Fixes #4391 stop background processes before rollback and update

[mostafa-hisham]

Description

stop background processes before rollback and update to avoid fatal if the processes still running while the plugin changes

Fixes #4391

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

Is the solution different from the one proposed during the grooming?

there is no grooming

How Has This Been Tested?

• we should create an alpha release with this branch so we can test it in both rollback and upgrade

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• My changes generate no new warnings
• New and existing unit tests pass locally with my changes

[iCaspar]

What's here looks good.
Can we add integration tests to cover this?

[mostafa-hisham]

@iCaspar
I successfully created Integration tests for
stop CPCSS background Process
stop homepage preload background process

in both
stop warmup background process
stop sitemap preload background process

i think the problem is I couldn't start them in the integration test
to check if the upgrade or rollback action will stop them

you can have a look at the classes in the previous commit if you want to give it a try

[iCaspar]

Nice work.

[piotrbak]

@mostafa-hisham
When rolling back from the branch to 3.9, there's no fatal error, but the RUCSS process can be stuck on warming up with wrong data:
"warmup_status":{"total":1,"warmed_count":0,"notwarmed_resources":[],"duration":70,"completed":false}.
While updating, it got stuck too, but the data was more accurate.

It seems not to be a problem with this branch, as it's only here to prevent fatal error from happening. There's no pattern to reproduce this though.

@Tabrisrp What do you think? Should we somehow make sure that RUCSS process will be continued and more reliable in this PR?

[Tabrisrp]

Since we cancel the process, we can't resume it easily after. I'd say it's ok for this PR, and we can follow up on another issue to handle this case.

[piotrbak]

@mostafa-hisham @Tabrisrp After one of the tries, my log got blasted with that kind of notices:

[05-Oct-2021 15:40:59 UTC] PHP Notice:  Undefined index: external in /var/www/rocketlab.ovh/htdocs/wp-content/plugins/wp-rocket/inc/Engine/Optimization/RUCSS/Warmup/ResourceFetcherProcess.php on line 123

[05-Oct-2021 15:40:59 UTC] PHP Notice:  Undefined index: path in /var/www/rocketlab.ovh/htdocs/wp-content/plugins/wp-rocket/inc/Engine/Optimization/RUCSS/Warmup/ResourceFetcherProcess.php on line 123

[05-Oct-2021 15:40:59 UTC] PHP Notice:  Undefined index: path in /var/www/rocketlab.ovh/htdocs/wp-content/plugins/wp-rocket/inc/Engine/Optimization/RUCSS/Warmup/ResourceFetcherProcess.php on line 135

Do you think we can do something about that?

[mostafa-hisham]

@piotrbak @Tabrisrp
i guarded the variables to avoid warnings

[piotrbak]

Good to go!
testrail-report-269.pdf