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Add a Fibonacci fitter for metrics bucketing
A Fibonacci fitter is useful in situations where you want more precision on the low end than an ExponentialFitter with exponent base 2 provides without the hassle of dealing with non-integer boundaries, such as would be created by an exponential fitter with a base of less than 2. Fibonacci fitters are ideal for integer metrics that are bounded across a certain range, e.g. integers between 1 and 1,000. This also cleans up some unit test comments. ------------- Created by MOE: https://github.com/google/moe MOE_MIGRATED_REVID=156773367
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java/google/registry/monitoring/metrics/FibonacciFitter.java
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// Copyright 2017 The Nomulus Authors. All Rights Reserved. | ||
// | ||
// Licensed 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. | ||
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package google.registry.monitoring.metrics; | ||
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import static com.google.common.base.Preconditions.checkArgument; | ||
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import com.google.auto.value.AutoValue; | ||
import com.google.common.collect.ImmutableSortedSet; | ||
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/** | ||
* A {@link DistributionFitter} with intervals of increasing size using the Fibonacci sequence. | ||
* | ||
* <p>A Fibonacci fitter is useful in situations where you want more precision on the low end than | ||
* an {@link ExponentialFitter} with exponent base 2 would provide without the hassle of dealing | ||
* with non-integer boundaries, such as would be created by an exponential fitter with a base of | ||
* less than 2. Fibonacci fitters are ideal for integer metrics that are bounded across a certain | ||
* range, e.g. integers between 1 and 1,000. | ||
* | ||
* <p>The interval boundaries are chosen as {@code (-inf, 0), [0, 1), [1, 2), [2, 3), [3, 5), [5, | ||
* 8), [8, 13)}, etc., up to {@code [fibonacciFloor(maxBucketSize), inf)}. | ||
*/ | ||
@AutoValue | ||
public abstract class FibonacciFitter implements DistributionFitter { | ||
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/** | ||
* Returns a new {@link FibonacciFitter}. | ||
* | ||
* @param maxBucketSize the maximum bucket size to create (rounded down to the nearest Fibonacci | ||
* number) | ||
* @throws IllegalArgumentException if {@code maxBucketSize <= 0} | ||
*/ | ||
public static FibonacciFitter create(long maxBucketSize) { | ||
checkArgument(maxBucketSize > 0, "maxBucketSize must be greater than 0"); | ||
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ImmutableSortedSet.Builder<Double> boundaries = ImmutableSortedSet.naturalOrder(); | ||
boundaries.add(Double.valueOf(0)); | ||
long i = 1; | ||
long j = 2; | ||
long k = 3; | ||
while (i <= maxBucketSize) { | ||
boundaries.add(Double.valueOf(i)); | ||
i = j; | ||
j = k; | ||
k = i + j; | ||
} | ||
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return new AutoValue_FibonacciFitter(boundaries.build()); | ||
} | ||
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@Override | ||
public abstract ImmutableSortedSet<Double> boundaries(); | ||
} |
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javatests/google/registry/monitoring/metrics/FibonacciFitterTest.java
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// Copyright 2017 The Nomulus Authors. All Rights Reserved. | ||
// | ||
// Licensed 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. | ||
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package google.registry.monitoring.metrics; | ||
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import static com.google.common.truth.Truth.assertThat; | ||
import static org.junit.Assert.fail; | ||
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import com.google.common.collect.ImmutableList; | ||
import org.junit.Test; | ||
import org.junit.runner.RunWith; | ||
import org.junit.runners.JUnit4; | ||
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/** Unit tests for {@link FibonacciFitter}. */ | ||
@RunWith(JUnit4.class) | ||
public class FibonacciFitterTest { | ||
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@Test | ||
public void testCreate_maxBucketSizeNegative_throwsException() { | ||
try { | ||
FibonacciFitter.create(-1); | ||
fail("Expected exception"); | ||
} catch (IllegalArgumentException e) { | ||
assertThat(e).hasMessageThat().isEqualTo("maxBucketSize must be greater than 0"); | ||
} | ||
} | ||
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@Test | ||
public void testCreate_maxBucketSizeZero_throwsException() { | ||
try { | ||
FibonacciFitter.create(0); | ||
fail("Expected exception"); | ||
} catch (IllegalArgumentException e) { | ||
assertThat(e).hasMessageThat().isEqualTo("maxBucketSize must be greater than 0"); | ||
} | ||
} | ||
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@Test | ||
public void testCreate_maxBucketSizeOne_createsTwoBoundaries() { | ||
assertThat(FibonacciFitter.create(1).boundaries()).containsExactly(0.0, 1.0).inOrder(); | ||
} | ||
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@Test | ||
public void testCreate_maxBucketSizeTwo_createsThreeBoundaries() { | ||
assertThat(FibonacciFitter.create(2).boundaries()).containsExactly(0.0, 1.0, 2.0).inOrder(); | ||
} | ||
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@Test | ||
public void testCreate_maxBucketSizeThree_createsFourBoundaries() { | ||
assertThat(FibonacciFitter.create(3).boundaries()) | ||
.containsExactly(0.0, 1.0, 2.0, 3.0) | ||
.inOrder(); | ||
} | ||
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@Test | ||
public void testCreate_maxBucketSizeFour_createsFourBoundaries() { | ||
assertThat(FibonacciFitter.create(4).boundaries()) | ||
.containsExactly(0.0, 1.0, 2.0, 3.0) | ||
.inOrder(); | ||
} | ||
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@Test | ||
public void testCreate_maxBucketSizeLarge_createsFibonacciSequenceBoundaries() { | ||
ImmutableList<Double> expectedBoundaries = | ||
ImmutableList.of( | ||
0.0, 1.0, 2.0, 3.0, 5.0, 8.0, 13.0, 21.0, 34.0, 55.0, 89.0, 144.0, 233.0, 377.0, 610.0, | ||
987.0); | ||
assertThat(FibonacciFitter.create(1000).boundaries()) | ||
.containsExactlyElementsIn(expectedBoundaries) | ||
.inOrder(); | ||
} | ||
} |
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