On Thu, 16 Jul 2020 at 14:36, Francesco Raviglione <francescorav.es...@gmail.com> wrote: > > Dear Adrian, > Thank you very much for your reply. > > I tried following your suggestion, by attempting to find a way to call an > external function reading the data from an external source, and returning > it when available. > > However, unfortunately, it seems to be slightly easier to control the > behaviour of the event loop in C than in Pyhton. > In particular, in Python, if I call any blocking function (even a > time.sleep(0.1), sleeping for just 100 ms) inside "on_sendable", the > messages are only buffered and never sent (do you know why? Is the > "on_sendable" handler supposed to be executed as fast as possible without > blocking to have the messages being sent immediately?).
There is only one thread, it is used for running the callbacks and performing the IO. Anynew IO is processed after the handlers return, so if you block the handlers, you block the IO thread, meaning it can't do any work and thus cant send anything. > If, instead, I just do not block and send the data only if available (for > instance by implementing a mechanism equivalent to a non-blocking read from > a pipe, with poll(), letting "on_sendable" finish without sending anything, > if there is no data available), only one "on_sendable" event is generated > and the event loop does not seem to return any other event which I could > use to send the data, which may be now available (for example, the > equivalent of C's PN_DELIVERY does not seem to exist). > The on_sendable is generated when credit to send initially arrives from the server, or does again later. I believe it's also 'regenerated' locally when you send, thus using some of the credit (so long as some credit remains). As neither occurred, no more on_sendable calls. I believe the EventInjector was the intended route for things like this, performing/provoking work from outwith the container thread: http://qpid.apache.org/releases/qpid-proton-0.31.0/proton/python/docs/proton.reactor.html#proton.reactor.EventInjector Its used in these examples: http://qpid.apache.org/releases/qpid-proton-0.31.0/proton/python/examples/db_send.py.html http://qpid.apache.org/releases/qpid-proton-0.31.0/proton/python/examples/db_recv.py.html http://qpid.apache.org/releases/qpid-proton-0.31.0/proton/python/examples/tx_recv_interactive.py.html You can also provoke your own callbacks by scheduling, so an alternative might be scheduling (while using the container thread, not your own) a task of your own to periodically run. Example: http://qpid.apache.org/releases/qpid-proton-0.31.0/proton/python/examples/recurring_timer.py.html > Do you know if there are other ways to solve this issue? > When you were "yielding" the control of the main loop to an external > function, was it blocking in some way, waiting for data to be available? > > Thank you very much, > Francesco > > > Il giorno mer 15 lug 2020 alle ore 18:40 Adrian Florea <florea....@gmail.com> > ha scritto: > > > Hi Francesco, > > > > I achieved similar behavior but using Qpid Proton-C (AMQP send-only > > program). > > > > After initialiazing proton and getting the first FLOW event, I simply > > "yield" main event loop control to an external/looping function that can > > read from a different source and then send the same message to an AMQP > > destination. > > > > It may seem hard in the beggining but once you get a hold on how to > > integrate proton events loop into your program loop, it has good chances to > > work. > > > > Adrian > > > > > > On Wed, Jul 15, 2020, 11:22 AM Francesco Raviglione < > > francescorav.es...@gmail.com> wrote: > > > > > Dear all, > > > I'm trying to use the Python version of Qpid Proton to send data to an > > AMQP > > > 1.0 broker. > > > I've seen that several examples are sending data which was > > > available/defined before the AMQP event loop is started. > > > However, I need to send data only when it becomes available from an > > > external process (for example by waiting for it on a Pipe, with > > > self.amqp_pipe_end.recv()), and then send it immediately to the broker. > > > If I try to wait on a pipe inside "on_sendable", no message is actually > > > transferred to the broker, as the event loop is "blocked" waiting for new > > > data and cannot manage properly the AMQP 1.0 connection (is this > > correct?). > > > How could I achieve the desired result? How can I make the loop wait for > > > external data and then immediately send it? > > > > > > Thank you very much in advance, > > > Francesco Raviglione > > > --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@qpid.apache.org For additional commands, e-mail: users-h...@qpid.apache.org
