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store.go
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store.go
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package raft
import (
"os"
"github.com/coreos/etcd/raft"
"github.com/coreos/etcd/raft/raftpb"
"github.com/coreos/etcd/snap"
"github.com/coreos/etcd/wal"
"github.com/coreos/etcd/wal/walpb"
"github.com/pkg/errors"
)
type Storage interface {
raft.Storage
IsEmpty() bool
Save(rd raft.Ready) error
}
type MemStorage struct {
raft.MemoryStorage
wal *wal.WAL
snapshotter *snap.Snapshotter
}
func NewMemStorage(walDir, snapDir string) (*MemStorage, error) {
m := MemStorage{
MemoryStorage: *raft.NewMemoryStorage(),
}
// create snapshotter
if err := os.MkdirAll(snapDir, 0750); err != nil {
return nil, errors.Wrapf(err, "cannot create snapshot dir %s", snapDir)
}
m.snapshotter = snap.New(snapDir)
// create wal
snapshot, err := m.snapshotter.Load()
if err != nil && err != snap.ErrNoSnapshot {
return nil, errors.Wrap(err, "failed to load snapshot")
}
w, err := openWAL(walDir, snapshot)
if err != nil {
return nil, errors.Wrap(err, "failed to open wal")
}
m.wal = w
_, st, ents, err := w.ReadAll()
if err != nil {
return nil, errors.Wrap(err, "failed to read wal")
}
if snapshot != nil {
if err := m.ApplySnapshot(*snapshot); err != nil {
return nil, errors.Wrap(err, "failed to apply snapshot")
}
}
if err := m.SetHardState(st); err != nil {
return nil, errors.Wrap(err, "failed to apply state")
}
if err := m.Append(ents); err != nil {
return nil, errors.Wrap(err, "failed to append entries")
}
return &m, nil
}
func (s *MemStorage) Save(rd raft.Ready) error {
if err := s.wal.Save(rd.HardState, rd.Entries); err != nil {
return err
}
if err := s.Append(rd.Entries); err != nil {
return err
}
s.needSnapshot()
// Ignore empty snapshot
if raft.IsEmptySnap(rd.Snapshot) {
return nil
}
if err := s.ApplySnapshot(rd.Snapshot); err != nil {
return err
}
if err := s.snapshotter.SaveSnap(rd.Snapshot); err != nil {
return err
}
walSnap := walpb.Snapshot{
Index: rd.Snapshot.Metadata.Index,
Term: rd.Snapshot.Metadata.Term,
}
if err := s.wal.SaveSnapshot(walSnap); err != nil {
return err
}
return s.wal.ReleaseLockTo(rd.Snapshot.Metadata.Index)
}
func (s *MemStorage) IsEmpty() bool {
lastIndex, _ := s.MemoryStorage.LastIndex()
return lastIndex == 0
}
func (s *MemStorage) needSnapshot() bool {
lastIndex, _ := s.MemoryStorage.LastIndex()
snap, _ := s.Snapshot()
return lastIndex-snap.Metadata.Index > 1000
}
func openWAL(dir string, snapshot *raftpb.Snapshot) (*wal.WAL, error) {
if !wal.Exist(dir) {
if err := os.MkdirAll(dir, 0750); err != nil {
return nil, errors.Wrapf(err, "failed to create wal dir")
}
w, err := wal.Create(dir, nil)
if err != nil {
return nil, errors.Wrapf(err, "failed to create wal")
}
if err := w.Close(); err != nil {
return nil, errors.Wrap(err, "failed to close wal")
}
}
walsnap := walpb.Snapshot{}
if snapshot != nil {
walsnap.Index, walsnap.Term = snapshot.Metadata.Index, snapshot.Metadata.Term
}
w, err := wal.Open(dir, walsnap)
if err != nil {
return nil, errors.Wrapf(err, "failed to load wal")
}
return w, nil
}