openstack/monasca-common
Code Issues Proposed changes

Threshold Engine is rejecting valid measurements

Browse Source 
In the default case of a period being 60 and the evalation period being 60, the
window was being alternately slid 0 slots and then 2 slots. This caused it to
reject some recent measurements.

To illustrate what was happening, assume a SlidingWindow with a period of 60, and
a viewEndTimestamp of 60, and the AlarmDelay default of 30 seconds.  AlarmDelay is
used to increase the likliehood a metric arrives before the window is evaluated.
Also assume the evaluation period is happening at 20 seconds after every minute.

On the first one, at time 20, the time is not past the viewEndTimeStamp so nothing
happens. On the second one, at time 80, the time is past the viewEndTimeStamp but
the window doesn't slide because the time has be > viewEndTimestamp + alarmDelay.
At time 140, time is > viewEndTimestamp + alarmDelay so the window is slid. However,
since the alarmDelay wasn't being accounted for in the number of slots to slide, it
was sliding it one too far. On the next period it wouldn't slide at all and then
the next one it would do two again.

This was fixed by accounting for alarmDelay when calculating the number of slots to
slide

Change-Id: I4fcfd41f2de515684b3d0054f9c46c925ee4807b
This commit is contained in:
Craig Bryant 2015-08-26 16:50:14 -06:00
parent ca45f80fbb
commit fd5c41d720
2 changed files with 35 additions and 1 deletions
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2
java/monasca-common-util/src/main/java/monasca/common/util/stats/SlidingWindowStats.java
View File

@ -216,7 +216,7 @@ public class SlidingWindowStats {
}
long timeDiff = timestamp - slotEndTimestamp;
int slotsToAdvance = (int) (timeDiff / slotWidth);
slotsToAdvance += timeDiff % slotWidth == 0 ? 0 : 1;
slotsToAdvance += (timeDiff % slotWidth) > minDelay ? 1 : 0;
for (int i = 0; i < slotsToAdvance; i++) {
windowBeginIndex = indexAfter(windowBeginIndex);

34
java/monasca-common-util/src/test/java/monasca/common/util/stats/SlidingWindowStatsTest.java
View File

@ -15,6 +15,8 @@ package monasca.common.util.stats;
import static monasca.common.testing.Assert.assertArraysEqual;
import static org.testng.Assert.assertEquals;
import static org.testng.Assert.assertTrue;
import static org.testng.Assert.assertFalse;
import static org.testng.Assert.fail;
import org.testng.annotations.Test;
@ -98,6 +100,38 @@ public class SlidingWindowStatsTest {
assertArraysEqual(window.getTimestamps(), new long[] { 12, 15, 18 });
}
public void testSlides() {
SlidingWindowStats window = new SlidingWindowStats(Statistics.Average.class,
TimeResolution.ABSOLUTE, 60, 1, 2, 0);
assertTrue(window.addValue(1.0, 20));
window.slideViewTo(20, 30);
assertTrue(window.addValue(1.0, 0));
window.slideViewTo(100, 30);
assertFalse(window.addValue(1.0, 0));
assertTrue(window.addValue(1.0, 61));
window.slideViewTo(121, 30);
assertTrue(window.addValue(1.0, 61));
assertTrue(window.addValue(1.0, 121));
window.slideViewTo(180, 30);
assertFalse(window.addValue(1.0, 61));
assertTrue(window.addValue(1.0, 121));
assertTrue(window.addValue(1.0, 181));
window.slideViewTo(241, 30);
assertFalse(window.addValue(1.0, 121));
assertTrue(window.addValue(1.0, 181));
assertTrue(window.addValue(1.0, 241));
window.slideViewTo(360, 30);
assertFalse(window.addValue(1.0, 241));
assertTrue(window.addValue(1.0, 300));
assertTrue(window.addValue(1.0, 361));
}
public void shouldAddValueAndGetWindowValues() {
SlidingWindowStats window = new SlidingWindowStats(Statistics.Average.class,
TimeResolution.ABSOLUTE, 3, 3, 2, 9);