[FW][FIX] registry: avoid re-signaling invalidated cache #41502
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In a multi-threaded environment, when the cache is being cleared through a call to `registry.clear_caches`, it's possible any number of other threads signal the database that the cache has been invalidated, causing extra, unnecessary invalidations, possibly in a looping fashion. A scenario where this can cause issues: 1) There are 2 threads busy handling a request each, [A] & [B]. 2) The database has its ´base_cache_signaling´ sequence incremented. 3) [A] calls `registry.check_signaling`, sees the cache should be invalidated and calls `registry.clear_caches`, setting `registry.cache_invalidated` to True for each model it clears the cache for. 4) [B] finished serving its request, calls `check_signaling`, sees `registry.clear_caches` is True and signals the database by increasing the `base_cache_signaling` sequence. 5) [A] finishes looping through the models being invalidated and attempts to clear the `registry.cache_invalidated`, but it's too late because [B] has already read it. Should 2 or more multi-threaded servers run in parallel on the same database (both handling many concurrent requests), it's possible this triggers alternatively on each server and loops indefinitely. To fix this problem, we avoid setting `registry.cache_invalidated` to True when clearing the cache. It's interesting to note that the cache invalidation is not thread-safe, and can lead to inconsistent cache states during its invalidation & clearing. Fixing this fully requires a bigger design change that may come in the future, but most likely not as a fix in a stable version. X-original-commit: 8a7fe5f
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This PR targets 13.0 and is part of the forward-port chain. Further PRs will be created up to master. More info at https://github.com/odoo/odoo/wiki/Mergebot#forward-port |
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In a multithreaded environment, when the cache is being cleared through
a call to
registry.clear_caches, it's possible any number of otherthreads signal the database that the cache has been invalidated.
One of multiple scenarios where this can cause issues:
check_signaling, sees it should beinvalidated and calls
registry.clear_caches, settingregistry.cache_invalidatedto True while it clears the cache foreach model.
check_signaling, seesregistry.clear_cachesis True and signals the database byincreasing the
base_cache_signalingsequence.Should 2 multi-threaded servers run in parallel on the same database
(both handling many requests), it's possible this triggers alternatively
on each worker and loops indefinitely.
To fix this problem, we avoid setting
registry.cache_invalidatedtoTrue when clearing the cache.
It's interesting to note that the cache invalidation is not thread-safe,
and can be in inconsistent states during its invalidation & clearing.
Fixing this fully requires a bigger design change that may come in the
future, but most likely not as a fix in a stable version.
Forward-Port-Of: #40983