walcache

Documentation

Index

• Variables
• type MemoryStorage
  • func NewMemoryStorage() MemoryStorage

Variables

var ErrCompacted = errors.New("requested index is unavailable due to compaction")

ErrCompacted is returned by Storage.Entries/Compact when a requested index is unavailable because it predates the last snapshot.

var ErrSnapOutOfDate = errors.New("requested index is older than the existing snapshot")

ErrSnapOutOfDate is returned by Storage.CreateSnapshot when a requested index is older than the existing snapshot.

var ErrSnapshotTemporarilyUnavailable = errors.New("snapshot is temporarily unavailable")

ErrSnapshotTemporarilyUnavailable is returned by the Storage interface when the required snapshot is temporarily unavailable.

var ErrUnavailable = errors.New("requested entry at index is unavailable")

ErrUnavailable is returned by Storage interface when the requested log entries are unavailable.

Types

type MemoryStorage

type MemoryStorage interface {
	// InitialState returns the saved HardState and ConfState information.
	HardState() (log.HardState, error)
	// Entries returns a slice of log entries in the range [lo,hi).
	// MaxSize limits the total size of the log entries returned, but
	// Entries returns at least one entry if any.
	Entries(lo, hi, maxSize uint64) ([]log.LogEntry, error)
	// Snapshot returns the most recent snapshot.
	// If snapshot is temporarily unavailable, it should return ErrSnapshotTemporarilyUnavailable,
	// so raft state machine could know that Storage needs some time to prepare
	// snapshot and call Snapshot later.
	Snapshot() (snappb.ShotData, error)
	// LastIndex returns the index of the last entry in the log.
	LastIndex() (uint64, error)
	// FirstIndex returns the index of the first log entry that is
	// possibly available via Entries (older entries have been incorporated
	// into the latest Snapshot; if storage only contains the dummy entry the
	// first log entry is not available).
	FirstIndex() (uint64, error)
	// SetHardState saves the current HardState.
	SetHardState(st log.HardState) error
	// ApplySnapshot overwrites the contents of this Storage object with
	// those of the given snapshot.
	ApplySnapshot(snap snappb.ShotData, ents []log.LogEntry) error
	// CreateSnapshot makes a snapshot which can be retrieved with Snapshot() and
	// can be used to reconstruct the state at that point.
	// If any configuration changes have been made since the last compaction,
	// the result of the last ApplyConfChange must be passed in.
	CreateSnapshot(snap snappb.ShotData) (snappb.ShotData, error)
	// Compact discards all log entries prior to compactIndex.
	// It is the application's responsibility to not attempt to compact an index
	// greater than raftLog.applied.
	Compact(compactIndex uint64) error
	// Append the new entries to storage.
	Append(entries []log.LogEntry) error
}

Storage is an interface that may be implemented by the application to retrieve log entries from storage.

If any Storage method returns an error, the raft instance will become inoperable and refuse to participate in elections; the application is responsible for cleanup and recovery in this case.

func NewMemoryStorage

func NewMemoryStorage() MemoryStorage

NewMemoryStorage creates an empty memoryStorage.