basic cluster mode

README.md

@@ -126,7 +126,7 @@ If you want to read my code in this repository, here is a simple guidance.
 
 I suggest focusing on the following directories:
 
-- server: the tcp server
+- tcp: the tcp server
 - redis: the redis protocol parser
 - datastruct: the implements of data structures
     - dict: a concurrent hash map

redis.conf

@@ -4,3 +4,6 @@ maxclients 128
 
 appendonly yes
 appendfilename appendonly.aof
+
+peers localhost:6399
+self  localhost:6399

src/cluster/cluster.go

@@ -0,0 +1,92 @@
+package cluster
+
+import (
+    "fmt"
+    "github.com/HDT3213/godis/src/config"
+    "github.com/HDT3213/godis/src/db"
+    "github.com/HDT3213/godis/src/interface/redis"
+    "github.com/HDT3213/godis/src/lib/consistenthash"
+    "github.com/HDT3213/godis/src/lib/logger"
+    "github.com/HDT3213/godis/src/redis/client"
+    "github.com/HDT3213/godis/src/redis/reply"
+    "runtime/debug"
+    "strings"
+)
+
+type Cluster struct {
+    self string
+
+    db         *db.DB
+    peerPicker *consistenthash.Map
+    peers      map[string]*client.Client
+}
+
+const (
+    replicas = 4
+)
+
+func MakeCluster() *Cluster {
+    cluster := &Cluster{
+        self: config.Properties.Self,
+
+        db:         db.MakeDB(),
+        peerPicker: consistenthash.New(replicas, nil),
+        peers:      make(map[string]*client.Client),
+    }
+    if config.Properties.Peers != nil && len(config.Properties.Peers) > 0 {
+        cluster.peerPicker.Add(config.Properties.Peers...)
+    }
+    return cluster
+}
+
+// args contains all
+type CmdFunc func(cluster *Cluster, c redis.Client, args [][]byte) redis.Reply
+
+func (cluster *Cluster) Close() {
+    cluster.db.Close()
+}
+
+var router = MakeRouter()
+
+func (cluster *Cluster) Exec(c redis.Client, args [][]byte) (result redis.Reply) {
+    defer func() {
+        if err := recover(); err != nil {
+            logger.Warn(fmt.Sprintf("error occurs: %v\n%s", err, string(debug.Stack())))
+            result = &reply.UnknownErrReply{}
+        }
+    }()
+
+    cmd := strings.ToLower(string(args[0]))
+    cmdFunc, ok := router[cmd]
+    if !ok {
+        return reply.MakeErrReply("ERR unknown command '" + cmd + "'")
+    }
+    result = cmdFunc(cluster, c, args)
+    return
+}
+
+// relay command to peer
+func (cluster *Cluster) Relay(key string, c redis.Client, args [][]byte) redis.Reply {
+    peer := cluster.peerPicker.Get(key)
+    if peer == cluster.self {
+        // to self db
+        return cluster.db.Exec(c, args)
+    } else {
+        peerClient, ok := cluster.peers[peer]
+        // lazy init
+        if !ok {
+            var err error
+            peerClient, err = client.MakeClient(peer)
+            if err != nil {
+                return reply.MakeErrReply(err.Error())
+            }
+            peerClient.Start()
+            cluster.peers[peer] = peerClient
+        }
+        return peerClient.Send(args)
+    }
+}
+
+func (cluster *Cluster) AfterClientClose(c redis.Client) {
+
+}

src/cluster/router.go

@@ -0,0 +1,102 @@
+package cluster
+
+import "github.com/HDT3213/godis/src/interface/redis"
+
+func defaultFunc(cluster *Cluster, c redis.Client, args [][]byte) redis.Reply {
+    key := string(args[1])
+    return cluster.Relay(key, c, args)
+}
+
+func MakeRouter() map[string]CmdFunc {
+    routerMap := make(map[string]CmdFunc)
+    //routerMap["ping"] = defaultFunc
+
+    //routerMap["del"] = Del
+    routerMap["expire"] = defaultFunc
+    routerMap["expireat"] = defaultFunc
+    routerMap["pexpire"] = defaultFunc
+    routerMap["pexpireat"] = defaultFunc
+    routerMap["ttl"] = defaultFunc
+    routerMap["pttl"] = defaultFunc
+    routerMap["persist"] = defaultFunc
+    routerMap["exists"] = defaultFunc
+    routerMap["type"] = defaultFunc
+    //routerMap["rename"] = Rename
+    //routerMap["renamenx"] = RenameNx
+
+    routerMap["set"] = defaultFunc
+    routerMap["setnx"] = defaultFunc
+    routerMap["setex"] = defaultFunc
+    routerMap["psetex"] = defaultFunc
+    //routerMap["mset"] = MSet
+    //routerMap["mget"] = MGet
+    //routerMap["msetnx"] = MSetNX
+    routerMap["get"] = defaultFunc
+    routerMap["getset"] = defaultFunc
+    routerMap["incr"] = defaultFunc
+    routerMap["incrby"] = defaultFunc
+    routerMap["incrbyfloat"] = defaultFunc
+    routerMap["decr"] = defaultFunc
+    routerMap["decrby"] = defaultFunc
+
+    routerMap["lpush"] = defaultFunc
+    routerMap["lpushx"] = defaultFunc
+    routerMap["rpush"] = defaultFunc
+    routerMap["rpushx"] = defaultFunc
+    routerMap["lpop"] = defaultFunc
+    routerMap["rpop"] = defaultFunc
+    //routerMap["rpoplpush"] = RPopLPush
+    routerMap["lrem"] = defaultFunc
+    routerMap["llen"] = defaultFunc
+    routerMap["lindex"] = defaultFunc
+    routerMap["lset"] = defaultFunc
+    routerMap["lrange"] = defaultFunc
+
+    routerMap["hset"] = defaultFunc
+    routerMap["hsetnx"] = defaultFunc
+    routerMap["hget"] = defaultFunc
+    routerMap["hexists"] = defaultFunc
+    routerMap["hdel"] = defaultFunc
+    routerMap["hlen"] = defaultFunc
+    routerMap["hmget"] = defaultFunc
+    routerMap["hmset"] = defaultFunc
+    routerMap["hkeys"] = defaultFunc
+    routerMap["hvals"] = defaultFunc
+    routerMap["hgetall"] = defaultFunc
+    routerMap["hincrby"] = defaultFunc
+    routerMap["hincrbyfloat"] = defaultFunc
+
+    routerMap["sadd"] = defaultFunc
+    routerMap["sismember"] = defaultFunc
+    routerMap["srem"] = defaultFunc
+    routerMap["scard"] = defaultFunc
+    routerMap["smembers"] = defaultFunc
+    routerMap["sinter"] = defaultFunc
+    routerMap["sinterstore"] = defaultFunc
+    routerMap["sunion"] = defaultFunc
+    routerMap["sunionstore"] = defaultFunc
+    routerMap["sdiff"] = defaultFunc
+    routerMap["sdiffstore"] = defaultFunc
+    routerMap["srandmember"] = defaultFunc
+
+    routerMap["zadd"] = defaultFunc
+    routerMap["zscore"] = defaultFunc
+    routerMap["zincrby"] = defaultFunc
+    routerMap["zrank"] = defaultFunc
+    routerMap["zcount"] = defaultFunc
+    routerMap["zrevrank"] = defaultFunc
+    routerMap["zcard"] = defaultFunc
+    routerMap["zrange"] = defaultFunc
+    routerMap["zrevrange"] = defaultFunc
+    routerMap["zrangebyscore"] = defaultFunc
+    routerMap["zrevrangebyscore"] = defaultFunc
+    routerMap["zrem"] = defaultFunc
+    routerMap["zremrangebyscore"] = defaultFunc
+    routerMap["zremrangebyrank"] = defaultFunc
+
+    //routerMap["flushdb"] = FlushDB
+    //routerMap["flushall"] = FlushAll
+    //routerMap["keys"] = Keys
+
+    return routerMap
+}

src/cluster/string.go

@@ -0,0 +1 @@
+package cluster

src/cmd/main.go

@@ -4,9 +4,8 @@ import (
 	"fmt"
 	"github.com/HDT3213/godis/src/config"
 	"github.com/HDT3213/godis/src/lib/logger"
-	"github.com/HDT3213/godis/src/redis/handler"
+    RedisServer "github.com/HDT3213/godis/src/redis/server"
-	"github.com/HDT3213/godis/src/server"
+	"github.com/HDT3213/godis/src/tcp"
-	"time"
 )
 
 func main() {
@@ -18,9 +17,7 @@ func main() {
 		TimeFormat: "2006-01-02",
 	})
 
-	server.ListenAndServe(&server.Config{
+	tcp.ListenAndServe(&tcp.Config{
 		Address:    fmt.Sprintf("%s:%d", config.Properties.Bind, config.Properties.Port),
-		MaxConnect: uint32(config.Properties.MaxClients),
+    }, RedisServer.MakeHandler())
-		Timeout:    2 * time.Second,
-	}, handler.MakeHandler())
 }

src/config/config.go

@@ -11,11 +11,13 @@ import (
 )
 
 type PropertyHolder struct {
-	Bind           string `cfg:"bind"`
+	Bind           string   `cfg:"bind"`
-	Port           int    `cfg:"port"`
+	Port           int      `cfg:"port"`
-	AppendOnly     bool   `cfg:"appendOnly"`
+	AppendOnly     bool     `cfg:"appendOnly"`
-	AppendFilename string `cfg:"appendFilename"`
+	AppendFilename string   `cfg:"appendFilename"`
-	MaxClients     int    `cfg:"maxclients"`
+	MaxClients     int      `cfg:"maxclients"`
+	Peers          []string `cfg:"peers"`
+	Self           string   `cfg:"self"`
 }
 
 var Properties *PropertyHolder
@@ -30,13 +32,7 @@ func init() {
 }
 
 func LoadConfig(configFilename string) *PropertyHolder {
-	// open config file
+	config := Properties
-	config := &PropertyHolder{
-		Bind:           "127.0.0.1",
-		Port:           6379,
-		AppendOnly:     true,
-		AppendFilename: "appendonly.aof",
-	}
 	file, err := os.Open(configFilename)
 	if err != nil {
 		log.Print(err)
@@ -55,7 +51,7 @@ func LoadConfig(configFilename string) *PropertyHolder {
 		pivot := strings.IndexAny(line, " ")
 		if pivot > 0 && pivot < len(line)-1 { // separator found
 			key := line[0:pivot]
-			value := line[pivot+1:]
+			value := strings.Trim(line[pivot+1:], " ")
 			rawMap[strings.ToLower(key)] = value
 		}
 	}
@@ -88,6 +84,11 @@ func LoadConfig(configFilename string) *PropertyHolder {
 			case reflect.Bool:
 				boolValue := "yes" == value
 				fieldVal.SetBool(boolValue)
+			case reflect.Slice:
+				if field.Type.Elem().Kind() == reflect.String {
+					slice := strings.Split(value, ",")
+					fieldVal.Set(reflect.ValueOf(slice))
+				}
 			}
 		}
 	}

src/lib/consistenthash/consistenthash.go

@@ -0,0 +1,62 @@
+package consistenthash
+
+import (
+    "hash/crc32"
+    "sort"
+    "strconv"
+)
+
+type HashFunc func(data []byte) uint32
+
+type Map struct {
+    hashFunc HashFunc
+    replicas int
+    keys     []int // sorted
+    hashMap  map[int]string
+}
+
+func New(replicas int, fn HashFunc) *Map {
+    m := &Map{
+        replicas: replicas,
+        hashFunc: fn,
+        hashMap:  make(map[int]string),
+    }
+    if m.hashFunc == nil {
+        m.hashFunc = crc32.ChecksumIEEE
+    }
+    return m
+}
+
+func (m *Map) IsEmpty() bool {
+    return len(m.keys) == 0
+}
+
+func (m *Map) Add(keys ...string) {
+    for _, key := range keys {
+        for i := 0; i < m.replicas; i++ {
+            hash := int(m.hashFunc([]byte(strconv.Itoa(i) + key)))
+            m.keys = append(m.keys, hash)
+            m.hashMap[hash] = key
+        }
+    }
+    sort.Ints(m.keys)
+}
+
+// Get gets the closest item in the hash to the provided key.
+func (m *Map) Get(key string) string {
+    if m.IsEmpty() {
+        return ""
+    }
+
+    hash := int(m.hashFunc([]byte(key)))
+
+    // Binary search for appropriate replica.
+    idx := sort.Search(len(m.keys), func(i int) bool { return m.keys[i] >= hash })
+
+    // Means we have cycled back to the first replica.
+    if idx == len(m.keys) {
+        idx = 0
+    }
+
+    return m.hashMap[m.keys[idx]]
+}

src/redis/client/client.go

@@ -0,0 +1,309 @@
+package client
+
+import (
+    "bufio"
+    "context"
+    "errors"
+    "github.com/HDT3213/godis/src/interface/redis"
+    "github.com/HDT3213/godis/src/lib/logger"
+    "github.com/HDT3213/godis/src/redis/reply"
+    "io"
+    "net"
+    "strconv"
+    "strings"
+    "sync"
+    "time"
+)
+
+type Client struct {
+    conn        net.Conn
+    sendingReqs chan *Request
+    waitingReqs chan *Request
+    ticker      *time.Ticker
+    addr        string
+
+    ctx        context.Context
+    cancelFunc context.CancelFunc
+    writing    *sync.WaitGroup
+}
+
+type Request struct {
+    args      [][]byte
+    reply     redis.Reply
+    heartbeat bool
+    waiting   *sync.WaitGroup
+}
+
+const (
+    chanSize = 256
+)
+
+func MakeClient(addr string) (*Client, error) {
+    conn, err := net.Dial("tcp", addr)
+    if err != nil {
+        return nil, err
+    }
+    ctx, cancel := context.WithCancel(context.Background())
+    return &Client{
+        addr:        addr,
+        conn:        conn,
+        sendingReqs: make(chan *Request, chanSize),
+        waitingReqs: make(chan *Request, chanSize),
+        ctx:         ctx,
+        cancelFunc:  cancel,
+        writing:     &sync.WaitGroup{},
+    }, nil
+}
+
+func (client *Client) Start() {
+    client.ticker = time.NewTicker(10 * time.Second)
+    go client.handleWrite()
+    go func() {
+        err := client.handleRead()
+        logger.Warn(err)
+    }()
+    go client.heartbeat()
+}
+
+func (client *Client) Close() {
+    // send stop signal
+    client.cancelFunc()
+
+    // wait stop process
+    client.writing.Wait()
+
+    // clean
+    _ = client.conn.Close()
+    close(client.sendingReqs)
+    close(client.waitingReqs)
+}
+
+func (client *Client) handleConnectionError(err error) error {
+    err1 := client.conn.Close()
+    if err1 != nil {
+        if opErr, ok := err1.(*net.OpError); ok {
+            if opErr.Err.Error() != "use of closed network connection" {
+                return err1
+            }
+        } else {
+            return err1
+        }
+    }
+    conn, err1 := net.Dial("tcp", client.addr)
+    if err1 != nil {
+        logger.Error(err1)
+        return err1
+    }
+    client.conn = conn
+    go func() {
+        _ = client.handleRead()
+    }()
+    return nil
+}
+
+func (client *Client) heartbeat() {
+loop:
+    for {
+        select {
+        case <-client.ticker.C:
+            client.sendingReqs <- &Request{
+                args:      [][]byte{[]byte("PING")},
+                heartbeat: true,
+            }
+        case <-client.ctx.Done():
+            break loop
+        }
+    }
+}
+
+func (client *Client) handleWrite() {
+    client.writing.Add(1)
+loop:
+    for {
+        select {
+        case req := <-client.sendingReqs:
+            client.doRequest(req)
+        case <-client.ctx.Done():
+            break loop
+        }
+    }
+    client.writing.Done()
+}
+
+func (client *Client) Send(args [][]byte) redis.Reply {
+    request := &Request{
+        args:      args,
+        heartbeat: false,
+        waiting:   &sync.WaitGroup{},
+    }
+    request.waiting.Add(1)
+    client.sendingReqs <- request
+    request.waiting.Wait()
+    return request.reply
+}
+
+func (client *Client) doRequest(req *Request) {
+    bytes := reply.MakeMultiBulkReply(req.args).ToBytes()
+    _, err := client.conn.Write(bytes)
+    i := 0
+    for err != nil && i < 3 {
+        err = client.handleConnectionError(err)
+        if err == nil {
+            _, err = client.conn.Write(bytes)
+        }
+        i++
+    }
+    if err == nil {
+        client.waitingReqs <- req
+    }
+}
+
+func (client *Client) finishRequest(reply redis.Reply) {
+    request := <-client.waitingReqs
+    request.reply = reply
+    if request.waiting != nil {
+        request.waiting.Done()
+    }
+}
+
+func (client *Client) handleRead() error {
+    reader := bufio.NewReader(client.conn)
+    downloading := false
+    expectedArgsCount := 0
+    receivedCount := 0
+    msgType := byte(0) // first char of msg
+    var args [][]byte
+    var fixedLen int64 = 0
+    var err error
+    var msg []byte
+    for {
+        // read line
+        if fixedLen == 0 { // read normal line
+            msg, err = reader.ReadBytes('\n')
+            if err != nil {
+                if err == io.EOF || err == io.ErrUnexpectedEOF {
+                    logger.Info("connection close")
+                } else {
+                    logger.Warn(err)
+                }
+
+                return errors.New("connection closed")
+            }
+            if len(msg) == 0 || msg[len(msg)-2] != '\r' {
+                return errors.New("protocol error")
+            }
+        } else { // read bulk line (binary safe)
+            msg = make([]byte, fixedLen+2)
+            _, err = io.ReadFull(reader, msg)
+            if err != nil {
+                if err == io.EOF || err == io.ErrUnexpectedEOF {
+                    return errors.New("connection closed")
+                } else {
+                    return err
+                }
+            }
+            if len(msg) == 0 ||
+                msg[len(msg)-2] != '\r' ||
+                msg[len(msg)-1] != '\n' {
+                return errors.New("protocol error")
+            }
+            fixedLen = 0
+        }
+
+        // parse line
+        if !downloading {
+            // receive new response
+            if msg[0] == '*' { // multi bulk response
+                // bulk multi msg
+                expectedLine, err := strconv.ParseUint(string(msg[1:len(msg)-2]), 10, 32)
+                if err != nil {
+                    return errors.New("protocol error: " + err.Error())
+                }
+                if expectedLine == 0 {
+                    client.finishRequest(&reply.EmptyMultiBulkReply{})
+                } else if expectedLine > 0 {
+                    msgType = msg[0]
+                    downloading = true
+                    expectedArgsCount = int(expectedLine)
+                    receivedCount = 0
+                    args = make([][]byte, expectedLine)
+                } else {
+                    return errors.New("protocol error")
+                }
+            } else if msg[0] == '$' { // bulk response
+                fixedLen, err = strconv.ParseInt(string(msg[1:len(msg)-2]), 10, 64)
+                if err != nil {
+                    return err
+                }
+                if fixedLen == -1 { // null bulk
+                    client.finishRequest(&reply.NullBulkReply{})
+                    fixedLen = 0
+                } else if fixedLen > 0 {
+                    msgType = msg[0]
+                    downloading = true
+                    expectedArgsCount = 1
+                    receivedCount = 0
+                    args = make([][]byte, 1)
+                } else {
+                    return errors.New("protocol error")
+                }
+            } else { // single line response
+                str := strings.TrimSuffix(string(msg), "\n")
+                str = strings.TrimSuffix(str, "\r")
+                var result redis.Reply
+                switch msg[0] {
+                case '+':
+                    result = reply.MakeStatusReply(str[1:])
+                case '-':
+                    result = reply.MakeErrReply(str[1:])
+                case ':':
+                    val, err := strconv.ParseInt(str[1:], 10, 64)
+                    if err != nil {
+                        return errors.New("protocol error")
+                    }
+                    result = reply.MakeIntReply(val)
+                }
+                client.finishRequest(result)
+            }
+        } else {
+            // receive following part of a request
+            line := msg[0 : len(msg)-2]
+            if line[0] == '$' {
+                fixedLen, err = strconv.ParseInt(string(line[1:]), 10, 64)
+                if err != nil {
+                    return err
+                }
+                if fixedLen <= 0 { // null bulk in multi bulks
+                    args[receivedCount] = []byte{}
+                    receivedCount++
+                    fixedLen = 0
+                }
+            } else {
+                args[receivedCount] = line
+                receivedCount++
+            }
+
+            // if sending finished
+            if receivedCount == expectedArgsCount {
+                downloading = false // finish downloading progress
+
+                request := <-client.waitingReqs
+                if msgType == '*' {
+                    request.reply = reply.MakeMultiBulkReply(args)
+                } else if msgType == '$' {
+                    request.reply = reply.MakeBulkReply(args[0])
+                }
+
+                if request.waiting != nil {
+                    request.waiting.Done()
+                }
+
+                // finish reply
+                expectedArgsCount = 0
+                receivedCount = 0
+                args = nil
+                msgType = byte(0)
+            }
+        }
+    }
+}

src/redis/client/client_test.go

@@ -0,0 +1,104 @@
+package client
+
+import (
+    "github.com/HDT3213/godis/src/lib/logger"
+    "github.com/HDT3213/godis/src/redis/reply"
+    "testing"
+)
+
+func TestClient(t *testing.T) {
+    logger.Setup(&logger.Settings{
+        Path:       "logs",
+        Name:       "godis",
+        Ext:        ".log",
+        TimeFormat: "2006-01-02",
+    })
+    client, err := MakeClient("localhost:6379")
+    if err != nil {
+        t.Error(err)
+    }
+    client.Start()
+
+    result := client.Send([][]byte{
+        []byte("PING"),
+    })
+    if statusRet, ok := result.(*reply.StatusReply); ok {
+        if statusRet.Status != "PONG" {
+            t.Error("`ping` failed, result: " + statusRet.Status)
+        }
+    }
+
+    result = client.Send([][]byte{
+        []byte("SET"),
+        []byte("a"),
+        []byte("a"),
+    })
+    if statusRet, ok := result.(*reply.StatusReply); ok {
+        if statusRet.Status != "OK" {
+            t.Error("`set` failed, result: " + statusRet.Status)
+        }
+    }
+
+    result = client.Send([][]byte{
+        []byte("GET"),
+        []byte("a"),
+    })
+    if bulkRet, ok := result.(*reply.BulkReply); ok {
+        if string(bulkRet.Arg) != "a" {
+            t.Error("`get` failed, result: " + string(bulkRet.Arg))
+        }
+    }
+
+    result = client.Send([][]byte{
+        []byte("DEL"),
+        []byte("a"),
+    })
+    if intRet, ok := result.(*reply.IntReply); ok {
+        if intRet.Code != 1 {
+            t.Error("`del` failed, result: " + string(intRet.Code))
+        }
+    }
+
+    result = client.Send([][]byte{
+        []byte("GET"),
+        []byte("a"),
+    })
+    if _, ok := result.(*reply.NullBulkReply); !ok {
+        t.Error("`get` failed, result: " + string(result.ToBytes()))
+    }
+
+    result = client.Send([][]byte{
+        []byte("DEL"),
+        []byte("arr"),
+    })
+
+    result = client.Send([][]byte{
+        []byte("RPUSH"),
+        []byte("arr"),
+        []byte("1"),
+        []byte("2"),
+        []byte("c"),
+    })
+    if intRet, ok := result.(*reply.IntReply); ok {
+        if intRet.Code != 3 {
+            t.Error("`rpush` failed, result: " + string(intRet.Code))
+        }
+    }
+
+    result = client.Send([][]byte{
+        []byte("LRANGE"),
+        []byte("arr"),
+        []byte("0"),
+        []byte("-1"),
+    })
+    if multiBulkRet, ok := result.(*reply.MultiBulkReply); ok {
+        if len(multiBulkRet.Args) != 3 ||
+            string(multiBulkRet.Args[0]) != "1" ||
+            string(multiBulkRet.Args[1]) != "2" ||
+            string(multiBulkRet.Args[2]) != "c" {
+            t.Error("`lrange` failed, result: " + string(multiBulkRet.ToBytes()))
+        }
+    }
+
+    client.Close()
+}

src/redis/server/client.go

@@ -1,4 +1,4 @@
-package handler
+package server
 
 import (
     "github.com/HDT3213/godis/src/lib/sync/atomic"

src/redis/server/handler.go

@@ -1,4 +1,4 @@
-package handler
+package server
 
 /*
  * A tcp.Handler implements redis protocol
@@ -7,6 +7,8 @@ package handler
 import (
     "bufio"
     "context"
+    "github.com/HDT3213/godis/src/cluster"
+    "github.com/HDT3213/godis/src/config"
     DBImpl "github.com/HDT3213/godis/src/db"
     "github.com/HDT3213/godis/src/interface/db"
     "github.com/HDT3213/godis/src/lib/logger"
@@ -30,8 +32,15 @@ type Handler struct {
 }
 
 func MakeHandler() *Handler {
+    var db db.DB
+    if config.Properties.Peers != nil &&
+        len(config.Properties.Peers) > 0 {
+        db = cluster.MakeCluster()
+    } else {
+        db = DBImpl.MakeDB()
+    }
     return &Handler{
-        db: DBImpl.MakeDB(),
+        db: db,
     }
 }
 

src/tcp/echo.go

@@ -1,4 +1,4 @@
-package server
+package tcp
 
 /**
  * A echo server to test whether the server is functioning normally

src/tcp/server.go

@@ -1,4 +1,4 @@
-package server
+package tcp
 
 /**
  * A tcp server