ZeroMQ vs Crossroads I/O
I am looking into using ZeroMQ as the messaging/transport layer for a fairly large distributed system, mainly targeting monitoring and data collection (many producers, a few consumers).
As far as I can see there are currently two different implementations of the same concept; ZeroMQ and Crossroads I/O, the latter being a fork of ZeroMQ (in 2012?).
I am trying to figure out which one to use and wonder about the differences between them, but have so far not found much information regarding this.
For example:
- Are they compatible on the wire?
- Are they API compatible, i.e. some kind of common base API, possibly with different add-ons?
- Do they both implement support for ZMTP (ZeroMQ Message Transport Protocol)?
- Do they share some kind of common understanding of future development or will they continue in two separate and possible different directions?
- What are the pros/cons in relation to the other?
Basically, how do one choose one over the other?
Answer
Crossroads.io is pretty dead since Martin Sustrik has started on a new stack, in C, called nano: https://github.com/250bpm/nanomsg
Crossroads.io does not, afaik, implement ZMTP/1.0 nor ZMTP/2.0 but its own version of the protocol.
Nano has pluggable transports and we'll probably make a ZMTP transport for that. Nano is really nice, a rethinking of the original libzmq library, and if it's successful would make a good new kernel.
Ideally, Nano would interoperate both at the API and the protocol level, so be a pluggable replacement for libzmq. It does have quite a long way to go, though.
Note that there are now several rewrites of libzmq emerging, including JeroMQ (Java) and NetMQ (C#). These two do implement ZMTP/1.0 and ZMTP/2.0 properly. There are also other libraries like Axon (https://github.com/visionmedia/axon) which are heavily inspired by 0MQ but not compatible.
Based on experience, users value interoperability more than almost anything else, so it's quite likely that different 0MQ-like stacks will end up speaking the same protocols.