The receive queue of subscriber socket is getting full

[kaushik-shrestha]

We have one publisher and two subscriber applications utilizing ZeroMQ's Pub-Sub pattern without implementing any heartbeat mechanism.

One application is running on (10.159.251.23) that publishes messages on port 6666:
publisher.publisherSocket = zContext.createSocket(SocketType.PUB);
publisher.publisherSocket.bind("tcp://*:6666");

And on the same host (10.159.251.23) another application is running that subscribes to this port 6666:
subscriberSocket = zContext.createSocket(SocketType.SUB);
subscriberSocket.subscribe("API-PROXY.INITIATOR.RES");
subscriberSocket.connect("10.159.251.23:6666");

Additionally, there's a different host (10.159.251.22) running the same subscriber application that subscribes to this publisher application on host 10.159.251.23:6666

The subscriber application on both hosts has been running since last 7 days. However on running netstat -an we see that the receive queue of the subscriber application running on (10.159.251.23) is full:
[kaushx@mslt4wct8080 ~]$ netstat -an | grep 6666
tcp6 0 0 :::6666 :::* LISTEN
tcp6 0 0 10.159.251.23:52440 10.159.251.22:6666 ESTABLISHED
tcp6 0 2588034 10.159.251.23:6666 10.159.251.23:50172 ESTABLISHED
tcp6 4196046 0 10.159.251.23:50172 10.159.251.23:6666 ESTABLISHED
tcp6 0 0 10.159.251.23:44368 10.159.251.22:6666 ESTABLISHED
tcp6 0 0 10.159.251.23:6666 10.159.251.22:45164 ESTABLISHED
tcp6 0 0 10.159.251.23:44148 10.159.251.22:6666 ESTABLISHED
tcp6 0 0 10.159.251.23:6666 10.159.251.22:45166 ESTABLISHED

This issue keeps occurring every few weeks which get resolved only on re-starting the subscriber application. Do you have any ideas what might be going wrong? Is there any way to clear the receive queue on reaching some threshold? We're using jeromq-0.5.1