[Meta] Upgrading to JRuby 9k

[ph]

With the release of Logstash 6.0 just around the corner we want to take the opportunity to upgrade to JRuby 9k, since 1.7 is EOL and a lot of gems are now breaking under 1.7 because they explicitely require JRuby 9k in their gemspec.

TODO

• Update Logstash to be able to run under JRuby 9k #Upgrade to JRuby 9k #5606 9k update #6713
• Create a feature branch with the JRuby 9k
• Update plugins .travis.yaml to build with jruby 9k Upgrade plugins .travis.yaml file to build JRuby 9k. #7126
• Move to java.time for timestamp instead of joda. Use Java 8 Time instead of Joda in LS and any plugins. #7149
• Fix plugins related issues, see meta issue JRuby 9k - Default plugins status #7252

cc @guyboertje

[ph]

I've created a PR on the beats input that makes sure we test the following matrix.

• Release Gems + JRuby 1.7.25
• Unreleased gems on LS 5.x + JRuby-1.7.25
• Logstash Master + JRuby-1.7.25
• Specific JRuby 9k Logstash feature branch + JRuby-1.7.25

What it does?

It make sure we test a plugin with the right jruby and also unreleased logstash branches, you can see an example run at https://travis-ci.org/logstash-plugins/logstash-input-beats. I've marked the JRuby 9k as a non-fatal job, but we will be able to query travis later to create a meta issue of problematic plugins.

There is some shell scripts to make sure we checkout the right branch, I've also added debug statement in the jobs itself to help debugging what version we are actually testing. Like this:

Checking out branch: master
Cloning into '../../logstash'...
remote: Counting objects: 1141, done.        
remote: Compressing objects: 100% (973/973), done.        
remote: Total 1141 (delta 111), reused 623 (delta 74), pack-reused 0        
Receiving objects: 100% (1141/1141), 11.29 MiB | 22.46 MiB/s, done.
Resolving deltas: 100% (111/111), done.
Checking connectivity... done.
Checked out Logstash revision: 0c282105ebb5a43ad044b8282842ebbd60076569
Building plugins with Logstash version:
---
logstash: 6.0.0-alpha2
logstash-core: 6.0.0-alpha2
logstash-core-plugin-api: 2.1.16
---

[guyboertje]

Created branch feature/9000 which is PR #6713 merged (kinda) to a new branch

[ph]

We decided to do Java8 time at a later date.