"Experimental" status of ZMQ_PAIR sockets. about zguide HOT 6 OPEN

For starters, ZMQ_PAIR sockets are designed for inter-thread communication... is concise and the context clearly relays that ZMQ_PAIR sockets as being intended for inter-thread communication. Using ZMQ_PAIR sockets are designed for in such an specific way, and than simply saying ZMQ_PAIR sockets are considered experimental and may have other missing or broken aspects really leaves a lot to be assumed.

from zguide.

If I didn't already have a years long grasp of zmq, or if I didn't have a solid background in thread related concepts/design outside of zmq, I'm not sure if I would be able to safely make assumptions on that foot note alone.

from zguide.

And clearly I'm not sure when it comes to specifics regarding this issue and that would be nice as well. For example, if I was to use a socket monitor to react when a tcp based ZQM_PAIR endpoint disconnected, would this solve the problem or is there deeper issues regarding IPC/IP ZQM_PAIR sockets. I'm not looking for an answer to this, it's purely hypothetical at this point of my design. But it would be nice if the documentation provided a bit more so that I wasn't left guessing or having to explore other avenues to find the answer.

from zguide.

"Don't do it" is well enough, but it's pointedly lacking.

from zguide.

To the point that I may start doing some deep evaluation to find and document the specific behavior involved in using ZMQ_PAIR over tcp:// or ipc. I don't see why that is necessary considering the lengths that have gone to both making the API consistent and to document it in both clear and complete form.

from zguide.

Also, ZeroMQ doesn't attempt to provide a 100% reliable or 100% fault tolerant solution for networking/IO, at least not purely as an implementation detail. ZMQ's current ecosystem instead attempts to fully document these aspects to allow development of higher-level protocols/patterns for handling these details. I believe documenting potential issues related to ZMQ_PAIR over icp/tcp would better fit this aspect of ZMQ's culture, and may be the start of solving the problem without necessarily making ZMQ_PAIR over true sockets 100% reliable at their core. It may simply be possible within the pattern detail once fully understood. In fact experience makes me think it very likely is solvable without core changes to the API.

from zguide.