Savonitar commented on PR #28920:
URL: https://github.com/apache/flink/pull/28920#issuecomment-5207432800

   @1996fanrui thanks for the questions and feedback.
   >  Two questions:
   > The gate now closes while capacity is still unused, so a cycle always 
emits less than capacityPerCycle and never reaches it — with 
capacityPerCycle=100 and 6 events per request, every cycle stops at 96.
   
   1. Yes, it undershoots now instead of overshooting, but isn't that the 
direction a rate limiter should err in? With capacityPerCycle=100, a single 
acquire(1000) was granted immediately and in full before this PR, because `100 
<= 0` is false. Also, doesn't it seem strange to use negative value for 
capacity(which can happen in pre-PR code)?
   
   > A single request larger than the cycle capacity still exceeds it: with 
capacityPerCycle=100 and acquire(10000), the first cycle emits nothing and then 
every following checkpoint releases the whole 10000, since 
notifyCheckpointComplete resets capacityLeft and drops the negative balance.
   
   2.That one is pre-existing, not introduced here: before the PR it produced 
[10000, 10000, ...], now it produces [0, 10000, ...]. 
   
   So this is an iterative improvement rather than a complete fix, a strict cap 
would need a redesign. This PR fixes three separate things: the gate, an NPE 
when a checkpoint completes before the first acquire(), and a missing argument 
check. I'm happy to drop the gate change and keep the overshoot if you think 
that's better by design. WDYT?


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