Not suitable for use with http.Serve

[glasser]

This isn't exactly a bug with this package, but we learned the hard way in production that this code (or anything implementing this interface) isn't suitable for use with http.Server.Serve. Might be worth mentioning in docs.

Specifically: http.Server.Serve looks like:

// Serve accepts incoming connections on the Listener l, creating a
// new service goroutine for each.  The service goroutines read requests and
// then call srv.Handler to reply to them.
func (srv *Server) Serve(l net.Listener) error {
    defer l.Close()
    var tempDelay time.Duration // how long to sleep on accept failure
    for {
        rw, e := l.Accept()
        if e != nil {
            if ne, ok := e.(net.Error); ok && ne.Temporary() {
                if tempDelay == 0 {
                    tempDelay = 5 * time.Millisecond
                } else {
                    tempDelay *= 2
                }
                if max := 1 * time.Second; tempDelay > max {
                    tempDelay = max
                }
                srv.logf("http: Accept error: %v; retrying in %v", e, tempDelay)
                time.Sleep(tempDelay)
                continue
            }
            return e
        }
        tempDelay = 0
        c, err := srv.newConn(rw)
        if err != nil {
            continue
        }
        c.setState(c.rwc, StateNew) // before Serve can return
        go c.serve()
    }
}

srv.newConn calls rw.RemoteAddr(), and if that's a proxyproto listener, it can block if the incoming connection doesn't actually send over any data. And this is before go c.serve(), so it's in the main http.Server.Serve goroutine!

Workarounds for this seem pretty complex, unfortunately...

[armon]

Hmm that is nasty. Not sure I see an obvious solution to this, it looks like it will always require ugly hacks.

[glasser]

Here's a CL for Go that should fix this. https://go-review.googlesource.com/#/c/15832/

[glasser]

and a workaround we're using: https://gist.github.com/glasser/ac531523a027cbe3955d

[glasser]

I got a simpler CL into Go: golang/go@b58515b

So this should work without a workaround in 1.6.

Issue in go repo: golang/go#12943

[armon]

@glasser Thanks for the heads up!

[owenthereal]

@glasser I'm curious what you ended up doing with this issue? I will need to handle proxy protocol in Go too...

[glasser]

As described above, this should be fixed in Go 1.6. My gist above is an annoying workaround for 1.5.

[owenthereal]

Cool thanks @glasser