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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)
Node
MQTT listener port
10053
10103
10153
...
...
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.