Improve "lag mitigation" TTL logic in WANObjectCache
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	aaron
	Jun 16 2021, 10:24 PM

Description

The lag-mitigation TTL logic in set() could be made smarter by:

Checking $walltime in a better way to distinguish high/low regeneration times. Right now, I see "0.005120992660522461" being reported as "high" for 4vN48nkBmhjHfZRTRKyF (could just be someone manually debugging on mwdebug though)
Ussing something higher than LOW_TTL (30 seconds) for the "slow callback case without lockTSE" case
Possibly scheduling async regenerations and making the asyncHandler flush replica snapshots (also nice for avoiding similar problems with preemptive refresh updates since they run at the end of the request)
Possibly making purge tombstones last longer (assuming the current automatic lockTSE and interim key logic is sufficient) so that MAX_READ_LAG could be higher

	Subject	Repo	Branch	Lines +/-
	objectcache: improve the WANObjectCache "lag mitigation" TTL logic	mediawiki/core	master	+130 -74

Mentioned Here: T282985: Show cached information on NewcomerTasksInfo special page

Change 700115 had a related patch set uploaded (by Aaron Schulz; author: Aaron Schulz):

[mediawiki/core@master] objectcache: improve the WANObjectCache "lag mitigation" TTL logic

Change 700258 had a related patch set uploaded (by Aaron Schulz; author: Aaron Schulz):

[mediawiki/core@master] rdbms: add "fetched" field to Database::setCacheOptions

Change 700115 merged by jenkins-bot:

[mediawiki/core@master] objectcache: improve the WANObjectCache \"lag mitigation\" TTL logic

Krinkle triaged this task as Medium priority.Sep 20 2021, 6:20 PM

aaron closed this task as Resolved.Sep 20 2021, 6:24 PM