Add async tests for plugins

[florianvazelle]

Description

1. Add asynchronous testing for plugins
2. Clean title in USER GUIDE for alerting section

Issues Resolved

1. To increase coverage
2. As requested here Index State Management support #398 (comment)

[codecov]

Codecov Report

Merging #425 (92fb09e) into main (4dba35d) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #425   +/-   ##
=======================================
  Coverage   71.49%   71.49%           
=======================================
  Files          81       81           
  Lines        7668     7668           
=======================================
  Hits         5482     5482           
  Misses       2186     2186           

[dblock]

LGTM, finish it up?

[florianvazelle]

Hi @dblock, there are two points I'd like to look at:

• the tests pass but the teardown of the last test is flaky, because the event loop seems closed
• and coverage isn't increasing, because it seems that coverage reports sent to codecov are from the test workflow (https://github.com/opensearch-project/opensearch-py/blob/main/.github/workflows/test.yml), and in the test workflow no OpenSearch is run. So in fact coverage doesn't really represent what's being tested. I'm taking a little more time to see if it isn't possible to have a workflow that would launch all the tests (with a running OpenSearch), and that would send a complete report, which would make it possible to have a real coverage report on plugins for example.

[dblock]

@florianvazelle I wouldn't worry about coverage

[florianvazelle]

@dblock Ok, so It's good to me now

[dblock]

LGTM, two small changes with the license headers please? Sorry for the hassle.

tl;dr:

• new files only need the SPDX header + first paragraph
• existing files license headers should not be changed

[dblock]

You can remove the modifications part from new files. That was added during the fork for files that had an ES license before.

[florianvazelle]

But the utils/license-headers.py enforce the Modifications Copyright OpenSearch Contributors part. Should I adapt checks made in the script ?

[dblock]

Hmmm, we can deal with this separately.

[dblock]

This is a new file, so I believe everything including and down from Modifications ... should be removed. Just leave the SPDX header and the paragraph that says "The OpenSearch ... open source license.".