snapshot_merge.go
// Copyright 2015 The etcd Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package etcdserver
import (
"io"
"log"
"github.com/coreos/etcd/mvcc/backend"
"github.com/coreos/etcd/raft/raftpb"
"github.com/coreos/etcd/snap"
)
// createMergedSnapshotMessage creates a snapshot message that contains: raft status (term, conf),
// a snapshot of v2 store inside raft.Snapshot as []byte, a snapshot of v3 KV in the top level message
// as ReadCloser.
func (s *EtcdServer) createMergedSnapshotMessage(m raftpb.Message, snapi uint64, confState raftpb.ConfState) snap.Message {
snapt, err := s.r.raftStorage.Term(snapi)
if err != nil {
log.Panicf("get term should never fail: %v", err)
}
// get a snapshot of v2 store as []byte
clone := s.store.Clone()
d, err := clone.SaveNoCopy()
if err != nil {
plog.Panicf("store save should never fail: %v", err)
}
dbsnap := s.be.Snapshot()
// get a snapshot of v3 KV as readCloser
rc := newSnapshotReaderCloser(dbsnap)
// put the []byte snapshot of store into raft snapshot and return the merged snapshot with
// KV readCloser snapshot.
snapshot := raftpb.Snapshot{
Metadata: raftpb.SnapshotMetadata{
Index: snapi,
Term: snapt,
ConfState: confState,
},
Data: d,
}
m.Snapshot = snapshot
return *snap.NewMessage(m, rc, dbsnap.Size())
}
func newSnapshotReaderCloser(snapshot backend.Snapshot) io.ReadCloser {
pr, pw := io.Pipe()
go func() {
n, err := snapshot.WriteTo(pw)
if err == nil {
plog.Infof("wrote database snapshot out [total bytes: %d]", n)
}
pw.CloseWithError(err)
snapshot.Close()
}()
return pr
}