replication slave side

2025-10-06 01:07:06 +08:00 · 2022-05-31 14:15:29 +08:00
parent f327000d3a
commit 380d936ed5
23 changed files with 774 additions and 142 deletions
--- a/config/config.go
+++ b/config/config.go
@@ -14,12 +14,16 @@ import (
 type ServerProperties struct {
 	Bind              string `cfg:"bind"`
 	Port              int    `cfg:"port"`
-	AppendOnly     bool   `cfg:"appendOnly"`
-	AppendFilename string `cfg:"appendFilename"`
+	AppendOnly        bool   `cfg:"appendonly"`
+	AppendFilename    string `cfg:"appendfilename"`
 	MaxClients        int    `cfg:"maxclients"`
 	RequirePass       string `cfg:"requirepass"`
 	Databases         int    `cfg:"databases"`
 	RDBFilename       string `cfg:"dbfilename"`
+	MasterAuth        string `cfg:"masterauth""`
+	SlaveAnnouncePort int    `cfg:"slave-announce-port"`
+	SlaveAnnounceIP   string `cfg:"slave-announce-ip"`
+	ReplTimeout       int    `cfg:"repl-timeout"`

 	Peers []string `cfg:"peers"`
 	Self  string   `cfg:"self"`
--- a/database/cluster_helper.go
+++ b/database/cluster_helper.go
@@ -129,11 +129,11 @@ func execCopyTo(db *DB, args [][]byte) redis.Reply {
 }

 func init() {
-	RegisterCommand("DumpKey", execDumpKey, writeAllKeys, undoDel, 2)
-	RegisterCommand("ExistIn", execExistIn, readAllKeys, nil, -1)
-	RegisterCommand("RenameFrom", execRenameFrom, readFirstKey, nil, 2)
-	RegisterCommand("RenameTo", execRenameTo, writeFirstKey, rollbackFirstKey, 4)
-	RegisterCommand("RenameNxTo", execRenameTo, writeFirstKey, rollbackFirstKey, 4)
-	RegisterCommand("CopyFrom", execCopyFrom, readFirstKey, nil, 2)
-	RegisterCommand("CopyTo", execCopyTo, writeFirstKey, rollbackFirstKey, 5)
+	RegisterCommand("DumpKey", execDumpKey, writeAllKeys, undoDel, 2, flagReadOnly)
+	RegisterCommand("ExistIn", execExistIn, readAllKeys, nil, -1, flagReadOnly)
+	RegisterCommand("RenameFrom", execRenameFrom, readFirstKey, nil, 2, flagWrite)
+	RegisterCommand("RenameTo", execRenameTo, writeFirstKey, rollbackFirstKey, 4, flagWrite)
+	RegisterCommand("RenameNxTo", execRenameTo, writeFirstKey, rollbackFirstKey, 4, flagWrite)
+	RegisterCommand("CopyFrom", execCopyFrom, readFirstKey, nil, 2, flagReadOnly)
+	RegisterCommand("CopyTo", execCopyTo, writeFirstKey, rollbackFirstKey, 5, flagWrite)
 }
--- a/database/database.go
+++ b/database/database.go
@@ -9,10 +9,12 @@ import (
 	"github.com/hdt3213/godis/lib/logger"
 	"github.com/hdt3213/godis/lib/utils"
 	"github.com/hdt3213/godis/pubsub"
+	"github.com/hdt3213/godis/redis/connection"
 	"github.com/hdt3213/godis/redis/protocol"
 	"runtime/debug"
 	"strconv"
 	"strings"
+	"sync/atomic"
 	"time"
 )

@@ -24,6 +26,11 @@ type MultiDB struct {
 	hub *pubsub.Hub
 	// handle aof persistence
 	aofHandler *aof.Handler
+
+	// store master node address
+	slaveOf     string
+	role        int32
+	replication *replicationStatus
 }

 // NewStandaloneServer creates a standalone redis server, with multi database and all other funtions
@@ -59,8 +66,11 @@ func NewStandaloneServer() *MultiDB {
 	}
 	if config.Properties.RDBFilename != "" && !validAof {
 		// load rdb
-		loadRdb(mdb)
+		loadRdbFile(mdb)
 	}
+	mdb.replication = initReplStatus()
+	mdb.startReplCron()
+	mdb.role = masterRole // The initialization process does not require atomicity
 	return mdb
 }

@@ -92,6 +102,25 @@ func (mdb *MultiDB) Exec(c redis.Connection, cmdLine [][]byte) (result redis.Rep
 	if !isAuthenticated(c) {
 		return protocol.MakeErrReply("NOAUTH Authentication required")
 	}
+	if cmdName == "slaveof" {
+		if c != nil && c.InMultiState() {
+			return protocol.MakeErrReply("cannot use slave of database within multi")
+		}
+		if len(cmdLine) != 3 {
+			return protocol.MakeArgNumErrReply("SLAVEOF")
+		}
+		return mdb.execSlaveOf(c, cmdLine[1:])
+	}
+
+	// read only slave
+	role := atomic.LoadInt32(&mdb.role)
+	if role == slaveRole &&
+		c.GetRole() != connection.ReplicationRecvCli {
+		// only allow read only command, forbid all special commands except `auth` and `slaveof`
+		if !isReadOnlyCommand(cmdName) {
+			return protocol.MakeErrReply("READONLY You can't write against a read only slave.")
+		}
+	}

 	// special commands which cannot execute within transaction
 	if cmdName == "subscribe" {
@@ -146,6 +175,8 @@ func (mdb *MultiDB) AfterClientClose(c redis.Connection) {

 // Close graceful shutdown database
 func (mdb *MultiDB) Close() {
+	// stop replication first
+	mdb.replication.close()
 	if mdb.aofHandler != nil {
 		mdb.aofHandler.Close()
 	}
--- a/database/geo.go
+++ b/database/geo.go
@@ -262,10 +262,10 @@ func geoRadius0(sortedSet *sortedset.SortedSet, lat float64, lng float64, radius
 }

 func init() {
-	RegisterCommand("GeoAdd", execGeoAdd, writeFirstKey, undoGeoAdd, -5)
-	RegisterCommand("GeoPos", execGeoPos, readFirstKey, nil, -2)
-	RegisterCommand("GeoDist", execGeoDist, readFirstKey, nil, -4)
-	RegisterCommand("GeoHash", execGeoHash, readFirstKey, nil, -2)
-	RegisterCommand("GeoRadius", execGeoRadius, readFirstKey, nil, -6)
-	RegisterCommand("GeoRadiusByMember", execGeoRadiusByMember, readFirstKey, nil, -5)
+	RegisterCommand("GeoAdd", execGeoAdd, writeFirstKey, undoGeoAdd, -5, flagWrite)
+	RegisterCommand("GeoPos", execGeoPos, readFirstKey, nil, -2, flagReadOnly)
+	RegisterCommand("GeoDist", execGeoDist, readFirstKey, nil, -4, flagReadOnly)
+	RegisterCommand("GeoHash", execGeoHash, readFirstKey, nil, -2, flagReadOnly)
+	RegisterCommand("GeoRadius", execGeoRadius, readFirstKey, nil, -6, flagReadOnly)
+	RegisterCommand("GeoRadiusByMember", execGeoRadiusByMember, readFirstKey, nil, -5, flagReadOnly)
 }
--- a/database/hash.go
+++ b/database/hash.go
@@ -498,20 +498,20 @@ func execHRandField(db *DB, args [][]byte) redis.Reply {
 }

 func init() {
-	RegisterCommand("HSet", execHSet, writeFirstKey, undoHSet, 4)
-	RegisterCommand("HSetNX", execHSetNX, writeFirstKey, undoHSet, 4)
-	RegisterCommand("HGet", execHGet, readFirstKey, nil, 3)
-	RegisterCommand("HExists", execHExists, readFirstKey, nil, 3)
-	RegisterCommand("HDel", execHDel, writeFirstKey, undoHDel, -3)
-	RegisterCommand("HLen", execHLen, readFirstKey, nil, 2)
-	RegisterCommand("HStrlen", execHStrlen, readFirstKey, nil, 3)
-	RegisterCommand("HMSet", execHMSet, writeFirstKey, undoHMSet, -4)
-	RegisterCommand("HMGet", execHMGet, readFirstKey, nil, -3)
-	RegisterCommand("HGet", execHGet, readFirstKey, nil, -3)
-	RegisterCommand("HKeys", execHKeys, readFirstKey, nil, 2)
-	RegisterCommand("HVals", execHVals, readFirstKey, nil, 2)
-	RegisterCommand("HGetAll", execHGetAll, readFirstKey, nil, 2)
-	RegisterCommand("HIncrBy", execHIncrBy, writeFirstKey, undoHIncr, 4)
-	RegisterCommand("HIncrByFloat", execHIncrByFloat, writeFirstKey, undoHIncr, 4)
-	RegisterCommand("HRandField", execHRandField, readFirstKey, nil, -2)
+	RegisterCommand("HSet", execHSet, writeFirstKey, undoHSet, 4, flagWrite)
+	RegisterCommand("HSetNX", execHSetNX, writeFirstKey, undoHSet, 4, flagWrite)
+	RegisterCommand("HGet", execHGet, readFirstKey, nil, 3, flagReadOnly)
+	RegisterCommand("HExists", execHExists, readFirstKey, nil, 3, flagReadOnly)
+	RegisterCommand("HDel", execHDel, writeFirstKey, undoHDel, -3, flagWrite)
+	RegisterCommand("HLen", execHLen, readFirstKey, nil, 2, flagReadOnly)
+	RegisterCommand("HStrlen", execHStrlen, readFirstKey, nil, 3, flagReadOnly)
+	RegisterCommand("HMSet", execHMSet, writeFirstKey, undoHMSet, -4, flagWrite)
+	RegisterCommand("HMGet", execHMGet, readFirstKey, nil, -3, flagReadOnly)
+	RegisterCommand("HGet", execHGet, readFirstKey, nil, -3, flagReadOnly)
+	RegisterCommand("HKeys", execHKeys, readFirstKey, nil, 2, flagReadOnly)
+	RegisterCommand("HVals", execHVals, readFirstKey, nil, 2, flagReadOnly)
+	RegisterCommand("HGetAll", execHGetAll, readFirstKey, nil, 2, flagReadOnly)
+	RegisterCommand("HIncrBy", execHIncrBy, writeFirstKey, undoHIncr, 4, flagWrite)
+	RegisterCommand("HIncrByFloat", execHIncrByFloat, writeFirstKey, undoHIncr, 4, flagWrite)
+	RegisterCommand("HRandField", execHRandField, readFirstKey, nil, -2, flagReadOnly)
 }
--- a/database/keys.go
+++ b/database/keys.go
@@ -372,17 +372,17 @@ func execCopy(mdb *MultiDB, conn redis.Connection, args [][]byte) redis.Reply {
 }

 func init() {
-	RegisterCommand("Del", execDel, writeAllKeys, undoDel, -2)
-	RegisterCommand("Expire", execExpire, writeFirstKey, undoExpire, 3)
-	RegisterCommand("ExpireAt", execExpireAt, writeFirstKey, undoExpire, 3)
-	RegisterCommand("PExpire", execPExpire, writeFirstKey, undoExpire, 3)
-	RegisterCommand("PExpireAt", execPExpireAt, writeFirstKey, undoExpire, 3)
-	RegisterCommand("TTL", execTTL, readFirstKey, nil, 2)
-	RegisterCommand("PTTL", execPTTL, readFirstKey, nil, 2)
-	RegisterCommand("Persist", execPersist, writeFirstKey, undoExpire, 2)
-	RegisterCommand("Exists", execExists, readAllKeys, nil, -2)
-	RegisterCommand("Type", execType, readFirstKey, nil, 2)
-	RegisterCommand("Rename", execRename, prepareRename, undoRename, 3)
-	RegisterCommand("RenameNx", execRenameNx, prepareRename, undoRename, 3)
-	RegisterCommand("Keys", execKeys, noPrepare, nil, 2)
+	RegisterCommand("Del", execDel, writeAllKeys, undoDel, -2, flagWrite)
+	RegisterCommand("Expire", execExpire, writeFirstKey, undoExpire, 3, flagWrite)
+	RegisterCommand("ExpireAt", execExpireAt, writeFirstKey, undoExpire, 3, flagWrite)
+	RegisterCommand("PExpire", execPExpire, writeFirstKey, undoExpire, 3, flagWrite)
+	RegisterCommand("PExpireAt", execPExpireAt, writeFirstKey, undoExpire, 3, flagWrite)
+	RegisterCommand("TTL", execTTL, readFirstKey, nil, 2, flagReadOnly)
+	RegisterCommand("PTTL", execPTTL, readFirstKey, nil, 2, flagReadOnly)
+	RegisterCommand("Persist", execPersist, writeFirstKey, undoExpire, 2, flagWrite)
+	RegisterCommand("Exists", execExists, readAllKeys, nil, -2, flagReadOnly)
+	RegisterCommand("Type", execType, readFirstKey, nil, 2, flagReadOnly)
+	RegisterCommand("Rename", execRename, prepareRename, undoRename, 3, flagReadOnly)
+	RegisterCommand("RenameNx", execRenameNx, prepareRename, undoRename, 3, flagReadOnly)
+	RegisterCommand("Keys", execKeys, noPrepare, nil, 2, flagReadOnly)
 }
--- a/database/list.go
+++ b/database/list.go
@@ -505,16 +505,16 @@ func execRPushX(db *DB, args [][]byte) redis.Reply {
 }

 func init() {
-	RegisterCommand("LPush", execLPush, writeFirstKey, undoLPush, -3)
-	RegisterCommand("LPushX", execLPushX, writeFirstKey, undoLPush, -3)
-	RegisterCommand("RPush", execRPush, writeFirstKey, undoRPush, -3)
-	RegisterCommand("RPushX", execRPushX, writeFirstKey, undoRPush, -3)
-	RegisterCommand("LPop", execLPop, writeFirstKey, undoLPop, 2)
-	RegisterCommand("RPop", execRPop, writeFirstKey, undoRPop, 2)
-	RegisterCommand("RPopLPush", execRPopLPush, prepareRPopLPush, undoRPopLPush, 3)
-	RegisterCommand("LRem", execLRem, writeFirstKey, rollbackFirstKey, 4)
-	RegisterCommand("LLen", execLLen, readFirstKey, nil, 2)
-	RegisterCommand("LIndex", execLIndex, readFirstKey, nil, 3)
-	RegisterCommand("LSet", execLSet, writeFirstKey, undoLSet, 4)
-	RegisterCommand("LRange", execLRange, readFirstKey, nil, 4)
+	RegisterCommand("LPush", execLPush, writeFirstKey, undoLPush, -3, flagWrite)
+	RegisterCommand("LPushX", execLPushX, writeFirstKey, undoLPush, -3, flagWrite)
+	RegisterCommand("RPush", execRPush, writeFirstKey, undoRPush, -3, flagWrite)
+	RegisterCommand("RPushX", execRPushX, writeFirstKey, undoRPush, -3, flagWrite)
+	RegisterCommand("LPop", execLPop, writeFirstKey, undoLPop, 2, flagWrite)
+	RegisterCommand("RPop", execRPop, writeFirstKey, undoRPop, 2, flagWrite)
+	RegisterCommand("RPopLPush", execRPopLPush, prepareRPopLPush, undoRPopLPush, 3, flagWrite)
+	RegisterCommand("LRem", execLRem, writeFirstKey, rollbackFirstKey, 4, flagWrite)
+	RegisterCommand("LLen", execLLen, readFirstKey, nil, 2, flagReadOnly)
+	RegisterCommand("LIndex", execLIndex, readFirstKey, nil, 3, flagReadOnly)
+	RegisterCommand("LSet", execLSet, writeFirstKey, undoLSet, 4, flagWrite)
+	RegisterCommand("LRange", execLRange, readFirstKey, nil, 4, flagReadOnly)
 }
--- a/database/rdb.go
+++ b/database/rdb.go
@@ -7,21 +7,30 @@ import (
 	SortedSet "github.com/hdt3213/godis/datastruct/sortedset"
 	"github.com/hdt3213/godis/interface/database"
 	"github.com/hdt3213/godis/lib/logger"
+	"github.com/hdt3213/rdb/core"
 	rdb "github.com/hdt3213/rdb/parser"
 	"os"
 )

-func loadRdb(mdb *MultiDB) {
+func loadRdbFile(mdb *MultiDB) {
 	rdbFile, err := os.Open(config.Properties.RDBFilename)
 	if err != nil {
-		logger.Error("open rdb file failed")
+		logger.Error("open rdb file failed " + err.Error())
 		return
 	}
 	defer func() {
 		_ = rdbFile.Close()
 	}()
 	decoder := rdb.NewDecoder(rdbFile)
-	err = decoder.Parse(func(o rdb.RedisObject) bool {
+	err = dumpRDB(decoder, mdb)
+	if err != nil {
+		logger.Error("dump rdb file failed " + err.Error())
+		return
+	}
+}
+
+func dumpRDB(dec *core.Decoder, mdb *MultiDB) error {
+	return dec.Parse(func(o rdb.RedisObject) bool {
 		db := mdb.selectDB(o.GetDBIndex())
 		switch o.GetType() {
 		case rdb.StringType:
--- a/database/replication.go
+++ b/database/replication.go
@@ -0,0 +1,401 @@
+package database
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"github.com/hdt3213/godis/config"
+	"github.com/hdt3213/godis/interface/redis"
+	"github.com/hdt3213/godis/lib/logger"
+	"github.com/hdt3213/godis/lib/utils"
+	"github.com/hdt3213/godis/redis/connection"
+	"github.com/hdt3213/godis/redis/parser"
+	"github.com/hdt3213/godis/redis/protocol"
+	rdb "github.com/hdt3213/rdb/parser"
+	"net"
+	"strconv"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+const (
+	masterRole = iota
+	slaveRole
+)
+
+type replicationStatus struct {
+	mutex    sync.Mutex
+	ctx      context.Context
+	cancel   context.CancelFunc
+	modCount int32 // execSlaveOf() or reconnect will cause modCount++
+
+	masterHost string
+	masterPort int
+
+	masterConn   net.Conn
+	masterChan   <-chan *parser.Payload
+	replId       string
+	replOffset   int64
+	lastRecvTime time.Time
+	running      sync.WaitGroup
+}
+
+func initReplStatus() *replicationStatus {
+	repl := &replicationStatus{}
+	// start cron
+	return repl
+}
+
+func (mdb *MultiDB) startReplCron() {
+	go func() {
+		defer func() {
+			if err := recover(); err != nil {
+				logger.Error("panic", err)
+			}
+		}()
+		ticker := time.Tick(time.Second)
+		for range ticker {
+			mdb.slaveCron()
+		}
+	}()
+}
+
+func (mdb *MultiDB) execSlaveOf(c redis.Connection, args [][]byte) redis.Reply {
+	if strings.ToLower(string(args[0])) == "no" &&
+		strings.ToLower(string(args[1])) == "one" {
+		mdb.slaveOfNone()
+		return protocol.MakeOkReply()
+	}
+	host := string(args[0])
+	port, err := strconv.Atoi(string(args[1]))
+	if err != nil {
+		return protocol.MakeErrReply("ERR value is not an integer or out of range")
+	}
+	mdb.replication.mutex.Lock()
+	atomic.StoreInt32(&mdb.role, slaveRole)
+	mdb.replication.masterHost = host
+	mdb.replication.masterPort = port
+	// use buffered channel in case receiver goroutine exited before controller send stop signal
+	atomic.AddInt32(&mdb.replication.modCount, 1)
+	mdb.replication.mutex.Unlock()
+	go mdb.syncWithMaster()
+	return protocol.MakeOkReply()
+}
+
+func (mdb *MultiDB) slaveOfNone() {
+	mdb.replication.mutex.Lock()
+	defer mdb.replication.mutex.Unlock()
+	mdb.replication.masterHost = ""
+	mdb.replication.masterPort = 0
+	mdb.replication.replId = ""
+	mdb.replication.replOffset = -1
+	mdb.replication.stopSlaveWithMutex()
+}
+
+// stopSlaveWithMutex stops in-progress connectWithMaster/fullSync/receiveAOF
+// invoker should have replication mutex
+func (repl *replicationStatus) stopSlaveWithMutex() {
+	// update modCount to stop connectWithMaster and fullSync
+	atomic.AddInt32(&repl.modCount, 1)
+	// send cancel to receiveAOF
+	if repl.cancel != nil {
+		repl.cancel()
+		repl.running.Wait()
+	}
+	repl.ctx = context.Background()
+	repl.cancel = nil
+	if repl.masterConn != nil {
+		_ = repl.masterConn.Close() // parser.ParseStream will close masterChan
+	}
+	repl.masterConn = nil
+	repl.masterChan = nil
+}
+
+func (repl *replicationStatus) close() error {
+	repl.mutex.Lock()
+	defer repl.mutex.Unlock()
+	repl.stopSlaveWithMutex()
+	return nil
+}
+
+func (mdb *MultiDB) syncWithMaster() {
+	defer func() {
+		if err := recover(); err != nil {
+			logger.Error(err)
+		}
+	}()
+	mdb.replication.mutex.Lock()
+	ctx, cancel := context.WithCancel(context.Background())
+	mdb.replication.ctx = ctx
+	mdb.replication.cancel = cancel
+	mdb.replication.mutex.Unlock()
+	err := mdb.connectWithMaster()
+	if err != nil {
+		// full sync failed, abort
+		return
+	}
+	err = mdb.doPsync()
+	if err != nil {
+		// full sync failed, abort
+		return
+	}
+	err = mdb.receiveAOF()
+	if err != nil {
+		// full sync failed, abort
+		return
+	}
+}
+
+func (mdb *MultiDB) connectWithMaster() error {
+	modCount := atomic.LoadInt32(&mdb.replication.modCount)
+	addr := mdb.replication.masterHost + ":" + strconv.Itoa(mdb.replication.masterPort)
+	conn, err := net.Dial("tcp", addr)
+	if err != nil {
+		mdb.slaveOfNone() // abort
+		return errors.New("connect master failed " + err.Error())
+	}
+	masterChan := parser.ParseStream(conn)
+
+	// ping
+	pingCmdLine := utils.ToCmdLine("ping")
+	pingReq := protocol.MakeMultiBulkReply(pingCmdLine)
+	_, err = conn.Write(pingReq.ToBytes())
+	if err != nil {
+		return errors.New("send failed " + err.Error())
+	}
+	pingResp := <-masterChan
+	if pingResp.Err != nil {
+		return errors.New("read response failed: " + pingResp.Err.Error())
+	}
+	switch reply := pingResp.Data.(type) {
+	case *protocol.StandardErrReply:
+		if !strings.HasPrefix(reply.Error(), "NOAUTH") &&
+			!strings.HasPrefix(reply.Error(), "NOPERM") &&
+			!strings.HasPrefix(reply.Error(), "ERR operation not permitted") {
+			logger.Error("Error reply to PING from master: " + string(reply.ToBytes()))
+			mdb.slaveOfNone() // abort
+			return nil
+		}
+	}
+
+	// just to reduce duplication of code
+	sendCmdToMaster := func(conn net.Conn, cmdLine CmdLine, masterChan <-chan *parser.Payload) error {
+		req := protocol.MakeMultiBulkReply(cmdLine)
+		_, err := conn.Write(req.ToBytes())
+		if err != nil {
+			mdb.slaveOfNone() // abort
+			return errors.New("send failed " + err.Error())
+		}
+		resp := <-masterChan
+		if resp.Err != nil {
+			mdb.slaveOfNone() // abort
+			return errors.New("read response failed: " + resp.Err.Error())
+		}
+		if !protocol.IsOKReply(resp.Data) {
+			mdb.slaveOfNone() // abort
+			return errors.New("unexpected auth response: " + string(resp.Data.ToBytes()))
+		}
+		return nil
+	}
+
+	// auth
+	if config.Properties.MasterAuth != "" {
+		authCmdLine := utils.ToCmdLine("auth", config.Properties.MasterAuth)
+		err = sendCmdToMaster(conn, authCmdLine, masterChan)
+		if err != nil {
+			return err
+		}
+	}
+
+	// announce port
+	var port int
+	if config.Properties.SlaveAnnouncePort != 0 {
+		port = config.Properties.SlaveAnnouncePort
+	} else {
+		port = config.Properties.Port
+	}
+	portCmdLine := utils.ToCmdLine("REPLCONF", "listening-port", strconv.Itoa(port))
+	err = sendCmdToMaster(conn, portCmdLine, masterChan)
+	if err != nil {
+		return err
+	}
+
+	// announce ip
+	if config.Properties.SlaveAnnounceIP != "" {
+		ipCmdLine := utils.ToCmdLine("REPLCONF", "ip-address", config.Properties.SlaveAnnounceIP)
+		err = sendCmdToMaster(conn, ipCmdLine, masterChan)
+		if err != nil {
+			return err
+		}
+	}
+
+	// announce capacity
+	capaCmdLine := utils.ToCmdLine("REPLCONF", "capa", "psync2")
+	err = sendCmdToMaster(conn, capaCmdLine, masterChan)
+	if err != nil {
+		return err
+	}
+
+	// update connection
+	mdb.replication.mutex.Lock()
+	if mdb.replication.modCount != modCount {
+		// replication conf changed during connecting and waiting mutex
+		return nil
+	}
+	mdb.replication.masterConn = conn
+	mdb.replication.masterChan = masterChan
+	mdb.replication.mutex.Unlock()
+	return nil
+}
+
+// doPsync send psync to master and sync repl-id then load rdb
+func (mdb *MultiDB) doPsync() error {
+	modCount := atomic.LoadInt32(&mdb.replication.modCount)
+	psyncCmdLine := utils.ToCmdLine("psync", "?", "-1")
+	psyncReq := protocol.MakeMultiBulkReply(psyncCmdLine)
+	_, err := mdb.replication.masterConn.Write(psyncReq.ToBytes())
+	if err != nil {
+		return errors.New("send failed " + err.Error())
+	}
+	ch := mdb.replication.masterChan
+	psyncPayload1 := <-ch
+	if psyncPayload1.Err != nil {
+		return errors.New("read response failed: " + psyncPayload1.Err.Error())
+	}
+	psyncHeader, ok := psyncPayload1.Data.(*protocol.StatusReply)
+	if !ok {
+		return errors.New("illegal payload header: " + string(psyncPayload1.Data.ToBytes()))
+	}
+	headers := strings.Split(psyncHeader.Status, " ")
+	if len(headers) != 3 {
+		return errors.New("illegal payload header: " + psyncHeader.Status)
+	}
+	logger.Info("receive psync header from master")
+	psyncPayload2 := <-ch
+	if psyncPayload2.Err != nil {
+		return errors.New("read response failed: " + psyncPayload2.Err.Error())
+	}
+	psyncData, ok := psyncPayload2.Data.(*protocol.BulkReply)
+	if !ok {
+		return errors.New("illegal payload header: " + string(psyncPayload2.Data.ToBytes()))
+	}
+	logger.Info(fmt.Sprintf("receive %d bytes of rdb from master", len(psyncData.Arg)))
+	rdbDec := rdb.NewDecoder(bytes.NewReader(psyncData.Arg))
+	rdbHolder := MakeBasicMultiDB()
+	err = dumpRDB(rdbDec, rdbHolder)
+	if err != nil {
+		return errors.New("dump rdb failed: " + err.Error())
+	}
+
+	mdb.replication.mutex.Lock()
+	defer mdb.replication.mutex.Unlock()
+	if mdb.replication.modCount != modCount {
+		// replication conf changed during connecting and waiting mutex
+		return nil
+	}
+	mdb.replication.replId = headers[1]
+	mdb.replication.replOffset, err = strconv.ParseInt(headers[2], 10, 64)
+	if err != nil {
+		return errors.New("get illegal repl offset: " + headers[2])
+	}
+	logger.Info("full resync from master: " + mdb.replication.replId)
+	logger.Info("current offset:", mdb.replication.replOffset)
+	for i, newDB := range rdbHolder.dbSet {
+		oldDB := mdb.selectDB(i)
+		oldDB.Load(newDB)
+	}
+	// there is no CRLF between RDB and following AOF, reset stream to avoid parser error
+	mdb.replication.masterChan = parser.ParseStream(mdb.replication.masterConn)
+	return nil
+}
+
+func (mdb *MultiDB) receiveAOF() error {
+	conn := connection.NewConn(mdb.replication.masterConn)
+	conn.SetRole(connection.ReplicationRecvCli)
+	mdb.replication.mutex.Lock()
+	modCount := mdb.replication.modCount
+	done := mdb.replication.ctx.Done()
+	mdb.replication.mutex.Unlock()
+	if done == nil {
+		// stopSlaveWithMutex() is called during waiting mutex
+		return nil
+	}
+	mdb.replication.running.Add(1)
+	defer mdb.replication.running.Done()
+	for {
+		select {
+		case payload, open := <-mdb.replication.masterChan:
+			if !open {
+				return errors.New("master channel unexpected close")
+			}
+			if payload.Err != nil {
+				return payload.Err
+			}
+			cmdLine, ok := payload.Data.(*protocol.MultiBulkReply)
+			if !ok {
+				return errors.New("unexpected payload: " + string(payload.Data.ToBytes()))
+			}
+			mdb.replication.mutex.Lock()
+			if mdb.replication.modCount != modCount {
+				// replication conf changed during connecting and waiting mutex
+				return nil
+			}
+			mdb.Exec(conn, cmdLine.Args)
+			// todo: directly get size from socket
+			n := len(cmdLine.ToBytes())
+			mdb.replication.replOffset += int64(n)
+			logger.Info(fmt.Sprintf("receive %d bytes from master, current offset %d",
+				n, mdb.replication.replOffset))
+			mdb.replication.mutex.Unlock()
+		case <-done:
+			return nil
+		}
+	}
+}
+
+func (mdb *MultiDB) slaveCron() {
+	repl := mdb.replication
+	if repl.masterConn == nil {
+		return
+	}
+	replTimeout := 60 * time.Second
+	if config.Properties.ReplTimeout != 0 {
+		replTimeout = time.Duration(config.Properties.ReplTimeout) * time.Second
+	}
+	minLastRecvTime := time.Now().Add(-replTimeout)
+	if repl.lastRecvTime.Before(minLastRecvTime) {
+		// reconnect with master
+		err := mdb.reconnectWithMaster()
+		if err != nil {
+			logger.Error("send failed " + err.Error())
+		}
+		return
+	}
+	// send ack to master
+	err := repl.sendAck2Master()
+	if err != nil {
+		logger.Error("send failed " + err.Error())
+	}
+}
+
+// Send a REPLCONF ACK command to the master to inform it about the current processed offset
+func (repl *replicationStatus) sendAck2Master() error {
+	psyncCmdLine := utils.ToCmdLine("REPLCONF", "ACK",
+		strconv.FormatInt(repl.replOffset, 10))
+	psyncReq := protocol.MakeMultiBulkReply(psyncCmdLine)
+	_, err := repl.masterConn.Write(psyncReq.ToBytes())
+	//logger.Info("send ack to master")
+	return err
+}
+
+func (mdb *MultiDB) reconnectWithMaster() error {
+	logger.Info("reconnecting with master")
+	mdb.replication.mutex.Lock()
+	defer mdb.replication.mutex.Unlock()
+	mdb.replication.stopSlaveWithMutex()
+	go mdb.syncWithMaster()
+	return nil
+}
--- a/database/replication_test.go
+++ b/database/replication_test.go
@@ -0,0 +1,135 @@
+package database
+
+import (
+	"bytes"
+	"github.com/hdt3213/godis/config"
+	"github.com/hdt3213/godis/lib/utils"
+	"github.com/hdt3213/godis/redis/client"
+	"github.com/hdt3213/godis/redis/connection"
+	"github.com/hdt3213/godis/redis/protocol"
+	"github.com/hdt3213/godis/redis/protocol/asserts"
+	"testing"
+	"time"
+)
+
+func TestReplication(t *testing.T) {
+	mdb := &MultiDB{}
+	mdb.dbSet = make([]*DB, 16)
+	for i := range mdb.dbSet {
+		singleDB := makeDB()
+		singleDB.index = i
+		mdb.dbSet[i] = singleDB
+	}
+	mdb.replication = initReplStatus()
+	masterCli, err := client.MakeClient("127.0.0.1:6379")
+	if err != nil {
+		t.Error(err)
+	}
+	masterCli.Start()
+
+	// sync with master
+	ret := masterCli.Send(utils.ToCmdLine("set", "1", "1"))
+	asserts.AssertStatusReply(t, ret, "OK")
+	conn := &connection.FakeConn{}
+	ret = mdb.Exec(conn, utils.ToCmdLine("SLAVEOF", "127.0.0.1", "6379"))
+	asserts.AssertStatusReply(t, ret, "OK")
+	success := false
+	for i := 0; i < 30; i++ {
+		// wait for sync
+		time.Sleep(time.Second)
+		ret = mdb.Exec(conn, utils.ToCmdLine("GET", "1"))
+		bulkRet, ok := ret.(*protocol.BulkReply)
+		if ok {
+			if bytes.Equal(bulkRet.Arg, []byte("1")) {
+				success = true
+				break
+			}
+		}
+	}
+	if !success {
+		t.Error("sync failed")
+		return
+	}
+
+	// receive aof
+	ret = masterCli.Send(utils.ToCmdLine("set", "1", "2"))
+	asserts.AssertStatusReply(t, ret, "OK")
+	success = false
+	for i := 0; i < 10; i++ {
+		// wait for sync
+		time.Sleep(time.Second)
+		ret = mdb.Exec(conn, utils.ToCmdLine("GET", "1"))
+		bulkRet, ok := ret.(*protocol.BulkReply)
+		if ok {
+			if bytes.Equal(bulkRet.Arg, []byte("2")) {
+				success = true
+				break
+			}
+		}
+	}
+	if !success {
+		t.Error("sync failed")
+		return
+	}
+	err = mdb.replication.sendAck2Master()
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	// test reconnect
+	config.Properties.ReplTimeout = 1
+	_ = mdb.replication.masterConn.Close()
+	ret = masterCli.Send(utils.ToCmdLine("set", "1", "3"))
+	asserts.AssertStatusReply(t, ret, "OK")
+	mdb.slaveCron()
+	success = false
+	for i := 0; i < 10; i++ {
+		// wait for sync
+		time.Sleep(time.Second)
+		ret = mdb.Exec(conn, utils.ToCmdLine("GET", "1"))
+		bulkRet, ok := ret.(*protocol.BulkReply)
+		if ok {
+			if bytes.Equal(bulkRet.Arg, []byte("3")) {
+				success = true
+				break
+			}
+		}
+	}
+	if !success {
+		t.Error("sync failed")
+		return
+	}
+
+	// test slave of no one
+	ret = mdb.Exec(conn, utils.ToCmdLine("SLAVEOF", "NO", "ONE"))
+	asserts.AssertStatusReply(t, ret, "OK")
+	ret = masterCli.Send(utils.ToCmdLine("set", "1", "4"))
+	asserts.AssertStatusReply(t, ret, "OK")
+	ret = mdb.Exec(conn, utils.ToCmdLine("GET", "1"))
+	asserts.AssertBulkReply(t, ret, "3")
+	ret = mdb.Exec(conn, utils.ToCmdLine("SLAVEOF", "127.0.0.1", "6379"))
+	asserts.AssertStatusReply(t, ret, "OK")
+	success = false
+	for i := 0; i < 30; i++ {
+		// wait for sync
+		time.Sleep(time.Second)
+		ret = mdb.Exec(conn, utils.ToCmdLine("GET", "1"))
+		bulkRet, ok := ret.(*protocol.BulkReply)
+		if ok {
+			if bytes.Equal(bulkRet.Arg, []byte("4")) {
+				success = true
+				break
+			}
+		}
+	}
+	if !success {
+		t.Error("sync failed")
+		return
+	}
+
+	err = mdb.replication.close()
+	if err != nil {
+		t.Error("cannot close")
+	}
+}
--- a/database/router.go
+++ b/database/router.go
@@ -14,15 +14,30 @@ type command struct {
 	flags    int
 }

+const (
+	flagWrite    = 0
+	flagReadOnly = 1
+)
+
 // RegisterCommand registers a new command
 // arity means allowed number of cmdArgs, arity < 0 means len(args) >= -arity.
 // for example: the arity of `get` is 2, `mget` is -2
-func RegisterCommand(name string, executor ExecFunc, prepare PreFunc, rollback UndoFunc, arity int) {
+func RegisterCommand(name string, executor ExecFunc, prepare PreFunc, rollback UndoFunc, arity int, flags int) {
 	name = strings.ToLower(name)
 	cmdTable[name] = &command{
 		executor: executor,
 		prepare:  prepare,
 		undo:     rollback,
 		arity:    arity,
+		flags:    flags,
 	}
 }
+
+func isReadOnlyCommand(name string) bool {
+	name = strings.ToLower(name)
+	cmd := cmdTable[name]
+	if cmd == nil {
+		return false
+	}
+	return cmd.flags&flagReadOnly > 0
+}
--- a/database/set.go
+++ b/database/set.go
@@ -479,17 +479,17 @@ func execSRandMember(db *DB, args [][]byte) redis.Reply {
 }

 func init() {
-	RegisterCommand("SAdd", execSAdd, writeFirstKey, undoSetChange, -3)
-	RegisterCommand("SIsMember", execSIsMember, readFirstKey, nil, 3)
-	RegisterCommand("SRem", execSRem, writeFirstKey, undoSetChange, -3)
-	RegisterCommand("SPop", execSPop, writeFirstKey, undoSetChange, -2)
-	RegisterCommand("SCard", execSCard, readFirstKey, nil, 2)
-	RegisterCommand("SMembers", execSMembers, readFirstKey, nil, 2)
-	RegisterCommand("SInter", execSInter, prepareSetCalculate, nil, -2)
-	RegisterCommand("SInterStore", execSInterStore, prepareSetCalculateStore, rollbackFirstKey, -3)
-	RegisterCommand("SUnion", execSUnion, prepareSetCalculate, nil, -2)
-	RegisterCommand("SUnionStore", execSUnionStore, prepareSetCalculateStore, rollbackFirstKey, -3)
-	RegisterCommand("SDiff", execSDiff, prepareSetCalculate, nil, -2)
-	RegisterCommand("SDiffStore", execSDiffStore, prepareSetCalculateStore, rollbackFirstKey, -3)
-	RegisterCommand("SRandMember", execSRandMember, readFirstKey, nil, -2)
+	RegisterCommand("SAdd", execSAdd, writeFirstKey, undoSetChange, -3, flagWrite)
+	RegisterCommand("SIsMember", execSIsMember, readFirstKey, nil, 3, flagReadOnly)
+	RegisterCommand("SRem", execSRem, writeFirstKey, undoSetChange, -3, flagWrite)
+	RegisterCommand("SPop", execSPop, writeFirstKey, undoSetChange, -2, flagWrite)
+	RegisterCommand("SCard", execSCard, readFirstKey, nil, 2, flagReadOnly)
+	RegisterCommand("SMembers", execSMembers, readFirstKey, nil, 2, flagReadOnly)
+	RegisterCommand("SInter", execSInter, prepareSetCalculate, nil, -2, flagReadOnly)
+	RegisterCommand("SInterStore", execSInterStore, prepareSetCalculateStore, rollbackFirstKey, -3, flagWrite)
+	RegisterCommand("SUnion", execSUnion, prepareSetCalculate, nil, -2, flagReadOnly)
+	RegisterCommand("SUnionStore", execSUnionStore, prepareSetCalculateStore, rollbackFirstKey, -3, flagWrite)
+	RegisterCommand("SDiff", execSDiff, prepareSetCalculate, nil, -2, flagReadOnly)
+	RegisterCommand("SDiffStore", execSDiffStore, prepareSetCalculateStore, rollbackFirstKey, -3, flagWrite)
+	RegisterCommand("SRandMember", execSRandMember, readFirstKey, nil, -2, flagReadOnly)
 }
--- a/database/single_db.go
+++ b/database/single_db.go
@@ -226,7 +226,15 @@ func (db *DB) Flush() {
 	db.data.Clear()
 	db.ttlMap.Clear()
 	db.locker = lock.Make(lockerSize)
+}

+func (db *DB) Load(db2 *DB) {
+	db.stopWorld.Add(1)
+	defer db.stopWorld.Done()
+
+	db.data = db2.data
+	db.ttlMap = db2.ttlMap
+	db.locker = lock.Make(lockerSize)
 }

 /* ---- Lock Function ----- */
@@ -280,6 +288,7 @@ func (db *DB) Persist(key string) {

 // IsExpired check whether a key is expired
 func (db *DB) IsExpired(key string) bool {
+	db.stopWorld.Wait()
 	rawExpireTime, ok := db.ttlMap.Get(key)
 	if !ok {
 		return false
@@ -295,6 +304,7 @@ func (db *DB) IsExpired(key string) bool {
 /* --- add version --- */

 func (db *DB) addVersion(keys ...string) {
+	db.stopWorld.Wait()
 	for _, key := range keys {
 		versionCode := db.GetVersion(key)
 		db.versionMap.Put(key, versionCode+1)
@@ -303,6 +313,7 @@ func (db *DB) addVersion(keys ...string) {

 // GetVersion returns version code for given key
 func (db *DB) GetVersion(key string) uint32 {
+	db.stopWorld.Wait()
 	entity, ok := db.versionMap.Get(key)
 	if !ok {
 		return 0
@@ -312,6 +323,7 @@ func (db *DB) GetVersion(key string) uint32 {

 // ForEach traverses all the keys in the database
 func (db *DB) ForEach(cb func(key string, data *database.DataEntity, expiration *time.Time) bool) {
+	db.stopWorld.Wait()
 	db.data.ForEach(func(key string, raw interface{}) bool {
 		entity, _ := raw.(*database.DataEntity)
 		var expiration *time.Time
--- a/database/sortedset.go
+++ b/database/sortedset.go
@@ -591,18 +591,18 @@ func undoZIncr(db *DB, args [][]byte) []CmdLine {
 }

 func init() {
-	RegisterCommand("ZAdd", execZAdd, writeFirstKey, undoZAdd, -4)
-	RegisterCommand("ZScore", execZScore, readFirstKey, nil, 3)
-	RegisterCommand("ZIncrBy", execZIncrBy, writeFirstKey, undoZIncr, 4)
-	RegisterCommand("ZRank", execZRank, readFirstKey, nil, 3)
-	RegisterCommand("ZCount", execZCount, readFirstKey, nil, 4)
-	RegisterCommand("ZRevRank", execZRevRank, readFirstKey, nil, 3)
-	RegisterCommand("ZCard", execZCard, readFirstKey, nil, 2)
-	RegisterCommand("ZRange", execZRange, readFirstKey, nil, -4)
-	RegisterCommand("ZRangeByScore", execZRangeByScore, readFirstKey, nil, -4)
-	RegisterCommand("ZRevRange", execZRevRange, readFirstKey, nil, -4)
-	RegisterCommand("ZRevRangeByScore", execZRevRangeByScore, readFirstKey, nil, -4)
-	RegisterCommand("ZRem", execZRem, writeFirstKey, undoZRem, -3)
-	RegisterCommand("ZRemRangeByScore", execZRemRangeByScore, writeFirstKey, rollbackFirstKey, 4)
-	RegisterCommand("ZRemRangeByRank", execZRemRangeByRank, writeFirstKey, rollbackFirstKey, 4)
+	RegisterCommand("ZAdd", execZAdd, writeFirstKey, undoZAdd, -4, flagWrite)
+	RegisterCommand("ZScore", execZScore, readFirstKey, nil, 3, flagReadOnly)
+	RegisterCommand("ZIncrBy", execZIncrBy, writeFirstKey, undoZIncr, 4, flagWrite)
+	RegisterCommand("ZRank", execZRank, readFirstKey, nil, 3, flagReadOnly)
+	RegisterCommand("ZCount", execZCount, readFirstKey, nil, 4, flagReadOnly)
+	RegisterCommand("ZRevRank", execZRevRank, readFirstKey, nil, 3, flagReadOnly)
+	RegisterCommand("ZCard", execZCard, readFirstKey, nil, 2, flagReadOnly)
+	RegisterCommand("ZRange", execZRange, readFirstKey, nil, -4, flagReadOnly)
+	RegisterCommand("ZRangeByScore", execZRangeByScore, readFirstKey, nil, -4, flagReadOnly)
+	RegisterCommand("ZRevRange", execZRevRange, readFirstKey, nil, -4, flagReadOnly)
+	RegisterCommand("ZRevRangeByScore", execZRevRangeByScore, readFirstKey, nil, -4, flagReadOnly)
+	RegisterCommand("ZRem", execZRem, writeFirstKey, undoZRem, -3, flagWrite)
+	RegisterCommand("ZRemRangeByScore", execZRemRangeByScore, writeFirstKey, rollbackFirstKey, 4, flagWrite)
+	RegisterCommand("ZRemRangeByRank", execZRemRangeByRank, writeFirstKey, rollbackFirstKey, 4, flagWrite)
 }
--- a/database/string.go
+++ b/database/string.go
@@ -826,29 +826,29 @@ func execBitPos(db *DB, args [][]byte) redis.Reply {
 }

 func init() {
-	RegisterCommand("Set", execSet, writeFirstKey, rollbackFirstKey, -3)
-	RegisterCommand("SetNx", execSetNX, writeFirstKey, rollbackFirstKey, 3)
-	RegisterCommand("SetEX", execSetEX, writeFirstKey, rollbackFirstKey, 4)
-	RegisterCommand("PSetEX", execPSetEX, writeFirstKey, rollbackFirstKey, 4)
-	RegisterCommand("MSet", execMSet, prepareMSet, undoMSet, -3)
-	RegisterCommand("MGet", execMGet, prepareMGet, nil, -2)
-	RegisterCommand("MSetNX", execMSetNX, prepareMSet, undoMSet, -3)
-	RegisterCommand("Get", execGet, readFirstKey, nil, 2)
-	RegisterCommand("GetEX", execGetEX, writeFirstKey, rollbackFirstKey, -2)
-	RegisterCommand("GetSet", execGetSet, writeFirstKey, rollbackFirstKey, 3)
-	RegisterCommand("GetDel", execGetDel, writeFirstKey, rollbackFirstKey, 2)
-	RegisterCommand("Incr", execIncr, writeFirstKey, rollbackFirstKey, 2)
-	RegisterCommand("IncrBy", execIncrBy, writeFirstKey, rollbackFirstKey, 3)
-	RegisterCommand("IncrByFloat", execIncrByFloat, writeFirstKey, rollbackFirstKey, 3)
-	RegisterCommand("Decr", execDecr, writeFirstKey, rollbackFirstKey, 2)
-	RegisterCommand("DecrBy", execDecrBy, writeFirstKey, rollbackFirstKey, 3)
-	RegisterCommand("StrLen", execStrLen, readFirstKey, nil, 2)
-	RegisterCommand("Append", execAppend, writeFirstKey, rollbackFirstKey, 3)
-	RegisterCommand("SetRange", execSetRange, writeFirstKey, rollbackFirstKey, 4)
-	RegisterCommand("GetRange", execGetRange, readFirstKey, nil, 4)
-	RegisterCommand("SetBit", execSetBit, writeFirstKey, rollbackFirstKey, 4)
-	RegisterCommand("GetBit", execGetBit, readFirstKey, nil, 3)
-	RegisterCommand("BitCount", execBitCount, readFirstKey, nil, -2)
-	RegisterCommand("BitPos", execBitPos, readFirstKey, nil, -3)
+	RegisterCommand("Set", execSet, writeFirstKey, rollbackFirstKey, -3, flagWrite)
+	RegisterCommand("SetNx", execSetNX, writeFirstKey, rollbackFirstKey, 3, flagWrite)
+	RegisterCommand("SetEX", execSetEX, writeFirstKey, rollbackFirstKey, 4, flagWrite)
+	RegisterCommand("PSetEX", execPSetEX, writeFirstKey, rollbackFirstKey, 4, flagWrite)
+	RegisterCommand("MSet", execMSet, prepareMSet, undoMSet, -3, flagWrite)
+	RegisterCommand("MGet", execMGet, prepareMGet, nil, -2, flagReadOnly)
+	RegisterCommand("MSetNX", execMSetNX, prepareMSet, undoMSet, -3, flagWrite)
+	RegisterCommand("Get", execGet, readFirstKey, nil, 2, flagReadOnly)
+	RegisterCommand("GetEX", execGetEX, writeFirstKey, rollbackFirstKey, -2, flagReadOnly)
+	RegisterCommand("GetSet", execGetSet, writeFirstKey, rollbackFirstKey, 3, flagWrite)
+	RegisterCommand("GetDel", execGetDel, writeFirstKey, rollbackFirstKey, 2, flagWrite)
+	RegisterCommand("Incr", execIncr, writeFirstKey, rollbackFirstKey, 2, flagWrite)
+	RegisterCommand("IncrBy", execIncrBy, writeFirstKey, rollbackFirstKey, 3, flagWrite)
+	RegisterCommand("IncrByFloat", execIncrByFloat, writeFirstKey, rollbackFirstKey, 3, flagWrite)
+	RegisterCommand("Decr", execDecr, writeFirstKey, rollbackFirstKey, 2, flagWrite)
+	RegisterCommand("DecrBy", execDecrBy, writeFirstKey, rollbackFirstKey, 3, flagWrite)
+	RegisterCommand("StrLen", execStrLen, readFirstKey, nil, 2, flagReadOnly)
+	RegisterCommand("Append", execAppend, writeFirstKey, rollbackFirstKey, 3, flagWrite)
+	RegisterCommand("SetRange", execSetRange, writeFirstKey, rollbackFirstKey, 4, flagWrite)
+	RegisterCommand("GetRange", execGetRange, readFirstKey, nil, 4, flagReadOnly)
+	RegisterCommand("SetBit", execSetBit, writeFirstKey, rollbackFirstKey, 4, flagWrite)
+	RegisterCommand("GetBit", execGetBit, readFirstKey, nil, 3, flagReadOnly)
+	RegisterCommand("BitCount", execBitCount, readFirstKey, nil, -2, flagReadOnly)
+	RegisterCommand("BitPos", execBitPos, readFirstKey, nil, -3, flagReadOnly)

 }
--- a/database/sys.go
+++ b/database/sys.go
@@ -41,5 +41,5 @@ func isAuthenticated(c redis.Connection) bool {
 }

 func init() {
-	RegisterCommand("ping", Ping, noPrepare, nil, -1)
+	RegisterCommand("ping", Ping, noPrepare, nil, -1, flagReadOnly)
 }
--- a/database/transaction.go
+++ b/database/transaction.go
@@ -1,17 +1,11 @@
 package database

 import (
-	"github.com/hdt3213/godis/datastruct/set"
 	"github.com/hdt3213/godis/interface/redis"
 	"github.com/hdt3213/godis/redis/protocol"
 	"strings"
 )

-var forbiddenInMulti = set.Make(
-	"flushdb",
-	"flushall",
-)
-
 // Watch set watching keys
 func Watch(db *DB, conn redis.Connection, args [][]byte) redis.Reply {
 	watching := conn.GetWatching()
@@ -29,7 +23,7 @@ func execGetVersion(db *DB, args [][]byte) redis.Reply {
 }

 func init() {
-	RegisterCommand("GetVer", execGetVersion, readAllKeys, nil, 2)
+	RegisterCommand("GetVer", execGetVersion, readAllKeys, nil, 2, flagReadOnly)
 }

 // invoker should lock watching keys
@@ -59,9 +53,6 @@ func EnqueueCmd(conn redis.Connection, cmdLine [][]byte) redis.Reply {
 	if !ok {
 		return protocol.MakeErrReply("ERR unknown command '" + cmdName + "'")
 	}
-	if forbiddenInMulti.Has(cmdName) {
-		return protocol.MakeErrReply("ERR command '" + cmdName + "' cannot be used in MULTI")
-	}
 	if cmd.prepare == nil {
 		return protocol.MakeErrReply("ERR command '" + cmdName + "' cannot be used in MULTI")
 	}
--- a/database/util_test.go
+++ b/database/util_test.go
@@ -11,8 +11,6 @@ func makeTestDB() *DB {
 		versionMap: dict.MakeConcurrent(dataDictSize),
 		ttlMap:     dict.MakeConcurrent(ttlDictSize),
 		locker:     lock.Make(lockerSize),
-		addAof: func(line CmdLine) {
-
-		},
+		addAof:     func(line CmdLine) {},
 	}
 }
--- a/interface/redis/conn.go
+++ b/interface/redis/conn.go
@@ -23,4 +23,7 @@ type Connection interface {
 	// used for multi database
 	GetDBIndex() int
 	SelectDB(int)
+	// returns role of conn, such as connection with client, connection with master node
+	GetRole() int32
+	SetRole(int32)
 }
--- a/redis.conf
+++ b/redis.conf
@@ -2,6 +2,6 @@ bind 0.0.0.0
 port 6399
 maxclients 128

-appendonly no
-appendfilename appendonly.aof
-dbfilename test.rdb
+#appendonly no
+#appendfilename appendonly.aof
+#dbfilename test.rdb
--- a/redis/connection/conn.go
+++ b/redis/connection/conn.go
@@ -8,6 +8,13 @@ import (
 	"time"
 )

+const (
+	// NormalCli is client with user
+	NormalCli = iota
+	// ReplicationRecvCli is fake client with replication master
+	ReplicationRecvCli
+)
+
 // Connection represents a connection with a redis-cli
 type Connection struct {
 	conn net.Conn
@@ -31,6 +38,7 @@ type Connection struct {

 	// selected db
 	selectedDB int
+	role       int32
 }

 // RemoteAddr returns the remote network address
@@ -148,6 +156,18 @@ func (c *Connection) ClearQueuedCmds() {
 	c.queue = nil
 }

+// GetRole returns role of connection, such as connection with master
+func (c *Connection) GetRole() int32 {
+	if c == nil {
+		return NormalCli
+	}
+	return c.role
+}
+
+func (c *Connection) SetRole(r int32) {
+	c.role = r
+}
+
 // GetWatching returns watching keys and their version code when started watching
 func (c *Connection) GetWatching() map[string]uint32 {
 	if c.watching == nil {
--- a/redis/parser/parser.go
+++ b/redis/parser/parser.go
@@ -65,6 +65,7 @@ type readState struct {
 	msgType           byte
 	args              [][]byte
 	bulkLen           int64
+	readingRepl       bool
 }

 func (s *readState) finished() bool {
@@ -74,9 +75,10 @@ func (s *readState) finished() bool {
 func parse0(reader io.Reader, ch chan<- *Payload) {
 	defer func() {
 		if err := recover(); err != nil {
-			logger.Error(string(debug.Stack()))
+			logger.Error(err, string(debug.Stack()))
 		}
 	}()
+
 	bufReader := bufio.NewReader(reader)
 	var state readState
 	var err error
@@ -187,16 +189,22 @@ func readLine(bufReader *bufio.Reader, state *readState) ([]byte, bool, error) {
 			return nil, false, errors.New("protocol error: " + string(msg))
 		}
 	} else { // read bulk line (binary safe)
-		msg = make([]byte, state.bulkLen+2)
+		// there is CRLF between BulkReply in normal stream
+		// but there is no CRLF between RDB and following AOF
+		bulkLen := state.bulkLen + 2
+		if state.readingRepl {
+			bulkLen -= 2
+		}
+		msg = make([]byte, bulkLen)
 		_, err = io.ReadFull(bufReader, msg)
 		if err != nil {
 			return nil, true, err
 		}
-		if len(msg) == 0 ||
-			msg[len(msg)-2] != '\r' ||
-			msg[len(msg)-1] != '\n' {
-			return nil, false, errors.New("protocol error: " + string(msg))
-		}
+		//if len(msg) == 0 ||
+		//	msg[len(msg)-2] != '\r' ||
+		//	msg[len(msg)-1] != '\n' {
+		//	return nil, false, errors.New("protocol error: " + string(msg))
+		//}
 		state.bulkLen = 0
 	}
 	return msg, false, nil
--- a/redis/protocol/reply.go
+++ b/redis/protocol/reply.go
@@ -108,6 +108,11 @@ func (r *StatusReply) ToBytes() []byte {
 	return []byte("+" + r.Status + CRLF)
 }

+// IsOKReply returns true if the given protocol is +OK
+func IsOKReply(reply redis.Reply) bool {
+	return string(reply.ToBytes()) == "+OK\r\n"
+}
+
 /* ---- Int Reply ---- */

 // IntReply stores an int64 number