[BUG] A sufficiently small interval value on a histogram can crash the node about opensearch

[bowenlan-amzn]

Did some work on this today.
Aggregation only knows the correct number of buckets for the response at the final reduce phase. Before that, aggregations are done on every shard which may lead to a larger number of buckets (larger than 65535, the limit) to reduce in the end.

OpenSearch/server/src/main/java/org/opensearch/search/aggregations/bucket/BucketsAggregator.java

Lines 123 to 128 in 501a702

	if (docCounts.increment(bucketOrd, docCount) == docCount) {
	// We calculate the final number of buckets only during the reduce phase. But we still need to
	// trigger bucket consumer from time to time in order to give it a chance to check available memory and break
	// the execution if we are running out. To achieve that we are passing 0 as a bucket count.
	multiBucketConsumer.accept(0);
	}

So before the reduce phase, what we can do best is to fail gracefully before OOM. Above is a snippet to do that.
I will raise a PR later to add this logic into histogram.

[icercel]

@bowenlan-amzn , hi, terribly sorry for the delay, wanted to thank you for looking into this and providing a fix 🙇
can't wait to see it in AWS!