Plugin Factory Support Mixin

This gem is a support adapter for Logstash plugins that can be used to ensure your plugin has access to an api-stable Plugin Factory for instantiating inner plugins, even when run on a Logstash version that does not provide a Plugin Factory.

Inner plugins generated by this factory will be fully-contextualized in the pipeline that the outer plugin is running in, and when instantiated without an explicit id parameter, a sensibly-descriptive distinct id will be generated.

1. Add version ~>1.0 of this gem as a runtime dependency of your Logstash plugin's gemspec:

   Gem::Specification.new do |s|
     # ...
   
     s.add_runtime_dependency 'logstash-mixin-plugin_factory_support', '~>1.0'
   end

2. In your plugin code, require this library and include it into your plugin class that already inherits LogStash::Plugin:

   require 'logstash/plugin_mixins/plugin_factory_support'
   
   class LogStash::Inputs::Foo < Logstash::Inputs::Base
     include LogStash::PluginMixins::PluginFactorySupport
   
     # ...
   end

3. When instantiating other plugins from inside your plugin, do not send new to the plugin class directly. Instead use the plugin_factory method to obtain a PluginFactory, and then use one of its #input, #output, #codec, or #filter methods with your plugin's name to obtain a proxy for the plugin class, and then send the proxy #new with your options as normal. This will ensure that the inner plugin instance is properly bound to the pipeline and execution context from the outer plugin.

     def register
       @internal_grok = plugin_factory.filter('grok').new("match" => {"message" => "^PATTERN"})
     end

   Expressed as a diff:

      def register
   -    @internal_grok = ::LogStash::Filter::Grok.new("match" => {"message" => "^PATTERN"})
   +    @internal_grok = plugin_factory.filter('grok').new("match" => {"message" => "^PATTERN"})
      end
   

   Note: when instantiating an inner plugin with a plugin factory, managing its lifecycle remains an implementation detail of the outer plugin. Lifecycle events like LogStash::Plugin#close, LogStash::Inputs::Base#stop, or LogStash::Codecs::Base#flush for the outer plugin are not automatically propagated to the inner plugin.

This gem:

• MUST remain API-stable at 1.x
• MUST NOT introduce additional runtime dependencies