consistent sampler prototypes using 56 bits of randomness (#1063)

consistent-sampling/build.gradle.kts

@@ -4,7 +4,7 @@ plugins {
 }
 
 description = "Sampler and exporter implementations for consistent sampling"
-otelJava.moduleName.set("io.opentelemetry.contrib.sampler.consistent")
+otelJava.moduleName.set("io.opentelemetry.contrib.sampler")
 
 dependencies {
   api("io.opentelemetry:opentelemetry-sdk-trace")

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

@@ -0,0 +1,26 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.contrib.sampler.consistent56;
+
+import javax.annotation.concurrent.Immutable;
+
+@Immutable
+final class ConsistentAlwaysOffSampler extends ConsistentSampler {
+
+  ConsistentAlwaysOffSampler(RandomValueGenerator randomValueGenerator) {
+    super(randomValueGenerator);
+  }
+
+  @Override
+  protected long getThreshold(long parentThreshold, boolean isRoot) {
+    return 0;
+  }
+
+  @Override
+  public String getDescription() {
+    return "ConsistentAlwaysOffSampler";
+  }
+}

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

@@ -0,0 +1,28 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.contrib.sampler.consistent56;
+
+import static io.opentelemetry.contrib.sampler.consistent56.ConsistentSamplingUtil.getMaxThreshold;
+
+import javax.annotation.concurrent.Immutable;
+
+@Immutable
+final class ConsistentAlwaysOnSampler extends ConsistentSampler {
+
+  ConsistentAlwaysOnSampler(RandomValueGenerator randomValueGenerator) {
+    super(randomValueGenerator);
+  }
+
+  @Override
+  protected long getThreshold(long parentThreshold, boolean isRoot) {
+    return getMaxThreshold();
+  }
+
+  @Override
+  public String getDescription() {
+    return "ConsistentAlwaysOnSampler";
+  }
+}

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

@@ -0,0 +1,56 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.contrib.sampler.consistent56;
+
+import static java.util.Objects.requireNonNull;
+
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * A consistent sampler composed of two consistent samplers.
+ *
+ * <p>This sampler samples if both samplers would sample.
+ */
+@Immutable
+final class ConsistentComposedAndSampler extends ConsistentSampler {
+
+  private final ConsistentSampler sampler1;
+  private final ConsistentSampler sampler2;
+  private final String description;
+
+  ConsistentComposedAndSampler(
+      ConsistentSampler sampler1,
+      ConsistentSampler sampler2,
+      RandomValueGenerator randomValueGenerator) {
+    super(randomValueGenerator);
+    this.sampler1 = requireNonNull(sampler1);
+    this.sampler2 = requireNonNull(sampler2);
+    this.description =
+        "ConsistentComposedAndSampler{"
+            + "sampler1="
+            + sampler1.getDescription()
+            + ",sampler2="
+            + sampler2.getDescription()
+            + '}';
+  }
+
+  @Override
+  protected long getThreshold(long parentThreshold, boolean isRoot) {
+    long threshold1 = sampler1.getThreshold(parentThreshold, isRoot);
+    long threshold2 = sampler2.getThreshold(parentThreshold, isRoot);
+    if (ConsistentSamplingUtil.isValidThreshold(threshold1)
+        && ConsistentSamplingUtil.isValidThreshold(threshold2)) {
+      return Math.min(threshold1, threshold2);
+    } else {
+      return ConsistentSamplingUtil.getInvalidThreshold();
+    }
+  }
+
+  @Override
+  public String getDescription() {
+    return description;
+  }
+}

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

@@ -0,0 +1,61 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.contrib.sampler.consistent56;
+
+import static java.util.Objects.requireNonNull;
+
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * A consistent sampler composed of two consistent samplers.
+ *
+ * <p>This sampler samples if any of the two samplers would sample.
+ */
+@Immutable
+final class ConsistentComposedOrSampler extends ConsistentSampler {
+
+  private final ConsistentSampler sampler1;
+  private final ConsistentSampler sampler2;
+  private final String description;
+
+  ConsistentComposedOrSampler(
+      ConsistentSampler sampler1,
+      ConsistentSampler sampler2,
+      RandomValueGenerator randomValueGenerator) {
+    super(randomValueGenerator);
+    this.sampler1 = requireNonNull(sampler1);
+    this.sampler2 = requireNonNull(sampler2);
+    this.description =
+        "ConsistentComposedOrSampler{"
+            + "sampler1="
+            + sampler1.getDescription()
+            + ",sampler2="
+            + sampler2.getDescription()
+            + '}';
+  }
+
+  @Override
+  protected long getThreshold(long parentThreshold, boolean isRoot) {
+    long threshold1 = sampler1.getThreshold(parentThreshold, isRoot);
+    long threshold2 = sampler2.getThreshold(parentThreshold, isRoot);
+    if (ConsistentSamplingUtil.isValidThreshold(threshold1)) {
+      if (ConsistentSamplingUtil.isValidThreshold(threshold2)) {
+        return Math.max(threshold1, threshold2);
+      }
+      return threshold1;
+    } else {
+      if (ConsistentSamplingUtil.isValidThreshold(threshold2)) {
+        return threshold2;
+      }
+      return ConsistentSamplingUtil.getInvalidThreshold();
+    }
+  }
+
+  @Override
+  public String getDescription() {
+    return description;
+  }
+}

consistent-sampling/src/main/java/io/opentelemetry/contrib/sampler/consistent56/ConsistentFixedThresholdSampler.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.calculateSamplingProbability;
+import static io.opentelemetry.contrib.sampler.consistent56.ConsistentSamplingUtil.checkThreshold;
+
+public class ConsistentFixedThresholdSampler extends ConsistentSampler {
+
+  private final long threshold;
+  private final String description;
+
+  protected ConsistentFixedThresholdSampler(
+      long threshold, RandomValueGenerator randomValueGenerator) {
+    super(randomValueGenerator);
+    checkThreshold(threshold);
+    this.threshold = threshold;
+
+    String thresholdString;
+    if (threshold == ConsistentSamplingUtil.getMaxThreshold()) {
+      thresholdString = "max";
+    } else {
+      thresholdString =
+          ConsistentSamplingUtil.appendLast56BitHexEncodedWithoutTrailingZeros(
+                  new StringBuilder(), threshold)
+              .toString();
+    }
+
+    this.description =
+        "ConsistentFixedThresholdSampler{threshold="
+            + thresholdString
+            + ", sampling probability="
+            + calculateSamplingProbability(threshold)
+            + "}";
+  }
+
+  @Override
+  public String getDescription() {
+    return description;
+  }
+
+  @Override
+  protected long getThreshold(long parentThreshold, boolean isRoot) {
+    return threshold;
+  }
+}

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

@@ -0,0 +1,51 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.contrib.sampler.consistent56;
+
+import static java.util.Objects.requireNonNull;
+
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * A consistent sampler that makes the same sampling decision as the parent. For root spans the
+ * sampling decision is delegated to the root sampler.
+ */
+@Immutable
+final class ConsistentParentBasedSampler extends ConsistentSampler {
+
+  private final ConsistentSampler rootSampler;
+
+  private final String description;
+
+  /**
+   * Constructs a new consistent parent based sampler using the given root sampler and the given
+   * thread-safe random generator.
+   *
+   * @param rootSampler the root sampler
+   * @param randomValueGenerator the function to use for generating the r-value
+   */
+  ConsistentParentBasedSampler(
+      ConsistentSampler rootSampler, RandomValueGenerator randomValueGenerator) {
+    super(randomValueGenerator);
+    this.rootSampler = requireNonNull(rootSampler);
+    this.description =
+        "ConsistentParentBasedSampler{rootSampler=" + rootSampler.getDescription() + '}';
+  }
+
+  @Override
+  protected long getThreshold(long parentThreshold, boolean isRoot) {
+    if (isRoot) {
+      return rootSampler.getThreshold(ConsistentSamplingUtil.getInvalidThreshold(), isRoot);
+    } else {
+      return parentThreshold;
+    }
+  }
+
+  @Override
+  public String getDescription() {
+    return description;
+  }
+}