go: net: ReadFromUDP hangs (randomly) even when ReadDeadline is crossed
What version of Go are you using (go version)?
$ go version > go1.13.4 linux/amd64
Does this issue reproduce with the latest release?
Yes.
What operating system and processor architecture are you using (go env)?
Ubuntu 18.04.2 LTS | Kernel version: 4.15.0-66-generic
What did you do?
This function is called as a gorutine:
// Listens infinitely for UDP packet arrivals and
// executes it's processing inside a gorutine.
func startUDPListener(netw string, router *Router) {
lAddr := getLocalIPAddress()
// Set listening port.
lAddr.Port = int(router.myPeerInfo.port)
PacketConnCreation:
// listen to incoming udp packets
pc, err := net.ListenUDP(netw, &lAddr)
if err != nil {
log.Panic(err)
}
// Set initial deadline.
pc.SetReadDeadline(time.Now().Add(time.Minute))
for {
//simple read
buffer := make([]byte, 1024)
byteNum, uAddr, err := pc.ReadFromUDP(buffer)
if err != nil {
// If we get an error, we just close the pc and create a new one.
log.Printf("%v", err)
pc.Close()
goto PacketConnCreation
} else {
// Set a new deadline for the connection.
pc.SetReadDeadline(time.Now().Add(5 * time.Minute))
go processPacket(*uAddr, byteNum, buffer, router)
}
}
}
What did you expect to see?
I was expecting ReadFromUDP to ALWAYS return an error if the DeadLine is crossed and I don’t recieve any UDP packet on my IP:Port interface before this happens.
What did you see instead?
Instead of that, it sometimes hangs completely without giving any kind of errors. It’s completely random, it sometimes hangs and sometimes doesn’t (providing the corresponding i/o timeout)
It just stays running forever without accepting new packets (or even reading them). The gorutine gets completely freezed (or at least it seems so).
About this issue
- Original URL
- State: closed
- Created 5 years ago
- Comments: 23 (4 by maintainers)
For the record, never write
for {}in a Go program. That will never work well. See #10958 for part of the problem.Please try precisely what I suggested. Don’t invent a new concept. If you want the main goroutine to go to sleep forever then select {} is the construct you should use.
Can you please try rewriting your code to use select {} rather than for {}