Golang redis(六)redigo 发布订阅模式

我不是女神ヾ 2021-12-09 22:41 602阅读 0赞

#### 发布订阅 ####

使用Send，Flush和Receive方法实现Pub / Sub

c.Send("SUBSCRIBE", "example")
    c.Flush()
    for {
        reply, err := c.Receive()
        if err != nil {
            return err
        }
        // process pushed message
    }

PubSubConn封装Conn以实现订阅者提供简便方法。Subscribe，PSubscribe，Unsubscribe和PUnsubscribe方法发送和刷新订阅。receive方法将推送的消息转换对应的类型

psc := redis.PubSubConn{Conn: c}
    psc.Subscribe("example")
    for {
        switch v := psc.Receive().(type) {
        case redis.Message:
            fmt.Printf("%s: message: %s\n", v.Channel, v.Data)
        case redis.Subscription:
            fmt.Printf("%s: %s %d\n", v.Channel, v.Kind, v.Count)
        case error:
            return v
        }
    }

#### PubSubConn ####

定义

type PubSubConn struct {
        Conn Conn
    }

提供的方法：

1.Close 关闭连接  
`func (c PubSubConn) Close() error`

2.PSubscribe PSubscribe发布  
`func (c PubSubConn) PSubscribe(channel ...interface{}) error`

3.PUnsubscribe 取消发布， 如果没有给定， 则取消所有  
`func (c PubSubConn) PUnsubscribe(channel ...interface{}) error`

4.Ping 指定的数据向服务器发送PING 调用此方法时，连接必须至少订阅一个通道或模式  
`func (c PubSubConn) Ping(data string) error`

5.Receive 获取消息  
`func (c PubSubConn) Receive() interface{}`

6.ReceiveWithTimeout 带有超时时间的获取消息函数  
`func (c PubSubConn) ReceiveWithTimeout(timeout time.Duration) interface{}`

7.Subscribe 订阅  
`func (c PubSubConn) Subscribe(channel ...interface{}) error`

8.Unsubscribe 取消订阅  
`func (c PubSubConn) Unsubscribe(channel ...interface{}) error`

示例程序：

package main
    
    import (
       "context"
       "fmt"
       "time"
    
       "github.com/gomodule/redigo/redis"
    )
    
    // listenPubSubChannels listens for messages on Redis pubsub channels. The
    // onStart function is called after the channels are subscribed. The onMessage
    // function is called for each message.
    func listenPubSubChannels(ctx context.Context, redisServerAddr string,
       onStart func() error,
       onMessage func(channel string, data []byte) error,
       channels ...string) error {
       // A ping is set to the server with this period to test for the health of
       // the connection and server.
       const healthCheckPeriod = time.Minute
    
       c, err := redis.Dial("tcp", redisServerAddr,
          // Read timeout on server should be greater than ping period.
          redis.DialReadTimeout(healthCheckPeriod+10*time.Second),
          redis.DialWriteTimeout(10*time.Second))
       if err != nil {
          return err
       }
       defer c.Close()
    
       psc := redis.PubSubConn{Conn: c}
    
       if err := psc.Subscribe(redis.Args{}.AddFlat(channels)...); err != nil {
          return err
       }
    
       done := make(chan error, 1)
    
       // Start a goroutine to receive notifications from the server.
       go func() {
          for {
             switch n := psc.Receive().(type) {
             case error:
                done <- n
                return
             case redis.Message:
                if err := onMessage(n.Channel, n.Data); err != nil {
                   done <- err
                   return
                }
             case redis.Subscription:
                switch n.Count {
                case len(channels):
                   // Notify application when all channels are subscribed.
                   if err := onStart(); err != nil {
                      done <- err
                      return
                   }
                case 0:
                   // Return from the goroutine when all channels are unsubscribed.
                   done <- nil
                   return
                }
             }
          }
       }()
    
       ticker := time.NewTicker(healthCheckPeriod)
       defer ticker.Stop()
    loop:
       for err == nil {
          select {
          case <-ticker.C:
             // Send ping to test health of connection and server. If
             // corresponding pong is not received, then receive on the
             // connection will timeout and the receive goroutine will exit.
             if err = psc.Ping(""); err != nil {
                break loop
             }
          case <-ctx.Done():
             break loop
          case err := <-done:
             // Return error from the receive goroutine.
             return err
          }
       }
    
       // Signal the receiving goroutine to exit by unsubscribing from all channels.
       psc.Unsubscribe()
    
       // Wait for goroutine to complete.
       return <-done
    }
    
    func publish() {
       c, err := redis.Dial("tcp", "127.0.0.1:6379")
       if err != nil {
          fmt.Println(err)
          return
       }
       defer c.Close()
    
       c.Do("PUBLISH", "c1", "hello")
       c.Do("PUBLISH", "c2", "world")
       c.Do("PUBLISH", "c1", "goodbye")
    }
    
    // This example shows how receive pubsub notifications with cancelation and
    // health checks.
    func main() {
       redisServerAddr := "127.0.0.1:6379"
    
       ctx, cancel := context.WithCancel(context.Background())
    
       err := listenPubSubChannels(ctx,
          redisServerAddr,
          func() error {
             // The start callback is a good place to backfill missed
             // notifications. For the purpose of this example, a goroutine is
             // started to send notifications.
             go publish()
             return nil
          },
          func(channel string, message []byte) error {
             fmt.Printf("channel: %s, message: %s\n", channel, message)
    
             // For the purpose of this example, cancel the listener's context
             // after receiving last message sent by publish().
             if string(message) == "goodbye" {
                cancel()
             }
             return nil
          },
          "c1", "c2")
    
       if err != nil {
          fmt.Println(err)
          return
       }
    
    }

输出：

channel: c1, message: hello
    channel: c2, message: world
    channel: c1, message: goodbye