[zeromq-dev] cleaning up TCP sockets

Pieter Hintjens ph at imatix.com
Thu Mar 21 14:58:07 CET 2013

On Thu, Mar 21, 2013 at 2:27 PM, Joel Lauener <Joel.Lauener at cern.ch> wrote:

> We are migrating an infrastructure with ~3500 active servers and ~1500 active clients from CORBA to ZMQ. We only provide the library, our users implement the clients/servers on top of it and deploy were/how they want. We also have many combinations of hardware/OS: low level front-ends, middle tier servers and workstations. As you can see our system is quite open and complex :/
> By "stuck client" I mean a client for which the process is blocked (deadlock, OS problem, hardware problem) but for which the TCP stack is still alive. Of course this is very unlikely to happen, but from our experience it can happen. For example a virtual machine going into hibernation can have very nasty  behaviour.
> This is not an hard requirement, just a nice to have. I guess the only (clean) way is to have one ZMQ socket per client instead of a single ROUTER.

Nice to hear that CERN is moving onto ZeroMQ in a large way. :-)

Unless you're spawning more and more virtual machines, the number of
stuck clients cannot exceed the number of normal live clients, right?
So you're not going to experience any leak of server resources.

Now, we could make ROUTER sockets smarter about this, I think. Simply:
if there's no activity on a connection, after some timeout, kill it.
If the client is just doing other things, it will reconnect when
there's new activity. If the client is dead, it won't.


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