go - go http.Client 的 DialContext KeepAlive 和 Transport IdleTimeout 的区别

Question

client := &http.Client{
        Transport: &http.Transport{
            DialContext: (&net.Dialer{
                KeepAlive: 5 * time.Second,
            }).DialContext,
            IdleConnTimeout: 3 * time.Second,
        },
    }

KeepAlive 和 IdleConnTimeout 有什么区别？

他们中的哪一个究竟是做什么的？

Answer 1

从文档:
https://github.com/golang/go/blob/go1.13.8/src/net/dial.go#L72

KeepAlive specifies the interval between keep-alive probes for an active network connection. If zero, keep-alive probes are sent with a default value (currently 15 seconds), if supported by the protocol and operating system. Network protocols or operating systems that do not support keep-alives ignore this field. If negative, keep-alive probes are disabled.

所以，如果你设置了 KeepAlive大于 0，它将表示从下一次探测开始所耗时，以便了解网络连接是否仍处于事件状态。
另一边， IdleConnTimeout :
https://github.com/golang/go/blob/go1.13.8/src/net/dial.go#L72

IdleConnTimeout is the maximum amount of time an idle (keep-alive) connection will remain idle before closing itself. Zero means no limit.

所以，如果你设置了 IdleConnTimeout大于0，表示连接仍然​​打开的时间。