[zeromq-dev] last message lost in pipeline

[Tomaz Beltram]

Thanks again for sharing all this knowledge. I would suggest to file an
issue so that this is known to all users if it will be improved, or else
to correct the documentation about blocking zmq_ctx_destroy and
zmq_close, esp. for zmq_setsocketopt in the part for ZMQ_LINGER that states:

The default value of -1 specifies an infinite linger period.
Pending messages shall not be discarded after a call to
zmq_close(); attempting to terminate the socket’s context with
zmq_term() shall block until all pending messages have been sent to
a peer.

wbr Tomaz

On 27. 01. 2016 19:01, Justin Karneges wrote:
> It would be cool if libzmq, during shutdown, would write as much to the
> socket as it can before quitting. This way, small messages could live in
> the operating system's send buffer and survive after the process
> terminates. Of course if messages are too large, or there are too many
> messages, then those might be lost.
>
> On Wed, Jan 27, 2016, at 06:28 AM, Tomaz Beltram wrote:
>> Thanks for this information. I can work around it now that I know its a
>> known issue. I already have another REQ/REP control connection that can
>> handle this case.
>>
>> On 27. 01. 2016 15:16, Pieter Hintjens wrote:
>>> There are issues using zmq_ctx_destroy where if we wait for messages
>>> to be sent, it can deadlock. Afair we do not wait and thus in some
>>> cases the last message can be lost.
>>>
>>> My advice is to not trust your transport to send the last message in a
>>> stream. Rather, use a handshake to close a connection. If you can't do
>>> this (and over push/pull you can't) then the only other option is to
>>> wait a while before closing the socket.
>>>
>>>
>>>
>>> On Wed, Jan 27, 2016 at 1:58 PM, Tomaz Beltram <tomaz.beltram at topit.si> wrote:
>>>> Hi,
>>>>
>>>> I am using the pipeline pattern with one PULL socket with zmq_bind() to
>>>> an arbitrary port on the localhost interface (tcp://127.0.0.1:*) and one
>>>> PUSH socket with zmq_connect() to the port that was assigned by the system.
>>>>
>>>> The sender may finish and call zmq_close() and zmq_ctx_destroy() before
>>>> the receiver gets all messages that were sent. This should be OK, since
>>>> according to the documentation zmq_close() should wait for undelivered
>>>> messages to be transferred.
>>>>
>>>> Very rarely I observe that the last message that was sent is never
>>>> received. I was not able to reproduce the issue with a minimum test case
>>>> that I prepared and even in the real application its occurrence is very
>>>> seldom. Still I would like to track it down and avoid if possible. Any
>>>> ideas what I should do differently?
>>>>
>>>> wbr
>>>> Tomaz
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