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36f4303fc3
When using Snapshot function, it is expected: 1. know the size of snapshot before writing data 2. split snapshot-ready phase and write-data phase. so we could cut snapshot first and write data later. Update its interface to fit the requirement of etcdserver.
130 lines
3.4 KiB
Go
130 lines
3.4 KiB
Go
// Copyright 2015 CoreOS, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package etcdserver
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import (
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"fmt"
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"io"
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"io/ioutil"
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"os"
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"path"
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"github.com/coreos/etcd/pkg/fileutil"
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"github.com/coreos/etcd/raft"
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"github.com/coreos/etcd/raft/raftpb"
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dstorage "github.com/coreos/etcd/storage"
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)
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type snapshot struct {
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r raftpb.Snapshot
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kv dstorage.Snapshot
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}
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func (s *snapshot) raft() raftpb.Snapshot { return s.r }
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func (s *snapshot) size() int64 { return s.kv.Size() }
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func (s *snapshot) writeTo(w io.Writer) (n int64, err error) { return s.kv.WriteTo(w) }
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func (s *snapshot) close() error { return s.kv.Close() }
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type snapshotStore struct {
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// dir to save snapshot data
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dir string
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kv dstorage.KV
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// send empty to reqsnapc to notify the channel receiver to send back latest
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// snapshot to snapc
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reqsnapc chan struct{}
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// a chan to receive the requested raft snapshot
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// snapshotStore will receive from the chan immediately after it sends empty to reqsnapc
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raftsnapc chan raftpb.Snapshot
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snap *snapshot
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}
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func newSnapshotStore(dir string, kv dstorage.KV) *snapshotStore {
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return &snapshotStore{
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dir: dir,
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kv: kv,
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reqsnapc: make(chan struct{}),
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raftsnapc: make(chan raftpb.Snapshot),
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}
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}
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// getSnap returns a snapshot.
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// If there is no available snapshot, ErrSnapshotTemporarilyUnavaliable will be returned.
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func (ss *snapshotStore) getSnap() (*snapshot, error) {
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if ss.snap != nil {
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return nil, raft.ErrSnapshotTemporarilyUnavailable
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}
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// ask to generate v2 snapshot
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ss.reqsnapc <- struct{}{}
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// generate KV snapshot
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kvsnap := ss.kv.Snapshot()
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raftsnap := <-ss.raftsnapc
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ss.snap = &snapshot{
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r: raftsnap,
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kv: kvsnap,
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}
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return ss.snap, nil
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}
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// saveSnap saves snapshot into disk.
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//
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// If snapshot has existed in disk, it keeps the original snapshot and returns error.
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// The function guarantees that it always saves either complete snapshot or no snapshot,
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// even if the call is aborted because program is hard killed.
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func (ss *snapshotStore) saveSnap(s *snapshot) error {
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f, err := ioutil.TempFile(ss.dir, "tmp")
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if err != nil {
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return err
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}
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_, err = s.writeTo(f)
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f.Close()
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if err != nil {
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os.Remove(f.Name())
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return err
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}
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fn := path.Join(ss.dir, fmt.Sprintf("%016x.db", s.raft().Metadata.Index))
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if fileutil.Exist(fn) {
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os.Remove(f.Name())
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return fmt.Errorf("snapshot to save has existed")
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}
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err = os.Rename(f.Name(), fn)
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if err != nil {
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os.Remove(f.Name())
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return err
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}
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return nil
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}
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// getSnapFilePath returns the file path for the snapshot with given index.
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// If the snapshot does not exist, it returns error.
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func (ss *snapshotStore) getSnapFilePath(index uint64) (string, error) {
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fns, err := fileutil.ReadDir(ss.dir)
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if err != nil {
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return "", err
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}
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wfn := fmt.Sprintf("%016x.db", index)
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for _, fn := range fns {
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if fn == wfn {
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return path.Join(ss.dir, fn), nil
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}
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}
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return "", fmt.Errorf("snapshot file doesn't exist")
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}
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