Remove empty temp dirs at plugin startup.

[mashhurs]

Release notes

[rn:skip]

What does this PR do?

For some environments, especially Windows OS, file scanning (such as antivirus enabled) tools hold temporarily created dirs' IO and a plugin cannot remove the temporarily dir after successfully uploading file to S3. Over time, there will be many empty temp dirs left under the temporary_directory. This PR introduces a logic which, at the Logstash start up, plugin cleans up temporary dirs.

Why is it important/What is the impact to the user?

The users who are facing empty temp dirs left issues get benefit from this automation.

Checklist

• [x] My code follows the style guidelines of this project
• [x] I have commented my code, particularly in hard-to-understand areas
• [] I have made corresponding changes to the documentation
• [ ] I have made corresponding change to the default configuration files (and/or docker env variables)
• [x] I have added tests that prove my fix is effective or that my feature works

Author's Checklist

• [ ]

How to test this PR locally

Related issues

• Closes #34

Use cases

Screenshots

Logs

[mashhurs]

🔴 CI is not relative and even re-run doesn't kick new run.

Analyzing the error a bit more provides a clear picture that it is due to docker 8.10 snapshot which uses JRuby 9.3.4.0 and has Concurrent::TimerTask regression. The error coming through stale sweeper initialization: @stale_sweeper = Concurrent::TimerTask.new(:execution_interval => @sweeper_interval) do.