[7.x] [ML] Fixing inference stats race condition (#55163) #55486
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`updateAndGet` could actually call the internal method more than once on contention. If I read the JavaDocs, it says: ```* @param updateFunction a side-effect-free function``` So, it could be getting multiple updates on contention, thus having a race condition where stats are double counted. To fix, I am going to use a `ReadWriteLock`. The `LongAdder` objects allows fast thread safe writes in high contention environments. These can be protected by the `ReadWriteLock::readLock`. When stats are persisted, I need to call reset on all these adders. This is NOT thread safe if additions are taking place concurrently. So, I am going to protect with `ReadWriteLock::writeLock`. This should prevent race conditions while allowing high (ish) throughput in the highly contention paths in inference. I did some simple throughput tests and this change is not significantly slower and is simpler to grok (IMO). closes elastic#54786
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Pinging @elastic/ml-core (:ml) |
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Backports the following commits to 7.x: