Heartbeat loop disconnects the socket unexpectedly

[wiredmb]

I'm using Stomp.py Version 4.1.15 and connecting the stomp consumer to Amazon MQ broker. I set heartbeat parameter to <0,30000>. Broker is sending heartbeat every 30 secs. Here is the scenario where consumer disconnects the connection:

1. Broker sends heartbeat at X.
2. Broker sends a message at X + 4.
3. Heartbeat loop wakes up in the meantime, calculates difference between received_heartbeat and now which is 11 secs and sleeps for 34 secs (receive_sleep is 45 secs).
4. Broker skips heartbeat at X + 30 (because of message sent in Error handling? #2).
5. Heartbeat loop wakes up after 34 secs, calculates difference between received_heartbeat and now which is slightly greater than receive_sleep (in my case, 45.02 secs) and disconnects the connection with heartbeat timeout event.
6. Also throws an exception:

on_heartbeat_timeout
Before Sleep: received_heartbeat: Fri Sep  7 16:43:41 2018, receive_sleep: 45.0, now: Fri Sep  7 16:44:27 2018
Exception in thread StompHeartbeatThread-2:
Traceback (most recent call last):
  File "/usr/lib/python2.7/threading.py", line 801, in __bootstrap_inner
    self.run()
  File "/usr/lib/python2.7/threading.py", line 754, in run
    self.__target(*self.__args, **self.__kwargs)
  File "/usr/local/lib/python2.7/dist-packages/stomp/listener.py", line 266, in __heartbeat_loop
    sleep_time = min(next_events)
ValueError: min() arg is an empty sequence

The possible solution could be to add grace time while checking for diff_receive > self.receive_sleep in heartbeat loop. Please suggest.

[emakarov]

hi @wiredmb
did you manage to resolve this issue?
and why your broker has sent the event 2? (Broker sends a message at X + 4.)

[jasonrbriggs]

Believe this is resolved in the latest version.

[HWiese1980]

It is not. We're experiencing this issue right now. We're on stomp.py v7.0.0.

[HWiese1980]

Cause is that next_events is empty. It is empty because self.next_outbound_heartbeat is None. Furthermore, self.received_heartbeat + self.receive_sleep - now is <= 0.0 so that eventually there's nothing added to next_events.

Source: stomp/listener.py:271 and following lines

[HWiese1980]

@jasonrbriggs Have you seen this one? The error persists and it's a behavior I see quite often.

I'll make a small change and send you a pull request for review that should fix this particular problem. I'm not sure if it has some implications or impacts downstream as I'm not that deep in your code yet.