add updateable threshold sampler

consistent-sampling/src/main/java/io/opentelemetry/contrib/sampler/consistent56/ConsistentFixedThresholdSampler.java

@@ -5,19 +5,9 @@
 
 package io.opentelemetry.contrib.sampler.consistent56;
 
-import static io.opentelemetry.contrib.sampler.consistent56.ConsistentSamplingUtil.calculateSamplingProbability;
 import static io.opentelemetry.contrib.sampler.consistent56.ConsistentSamplingUtil.calculateThreshold;
-import static io.opentelemetry.contrib.sampler.consistent56.ConsistentSamplingUtil.checkThreshold;
-import static io.opentelemetry.contrib.sampler.consistent56.ConsistentSamplingUtil.getInvalidThreshold;
-import static io.opentelemetry.contrib.sampler.consistent56.ConsistentSamplingUtil.getMaxThreshold;
 
-import io.opentelemetry.api.common.Attributes;
-import io.opentelemetry.api.trace.SpanKind;
-import io.opentelemetry.context.Context;
-import io.opentelemetry.sdk.trace.data.LinkData;
-import java.util.List;
-
-public class ConsistentFixedThresholdSampler extends ConsistentSampler {
+public class ConsistentFixedThresholdSampler extends ConsistentThresholdSampler {
 
  private final long threshold;
  private final String description;
@@ -31,47 +21,13 @@ protected ConsistentFixedThresholdSampler(double samplingProbability) {
  this(calculateThreshold(samplingProbability));
  }
 
- private static long getThreshold(long threshold) {
- checkThreshold(threshold);
- return threshold;
- }
-
- private static String getThresholdDescription(long threshold) {
- String thresholdString;
- if (threshold == getMaxThreshold()) {
- thresholdString = "max";
- } else {
- thresholdString =
- ConsistentSamplingUtil.appendLast56BitHexEncodedWithoutTrailingZeros(
- new StringBuilder(), threshold)
- .toString();
- }
-
- return "ConsistentFixedThresholdSampler{threshold="
- + thresholdString
- + ", sampling probability="
- + calculateSamplingProbability(threshold)
- + "}";
- }
-
  @Override
  public String getDescription() {
  return description;
  }
 
  @Override
- public SamplingIntent getSamplingIntent(
- Context parentContext,
- String name,
- SpanKind spanKind,
- Attributes attributes,
- List<LinkData> parentLinks) {
-
- return () -> {
- if (threshold == getMaxThreshold()) {
- return getInvalidThreshold();
- }
- return threshold;
- };
+ public long getThreshold() {
+ return threshold;
  }
 }

consistent-sampling/src/main/java/io/opentelemetry/contrib/sampler/consistent56/ConsistentSampler.java

@@ -55,6 +55,17 @@ public static ConsistentSampler probabilityBased(double samplingProbability) {
  return new ConsistentFixedThresholdSampler(threshold);
  }
 
+ /**
+ * Returns a {@link ConsistentSampler} that samples each span with a known probability, where the
+ * probablity can be dynamically updated.
+ *
+ * @param samplingProbability the sampling probability
+ * @return a sampler
+ */
+ public static ConsistentSampler updateableProbabilityBased(double samplingProbability) {
+ return new ConsistentVariableThresholdSampler(samplingProbability);
+ }
+
  /**
  * Returns a new {@link ConsistentSampler} that respects the sampling decision of the parent span
  * or falls-back to the given sampler if it is a root span.

consistent-sampling/src/main/java/io/opentelemetry/contrib/sampler/consistent56/ConsistentThresholdSampler.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.contrib.sampler.consistent56;
+
+import static io.opentelemetry.contrib.sampler.consistent56.ConsistentSamplingUtil.appendLast56BitHexEncodedWithoutTrailingZeros;
+import static io.opentelemetry.contrib.sampler.consistent56.ConsistentSamplingUtil.calculateSamplingProbability;
+import static io.opentelemetry.contrib.sampler.consistent56.ConsistentSamplingUtil.checkThreshold;
+import static io.opentelemetry.contrib.sampler.consistent56.ConsistentSamplingUtil.getInvalidThreshold;
+import static io.opentelemetry.contrib.sampler.consistent56.ConsistentSamplingUtil.getMaxThreshold;
+
+import io.opentelemetry.api.common.Attributes;
+import io.opentelemetry.api.trace.SpanKind;
+import io.opentelemetry.context.Context;
+import io.opentelemetry.sdk.trace.data.LinkData;
+import java.util.List;
+
+public abstract class ConsistentThresholdSampler extends ConsistentSampler {
+
+ protected abstract long getThreshold();
+
+ protected static long getThreshold(long threshold) {
+ checkThreshold(threshold);
+ return threshold;
+ }
+
+ protected static String getThresholdDescription(long threshold) {
+ String thresholdString;
+ if (threshold == getMaxThreshold()) {
+ thresholdString = "max";
+ } else {
+ thresholdString =
+ appendLast56BitHexEncodedWithoutTrailingZeros(new StringBuilder(), threshold).toString();
+ }
+
+ return "ConsistentFixedThresholdSampler{threshold="
+ + thresholdString
+ + ", sampling probability="
+ + calculateSamplingProbability(threshold)
+ + "}";
+ }
+
+ @Override
+ public SamplingIntent getSamplingIntent(
+ Context parentContext,
+ String name,
+ SpanKind spanKind,
+ Attributes attributes,
+ List<LinkData> parentLinks) {
+
+ return () -> {
+ if (getThreshold() == getMaxThreshold()) {
+ return getInvalidThreshold();
+ }
+ return getThreshold();
+ };
+ }
+}

consistent-sampling/src/main/java/io/opentelemetry/contrib/sampler/consistent56/ConsistentVariableThresholdSampler.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.contrib.sampler.consistent56;
+
+import static io.opentelemetry.contrib.sampler.consistent56.ConsistentSamplingUtil.calculateSamplingProbability;
+import static io.opentelemetry.contrib.sampler.consistent56.ConsistentSamplingUtil.calculateThreshold;
+import static io.opentelemetry.contrib.sampler.consistent56.ConsistentSamplingUtil.checkThreshold;
+import static io.opentelemetry.contrib.sampler.consistent56.ConsistentSamplingUtil.getMaxThreshold;
+
+public class ConsistentVariableThresholdSampler extends ConsistentThresholdSampler {
+
+ private volatile long threshold;
+ private volatile String description = "";
+
+ protected ConsistentVariableThresholdSampler(double samplingProbability) {
+ setSamplingProbability(samplingProbability);
+ }
+
+ @Override
+ public String getDescription() {
+ return description;
+ }
+
+ @Override
+ public long getThreshold() {
+ return threshold;
+ }
+
+ public void setSamplingProbability(double samplingProbability) {
+ long threshold = calculateThreshold(samplingProbability);
+ checkThreshold(threshold);
+ this.threshold = threshold;
+
+ String thresholdString;
+ if (threshold == getMaxThreshold()) {
+ thresholdString = "max";
+ } else {
+ thresholdString =
+ ConsistentSamplingUtil.appendLast56BitHexEncodedWithoutTrailingZeros(
+ new StringBuilder(), threshold)
+ .toString();
+ }
+
+ // tiny eventual consistency where the description would be out of date with the threshold,
+ // but this doesn't really matter
+ this.description =
+ "ConsistentVariableThresholdSampler{threshold="
+ + thresholdString
+ + ", sampling probability="
+ + calculateSamplingProbability(threshold)
+ + "}";
+ }
+}

consistent-sampling/src/test/java/io/opentelemetry/contrib/sampler/consistent56/ConsistentVariableThresholdSamplerTest.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.contrib.sampler.consistent56;
+
+import static io.opentelemetry.contrib.sampler.consistent56.ConsistentSamplingUtil.calculateThreshold;
+import static io.opentelemetry.contrib.sampler.consistent56.ConsistentSamplingUtil.getMaxThreshold;
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+class ConsistentVariableThresholdSamplerTest {
+
+ @Test
+ void testSetSamplingProbability() {
+ double probability = 0.5;
+ ConsistentVariableThresholdSampler sampler =
+ new ConsistentVariableThresholdSampler(probability);
+ testSetSamplingProbability(probability, sampler, /* updateProbability= */ false);
+ testSetSamplingProbability(0.25, sampler, /* updateProbability= */ true);
+ testSetSamplingProbability(0.0, sampler, /* updateProbability= */ true);
+ testSetSamplingProbability(1.0, sampler, /* updateProbability= */ true);
+ }
+
+ private static void testSetSamplingProbability(
+ double probability, ConsistentVariableThresholdSampler sampler, boolean updateProbability) {
+ long threshold = calculateThreshold(probability);
+ String thresholdString =
+ ConsistentSamplingUtil.appendLast56BitHexEncodedWithoutTrailingZeros(
+ new StringBuilder(), threshold)
+ .toString();
+ if (threshold == getMaxThreshold()) {
+ thresholdString = "max";
+ }
+ if (updateProbability) {
+ sampler.setSamplingProbability(probability);
+ }
+ assertThat(sampler.getThreshold()).isEqualTo(threshold);
+ assertThat(sampler.getDescription())
+ .isEqualTo(
+ "ConsistentVariableThresholdSampler{threshold="
+ + thresholdString
+ + ", sampling probability="
+ + probability
+ + "}");
+ }
+}