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package raft
import (
// InmemSnapshotStore implements the SnapshotStore interface and
// retains only the most recent snapshot
type InmemSnapshotStore struct {
latest *InmemSnapshotSink
hasSnapshot bool
// InmemSnapshotSink implements SnapshotSink in memory
type InmemSnapshotSink struct {
meta SnapshotMeta
contents *bytes.Buffer
// NewInmemSnapshotStore creates a blank new InmemSnapshotStore
func NewInmemSnapshotStore() *InmemSnapshotStore {
return &InmemSnapshotStore{
latest: &InmemSnapshotSink{
contents: &bytes.Buffer{},
// Create replaces the stored snapshot with a new one using the given args
func (m *InmemSnapshotStore) Create(version SnapshotVersion, index, term uint64,
configuration Configuration, configurationIndex uint64, trans Transport) (SnapshotSink, error) {
// We only support version 1 snapshots at this time.
if version != 1 {
return nil, fmt.Errorf("unsupported snapshot version %d", version)
name := snapshotName(term, index)
defer m.Unlock()
sink := &InmemSnapshotSink{
meta: SnapshotMeta{
Version: version,
ID: name,
Index: index,
Term: term,
Peers: encodePeers(configuration, trans),
Configuration: configuration,
ConfigurationIndex: configurationIndex,
contents: &bytes.Buffer{},
m.hasSnapshot = true
m.latest = sink
return sink, nil
// List returns the latest snapshot taken
func (m *InmemSnapshotStore) List() ([]*SnapshotMeta, error) {
defer m.RUnlock()
if !m.hasSnapshot {
return []*SnapshotMeta{}, nil
return []*SnapshotMeta{&m.latest.meta}, nil
// Open wraps an io.ReadCloser around the snapshot contents
func (m *InmemSnapshotStore) Open(id string) (*SnapshotMeta, io.ReadCloser, error) {
defer m.RUnlock()
if m.latest.meta.ID != id {
return nil, nil, fmt.Errorf("[ERR] snapshot: failed to open snapshot id: %s", id)
// Make a copy of the contents, since a bytes.Buffer can only be read
// once.
contents := bytes.NewBuffer(m.latest.contents.Bytes())
return &m.latest.meta, ioutil.NopCloser(contents), nil
// Write appends the given bytes to the snapshot contents
func (s *InmemSnapshotSink) Write(p []byte) (n int, err error) {
written, err := io.Copy(s.contents, bytes.NewReader(p))
s.meta.Size += written
return int(written), err
// Close updates the Size and is otherwise a no-op
func (s *InmemSnapshotSink) Close() error {
return nil
func (s *InmemSnapshotSink) ID() string {
return s.meta.ID
func (s *InmemSnapshotSink) Cancel() error {
return nil
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