[Cache] Fix versioned namespace atomic clears #35803
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When using namespace versioning to achieve atomic cache clears, only delete cache keys matching the old/current version. This resolves tag inconsistency issues whereby the process running the clear would delete keys set against the new version by more recently spawned concurreny processes. Most seriously this could result in newly set data keys remaining, but with empty associated tag sets meaning the invalidation via tags was no longer possible. Clearing specific prefixes is not supported when using versioned namespaces as it is desirable to clear all old keys as they will no longer be used and would otherwise eventually fill cache memory.
trvrnrth
changed the title
nicolas-grekas
approved these changes
Feb 24, 2020
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Thank you @trvrnrth. |
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When using namespace versioning to achieve atomic cache clears, only delete cache keys matching the old/current version.
This resolves tag inconsistency issues whereby the process running the clear would delete keys set against the new version by more recently spawned concurrent processes. Most seriously this could result in newly set data keys remaining, but with empty associated tag sets meaning the invalidation via tags was no longer possible.
Clearing specific prefixes is not supported when using versioned namespaces as it is desirable to clear all old keys as they will no longer be used and would otherwise eventually fill cache memory.