puma--puma/docs/plugins.md

Plugins

Puma 3.0 added support for plugins that can augment configuration and service operations.

2 canonical plugins to look to aid in development of further plugins:

• tmp_restart: Restarts the server if the file tmp/restart.txt is touched
• heroku: Packages up the default configuration used by puma on Heroku

Plugins are activated in a puma configuration file (such as config/puma.rb') by adding plugin "name", such as plugin "heroku".

Plugins are activated based simply on path requirements so, activating the heroku plugin will simply be doing require "puma/plugin/heroku". This allows gems to provide multiple plugins (as well as unrelated gems to provide puma plugins).

The tmp_restart plugin is bundled with puma, so it can always be used.

To use the heroku plugin, add puma-heroku to your Gemfile or install it.

API

Server-wide hooks

Plugins can use a couple of hooks at server level: start and config.

start runs when the server has started and allows the plugin to start other functionality to augment puma.

config runs when the server is being configured and is passed a Puma::DSL object that can be used to add additional configuration.

Any public methods in Puma::Plugin are the public API that any plugin may use.