[HBASE-25052] FastLongHistogram#getCountAtOrBelow method is broken.

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 3.0.0-alpha-1, 2.3.0, 1.6.0, 2.2.3
• Component/s: metrics
• Assignee: Unassigned
• Reporter: Rushabh Shah
• Created: 16/Sep/20 18:46
• Updated: 18/Sep/20 17:02

Description

FastLongHistogram#getCountAtOrBelow method is broken.
If I revert HBASE-23245 then it works fine.
Wrote a small test case in TestHistogramImpl.java :

  @Test
  public void testAdd1() {
    HistogramImpl histogram = new HistogramImpl();
    for (int i = 0; i < 100; i++) {
      histogram.update(i);
    }
    Snapshot snapshot = histogram.snapshot();
    // This should return count as 6 since we added 0, 1, 2, 3, 4, 5
    Assert.assertEquals(6, snapshot.getCountAtOrBelow(5));

It fails as below:

java.lang.AssertionError:
Expected :6
Actual :100

Issue Links

• is broken by: HBASE-23245 All MutableHistogram implementations should remove maxExpected