Add compatibility on ruby pipeline for plugins not in support matrix

[kaisecheng]

[rn:skip]

This PR is a follow-up of ruby execution engine removal. It adds a better backward compatibility experience for plugins not in the support matrix

follow-up on #12517

[yaauie]

It is unclear to me how this "adds a better backward compatibility experience for plugins not in the support matrix".

• What differentiates plugins "not in the support matrix", and why does change this benefit them in particular?
• Do unsupported plugins create their own Pipeline, and if so which ones? I would consider doing so to be a Very Bad practice in production code, but could see an argument for doing it in tests if there was no other way.
• Arguably something depends on LogStash::Pipeline.new, and now that a JavaPipeline is returned, are there unexpected side-effects from its initialization, such as queue opening?

[kaisecheng]

I check this page to differentiate the plugins we are actively maintaining. For tier 1 & 2 plugins, all require logstash/pipeline are removed, while the others will keep the reference to pipeline.rb. By searching in GitHub, there are two references in the test case of an archived project to LogStash::Pipeline.new. So we are not using it in production. Considering the plugins not list in https://github.com/logstash-plugins, pointing Pipeline to JavaPipeline gives a better chance to keep the old code work. JavaPipeline takes the same parameters in initialize() as Pipeline and provides back-compatibility for deprecated methods(not all of them). I consider JavaPipeline a proper replacement. My knowledge of both pipelines may not be completed. Please let me if I miss something

[kaisecheng]

The test cases like this will be beneficial. So, we don't need to change the test cases in every project and keep them running

[kares]

@yaauie I was the one to suggest this due a few require 'logstash/pipeline' places.

The require seemed legit (loading whatever pipeline there is in LS not tying things to a "java" pipeline), although it's questionable why anyone except the devutils case would need to require this. Seemed like worth saving a few hops but given it's only present one of the supported plugins (integration-rabbitmq) I have not strong feelings about this.

[kaisecheng]

@yaauie Do you have a further concern?

[yaauie]

LGTM 👍