Golang 實(shí)現(xiàn) Redis系列(六)如何實(shí)現(xiàn) pipeline 模式的 redis 客戶端

type Client struct {
    conn        net.Conn // 與服務(wù)端的 tcp 連接
    pendingReqs chan *Request // 等待發(fā)送的請(qǐng)求
    waitingReqs chan *Request // 等待服務(wù)器響應(yīng)的請(qǐng)求
    ticker      *time.Ticker // 用于觸發(fā)心跳包的計(jì)時(shí)器
    addr        string

    ctx        context.Context
    cancelFunc context.CancelFunc
    writing    *sync.WaitGroup // 有請(qǐng)求正在處理不能立即停止，用于實(shí)現(xiàn) graceful shutdown
}

type Request struct {
    id        uint64 // 請(qǐng)求id
    args      [][]byte // 上行參數(shù)
    reply     redis.Reply // 收到的返回值
    heartbeat bool // 標(biāo)記是否是心跳請(qǐng)求
    waiting   *wait.Wait // 調(diào)用協(xié)程發(fā)送請(qǐng)求后通過 waitgroup 等待請(qǐng)求異步處理完成
    err       error
}

func (client *Client) Send(args [][]byte) redis.Reply {
	request := request{
		args:      args,
		heartbeat: false,
		waiting:   wait.Wait{},
	}
	request.waiting.Add(1)
	client.working.Add(1)
	defer client.working.Done()
	client.pendingReqs - request // 請(qǐng)求入隊(duì)
	timeout := request.waiting.WaitWithTimeout(maxWait) // 等待響應(yīng)或者超時(shí)
	if timeout {
		return reply.MakeErrReply("server time out")
	}
	if request.err != nil {
		return reply.MakeErrReply("request failed")
	}
	return request.reply
}

// 寫協(xié)程入口
func (client *Client) handleWrite() {
	for req := range client.pendingReqs {
		client.doRequest(req)
	}
}

// 發(fā)送請(qǐng)求
func (client *Client) doRequest(req *request) {
	if req == nil || len(req.args) == 0 {
		return
	}
    // 序列化請(qǐng)求
	re := reply.MakeMultiBulkReply(req.args)
	bytes := re.ToBytes()
	_, err := client.conn.Write(bytes)
	i := 0
    // 失敗重試
	for err != nil  i  3 {
		err = client.handleConnectionError(err)
		if err == nil {
			_, err = client.conn.Write(bytes)
		}
		i++
	}
	if err == nil {
        // 發(fā)送成功等待服務(wù)器響應(yīng)
		client.waitingReqs - req
	} else {
		req.err = err
		req.waiting.Done()
	}
}

// 收到服務(wù)端的響應(yīng)
func (client *Client) finishRequest(reply redis.Reply) {
	defer func() {
		if err := recover(); err != nil {
			debug.PrintStack()
			logger.Error(err)
		}
	}()
	request := -client.waitingReqs
	if request == nil {
		return
	}
	request.reply = reply
	if request.waiting != nil {
		request.waiting.Done()
	}
}

// 讀協(xié)程是個(gè) RESP 協(xié)議解析器
func (client *Client) handleRead() error {
	ch := parser.ParseStream(client.conn)
	for payload := range ch {
		if payload.Err != nil {
			client.finishRequest(reply.MakeErrReply(payload.Err.Error()))
			continue
		}
		client.finishRequest(payload.Data)
	}
	return nil
}

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() {
    // 先阻止新請(qǐng)求進(jìn)入隊(duì)列
    close(client.sendingReqs)

    // 等待處理中的請(qǐng)求完成
    client.writing.Wait()

    // 釋放資源
    _ = client.conn.Close() // 關(guān)閉與服務(wù)端的連接，連接關(guān)閉后讀協(xié)程會(huì)退出
    client.cancelFunc() // 使用 context 關(guān)閉讀協(xié)程
    close(client.waitingReqs) // 關(guān)閉隊(duì)列
}

func TestClient(t *testing.T) {
    client, err := MakeClient("localhost:6379")
    if err != nil {
        t.Error(err)
    }
    client.Start()

    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))
        }
    }
}