It's a deliberate trade-off. ØMQ itself doesn't handle HA automatically. As a client, you can create a REQ socket and connect it to multiple redundant devices.

It's a deliberate trade-off. ØMQ itself doesn't handle HA automatically. As a client, you can create a REQ socket and connect it to multiple redundant devices. But if a device goes down, you will have to handle timeouts and repeat requests yourself. Additionally, ØMQ will not "kick out" the dead endpoint, so you will end up with 1 out of N requests timing out. So you have to add a decent amount of code in your RPC layer to make everything work properly. And you need to run ZMQ devices anyway. Running a local HAProxy with a 5 lines configuration is, IMHO, simpler than running an extra device somewhere + having to add a lot of HA-related code in the RPC layer. Of course, in the long run, it's more elegant to use XREQ + heartbeat to connect to multiple endpoints and send requests only to those which are alive. But in the short run, the HAProxy broker is dead simple and works very well :-)