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* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.cassandra.metrics;
import org.junit.Test;
import com.codahale.metrics.Clock;
import com.codahale.metrics.Snapshot;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;
public class DecayingEstimatedHistogramReservoirTest
{
private static final double DOUBLE_ASSERT_DELTA = 0;
@Test
public void testSimple()
{
{
// 0 and 1 map to the same, first bucket
DecayingEstimatedHistogramReservoir histogram = new DecayingEstimatedHistogramReservoir();
histogram.update(0);
assertEquals(1, histogram.getSnapshot().getValues()[0]);
histogram.update(1);
assertEquals(2, histogram.getSnapshot().getValues()[0]);
}
{
// 0 and 1 map to different buckets
DecayingEstimatedHistogramReservoir histogram = new DecayingEstimatedHistogramReservoir(true, DecayingEstimatedHistogramReservoir.DEFAULT_BUCKET_COUNT);
histogram.update(0);
assertEquals(1, histogram.getSnapshot().getValues()[0]);
histogram.update(1);
Snapshot snapshot = histogram.getSnapshot();
assertEquals(1, snapshot.getValues()[0]);
assertEquals(1, snapshot.getValues()[1]);
}
}
@Test
public void testOverflow()
{
DecayingEstimatedHistogramReservoir histogram = new DecayingEstimatedHistogramReservoir(DecayingEstimatedHistogramReservoir.DEFAULT_ZERO_CONSIDERATION, 1);
histogram.update(100);
assert histogram.isOverflowed();
assertEquals(Long.MAX_VALUE, histogram.getSnapshot().getMax());
}
@Test
public void testMinMax()
{
DecayingEstimatedHistogramReservoir histogram = new DecayingEstimatedHistogramReservoir();
histogram.update(16);
Snapshot snapshot = histogram.getSnapshot();
assertEquals(15, snapshot.getMin());
assertEquals(17, snapshot.getMax());
}
@Test
public void testMean()
{
{
TestClock clock = new TestClock();
DecayingEstimatedHistogramReservoir histogram = new DecayingEstimatedHistogramReservoir(DecayingEstimatedHistogramReservoir.DEFAULT_ZERO_CONSIDERATION, DecayingEstimatedHistogramReservoir.DEFAULT_BUCKET_COUNT, clock);
for (int i = 0; i < 40; i++)
histogram.update(0);
for (int i = 0; i < 20; i++)
histogram.update(1);
for (int i = 0; i < 10; i++)
histogram.update(2);
assertEquals(1.14D, histogram.getSnapshot().getMean(), 0.1D);
}
{
TestClock clock = new TestClock();
DecayingEstimatedHistogramReservoir histogram = new DecayingEstimatedHistogramReservoir(true, DecayingEstimatedHistogramReservoir.DEFAULT_BUCKET_COUNT, clock);
for (int i = 0; i < 40; i++)
histogram.update(0);
for (int i = 0; i < 20; i++)
histogram.update(1);
for (int i = 0; i < 10; i++)
histogram.update(2);
assertEquals(0.57D, histogram.getSnapshot().getMean(), 0.1D);
}
}
@Test
public void testStdDev()
{
{
TestClock clock = new TestClock();
DecayingEstimatedHistogramReservoir histogram = new DecayingEstimatedHistogramReservoir(DecayingEstimatedHistogramReservoir.DEFAULT_ZERO_CONSIDERATION, DecayingEstimatedHistogramReservoir.DEFAULT_BUCKET_COUNT, clock);
for (int i = 0; i < 20; i++)
histogram.update(10);
for (int i = 0; i < 40; i++)
histogram.update(20);
for (int i = 0; i < 20; i++)
histogram.update(30);
Snapshot snapshot = histogram.getSnapshot();
assertEquals(20.0D, snapshot.getMean(), 2.0D);
assertEquals(7.07D, snapshot.getStdDev(), 2.0D);
}
}
@Test
public void testFindingCorrectBuckets()
{
TestClock clock = new TestClock();
DecayingEstimatedHistogramReservoir histogram = new DecayingEstimatedHistogramReservoir(DecayingEstimatedHistogramReservoir.DEFAULT_ZERO_CONSIDERATION, 90, clock);
histogram.update(23282687);
assertFalse(histogram.isOverflowed());
assertEquals(1, histogram.getSnapshot().getValues()[89]);
histogram.update(9);
assertEquals(1, histogram.getSnapshot().getValues()[8]);
histogram.update(21);
histogram.update(22);
Snapshot snapshot = histogram.getSnapshot();
assertEquals(2, snapshot.getValues()[13]);
assertEquals(6277304.5D, snapshot.getMean(), DOUBLE_ASSERT_DELTA);
}
@Test
public void testPercentile()
{
{
TestClock clock = new TestClock();
DecayingEstimatedHistogramReservoir histogram = new DecayingEstimatedHistogramReservoir(DecayingEstimatedHistogramReservoir.DEFAULT_ZERO_CONSIDERATION, DecayingEstimatedHistogramReservoir.DEFAULT_BUCKET_COUNT, clock);
// percentile of empty histogram is 0
assertEquals(0D, histogram.getSnapshot().getValue(0.99), DOUBLE_ASSERT_DELTA);
histogram.update(1);
// percentile of a histogram with one element should be that element
assertEquals(1D, histogram.getSnapshot().getValue(0.99), DOUBLE_ASSERT_DELTA);
histogram.update(10);
assertEquals(10D, histogram.getSnapshot().getValue(0.99), DOUBLE_ASSERT_DELTA);
}
{
TestClock clock = new TestClock();
DecayingEstimatedHistogramReservoir histogram = new DecayingEstimatedHistogramReservoir(DecayingEstimatedHistogramReservoir.DEFAULT_ZERO_CONSIDERATION, DecayingEstimatedHistogramReservoir.DEFAULT_BUCKET_COUNT, clock);
histogram.update(1);
histogram.update(2);
histogram.update(3);
histogram.update(4);
histogram.update(5);
Snapshot snapshot = histogram.getSnapshot();
assertEquals(0, snapshot.getValue(0.00), DOUBLE_ASSERT_DELTA);
assertEquals(3, snapshot.getValue(0.50), DOUBLE_ASSERT_DELTA);
assertEquals(3, snapshot.getValue(0.60), DOUBLE_ASSERT_DELTA);
assertEquals(5, snapshot.getValue(1.00), DOUBLE_ASSERT_DELTA);
}
{
TestClock clock = new TestClock();
DecayingEstimatedHistogramReservoir histogram = new DecayingEstimatedHistogramReservoir(DecayingEstimatedHistogramReservoir.DEFAULT_ZERO_CONSIDERATION, DecayingEstimatedHistogramReservoir.DEFAULT_BUCKET_COUNT, clock);
for (int i = 11; i <= 20; i++)
histogram.update(i);
// Right now the histogram looks like:
// 10 12 14 17 20
// 0 2 2 3 3
// %: 0 20 40 70 100
Snapshot snapshot = histogram.getSnapshot();
assertEquals(12, snapshot.getValue(0.01), DOUBLE_ASSERT_DELTA);
assertEquals(14, snapshot.getValue(0.30), DOUBLE_ASSERT_DELTA);
assertEquals(17, snapshot.getValue(0.50), DOUBLE_ASSERT_DELTA);
assertEquals(17, snapshot.getValue(0.60), DOUBLE_ASSERT_DELTA);
assertEquals(20, snapshot.getValue(0.80), DOUBLE_ASSERT_DELTA);
}
{
TestClock clock = new TestClock();
DecayingEstimatedHistogramReservoir histogram = new DecayingEstimatedHistogramReservoir(true, DecayingEstimatedHistogramReservoir.DEFAULT_BUCKET_COUNT, clock);
histogram.update(0);
histogram.update(0);
histogram.update(1);
Snapshot snapshot = histogram.getSnapshot();
assertEquals(0, snapshot.getValue(0.5), DOUBLE_ASSERT_DELTA);
assertEquals(1, snapshot.getValue(0.99), DOUBLE_ASSERT_DELTA);
}
}
@Test
public void testDecayingPercentile()
{
{
TestClock clock = new TestClock();
DecayingEstimatedHistogramReservoir histogram = new DecayingEstimatedHistogramReservoir(DecayingEstimatedHistogramReservoir.DEFAULT_ZERO_CONSIDERATION, DecayingEstimatedHistogramReservoir.DEFAULT_BUCKET_COUNT, clock);
// percentile of empty histogram is 0
assertEquals(0, histogram.getSnapshot().getValue(1.0), DOUBLE_ASSERT_DELTA);
for (int v = 1; v <= 100; v++)
{
for (int i = 0; i < 10_000; i++)
{
histogram.update(v);
}
}
Snapshot snapshot = histogram.getSnapshot();
assertEstimatedQuantile(05, snapshot.getValue(0.05));
assertEstimatedQuantile(20, snapshot.getValue(0.20));
assertEstimatedQuantile(40, snapshot.getValue(0.40));
assertEstimatedQuantile(99, snapshot.getValue(0.99));
clock.addSeconds(DecayingEstimatedHistogramReservoir.HALF_TIME_IN_S);
snapshot = histogram.getSnapshot();
assertEstimatedQuantile(05, snapshot.getValue(0.05));
assertEstimatedQuantile(20, snapshot.getValue(0.20));
assertEstimatedQuantile(40, snapshot.getValue(0.40));
assertEstimatedQuantile(99, snapshot.getValue(0.99));
for (int v = 1; v <= 50; v++)
{
for (int i = 0; i < 10_000; i++)
{
histogram.update(v);
}
}
snapshot = histogram.getSnapshot();
assertEstimatedQuantile(04, snapshot.getValue(0.05));
assertEstimatedQuantile(14, snapshot.getValue(0.20));
assertEstimatedQuantile(27, snapshot.getValue(0.40));
assertEstimatedQuantile(98, snapshot.getValue(0.99));
clock.addSeconds(DecayingEstimatedHistogramReservoir.HALF_TIME_IN_S);
snapshot = histogram.getSnapshot();
assertEstimatedQuantile(04, snapshot.getValue(0.05));
assertEstimatedQuantile(14, snapshot.getValue(0.20));
assertEstimatedQuantile(27, snapshot.getValue(0.40));
assertEstimatedQuantile(98, snapshot.getValue(0.99));
for (int v = 1; v <= 50; v++)
{
for (int i = 0; i < 10_000; i++)
{
histogram.update(v);
}
}
snapshot = histogram.getSnapshot();
assertEstimatedQuantile(03, snapshot.getValue(0.05));
assertEstimatedQuantile(12, snapshot.getValue(0.20));
assertEstimatedQuantile(23, snapshot.getValue(0.40));
assertEstimatedQuantile(96, snapshot.getValue(0.99));
clock.addSeconds(DecayingEstimatedHistogramReservoir.HALF_TIME_IN_S);
snapshot = histogram.getSnapshot();
assertEstimatedQuantile(03, snapshot.getValue(0.05));
assertEstimatedQuantile(12, snapshot.getValue(0.20));
assertEstimatedQuantile(23, snapshot.getValue(0.40));
assertEstimatedQuantile(96, snapshot.getValue(0.99));
for (int v = 11; v <= 20; v++)
{
for (int i = 0; i < 5_000; i++)
{
histogram.update(v);
}
}
snapshot = histogram.getSnapshot();
assertEstimatedQuantile(04, snapshot.getValue(0.05));
assertEstimatedQuantile(12, snapshot.getValue(0.20));
assertEstimatedQuantile(20, snapshot.getValue(0.40));
assertEstimatedQuantile(95, snapshot.getValue(0.99));
clock.addSeconds(DecayingEstimatedHistogramReservoir.HALF_TIME_IN_S);
snapshot = histogram.getSnapshot();
assertEstimatedQuantile(04, snapshot.getValue(0.05));
assertEstimatedQuantile(12, snapshot.getValue(0.20));
assertEstimatedQuantile(20, snapshot.getValue(0.40));
assertEstimatedQuantile(95, snapshot.getValue(0.99));
}
{
TestClock clock = new TestClock();
DecayingEstimatedHistogramReservoir histogram = new DecayingEstimatedHistogramReservoir(DecayingEstimatedHistogramReservoir.DEFAULT_ZERO_CONSIDERATION, DecayingEstimatedHistogramReservoir.DEFAULT_BUCKET_COUNT, clock);
// percentile of empty histogram is 0
assertEquals(0, histogram.getSnapshot().getValue(0.99), DOUBLE_ASSERT_DELTA);
for (int m = 0; m < 40; m++)
{
for (int i = 0; i < 1_000_000; i++)
{
histogram.update(2);
}
// percentile of a histogram with one element should be that element
clock.addSeconds(DecayingEstimatedHistogramReservoir.HALF_TIME_IN_S);
assertEquals(2, histogram.getSnapshot().getValue(0.99), DOUBLE_ASSERT_DELTA);
}
clock.addSeconds(DecayingEstimatedHistogramReservoir.HALF_TIME_IN_S * 100);
assertEquals(0, histogram.getSnapshot().getValue(0.99), DOUBLE_ASSERT_DELTA);
}
{
TestClock clock = new TestClock();
DecayingEstimatedHistogramReservoir histogram = new DecayingEstimatedHistogramReservoir(DecayingEstimatedHistogramReservoir.DEFAULT_ZERO_CONSIDERATION, DecayingEstimatedHistogramReservoir.DEFAULT_BUCKET_COUNT, clock);
histogram.update(20);
histogram.update(21);
histogram.update(22);
Snapshot snapshot = histogram.getSnapshot();
assertEquals(1, snapshot.getValues()[12]);
assertEquals(2, snapshot.getValues()[13]);
clock.addSeconds(DecayingEstimatedHistogramReservoir.HALF_TIME_IN_S);
histogram.update(20);
histogram.update(21);
histogram.update(22);
snapshot = histogram.getSnapshot();
assertEquals(2, snapshot.getValues()[12]);
assertEquals(4, snapshot.getValues()[13]);
}
}
@Test
public void testDecayingMean()
{
{
TestClock clock = new TestClock();
DecayingEstimatedHistogramReservoir histogram = new DecayingEstimatedHistogramReservoir(DecayingEstimatedHistogramReservoir.DEFAULT_ZERO_CONSIDERATION, DecayingEstimatedHistogramReservoir.DEFAULT_BUCKET_COUNT, clock);
clock.addMillis(DecayingEstimatedHistogramReservoir.LANDMARK_RESET_INTERVAL_IN_MS - 1_000L);
while (clock.getTime() < DecayingEstimatedHistogramReservoir.LANDMARK_RESET_INTERVAL_IN_MS + 1_000L)
{
clock.addMillis(900);
for (int i = 0; i < 1_000_000; i++)
{
histogram.update(1000);
histogram.update(2000);
histogram.update(3000);
histogram.update(4000);
histogram.update(5000);
}
assertEquals(3000D, histogram.getSnapshot().getMean(), 500D);
}
}
}
private void assertEstimatedQuantile(long expectedValue, double actualValue)
{
assertTrue("Expected at least [" + expectedValue + "] but actual is [" + actualValue + "]", actualValue >= expectedValue);
assertTrue("Expected less than [" + Math.round(expectedValue * 1.2) + "] but actual is [" + actualValue + "]", actualValue < Math.round(expectedValue * 1.2));
}
public class TestClock extends Clock {
private long tick = 0;
public void addMillis(long millis)
{
tick += millis * 1_000_000L;
}
public void addSeconds(long seconds)
{
tick += seconds * 1_000_000_000L;
}
public long getTick()
{
return tick;
}
public long getTime()
{
return tick / 1_000_000L;
};
}
}