epoll: always retrieve events from triggered sockets #88
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This fixes a hang in the epoll code that triggers on heavy, bursty connections (such as the live SPNS APNs notifier). It turns out that side-effects of processing our sockets could leave other sockets (that we processed earlier in the loop) in a needs-attention state which we might not notice if we go back to epoll_wait right away. zmq::poll apparently takes care of this (and so is safe to re-poll even in this state), but when we are using epoll we need to worry about it by always checking for zmq events (which itself has side effects) and, if we get any, re-enter the loop body immediately *without* polling to deal with them.
tewinget
approved these changes
Sep 15, 2023
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The epoll approach from #87 sometimes hangs a socket: apparently the call to getting the ZMQ events off a socket can have internal ZMQ side effects (see libzmq issue 3641 for more), so make sure we always call it on triggered sockets when using epoll.