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// Copyright 2017 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 (
"fmt"
"os"
"time"
"go.etcd.io/etcd/raft/v3/raftpb"
"go.etcd.io/etcd/server/v3/config"
"go.etcd.io/etcd/server/v3/etcdserver/api/snap"
"go.etcd.io/etcd/server/v3/etcdserver/cindex"
"go.etcd.io/etcd/server/v3/mvcc/backend"
"go.uber.org/zap"
)
func newBackend(cfg config.ServerConfig, hooks backend.Hooks) backend.Backend {
bcfg := backend.DefaultBackendConfig()
bcfg.Path = cfg.BackendPath()
bcfg.UnsafeNoFsync = cfg.UnsafeNoFsync
if cfg.BackendBatchLimit != 0 {
bcfg.BatchLimit = cfg.BackendBatchLimit
if cfg.Logger != nil {
cfg.Logger.Info("setting backend batch limit", zap.Int("batch limit", cfg.BackendBatchLimit))
}
}
if cfg.BackendBatchInterval != 0 {
bcfg.BatchInterval = cfg.BackendBatchInterval
if cfg.Logger != nil {
cfg.Logger.Info("setting backend batch interval", zap.Duration("batch interval", cfg.BackendBatchInterval))
}
}
bcfg.BackendFreelistType = cfg.BackendFreelistType
bcfg.Logger = cfg.Logger
if cfg.QuotaBackendBytes > 0 && cfg.QuotaBackendBytes != DefaultQuotaBytes {
// permit 10% excess over quota for disarm
bcfg.MmapSize = uint64(cfg.QuotaBackendBytes + cfg.QuotaBackendBytes/10)
}
bcfg.Mlock = cfg.ExperimentalMemoryMlock
bcfg.Hooks = hooks
return backend.New(bcfg)
}
// openSnapshotBackend renames a snapshot db to the current etcd db and opens it.
func openSnapshotBackend(cfg config.ServerConfig, ss *snap.Snapshotter, snapshot raftpb.Snapshot, hooks backend.Hooks) (backend.Backend, error) {
snapPath, err := ss.DBFilePath(snapshot.Metadata.Index)
if err != nil {
return nil, fmt.Errorf("failed to find database snapshot file (%v)", err)
}
if err := os.Rename(snapPath, cfg.BackendPath()); err != nil {
return nil, fmt.Errorf("failed to rename database snapshot file (%v)", err)
}
return openBackend(cfg, hooks), nil
}
// openBackend returns a backend using the current etcd db.
func openBackend(cfg config.ServerConfig, hooks backend.Hooks) backend.Backend {
fn := cfg.BackendPath()
now, beOpened := time.Now(), make(chan backend.Backend)
go func() {
beOpened <- newBackend(cfg, hooks)
}()
select {
case be := <-beOpened:
cfg.Logger.Info("opened backend db", zap.String("path", fn), zap.Duration("took", time.Since(now)))
return be
case <-time.After(10 * time.Second):
cfg.Logger.Info(
"db file is flocked by another process, or taking too long",
zap.String("path", fn),
zap.Duration("took", time.Since(now)),
)
}
return <-beOpened
}
// recoverBackendSnapshot recovers the DB from a snapshot in case etcd crashes
// before updating the backend db after persisting raft snapshot to disk,
// violating the invariant snapshot.Metadata.Index < db.consistentIndex. In this
// case, replace the db with the snapshot db sent by the leader.
func recoverSnapshotBackend(cfg config.ServerConfig, oldbe backend.Backend, snapshot raftpb.Snapshot, beExist bool, hooks backend.Hooks) (backend.Backend, error) {
consistentIndex := uint64(0)
if beExist {
consistentIndex, _ = cindex.ReadConsistentIndex(oldbe.ReadTx())
}
if snapshot.Metadata.Index <= consistentIndex {
return oldbe, nil
}
oldbe.Close()
return openSnapshotBackend(cfg, snap.New(cfg.Logger, cfg.SnapDir()), snapshot, hooks)
}
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