After some further testing with czmq, I have discovered that the behaviour of not being able to read from a socket when not bound is particular to the ruby rbczmq bindings, and that czmq does not operate this way. I’m curious if other bindings such as python are the same as czmq.
I can update the rbczmq bindings to allow the read from a socket that has no connections/binds. So another question then: Consider doing a blocking read from a socket with no active endpoints (connect/bind). If there are messages, they should be returned. Should this call block indefinitely when there are no messages in the internal queue? Or would it be better to return an error code (e.g.: EAGAIN)? -Matt On 29 Dec 2013, at 9:34 pm, Matt Connolly <[email protected]> wrote: > Dear list, > > I’ve been playing around with how to ensure that a service has processed all > messages that it has received (in the receiving socket queue) before shutting > down. In particular, I’m using the rbczmq ruby bindings, so this question is > also to see if those bindings are consistent with other languages. > > Scenario: > > A service has a ROUTER socket, bound to a tcp endpoint. > A client has a DEALER socket, connected to that tcp endpoint. > The client has sent one or more messages and is expecting a reply to each > message. > The messages have been transmitted and are in the service’s inbound message > queue waiting for processing. > The service receives a shutdown request (for example, a system being > restarted for maintenance). > The service should process all received messages or store them for processing > on next start-up. > > — > > When I do a socket.disconnect in the service, it is unable to read any > message in the queue for that socket. However, if I subsequently connect that > socket to a dummy endpoint, such as “ipc://foo”, then I can receive all of > the messages in the queue that were sent to the real address. Once > disconnected, the service is unable to send a response to the client, but at > least the message can be saved, and a reply could be sent when the service > comes back online. > > The service should only be down for a small amount of time (just a few > minutes I suppose) so for messages queued at the client side, this is not a > problem because the client will wait for a reply and the io thread will > continue to reconnect and send when it connects to the service. > > Is the behaviour normal that socket.receive will fail with an error if the > socket has no active endpoints (bind or connect)? I suppose this only makes > sense for a non-blocking call, otherwise if there are no messages in queue, > then the call will BlockForever™… > > Also, I notice that if I disconnect/unbind the socket from the service, that > ZMQ::Poller#poll and ZMQ::Socket#poll both report the socket as being > readable, but reading from the socket still fails. Is this particular to > rbczmq? > > > Cheers, > Matt > > PS: happy holidays all! > > _______________________________________________ > zeromq-dev mailing list > [email protected] > http://lists.zeromq.org/mailman/listinfo/zeromq-dev _______________________________________________ zeromq-dev mailing list [email protected] http://lists.zeromq.org/mailman/listinfo/zeromq-dev
