On Wed, Mar 16, 2016 at 11:06 AM, Pieter Hintjens <[email protected]> wrote:
> Off-topic, but I need to ask, how do you do the syntax highlighting in > emails? > http://markdown-here.com/ > > On Mon, Mar 14, 2016 at 4:42 PM, MinRK <[email protected]> wrote: > > On Sat, Mar 12, 2016 at 9:00 PM, Dave Kuhlman <[email protected]> > > wrote: > >> > >> For those of us who use Python and the pyzmq library for ZeroMQ, I'm > >> wondering whether the solution to the problem and need for thread > >> safety is to avoid threads and to use either the tornado ioloop > >> support or asyncio ioloop. Am I right that doing so would give a > >> Python developer the capabilities of multiple threads without the > >> worries about thread safety. > >> > >> One reason I'm asking is that I'm the one who added the ioloop > >> examples to zguide (in examples/Python/tornado_ioloop and > >> examples/Python/ascyncio_ioloop). A number of those examples use > >> (what I understand as) multiple concurrent tasks within a single > >> thread. So, I'm wondering whether that really is thread safe (or > >> whatever the equivalent is for tasks), as I believe it is. > > > > Yup, asyncio/tornado are single-threaded eventloops, so you won’t get > > threadsafety problems if everything happens in a callback/coroutine on > those > > loops. You can also use these to make threadsafe actions, even when using > > actual threads. In the tornado case, there is one (and only one) > threadsafe > > method, and it’s IOLoop.add_callback. You can use this to schedule calls > to > > be made on the IOLoop, from other threads. For instance: > > > > loop = start_loop_in_background_thread() > > > > def threadsafe_send(socket, msg): > > loop.add_callback(lambda : socket.send_multipart(msg)) > > > > In this way, you can schedule sends from any number of threads perfectly > > safely, because the actual zmq socket is only ever operated on in the IO > > thread. Threadsafe recv is similarly doable, but a bit more code. > > > > On the other hand, you can also write coroutine-unsafe code if you have > > yields in the middle of sending multipart messages, for instance: > > > > @coroutine > > def bad_coroutine_send(socket, msg): > > for frame in msg[:-1]: > > yield socket.send(frame, zmq.SNDMORE) > > yield socket.send(msg[-1]) > > > > Where each yield is an opportunity to take over and do some other > operation > > on the socket. I think it is a lot easier to write coroutine-safe code > than > > thread-safe code, since all context switching is explicit (make sure you > > have no yield calls in the middle of an operation). > > > > -MinRK > >> > >> > >> Any enlightenment will be welcome. > >> > >> And, by the way, I suspect that something equivalent could be done > >> in Node.js (JavaScript), which also uses a single threaded approach > >> to "concurrency" (psuedo-concurrency, quasi-concurrency, whatever). > >> In Node.js, you could use callbacks, but there are libraries that > >> can wrap your code to make is seem more simple and parallel. For > >> example, see async.js. Here are a few quick examples from the > >> async.js Web page (https://www.npmjs.com/package/async): > >> > >> async.map([`file1`,`file2`,`file3`], fs.stat, function(err, > results){ > >> // results is now an array of stats for each file > >> }); > >> > >> async.filter([`file1`,`file2`,`file3`], fs.exists, > function(results){ > >> // results now equals an array of the existing files > >> }); > >> > >> async.parallel([ > >> function(){ ... }, > >> function(){ ... } > >> ], callback); > >> > >> async.series([ > >> function(){ ... }, > >> function(){ ... } > >> ]); > >> > >> As a bit of justification for this question, the main intension of > >> the Python ioloop support in tornado and asyncio is to address > >> problems of network and I/O delays and to enable our code to do > >> something useful during those delays. That seems like a central > >> concern for users of ZeroMQ. > >> > >> Dave > >> > >> > >> On Sat, Mar 12, 2016 at 03:00:58AM +0200, Doron Somech wrote: > >> > Hi All, > >> > During the ZeroMQ hackathon I have added the Radio/Dish pattern > >> > (thread > >> > safe version of pubsub) and multicast support (only for Radio/Dish > >> > sockets) to both libzmq and czmq. > >> > Radio/Dish is very similar to pub/sub with some differences: > >> > * Thread safe, you can send and receive messages from multiple > >> > threads, so for publisher you now don't need internal device to > >> > publish from multiple threads and with subscriber you can use > it > >> > as > >> > load balancer. > >> > * Only single frame can be sent > >> > * Radio/Dish matching is exact matching (vs prefix of pubsub) > >> > * Group (Radio/Dish topic) is string and currently limited to 15 > >> > chars (might be increased in the future) > >> > * Group is set as part of the zmq_msg (libzmq) or zframe (czmq). > >> > * You call join or leave on the socket (with methods instead of > >> > socket options) > >> > > >> > To learn how to use it with czmq take a loot at the following gist: > >> > [1]https://gist.github.com/somdoron/9423196a228775c8f5af > >> > For libzmq take a loot at the test: > >> > > >> > [2] > https://github.com/zeromq/libzmq/blob/master/tests/test_radio_dish.c > >> > pp#L90 > >> > And the most exciting news, with radio-dish you can use multicast > >> > transport, just replace the address from following gist with udp > >> > transport and multicast address, following is a valid address for > >> > example: > >> > udp://[3]239.0.0.1:55555 > >> > Regards > >> > Doron > >> > > >> > References > >> > > >> > 1. https://gist.github.com/somdoron/9423196a228775c8f5af > >> > 2. > >> > > https://github.com/zeromq/libzmq/blob/master/tests/test_radio_dish.cpp#L90 > >> > 3. http://239.0.0.1:55555/ > >> > >> > _______________________________________________ > >> > zeromq-dev mailing list > >> > [email protected] > >> > http://lists.zeromq.org/mailman/listinfo/zeromq-dev > >> > >> > >> -- > >> > >> Dave Kuhlman > >> http://www.davekuhlman.org > >> _______________________________________________ > >> 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 > > > _______________________________________________ > zeromq-dev mailing list > [email protected] > http://lists.zeromq.org/mailman/listinfo/zeromq-dev >
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