Added cron to remove old index events for manual indexers

[tobihille]

Description (*)

As discussed in #199 I created a new PR which tackles the problem from another direction: Instead of completely omitting to write the index event to the database I created a cron that will delete these events if they are not processed.
This way we maintain BC and avoid filling the DB with garbage that might not be needed.

Related Pull Requests

#199

Manual testing scenarios (*)

1. Set index mode to manual in admin
2. Save a product
3. Execute select count(*) from index_event
4. Wait 24 hours
5. Run php cron.php (I executed the job from Aoe_Scheduler but the result should be the same)
6. Execute select count(*) from index_event

Questions or comments

I would gladly discuss the introduction of Mage_Index_Model_Observer::OLD_INDEX_EVENT_THRESHOLD_SECONDS, in my opinion this is a quick-and-dirty way to start this PR but I do not expect it to be in the final merge.
I would prefer a config but Mage_Index does not have a system.xml - so where would be good place for it?
If we add a config: what should be the default value?
Is one day a sufficient threshold for e.g. the Hackathon_AsyncIndex (on my workplace we index every day even if we have over 100.000 products and thousand categories)?

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All automated tests passed successfully (all builds are green)
• Add yourself to contributors list

[Sdfendor]

Is the introduction of a cronjob a reason to bump the version number of the module 🤔?

[fballiano]

Is the introduction of a cronjob a reason to bump the version number of the module 🤔?

I'd bump only if there's a new install script to modify the database

[Sdfendor]

Fair point after all its one of the main reason to have versions of OpenMage modules to begin with.

[fballiano]

I think this one should be merged

[fballiano]

we could merge because it's 1 green + 2 gray but I notice now that it's the wrong branch, can't merge on 1.9.4.x, we've to rebase on main

The base branch was changed.

The base branch was changed.

[fballiano]

I'm merging because it was already approved (1green + 2gray checks) but I had to rebase (checked and the diff is exactly the same)