Always close completed app sessions#36651
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rosstimothy merged 3 commits intomasterfrom Jan 13, 2024
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The FnCacheConfig now provides an optional OnExpires callback which will be called when any item in the cache is removed due to expiry. Eviction of expired entries used to only happen on retrieval attempts, but this can now be triggered on demand using (FnCache) RemoveExpired. A new Shutdown method was also added to allow all items in the cache to be removed. If OnExpires is set then it will be called for every item in the cache during Shutdown.
The previous use of gravitational/ttlmap with a fixed capacity led to sessions leaking and never being closed if a spike of sessions greater than the capcity occurred. The sessionChunkCache relied on the expiry callback function set on the ttlmap to be called in order to close the app session and release resources. However, if an item was evicted from the ttlmap because the capacity had been exceeded the expiry callback was fired. Instead of increasing the capacity to a larger size the ttlmap was replaced entirely by utils.FnCache. It offers equivalent functionality while still being actively maintained. This also allowed refactoring to remove the sessionChunkCache entirely since the FnCache took care of most of the added functionality that the ttlmap wrapper was providing. Partially addressed #36541.
zmb3
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Overall looks great but I wonder if we need to expire sessions every second.
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Why one second? Seems pretty frequent.
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rosstimothy
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tigrato
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@rosstimothy See the table below for backport results.
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This was referenced Jan 18, 2024
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The previous use of gravitational/ttlmap with a fixed capacity led to sessions leaking and never being closed if a spike of sessions greater than the capacity occurred. The sessionChunkCache relied on the expiry callback function set on the ttlmap to be called in order to close the app session and release resources. However, if an item was evicted from the ttlmap because the capacity had been exceeded the expiry callback was fired.
Instead of increasing the capacity to a larger size the ttlmap was replaced entirely by utils.FnCache. It offers equivalent functionality while still being actively maintained. This also allowed refactoring to remove the sessionChunkCache entirely since the FnCache took care of most of the added functionality that the ttlmap wrapper was providing.
Partially addressed #36541.
changelog: Ensure that any opened app session is always closed on completion