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56
x-pack/plugin/profiling/src/main/java/org/elasticsearch/xpack/profiling/Resampler.java
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| /* | ||
| * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one | ||
| * or more contributor license agreements. Licensed under the Elastic License | ||
| * 2.0; you may not use this file except in compliance with the Elastic License | ||
| * 2.0. | ||
| */ | ||
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| package org.elasticsearch.xpack.profiling; | ||
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| import java.util.Random; | ||
| import java.util.random.RandomGenerator; | ||
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| class Resampler { | ||
| private final boolean requiresResampling; | ||
| private final RandomGenerator r; | ||
| private final double adjustedSampleRate; | ||
| private final double p; | ||
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| Resampler(GetStackTracesRequest request, double sampleRate, long totalCount) { | ||
| // Manually reduce sample count if totalCount exceeds sampleSize by 10%. | ||
| if (totalCount > request.getSampleSize() * 1.1) { | ||
| this.requiresResampling = true; | ||
| // Make the RNG predictable to get reproducible results. | ||
| this.r = createRandom(request); | ||
| this.p = (double) request.getSampleSize() / totalCount; | ||
| } else { | ||
| this.requiresResampling = false; | ||
| this.r = null; | ||
| this.p = 1.0d; | ||
| } | ||
| // TODO: Just use the sample rate as is once all resampling is done server-side | ||
| this.adjustedSampleRate = request.isAdjustSampleCount() ? sampleRate : 1.0d; | ||
| } | ||
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| protected RandomGenerator createRandom(GetStackTracesRequest request) { | ||
| return new Random(request.hashCode()); | ||
| } | ||
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| public int adjustSampleCount(int originalCount) { | ||
| int rawCount; | ||
| if (requiresResampling) { | ||
| rawCount = 0; | ||
| for (int i = 0; i < originalCount; i++) { | ||
| if (r.nextDouble() < p) { | ||
| rawCount++; | ||
| } | ||
| } | ||
| } else { | ||
| rawCount = originalCount; | ||
| } | ||
| // Adjust the sample counts from down-sampled to fully sampled. | ||
| // Be aware that downsampling drops entries from stackTraceEvents, so that | ||
| // the sum of the upscaled count values is less that totalCount. | ||
| return (int) Math.floor(rawCount / (p * adjustedSampleRate)); | ||
| } | ||
| } |
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108
x-pack/plugin/profiling/src/test/java/org/elasticsearch/xpack/profiling/ResamplerTests.java
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| @@ -0,0 +1,108 @@ | ||
| /* | ||
| * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one | ||
| * or more contributor license agreements. Licensed under the Elastic License | ||
| * 2.0; you may not use this file except in compliance with the Elastic License | ||
| * 2.0. | ||
| */ | ||
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| package org.elasticsearch.xpack.profiling; | ||
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| import org.elasticsearch.test.ESTestCase; | ||
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| import java.util.random.RandomGenerator; | ||
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| public class ResamplerTests extends ESTestCase { | ||
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| private Resampler createResampler(GetStackTracesRequest request, double sampleRate, long totalCount) { | ||
| return new Resampler(request, sampleRate, totalCount) { | ||
| @Override | ||
| protected RandomGenerator createRandom(GetStackTracesRequest request) { | ||
| return DeterministicRandom.of(0.0d, 1.0d); | ||
| } | ||
| }; | ||
| } | ||
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| public void testNoResamplingNoSampleRateAdjustment() { | ||
| // corresponds to profiling-events-5pow01 | ||
| double sampleRate = 1.0d / Math.pow(5.0d, 1); | ||
| int requestedSamples = 20_000; | ||
| int actualTotalSamples = 10_000; | ||
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| GetStackTracesRequest request = new GetStackTracesRequest(requestedSamples, null); | ||
| request.setAdjustSampleCount(false); | ||
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| Resampler resampler = createResampler(request, sampleRate, actualTotalSamples); | ||
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| int actualSamplesSingleTrace = 5_000; | ||
| assertEquals(5_000, resampler.adjustSampleCount(actualSamplesSingleTrace)); | ||
| } | ||
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| public void testNoResamplingButAdjustSampleRate() { | ||
| // corresponds to profiling-events-5pow01 | ||
| double sampleRate = 1.0d / Math.pow(5.0d, 1); | ||
| int requestedSamples = 20_000; | ||
| int actualTotalSamples = 10_000; | ||
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| GetStackTracesRequest request = new GetStackTracesRequest(requestedSamples, null); | ||
| request.setAdjustSampleCount(true); | ||
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| Resampler resampler = createResampler(request, sampleRate, actualTotalSamples); | ||
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| int actualSamplesSingleTrace = 5_000; | ||
| assertEquals(25_000, resampler.adjustSampleCount(actualSamplesSingleTrace)); | ||
| } | ||
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| public void testResamplingNoSampleRateAdjustment() { | ||
| // corresponds to profiling-events-5pow01 | ||
| double sampleRate = 1.0d / Math.pow(5.0d, 1); | ||
| int requestedSamples = 20_000; | ||
| int actualTotalSamples = 40_000; | ||
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| GetStackTracesRequest request = new GetStackTracesRequest(requestedSamples, null); | ||
| request.setAdjustSampleCount(false); | ||
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| Resampler resampler = createResampler(request, sampleRate, actualTotalSamples); | ||
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| int actualSamplesSingleTrace = 20_000; | ||
| assertEquals(20_000, resampler.adjustSampleCount(actualSamplesSingleTrace)); | ||
| } | ||
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| public void testResamplingAndSampleRateAdjustment() { | ||
| // corresponds to profiling-events-5pow01 | ||
| double sampleRate = 1.0d / Math.pow(5.0d, 1); | ||
| int requestedSamples = 20_000; | ||
| int actualTotalSamples = 40_000; | ||
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| GetStackTracesRequest request = new GetStackTracesRequest(requestedSamples, null); | ||
| request.setAdjustSampleCount(true); | ||
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| Resampler resampler = createResampler(request, sampleRate, actualTotalSamples); | ||
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| int actualSamplesSingleTrace = 20_000; | ||
| assertEquals(100_000, resampler.adjustSampleCount(actualSamplesSingleTrace)); | ||
| } | ||
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| private static class DeterministicRandom implements RandomGenerator { | ||
| private final double[] values; | ||
| private int idx; | ||
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| private DeterministicRandom(double... values) { | ||
| this.values = values; | ||
| this.idx = 0; | ||
| } | ||
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| public static RandomGenerator of(double... values) { | ||
| return new DeterministicRandom(values); | ||
| } | ||
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| @Override | ||
| public long nextLong() { | ||
| return Double.doubleToLongBits(nextDouble()); | ||
| } | ||
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| @Override | ||
| public double nextDouble() { | ||
| return values[idx++ % values.length]; | ||
| } | ||
| } | ||
| } |