[zeromq-dev] Dropped messages when not sleeping, using 0MQ 2.1.x

Wolfgang Richter wolf at cs.cmu.edu
Sun Sep 18 18:05:40 CEST 2011

You aren't using threads are you?  You mentioned it was a large system.

Make sure you don't pass sockets around between threads.


On Sun, Sep 18, 2011 at 11:52 AM, James Cipar <jcipar at cmu.edu> wrote:

> Hi,
>    I'm using PUSH/PULL sockets in a system where I have many pushers
> connected to a single puller.  The pushers connect, send a few hundred
> messages, then send a special "end" message and close the socket.  The
> puller counts how many "end" messages it has received, and once it has
> enough, it quits.
> I'm having a problem where the "end" messages are occasionally dropped (and
> perhaps other messages as well).  However, if I put a "sleep(1)" immediately
> before the "close()" call, it works as expected, and all messages arrive.  I
> am using 0MQ 2.1.9 (and also tried on 2.1.7) on Debian Squeeze..  I thought
> that the sleep before close was no longer necessary on 2.1.x.  It also seems
> dependent on the data set that the pushers are sending.  Sometimes it works
> without the sleep, and sometimes it does not.  Strangely, it is the
> *smaller* data set that causes problems.  I'd like to avoid the sleep call,
> because I want the pushers to go on to other work as soon as they finish
> sending data.
> Unfortunately, I'm having trouble constructing a minimal test case.  As
> it's a large system, and the occurrence of the error seems dependent on the
> data being sent.  Here is the relevant code for the error:
>    int linger;
>    size_t l_size = sizeof(linger);
>    sender.getsockopt(ZMQ_LINGER, (void *)(&linger), &l_size);
>    assert(l_size == sizeof(linger));
>    cout <<"closing sender, messages will linger for "<<linger<<"
> milliseconds\n";
>    sleep(1);
>    sender.close();
> If that "sleep" call is commented out, it will drop messages; with the
> sleep, it will not.  The "cout" is printing -1, as expected.
> Is there any reason to expect this system to be dropping messages?
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