Rework workflow threads reporting from using blocking ThreadPoolExecutor#getActiveThreads #1421
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…tor#getActiveThreads
Spikhalskiy
requested review from
Sushisource,
bergundy,
cretz,
mfateev and
mmcshane
as code owners
cretz
approved these changes
Sep 13, 2022
| task.run(); | ||
| } finally { | ||
| tasksCount = tasksInFlight.decrementAndGet(); | ||
| metricsScope.gauge(MetricsType.WORKFLOW_ACTIVE_THREAD_COUNT).update(tasksCount); |
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Technically this is racy (line 55 can run on thread A, then line 50 and 51 can run on thread B, then line 56 runs back on thread A setting to old value), but after off-PR discussion: 1) this is how the old one worked, 2) it will get right eventually, 3) a bit off is acceptable, and 4) the alternative of synchronized access to gauge update is bad.
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ACK. I consider it's fine to publish sometimes a slightly outdated value to this gauge (and override a newer value). Because alternatives either bring synchronization of all workflow threads or are blocked by uber-tally interface.
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ThreadPoolExecutor#getActiveThreadsimplementation is taking a pool-wide lock and implements an actual counting inside this lock. This PR replaces it with an explicit counter to remove the points of threads serialization.