The only WSGI servers where this would work is those which are implemented using greenlets. Thus, eventlet and gevent modes of gunicorn. Any WSGI server which uses normal processes/threads, SSE will not really work well because of restrictions on size of workers available.
> On 5 Aug 2019, at 10:05 pm, Orestis Zambounis <orestis.zambou...@gmail.com> > wrote: > > My flask application implements SSE to push updates to each of my users. I.e. > each of my users gets individual updates and therefore unique SSE > connections. I deploy the application to mod_wsgi. Now mod_wsgi allows me to > use a fixed number of threads (default 15) which are quickly all blocked when > the number of users grows. This happens as the SSE connection are kept open > and are therefore blocking the thread. Subsequent requests can't get in > anymore and I get a Script timed out before returning headers: wsgi.pyerror. > > My current workaround is to put a timer in my SSE generator and break it > after a certain threshold. Still, with many users a fixed number of threads > will still lead to blocked requests. > > def stream(): > ... > queue = memory.get(...) > @stream_with_context > def eventStream(): > try: > start = time.time() > while True: > delta = start - time.time() > if delta > app.config["SSE_TIMEOUT"]: > break > # wait for source data to be available, then push it > try: > entry = queue.get( True, timeout=app.config["SSE_TIMEOUT"] > - delta) > except Empty: > break > ev = ServerSentEvent(json.dumps(entry)) > yield ev.encode() > finally: > ... > return Response(eventStream(), mimetype="text/event-stream") > > I'd like top find a clean solution to be able to handle an arbitrary amount > of users which are able to receive updates through SSE without blocking all > threads in wsgi. > > > I posted the issue also on stackoverflow: > https://stackoverflow.com/questions/57345375/server-sent-events-sse-blocking-threads-in-mod-wsgi > > -- > You received this message because you are subscribed to the Google Groups > "modwsgi" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to modwsgi+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/modwsgi/7528d624-f52b-4520-8509-0db74d31a2cd%40googlegroups.com. -- You received this message because you are subscribed to the Google Groups "modwsgi" group. To unsubscribe from this group and stop receiving emails from it, send an email to modwsgi+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/modwsgi/3F2BD34D-94ED-4348-A15E-5FD2CCF492C7%40gmail.com.
