accept tcp4 0.0.0.0:6988: use of closed network connection

[un000]

Hey, there is a problem when service stops and calls .Shutdown(). ListenAndServe errors with a:

{"level":"error","ts":"2022-08-25T10:30:36.236Z","caller":"http/server.go:256","msg":"error closing server","version":"ce33dc19", "system":"http","error":"accept tcp4 0.0.0.0:6988: use of closed network connection"}

ListenAndServe started returning errors after an upgrading fasthttp from 1.31 -> 1.39. Then I've added IdleTimeout,ReadTimeout, WriteTimeout and it continues doing error. Fasthttp app is behind nginx with keep-alives.

Before to stop fasthttp server, k8s deregister app from DNS, then nginx is closing connections in 2 seconds, then server waits 10 seconds to call .Shutdown().

&fasthttp.Server{
		NoDefaultDate:                true,
		NoDefaultServerHeader:        true,
		NoDefaultContentType:         true,
		DisablePreParseMultipartForm: true,
		TCPKeepalive:                 true,
		TCPKeepalivePeriod:           10 * time.Second,
		ReadTimeout:                  10 * time.Second,
		WriteTimeout:                 10 * time.Second,
		IdleTimeout:                  5 * time.Second,
		ReadBufferSize:               2 << 14,
		MaxRequestsPerConn:           2 << 16,
	}

func (s *Server) Run() {
	go func() {
		s.logger.Info("starting http server", zap.String("address", s.config.Address))
		go middlewares.HTTPServerStatMonitor(s.server)

		if err := s.server.ListenAndServe(s.config.Address); err != nil {
			if strings.Contains(err.Error(), "use of closed network connection") {
				s.logger.Error("error closing server", field.Error(err))
			} else {
				s.logger.Fatal("error while starting http server", field.Error(err))
			}
		}
	}()
}

func (s *Server) Stop(timeout time.Duration) {
        time.Sleep(10 * time.Second)
	done := make(chan struct{})
	go func() {
		if err := s.server.Shutdown(); err != nil {
			s.logger.Error("error stopping server", field.Error(err))
		}
		close(done)
	}()

	ctx, cancel := context.WithTimeout(context.Background(), timeout)
	defer cancel()
	select {
	case <-ctx.Done():
		s.logger.Error("server is not gracefully stopped")
		return
	case <-done:
		s.logger.Info("server stopped")
		return
	}
}

How to prevent this behaviour?

[un000]

It reproduces from fasthttp v1.38+ (Consolidate TCPKeepalive in server.Serve (#1320) #1324 )

This code doesn't check "use of closed network connection" as it was before
https://github.com/valyala/fasthttp/pull/1324/files#diff-366e46a40f6f60b4f7614eb0976bb51820364bf5ca6ccc4787eb49d7bdbef3e6R1869

[erikdubbelboer]

You are right, good find. I fixed it in: 28bec71