Aleksandr Savonin created FLINK-40326:
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Summary: GatedRateLimiter admits more events per cycle than
configured
Key: FLINK-40326
URL: https://issues.apache.org/jira/browse/FLINK-40326
Project: Flink
Issue Type: Bug
Components: Connectors / Common
Reporter: Aleksandr Savonin
GatedRateLimiter.acquire(int numberOfEvents) closes its gate only once
capacityLeft has reached zero:
{code:java}
if (capacityLeft <= 0) { gatingFuture = new CompletableFuture<>(); return
gatingFuture.thenRun(() -> capacityLeft -= numberOfEvents);
{code}
When 0 < capacityLeft < numberOfEvents the request is granted anyway and
capacityLeft goes negative, so the cycle admits more events than
capacityPerCycle.
With capacityPerCycle = 5 and 3 events per request, two requests admit 6. It
recurs every cycle, because notifyCheckpointComplete resets the capacity
instead of carrying the deficit.
The condition was correct while every request was for a single event. FLIP-535
changed the decrement from 1 to numberOfEvents, which is what turned the
per-cycle cap soft. Two smaller defects in the same class:
* acquire(int) does not validate numberOfEvents: a negative value increases the
remaining capacity, and zero consumes none. Not reachable from current callers.
* notifyCheckpointComplete() dereferences the lazily initialised gatingFuture,
so a checkpoint completing before the first acquire() throws a
NullPointerException.
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