time.Time
}

WALInfo represents file information about a WAL file.

type WALInfoSlice 

type WALInfoSlice []WALInfo

WALInfoSlice represents a slice of WAL metadata.

func (WALInfoSlice) Len 

func (a WALInfoSlice) Len() int

func (WALInfoSlice) Less 

func (a WALInfoSlice) Less(i, j int) bool

func (WALInfoSlice) Swap 

func (a WALInfoSlice) Swap(i, j int)

type WALSegmentInfo 

type WALSegmentInfo struct {
	Generation string
	Index      int
	Offset     int64
	Size       int64
	CreatedAt  time.Time
}

WALSegmentInfo represents file information about a WAL segment file.

func SliceWALSegmentIterator 

func SliceWALSegmentIterator(itr WALSegmentIterator) ([]WALSegmentInfo, error)

SliceWALSegmentIterator returns all WAL segment files from an iterator as a slice.

func (*WALSegmentInfo) Pos 

func (info *WALSegmentInfo) Pos() Pos

Pos returns the WAL position when the segment was made.

type WALSegmentInfoSlice 

type WALSegmentInfoSlice []WALSegmentInfo

WALSegmentInfoSlice represents a slice of WAL segment metadata.

func (WALSegmentInfoSlice) Len 

func (a WALSegmentInfoSlice) Len() int

func (WALSegmentInfoSlice) Less 

func (a WALSegmentInfoSlice) Less(i, j int) bool

func (WALSegmentInfoSlice) Swap 

func (a WALSegmentInfoSlice) Swap(i, j int)

type WALSegmentInfoSliceIterator 

type WALSegmentInfoSliceIterator struct {
	// contains filtered or unexported fields
}

WALSegmentInfoSliceIterator represents an iterator for iterating over a slice of wal segments.

func NewWALSegmentInfoSliceIterator 

func NewWALSegmentInfoSliceIterator(a []WALSegmentInfo) *WALSegmentInfoSliceIterator

NewWALSegmentInfoSliceIterator returns a new instance of WALSegmentInfoSliceIterator.

func (*WALSegmentInfoSliceIterator) Close 

func (itr *WALSegmentInfoSliceIterator) Close() error

Close always returns nil.

func (*WALSegmentInfoSliceIterator) Err 

func (itr *WALSegmentInfoSliceIterator) Err() error

Err always returns nil.

func (*WALSegmentInfoSliceIterator) Next 

func (itr *WALSegmentInfoSliceIterator) Next() bool

Next moves to the next wal segment. Returns true if another segment is available.

func (*WALSegmentInfoSliceIterator) WALSegment 

func (itr *WALSegmentInfoSliceIterator) WALSegment() WALSegmentInfo

WALSegment returns the metadata from the currently positioned wal segment.

type WALSegmentIterator 

type WALSegmentIterator interface {
	io.Closer

	// Prepares the the next WAL for reading with the WAL() method.
	// Returns true if another WAL is available. Returns false if no more
	// WAL files are available or if an error occured.
	Next() bool

	// Returns an error that occurred during iteration.
	Err() error

	// Returns metadata for the currently positioned WAL segment file.
	WALSegment() WALSegmentInfo
}

WALSegmentIterator represents an iterator over a collection of WAL segments.

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