bug fix prefer replica in master-slave mode

internal/client/redis.go

@@ -5,7 +5,9 @@ import (
 	"context"
 	"crypto/tls"
 	"net"
+	"regexp"
 	"strconv"
+	"strings"
 	"time"
 
 	"RedisShake/internal/client/proto"
@@ -20,11 +22,11 @@ type Redis struct {
 	protoWriter *proto.Writer
 }
 
-func NewSentinelClient(ctx context.Context, address string, Tls bool) *Redis {
-	return NewRedisClient(ctx, address, "", "", Tls)
+func NewSentinelMasterClient(ctx context.Context, address string, Tls bool) *Redis {
+	return NewRedisClient(ctx, address, "", "", Tls, false)
 }
 
-func NewRedisClient(ctx context.Context, address string, username string, password string, Tls bool) *Redis {
+func NewRedisClient(ctx context.Context, address string, username string, password string, Tls bool, replica bool) *Redis {
 	r := new(Redis)
 	var conn net.Conn
 	var dialer = &net.Dialer{
@@ -71,10 +73,73 @@ func NewRedisClient(ctx context.Context, address string, username string, passwo
 	if reply != "PONG" {
 		panic("ping failed with reply: " + reply)
 	}
+	reply = r.DoWithStringReply("info", "replication")
+	// get best replica
+	if replica {
+		replicaInfo := getReplicaAddr(reply)
+		log.Infof("best replica: %s", replicaInfo.BestReplica)
+		r = NewRedisClient(ctx, replicaInfo.BestReplica, username, password, Tls, false)
+	}
 
 	return r
 }
 
+type Replica struct {
+	Addr   string
+	Offset string
+}
+
+type RedisReplicaInfo struct {
+	Role        string
+	BestReplica string
+}
+
+func getReplicaAddr(info string) RedisReplicaInfo {
+	infoReplica := RedisReplicaInfo{}
+	replicas := make([]Replica, 0)
+	slaveInfoRegexp := regexp.MustCompile(`slave\d+:ip=.*`)
+	for _, line := range strings.Split(info, "\n") {
+		line = strings.TrimSpace(line)
+		switch {
+		case strings.HasPrefix(line, "role:slave"):
+			infoReplica.Role = "slave"
+			return infoReplica
+		case strings.HasPrefix(line, "role:master"):
+			infoReplica.Role = "master"
+		case slaveInfoRegexp.MatchString(line):
+			slaveInfo := strings.Split(line, ":")
+			s1 := slaveInfo[1]
+			slaveInfo = strings.Split(s1, ",")
+			replica := Replica{}
+			var host string
+			var port string
+			var offset string
+			for _, item := range slaveInfo {
+				if strings.HasPrefix(item, "ip=") {
+					host = strings.Split(item, "=")[1]
+				}
+				if strings.HasPrefix(item, "port=") {
+					port = strings.Split(item, "=")[1]
+				}
+				if strings.HasPrefix(item, "offset=") {
+					offset = strings.Split(item, "=")[1]
+				}
+			}
+			replica.Addr = host + ":" + port
+			replica.Offset = offset
+			replicas = append(replicas, replica)
+		}
+	}
+	best := replicas[0]
+	for _, replica := range replicas {
+		if replica.Offset > best.Offset {
+			best = replica
+		}
+	}
+	infoReplica.BestReplica = best.Addr
+	return infoReplica
+}
+
 func (r *Redis) DoWithStringReply(args ...interface{}) string {
 	r.Send(args...)
 

internal/reader/scan_standalone_reader.go

@@ -63,7 +63,7 @@ type scanStandaloneReader struct {
 func NewScanStandaloneReader(ctx context.Context, opts *ScanReaderOptions) Reader {
 	r := new(scanStandaloneReader)
 	// dbs
-	c := client.NewRedisClient(ctx, opts.Address, opts.Username, opts.Password, opts.Tls)
+	c := client.NewRedisClient(ctx, opts.Address, opts.Username, opts.Password, opts.Tls, opts.PreferReplica)
 	if c.IsCluster() { // not use opts.Cluster, because user may use standalone mode to scan a cluster node
 		r.dbs = []int{0}
 	} else {
@@ -100,7 +100,7 @@ func (r *scanStandaloneReader) StartRead(ctx context.Context) chan *entry.Entry
 }
 
 func (r *scanStandaloneReader) subscript() {
-	c := client.NewRedisClient(r.ctx, r.opts.Address, r.opts.Username, r.opts.Password, r.opts.Tls)
+	c := client.NewRedisClient(r.ctx, r.opts.Address, r.opts.Username, r.opts.Password, r.opts.Tls, r.opts.PreferReplica)
 	if len(r.dbs) == 0 {
 		c.Send("psubscribe", "__keyevent@*__:*")
 	} else {
@@ -149,7 +149,7 @@ func (r *scanStandaloneReader) subscript() {
 }
 
 func (r *scanStandaloneReader) scan() {
-	c := client.NewRedisClient(r.ctx, r.opts.Address, r.opts.Username, r.opts.Password, r.opts.Tls)
+	c := client.NewRedisClient(r.ctx, r.opts.Address, r.opts.Username, r.opts.Password, r.opts.Tls, r.opts.PreferReplica)
 	defer c.Close()
 	for _, dbId := range r.dbs {
 		if dbId != 0 {
@@ -194,7 +194,7 @@ func (r *scanStandaloneReader) scan() {
 
 func (r *scanStandaloneReader) dump() {
 	nowDbId := 0
-	r.dumpClient = client.NewRedisClient(r.ctx, r.opts.Address, r.opts.Username, r.opts.Password, r.opts.Tls)
+	r.dumpClient = client.NewRedisClient(r.ctx, r.opts.Address, r.opts.Username, r.opts.Password, r.opts.Tls, r.opts.PreferReplica)
 	// Support prefer_replica=true in both Cluster and Standalone mode
 	if r.opts.PreferReplica {
 		r.dumpClient.Do("READONLY")

internal/reader/sync_standalone_reader.go

@@ -83,7 +83,7 @@ type syncStandaloneReader struct {
 func NewSyncStandaloneReader(ctx context.Context, opts *SyncReaderOptions) Reader {
 	r := new(syncStandaloneReader)
 	r.opts = opts
-	r.client = client.NewRedisClient(ctx, opts.Address, opts.Username, opts.Password, opts.Tls)
+	r.client = client.NewRedisClient(ctx, opts.Address, opts.Username, opts.Password, opts.Tls, opts.PreferReplica)
 	r.rd = r.client.BufioReader()
 	r.stat.Name = "reader_" + strings.Replace(opts.Address, ":", "_", -1)
 	r.stat.Address = opts.Address

internal/utils/cluster_nodes.go

@@ -11,7 +11,7 @@ import (
 )
 
 func GetRedisClusterNodes(ctx context.Context, address string, username string, password string, Tls bool, perferReplica bool) (addresses []string, slots [][]int) {
-	c := client.NewRedisClient(ctx, address, username, password, Tls)
+	c := client.NewRedisClient(ctx, address, username, password, Tls, false)
 	reply := c.DoWithStringReply("cluster", "nodes")
 	reply = strings.TrimSpace(reply)
 	slotsCount := 0

internal/writer/redis_sentinel_writer.go

@@ -8,7 +8,7 @@ import (
 )
 
 func NewRedisSentinelWriter(ctx context.Context, opts *RedisWriterOptions) Writer {
-	sentinel := client.NewSentinelClient(ctx, opts.Address, opts.Tls)
+	sentinel := client.NewSentinelMasterClient(ctx, opts.Address, opts.Tls)
 	sentinel.Send("SENTINEL", "GET-MASTER-ADDR-BY-NAME", opts.Master)
 	addr, err := sentinel.Receive()
 	if err != nil {

internal/writer/redis_standalone_writer.go

@@ -48,7 +48,7 @@ func NewRedisStandaloneWriter(ctx context.Context, opts *RedisWriterOptions) Wri
 	rw := new(redisStandaloneWriter)
 	rw.address = opts.Address
 	rw.stat.Name = "writer_" + strings.Replace(opts.Address, ":", "_", -1)
-	rw.client = client.NewRedisClient(ctx, opts.Address, opts.Username, opts.Password, opts.Tls)
+	rw.client = client.NewRedisClient(ctx, opts.Address, opts.Username, opts.Password, opts.Tls, false)
 	if opts.OffReply {
 		log.Infof("turn off the reply of write")
 		rw.offReply = true