You may also be able to
use the "ZMQ_TCP_KEEPALIVE" option to help with observation 2.
Joshua
Hello
zmq guys,
I am writing this letter to confirm whether zmq
PUB/SUB socket tcp connection have no timeout mechanism. Recently,
I am coding with ZMQ3.2.2 API. In my program, there are two nodes, one
is publisher, the other is subscriber, communicated with zmq tcp
PUB/SUB sockets. These two nodes are running on virtual machine. When
the publisher's VM is RESET(code restart), the subscriber won't
received any message from the restarted publisher. However, restart the
publisher program, reboot in guest os, disconnect interface for a
period of time won't lead to such result, subscriber always reconnects
to the new started publisher.
With tcpdump, we noticed that 1) restart the
publisher program or reboot the guest os, makes publisher zmq send a FIN
to terminate the connection. And when publisher restarts, subscriber
will reconnect to it automatically.
2) Reset the VM of publisher, no FIN is sent out and when publisher
restarts, the subscribe do nothing, no communication is observed, so the
subscribe can't detect the previous connection is lost. 3)
Reset the VM of subscriber, no FIN is sent out, and publisher is always
sending messages to the previous connection. Of course, a new
connection is established, and messages are also sent out via this
connection.
With the above observation, we guess that zmq PUB/SUB has no
connection timeout mechanism, the connection only be terminated when one
of the ends sends a FIN. I am curious about the whether it is the
design target, or a bug. Maybe we must implements timeout with heatbeat
on uplayer, to avoid lost connection when publisher is down for power
losing.
Thanks for your information. Hailing.
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