ZeroMQ is dropping messages

Question

I am using ZeroMQ to communicate between multiple services. I ran into an issue where I was sending responses but they were never getting to the caller. I did a lot of debugging and couldn't figure out what was happening. I eventually reduced the message size (I was returning the results of a query) and the messages started coming in. Then I increased the memory size of my JVM and the original messages started coming back.

This leads me to believe that the messages were too big to fit into memory and ZeroMQ just dropped them. My question is, how can I properly debug this? Does ZeroMQ output any logs or memory dumps?

I am using the Java version of ZeroMQ.

Answer 1

Q : "...how can I properly debug this?"

Well, if one were aware of the native ZeroMQ API settings, at least of both the buffering "mechanics" and the pair of { SNDHWM | RCVHWM }-hard-cut-off limits, one might do some trial-error testing for fine-tuning these parameters.

Q : "Does ZeroMQ output any logs or memory dumps?"

Well, no, the native ZeroMQ knowingly did not ever attempted to do so. The key priority of the ZeroMQ concept is the almost linearly scalable performance and the Zen-of-Zero reflecting that excluded any single operation, that did not support achieving this at minimalistic low-latency envelopes.

Yet, newer versions of the native API provide a tool called socket-monitor. That may help you write your own internal socket-events' analyser, if in such a need.

My 11+ years with ZeroMQ have never got me into an unsolvable corner. Best get the needed insights into the Context()-instance and Socket()-instance parameters, that will better configure the L3, protocol-dependent and O/S-related buffering attributes ( some of which need not be present in the java-bindings, yet the native API shows at its best all the possible and tweakable parameters of the ZeroMQ data-pumping engines ).