WikiPageEntityMetaDataLookup should only fallback to master when EntityRevisionLookup::LATEST_FROM_MASTER is explicitly set. (in cases where we need to be concerned about slave lag)
In many cases, if there is some slave lag, it is okay. (e.g. accessing an entity from lua)
see T108841
| Status | Subtype | Assigned | Task | ||
|---|---|---|---|---|---|
| Resolved | hoo | T108841 [Bug] Expectation (masterConns <= 0) by MediaWiki::main not met: (via Wikibase Lua code) | |||
| Resolved | hoo | T88986 [Task] Avoid inconsistencies in Wikidata editing due to slave lag | |||
| Resolved | hoo | T108929 [Task] only fallback to master in WikiPageEntityMetaDataLookup when explicitly requested |
Just to give a short update here: I poked at this and there is a "draft" on gerrit… the "hard" part is to make sure all code paths use the right type of connection (master for writes, slaves otherwise) and we have the appropriate fallbacks in place if needed.
https://gerrit.wikimedia.org/r/279135
I'll have another look at this sometime soon.
Has anyone had a chance to look at this lately?
The patch doesn't seem to load for me.
FYI: I just picked this up again and will probably provide patches during this weekend… I'll do it step by step to minimize the risk of us introducing data inconsistencies this way.
Change 302199 had a related patch set uploaded (by Hoo man):
Introduce EntityRevisionLookup::LATEST_FROM_SLAVE_WITH_FALLBACK
Todo (mostly a note to myself):
Change 302199 merged by jenkins-bot:
Introduce EntityRevisionLookup::LATEST_FROM_SLAVE_WITH_FALLBACK
Change 279135 merged by jenkins-bot:
Don't fallback to master in WikiPageEntityMetaDataLookup etc.