golang：对redigo的发布订阅机制的使用

红太狼 2022-01-28 04:21 189阅读 0赞

# golang中redis对redigo的发布订阅机制的使用 #

redigo 对redis的订阅机制放在pubsub.go里面,

订阅主题后通过Receive()函数接收发布到订阅主题的消息。

// Receive returns a pushed message as a Subscription, Message, Pong or error.
    // The return value is intended to be used directly in a type switch as
    // illustrated in the PubSubConn example.
    func (c PubSubConn) Receive() interface{
        } {
        
    	return c.receiveInternal(c.Conn.Receive())
    }

返回的是一个空接口类型 interface\{\}，由于空接口没有方法，因此所有类型都实现了空接口，也就是说可以返回任意类型。

具体会返回哪些类型在receiveInternal()里面可以看到，  
目前返回的三种Message、Subscription、Pong都定义在了pubsub.go 里面。

func (c PubSubConn) receiveInternal(replyArg interface{
        }, errArg error) interface{
        } {
        
    	reply, err := Values(replyArg, errArg)
    	if err != nil {
        
    		return err
    	}
    
    	var kind string
    	reply, err = Scan(reply, &kind)
    	if err != nil {
        
    		return err
    	}
    
    	switch kind {
        
    	case "message":
    		var m Message
    		if _, err := Scan(reply, &m.Channel, &m.Data); err != nil {
        
    			return err
    		}
    		return m
    	case "pmessage":
    		var m Message
    		if _, err := Scan(reply, &m.Pattern, &m.Channel, &m.Data); err != nil {
        
    			return err
    		}
    		return m
    	case "subscribe", "psubscribe", "unsubscribe", "punsubscribe":
    		s := Subscription{
        Kind: kind}
    		if _, err := Scan(reply, &s.Channel, &s.Count); err != nil {
        
    			return err
    		}
    		return s
    	case "pong":
    		var p Pong
    		if _, err := Scan(reply, &p.Data); err != nil {
        
    			return err
    		}
    		return p
    	}

## 订阅示例 ##

因为平时用的cpp\_redis，习惯了那种订阅一个主题，收到消息后通过注册的回调函数处理的方式，所以示例代码多了长map存放回调函数。

package main
    
    import(
    	//"github.com/go-redis/redis"
      "fmt"
      "time"
      //"reflect"
      "unsafe"
    	"github.com/gomodule/redigo/redis"
    	log "github.com/astaxie/beego/logs"
    )
    
    type SubscribeCallback func (channel, message string)
    
    type Subscriber struct {
        
      client redis.PubSubConn
      cbMap map[string]SubscribeCallback
    }
    
    func (c *Subscriber) Connect(ip string, port uint16) {
        
      conn, err := redis.Dial("tcp", "127.0.0.1:6379")
      if err != nil {
        
          log.Critical("redis dial failed.")
      }
    
      c.client = redis.PubSubConn{
        conn}
      c.cbMap = make(map[string]SubscribeCallback)
    
      go func() {
        
        for {
        
            log.Debug("wait...")
            switch res := c.client.Receive().(type) {
        
              case redis.Message:
                  channel := (*string)(unsafe.Pointer(&res.Channel))
                  message := (*string)(unsafe.Pointer(&res.Data))
                  c.cbMap[*channel](*channel, *message)
              case redis.Subscription:
                  fmt.Printf("%s: %s %d\n", res.Channel, res.Kind, res.Count)
              case error:
                log.Error("error handle...")
                continue
            }
        }
      }()
    
    }
    
    func (c *Subscriber) Close() {
        
      err := c.client.Close()
      if err != nil{
        
        log.Error("redis close error.")
      }
    }
    
    func (c *Subscriber) Subscribe(channel interface{
        }, cb SubscribeCallback) {
        
      err := c.client.Subscribe(channel)
      if err != nil{
        
        log.Critical("redis Subscribe error.")
      }
    
      c.cbMap[channel.(string)] = cb
    }
    
    func TestCallback1(chann, msg string){
        
      log.Debug("TestCallback1 channel : ", chann, " message : ", msg)
    }
    
    func TestCallback2(chann, msg string){
        
      log.Debug("TestCallback2 channel : ", chann, " message : ", msg)
    }
    
    func TestCallback3(chann, msg string){
        
      log.Debug("TestCallback3 channel : ", chann, " message : ", msg)
    }
    
    func main() {
        
    
      log.Info("===========main start============")
    
      var sub Subscriber
      sub.Connect("127.0.0.1", 6397)
      sub.Subscribe("test_chan1", TestCallback1)
      sub.Subscribe("test_chan2", TestCallback2)
      sub.Subscribe("test_chan3", TestCallback3)
    
      for{
        
       time.Sleep(1 * time.Second)
      }
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3poaXpoZW5nZ3Vhbg_size_16_color_FFFFFF_t_70]

## 发布示例 ##

发布直接使用默认的Conn来Send “Publish“ 命令即可.  
redigo的管道的使用方法设计到三个函数，Do函数也是下面这三个函数的合并：

1、c.Send()
    2、c.Flush()
    3、c.Receive()

send()方法把命令写到输出缓冲区，Flush()把缓冲区的命令刷新到redis服务器，Receive()函数接收redis给予的响应，三个操作共同完成一套命令流程。

package main
    
    import(
      //"github.com/go-redis/redis"
      "github.com/gomodule/redigo/redis"
      log "github.com/astaxie/beego/logs"
    )
    
    func main() {
        
    
      client, err := redis.Dial("tcp", "127.0.0.1:6379")
      if err != nil {
        
          log.Critical("redis dial failed.")
      }
      defer client.Close()
    
      _, err = client.Do("Publish", "test_chan1", "hello")
      if err != nil {
        
        log.Critical("redis Publish failed.")
      }
    
      _, err = client.Do("Publish", "test_chan2", "hello")
      if err != nil {
        
        log.Critical("redis Publish failed.")
      }
    
      _, err = client.Do("Publish", "test_chan3", "hello")
      if err != nil {
        
        log.Critical("redis Publish failed.")
      }
    
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3poaXpoZW5nZ3Vhbg_size_16_color_FFFFFF_t_70 1]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3poaXpoZW5nZ3Vhbg_size_16_color_FFFFFF_t_70]: /images/20220128/8eae0147404a43cb922f0870c30c62a7.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3poaXpoZW5nZ3Vhbg_size_16_color_FFFFFF_t_70 1]: /images/20220128/31858554da814a4b83d25a87cc0117ab.png