go - 如何在Go中获取空闲和 “active”连接的数量？

Question

假设我在Go中有一个常规的HTTP Server。如何获得当前空闲和 Activity 的TCP连接？

httpServer := &http.Server{
    Handler: newHandler123(),
}

l, err := net.Listen("tcp", ":8080")
if err != nil {
    log.Fatal(err)
}

err = httpServer.Serve(l)
if err != nil {
    log.Fatal(err)
}

Answer 1

创建一个类型以计算响应于服务器connection state更改而打开的连接数:

type ConnectionWatcher struct {
    n int64
}

// OnStateChange records open connections in response to connection
// state changes. Set net/http Server.ConnState to this method
// as value.
func (cw *ConnectionWatcher) OnStateChange(conn net.Conn, state http.ConnState) {
    switch state {
    case http.StateNew:
        atomic.AddInt64(&cw.n, 1)
    case http.StateHijacked, http.StateClosed:
        atomic.AddInt64(&cw.n, -1)
    }
}

// Count returns the number of connections at the time
// the call.    
func (cw *ConnectionWatcher) Count() int {
    return int(atomic.LoadInt64(&cw.n))
}

配置net.Server以使用 method value:

var cw ConnectionWatcher
s := &http.Server{
   ConnState: cw.OnStateChange
}

使用 ListenAndServe， Serve或这些方法的TLS变体启动服务器。
调用 cw.Count()以获取打开的连接数。
Run it on the playground。