Socket timeout handling breaks message guarantees

[skaes]

The handling of send/receive timeouts is buggy in the current implementation. Messages will be lost when they arrive after a socket timeout.

This patch fixes the problem by moving the timeout handling from the erlang code to the poller thread.

[lukaszsamson]

@skaes this version of erlzmq is extremely unstable and breaks not only zmq but also erlang NIF guarantees. It has a serious design flaw - It breaks zmq sockets by using them from different threads. Zmq sockets (with exception of experimental client/server and radio/dish) are NOT thread safe. The result are assertion failures deep in libzmq happening randomly. It also has data races, mutex usage issues, resource leaks (thread, file descriptors, memory, erlang NIF resources). I'd strongly advise against using it in production. Please check out my fork https://github.com/lukaszsamson/erlzmq that fixes those issues and also introduces new features and support for more recent libzmq versions

[skaes]

@lukaszsamson that's interesting. For some reason I did not find your fork. I was aware that there are other problems with the erzlmq code and I had seen that most of the PRs did not receive any feedback. Unfortunately, this library is what you get when you install erlzmq from hex.pm. I'll have a look at your fork, though.

[skaes]

@lukaszsamson I have cloned your project and ran the tests. One fails out of the box. Would you mind enabling issues on your Github project?

[lukaszsamson]

@skaes enabled