redigo 学习笔记

redigo

接口 Conn

type Conn interface {
	// Close closes the connection.
	Close() error

	// Err returns a non-nil value when the connection is not usable.
	Err() error

	// Do sends a command to the server and returns the received reply.
	Do(commandName string, args ...interface{}) (reply interface{}, err error)

	// Send writes the command to the client's output buffer.
	Send(commandName string, args ...interface{}) error

	// Flush flushes the output buffer to the Redis server.
	Flush() error

	// Receive receives a single reply from the Redis server
	Receive() (reply interface{}, err error)
}

获取 Conn

常用 Dial 方法来获取一个 redis 链接

c, err := redis.Dial("tcp", "localhost:6379",
    redis.DialUsername("username"),
    redis.DialPassword("password"),
)
if err != nil {
    // handle error
}
defer c.Close()

// Dial connects to the Redis server at the given network and
// address using the specified options.
func Dial(network, address string, options ...DialOption) (Conn, error) {
	return DialContext(context.Background(), network, address, options...)
}

// DialContext connects to the Redis server at the given network and
// address using the specified options and context.
func DialContext(ctx context.Context, network, address string, options ...DialOption) (Conn, error) {
	do := dialOptions{
		dialer: &net.Dialer{
			KeepAlive: time.Minute * 5,
		}, 
	}
	for _, option := range options {
		option.f(&do) // 简化 赋值 
	}
	if do.dialContext == nil {
		do.dialContext = do.dialer.DialContext
	}

	netConn, err := do.dialContext(ctx, network, address) //使用 net.Dialer  dialContext 连接服务器
	if err != nil {
		return nil, err
	}

	if do.useTLS {
		var tlsConfig *tls.Config
		if do.tlsConfig == nil {
			tlsConfig = &tls.Config{InsecureSkipVerify: do.skipVerify}
		} else {
			tlsConfig = cloneTLSConfig(do.tlsConfig)
		}
		if tlsConfig.ServerName == "" {
			host, _, err := net.SplitHostPort(address)
			if err != nil {
				netConn.Close()
				return nil, err
			}
			tlsConfig.ServerName = host
		}

		tlsConn := tls.Client(netConn, tlsConfig)
		if err := tlsConn.Handshake(); err != nil {
			netConn.Close()
			return nil, err
		}
		netConn = tlsConn
	}

	c := &conn{
		conn:         netConn, // net.Conn 构造 Conn返回
		bw:           bufio.NewWriter(netConn),
		br:           bufio.NewReader(netConn),
		readTimeout:  do.readTimeout,
		writeTimeout: do.writeTimeout,
	}

	if do.password != "" {
		authArgs := make([]interface{}, 0, 2)
		if do.username != "" {
			authArgs = append(authArgs, do.username)
		}
		authArgs = append(authArgs, do.password)
		if _, err := c.Do("AUTH", authArgs...); err != nil { // auth
			netConn.Close()
			return nil, err
		}
	}

	if do.clientName != "" {
		if _, err := c.Do("CLIENT", "SETNAME", do.clientName); err != nil {
			netConn.Close()
			return nil, err
		}
	}

	if do.db != 0 {
		if _, err := c.Do("SELECT", do.db); err != nil { // db
			netConn.Close()
			return nil, err
		}
	}

	return c, nil
}

执行 Do

func (c *conn) Do(cmd string, args ...interface{}) (interface{}, error) {
	return c.DoWithTimeout(c.readTimeout, cmd, args...)
}

func (c *conn) DoWithTimeout(readTimeout time.Duration, cmd string, args ...interface{}) (interface{}, error) {
	c.mu.Lock()
	pending := c.pending
	c.pending = 0
	c.mu.Unlock()

	if cmd == "" && pending == 0 {
		return nil, nil
	}

	if c.writeTimeout != 0 {
		c.conn.SetWriteDeadline(time.Now().Add(c.writeTimeout)) //设置 写超时时间
	}

	if cmd != "" {
		if err := c.writeCommand(cmd, args); err != nil { //写命令
			return nil, c.fatal(err)
		}
	}

	if err := c.bw.Flush(); err != nil {
		return nil, c.fatal(err)
	}

	var deadline time.Time
	if readTimeout != 0 {
		deadline = time.Now().Add(readTimeout)
	}
	c.conn.SetReadDeadline(deadline) // 设置 读超时时间

	if cmd == "" {
		reply := make([]interface{}, pending)
		for i := range reply {
			r, e := c.readReply()
			if e != nil {
				return nil, c.fatal(e)
			}
			reply[i] = r
		}
		return reply, nil
	}

	var err error
	var reply interface{}
	for i := 0; i <= pending; i++ {
		var e error
		if reply, e = c.readReply(); e != nil { //readReply 读取结果
			return nil, c.fatal(e)
		}
		if e, ok := reply.(Error); ok && err == nil {
			err = e
		}
	}
	return reply, err
}

发送命令

redis 基本协议

*<参数数量> CR LF
$<参数 1 的字节数量> CR LF
<参数 1 的数据> CR LF
...
$<参数 N 的字节数量> CR LF
<参数 N 的数据> CR LF

示例：
*3
$3
SET
$5
mykey
$7
myvalue

func (c *conn) writeCommand(cmd string, args []interface{}) error {
	c.writeLen('*', 1+len(args))  // *<参数数量> CR LF
	if err := c.writeString(cmd); err != nil { // $<参数 1 的字节数量> CR LF <参数 1 的数据> CR LF
		return err 
	}
	for _, arg := range args {
		if err := c.writeArg(arg, true); err != nil { // $<参数 N 的字节数量> CR LF <参数 N 的数据> CR LF
			return err
		}
	}
	return nil
}

读取结果

func (c *conn) readReply() (interface{}, error) {
	line, err := c.readLine()
	if err != nil {
		return nil, err
	}
	if len(line) == 0 {
		return nil, protocolError("short response line")
	}
	switch line[0] {
	case '+':
		switch string(line[1:]) {
		case "OK":
			// Avoid allocation for frequent "+OK" response.
			return okReply, nil
		case "PONG":
			// Avoid allocation in PING command benchmarks :)
			return pongReply, nil
		default:
			return string(line[1:]), nil
		}
	case '-':
		return Error(string(line[1:])), nil
	case ':':
		return parseInt(line[1:])
	case '$':
		n, err := parseLen(line[1:])
		if n < 0 || err != nil {
			return nil, err
		}
		p := make([]byte, n)
		_, err = io.ReadFull(c.br, p)
		if err != nil {
			return nil, err
		}
		if line, err := c.readLine(); err != nil {
			return nil, err
		} else if len(line) != 0 {
			return nil, protocolError("bad bulk string format")
		}
		return p, nil
	case '*':
		n, err := parseLen(line[1:])
		if n < 0 || err != nil {
			return nil, err
		}
		r := make([]interface{}, n)
		for i := range r {
			r[i], err = c.readReply()
			if err != nil {
				return nil, err
			}
		}
		return r, nil
	}
	return nil, protocolError("unexpected response line")
}

结果转化

reply.go 中提供各种方法格式化返回结果

例如 String 方法

func String(reply interface{}, err error) (string, error) {
	if err != nil {
		return "", err
	}
	switch reply := reply.(type) {
	case []byte:
		return string(reply), nil
	case string:
		return reply, nil
	case nil:
		return "", ErrNil
	case Error:
		return "", reply
	}
	return "", fmt.Errorf("redigo: unexpected type for String, got type %T", reply)
}