On May 9, 2012, at 12:45 AM, Steffen Mueller wrote: > Dear all, > > I have an application of 0MQ where I have one or multiple server > instances that use a PUSH socket to send messages that must be processed > by any one of potentially many workers. The servers are single-threaded > apart from 0MQ's IO thread and this is hard to change. > > The documentation for the PUSH socket type (and others like XREQ) > explain that sending messages on such a socket will be a blocking > operation IF > > - the HWM is hit > - OR there are no peers > > In my scenarios, I want to be resilient against intermittent client > failure (due to whatever -- coordinated restart, failure, ...). But for > this time, the server processes will block on the write and that is not > acceptable. Is it reasonable to hope for a way to achieve the following > behaviour? > > Sending a messages down a socket of this time will block if: > > - the HWM is hit for all peers (as per docs, presumably, this means > all and each separately since the buffers are probably per-client) > - OR a single global HWM is hit if there are no peers > > IOW, I'd like to be able to shove up to $HWM messages down a pipe no > matter what, and have the PUSH/whatever socket use a single $HWM-depth > buffer if there is no peer. As soon as a peer connects, it could do one > of two things: > > - simply swap that buffer in to become the first connecting peer's > send queue (which might be undesirable in some cases since it doesn't > load balance but it's likely much easier to implement and more efficient) > - use that buffer as another queue stage to load balance from > > Any chance I could have such a functionality? Of course, being able to > determine whether there are any peers connected would be great, too.
I recommend that you do non-blocking writes and check the return code. If zmq_errno is equal to EAGAIN, then you know that you have either hit HWM or that there are no peers. cr _______________________________________________ zeromq-dev mailing list zeromq-dev@lists.zeromq.org http://lists.zeromq.org/mailman/listinfo/zeromq-dev
