[QUESTION] - How to get Listener from server.Default() so that I could use it in different libraries?

[sujit-baniya]

Describe the Question

I'm trying to use hertz framework with https://github.com/pedia/endless to allow zero downtime restart. There's an example to include Listener but I'm not sure how to use it with hertz

Reproducible Code

func serve_http(addr string, ln net.Listener) (*fasthttp.Server, error) {
	server := &fasthttp.Server{Handler: func(ctx *fasthttp.RequestCtx) {
		ctx.WriteString(fmt.Sprintf("%d\n", os.Getpid()))
	}}

	go server.Serve(ln)

	return server, nil
}

func main() {
	addr := ":3030"
	var s *fasthttp.Server

	endless.Start(
		func(p *endless.Parent) error {
			ln, err := net.Listen("tcp", addr)
			if err != nil {
				return err
			}

			p.AddListener(ln, addr)
			s, err = serve_http(addr, ln)
			return err
		}, func(c *endless.Child) error {
			nf, ok := c.NamedFiles[addr]
			fmt.Printf("got %#v\n", nf)
			if !ok {
				return fmt.Errorf("inherit %s not found", addr)
			}

			c.AddListener(nf.LN, addr)
			server, err := serve_http(addr, nf.LN)
			s = server
			return err
		},
		func(ctx context.Context) error {
			return s.Shutdown()
		},
	)
	fmt.Printf("Quit %d\n", os.Getpid())
}

Expected behavior

Able to get listener

Screenshots

If applicable, add screenshots to help explain your question.

Hertz version:

Latest

[li-jin-gou]

I will research it and welcome it together.💕

[sujit-baniya]

@li-jin-gou Thanks. Please suggest if you've any idea

[welkeyever]

Seems that you wanna pass a customized listener to Hertz?
Actually it doesn't support that now, but I will looking into it - there isn't much work to do.

[sujit-baniya]

@welkeyever Yes and also, I want to get a listener from Hertz and use it for different purposes. So basically when Hertz is set up for Spin if it could store Listener somewhere and I could access that Listener from RequestContext, then that would also work.

[welkeyever]

@sujit-baniya It's reasonable to store it in network layer of hertz instance - you may get it through transport-related APIs. But it would be strange that relate listener to RequestContext - RequestContext is main for application-related jobs - you may save hertz instance somewhere, and get it to do whatever you wanna later.

[sujit-baniya]

@welkeyever Yes getting listener from hertz instance would also work. I was giving RequestContext as an example :)

[sujit-baniya]

Anything like hertzInstance.GetListener() or hertzInstance.Listener would work.

[welkeyever]

Okay, let me have a try.
I will update if there is any progress.

[sujit-baniya]

@welkeyever any thought on this issue?

[welkeyever]

@welkeyever any thought on this issue?

@sujit-baniya Sorry for the late. I was stumped by other things before. I will continue with this part.

[welkeyever]

Possible solution goes here: develop...welkeyever:hertz:feat/more_options_for_transporter

Please feel free to add your review comments.

The endless example works, however there is a issue related to a third party lib:

And we will finally get rid of this lib after this #541.

[sujit-baniya]

@welkeyever Please let me know your thought if we use Options.Listener net.Listener for Engine and pass it to transporter.

Something like this:

type Options struct {
    ....
    Listener net.Listener
}

func WithListener(ln net.Listener) config.Option {
	return config.Option{F: func(o *config.Options) {
		o.Listener = ln
	}}
}

And for each transport we assign this listener to transport

// For transporter switch
func NewTransporter(options *config.Options) network.Transporter {
	return &transport{
		readBufferSize:   options.ReadBufferSize,
		network:          options.Network,
		addr:             options.Addr,
		keepAliveTimeout: options.KeepAliveTimeout,
		readTimeout:      options.ReadTimeout,
		tls:              options.TLS,
		listenConfig:     options.ListenConfig,
                ln: options.Listener,
		OnAccept:         options.OnAccept,
		OnConnect:        options.OnConnect,
	}
}

And in transport.serve()

    if t.ln == nil {
    network.UnlinkUdsFile(t.network, t.addr) //nolint:errcheck
	t.lock.Lock()
	if t.listenConfig != nil {
		t.ln, err = t.listenConfig.Listen(context.Background(), t.network, t.addr)
	} else {
		t.ln, err = net.Listen(t.network, t.addr)
	}
	t.lock.Unlock()
	if err != nil {
		return err
	}
    }

[sujit-baniya]

I did above and got the same error as yours

[welkeyever]

WithListener

Continuously adding options like WithListener will make it confusing when user adding both WithListenConfig and WithListener - there is a potential effective priority under this scenario, but it cannot be well informed to the user.

So I just provider a config-independent way to do so.

[bjdgyc]

if t.listenConfig != nil {
    t.listener, err = t.listenConfig.Listen(context.Background(), t.network, t.addr)
} else {
    t.listener, err = net.Listen(t.network, t.addr)
}

以上为 hertz 的代码，listenConfig 直接调用了 Listen 方法，并没有进行特殊处理。
我认为框架内只需传入 Listener net.Listener 参数，不应传入 listenConfig *net.ListenConfig 参数，让用户去自定义 net.Listener。

代码参考：

t.lock.Lock()
if t.ln == nil {
   t.listener, err = net.Listen(t.network, t.addr)
}
t.lock.Unlock()