Clustering during development

This describes a quick way to create a VerneMQ cluster on developer's machines
Sometimes you want to have a quick way to test a cluster on your development machine as a VerneMQ developer.
You need to take care of a couple things if you want to run multiple VerneMQ instances on the same machine. There is a make option that let's you build multiple releases, as a commodity, taking care of all the configuration.
First, build a normal release (this is just needed the first time) with:
➜ default git:(master) ✗ make rel
The following command will then prepare 3 correctly configured vernemq.conf files, with different ports for the MQTT listeners etc. It will also build 3 full VerneMQ releases.
➜ default git:(master) ✗ make dev1 dev2 dev3
Check if you have the 3 new releases in the _build directory of your VerneMQ code repo.
You can then start the respective broker instances in 3 terminal windows, by using the respective commands and directory paths. Example:
➜ (_build/dev2/rel/vernemq/bin) ✗ vernemq console
The MQTT listeners will of course be configured differently for each node (the default 1883 port is not used, so that you can still run a default MQTT broker besides your dev nodes). A couple of other ports are also adapted (HTTP status page, cluster communication). The MQTT ports are automically configured in increasing steps of 50: (if in doubt, consult the respective vernemq.conf files)
MQTT listener port
Note that the dev nodes are not automatically clustered. You still need to manually cluster them with commands like the following:
➜ (_build/dev2/rel/vernemq/bin) ✗ vmq-admin cluster join [email protected]
In case this wasn't clear so far: You can configure an arbitrary number of cluster nodes, from dev1 to devn.