rmdmattingly opened a new pull request, #5683:
URL: https://github.com/apache/hbase/pull/5683
We've been experiencing RpcThrottlingException with 0ms waitInterval. This
seems odd and wasteful, since the client side will immediately retry without
backoff. I think the problem is related to the synchronization of RateLimiter.
The TimeBasedLimiter checkQuota method does the following:
```
if (!reqSizeLimiter.canExecute(estimateWriteSize + estimateReadSize)) {
RpcThrottlingException.throwRequestSizeExceeded(
reqSizeLimiter.waitInterval(estimateWriteSize + estimateReadSize));
}
```
Both canExecute and waitInterval are synchronized, but we're calling them
independently. So it's possible under high concurrency for canExecute to return
false, but then waitInterval returns 0 (would have been true).
This simplifies the API by having canExecute return the waitInterval, it
being greater than 0 if we should throttle the client.
This also implicitly fixes a bug with request number quotas — we were
returning a waitInterval assuming a single resource consumption, regardless of
the resources consumed by the operation:
https://github.com/apache/hbase/blob/9c8c9e7fbf8005ea89fa9b13d6d063b9f0240443/hbase-server/src/main/java/org/apache/hadoop/hbase/quotas/TimeBasedLimiter.java#L144-L146
I'm marking this as a draft while I deploy this onto a test cluster to
confirm that it resolves our 0ms throttle backoffs
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