[jira] [Resolved] (FLINK-40326) GatedRateLimiter admits more events per cycle than configured

["Martijn Visser (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLINK-40326?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Martijn Visser resolved FLINK-40326.
------------------------------------
    Fix Version/s: 2.2.2
                   2.3.1
       Resolution: Fixed

> 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
>            Assignee: Aleksandr Savonin
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 2.2.2, 2.3.1, 2.4.0
>
>
> 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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