Description:

Fixes #20537

Based on @sgiehl's changes in #20540 and also incorporating the feedback from @tsteur:

Another way would be something like below code to check if SharedSiteIds is supported and only then use it. Otherwise use the FixedSiteIds. This can make it worse though in cases where there are many sites and getmypid() is disabled. In this case Matomo would always start archiving with idsite 1 etc and never make it to the higher idsites. Meaning the created PR could work better overall even though it means the logic may not always run concurrently.

Disabling SharedSiteIds seems like the safer option if using random process ids. Since the current state is that archiving doesn't run at all and fails with an error on hosts without getmypid() I'd suggest a fix that may degrade performance on some edge cases (only if getmyid() is disabled) is preferable to no fix at all. We could perhaps document somewhere that hosting providers who disable getmypid() are not recommended for installations with many sites or high traffic.

I've tested this by disabling getmypid() locally, recreating the original issue and then successfully running archiving with the fix applied.

Review

• Functional review done
• Potential edge cases thought about (behavior of the code with strange input, with strange internal state or possible interactions with other Matomo subsystems)
• Usability review done (is anything maybe unclear or think about anything that would cause people to reach out to support)
• Security review done
• Wording review done
• Code review done
• Tests were added if useful/possible
• Reviewed for breaking changes
• Developer changelog updated if needed
• Documentation added if needed
• Existing documentation updated if needed