A few EMQX Enterprise customers were asking how they can develop their own EMQX plugins and use them in the enterprise edition. This article is to document the steps.
How to build your own plugin
Since EMQX v4.3, community plugins can be built in the umbrella project with only a few lines of config change. Please find the instructions in this README
Where to install your plugin
Starting from community edition v4.3.2 and enterprise edition e4.3.1, external plugins can be installed in
<expand_plubins_dir> is configurable in
emqx.conf by they config key
plugins.expand_plugins_dir. By default the directory is configured as
$INSTALL_DIR/etc/plugins when EMQX is installed from zip package, and
/etc/emqx/plugins/ when installed from RPM or DEB packages.
What should a plugin release contain
An EMQX plugin, is an Erlang application that implements some of the EMQX’s hook-points. In this sense, the build artifacts to be deployed to production is similar to the built-in plugins, it consists of directories as below (taking the plugin emqx_psk_pgsql for example)
$ tree _build/default/lib/emqx_psk_pgsql/ _build/default/lib/emqx_psk_pgsql/ ├── ebin │ ├── emqx_psk_pgsql.app │ ├── emqx_psk_pgsql.beam │ ├── emqx_psk_pgsql_app.beam │ ├── emqx_psk_pgsql_client.beam │ └── emqx_psk_pgsql_sup.beam ├── etc │ └── emqx_psk_pgsql.conf ├── include │ └── emqx_psk_pgsql.hrl ├── priv │ └── emqx_psk_pgsql.schema └── src ├── emqx_psk_pgsql.app.src ├── emqx_psk_pgsql.erl ├── emqx_psk_pgsql_app.erl ├── emqx_psk_pgsql_client.erl └── emqx_psk_pgsql_sup.erl
include are optional since all they have inside are source code.
ebin directory is where the compiled beam files reside.
etc is per EMQX’s convention, the directory to store the plugin’s config file, and
priv directory is, per Erlang’s convention, to keep build artifacts to be released (in our case, the plugin’s config schema file).
How to load/unload your plugin
After the plugin is installed, the node needs a restart to have the new code loaded, then the external plugin works the same as the built-in plugins delivered as a part of EMQX packages. That is, the
emqx_ctl plugins command can be used to list, load, and unload plugins.
If your plugin has other dependencies
A plugin (as an Erlang or Elixir) application may have other applications as dependencies.
The dependency applications should also be installed to
e.g. In a rebar3 project, after the code is compiled, you should be able to find all the dependencies in
_build/default/lib/ – which are to be copied to
Please note though, if a dependency application is included in the EMQX release package, it should not be installed to external plugin dir.
You can list
$INSTALL_DIR/lib/ directory to find all the applications released in the EMQX package.