Add experimental composite samplers

custom/build.gradle.kts

@@ -24,6 +24,11 @@ dependencies {
   compileOnly("io.opentelemetry.javaagent:opentelemetry-javaagent-tooling")
   compileOnly(libs.bundles.semconv)
 
+  implementation(libs.contribConsistentSampling) {
+    // exclude transitive dependency as it's provided through agent packaging
+    exclude(group = "io.opentelemetry", module = "opentelemetry-sdk-trace")
+    exclude(group = "io.opentelemetry", module = "opentelemetry-sdk-extension-autoconfigure-spi")
+  }
   implementation(libs.contribSpanStacktrace) {
     // exclude transitive dependency as it's provided through agent packaging
     exclude(group = "io.opentelemetry", module = "opentelemetry-sdk")

custom/src/main/java/co/elastic/otel/compositesampling/CompositeParentBasedTraceIdRatioBasedSamplerProvider.java

@@ -0,0 +1,43 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. 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 co.elastic.otel.compositesampling;
+
+import com.google.auto.service.AutoService;
+import io.opentelemetry.sdk.autoconfigure.spi.ConfigProperties;
+import io.opentelemetry.sdk.autoconfigure.spi.traces.ConfigurableSamplerProvider;
+import io.opentelemetry.sdk.trace.samplers.Sampler;
+
+@AutoService(ConfigurableSamplerProvider.class)
+public class CompositeParentBasedTraceIdRatioBasedSamplerProvider
+    implements ConfigurableSamplerProvider {
+
+  @Override
+  public Sampler createSampler(ConfigProperties config) {
+    DynamicCompositeParentBasedTraceIdRatioBasedSampler.setRatio(
+        config.getDouble(
+            "otel.traces.sampler.arg",
+            DynamicCompositeParentBasedTraceIdRatioBasedSampler.DEFAULT_TRACEIDRATIO_SAMPLE_RATIO));
+    return DynamicCompositeParentBasedTraceIdRatioBasedSampler.INSTANCE;
+  }
+
+  @Override
+  public String getName() {
+    return "experimental_composite_parentbased_traceidratio";
+  }
+}

custom/src/main/java/co/elastic/otel/compositesampling/DynamicCompositeParentBasedTraceIdRatioBasedSampler.java

@@ -0,0 +1,60 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. 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 co.elastic.otel.compositesampling;
+
+import io.opentelemetry.api.common.Attributes;
+import io.opentelemetry.api.trace.SpanKind;
+import io.opentelemetry.context.Context;
+import io.opentelemetry.contrib.sampler.consistent56.ConsistentSampler;
+import io.opentelemetry.sdk.trace.data.LinkData;
+import io.opentelemetry.sdk.trace.samplers.Sampler;
+import io.opentelemetry.sdk.trace.samplers.SamplingResult;
+import java.util.List;
+
+public enum DynamicCompositeParentBasedTraceIdRatioBasedSampler implements Sampler {
+  INSTANCE;
+
+  static final double DEFAULT_TRACEIDRATIO_SAMPLE_RATIO = 1.0d;
+
+  private static Sampler delegate = newSampler(DEFAULT_TRACEIDRATIO_SAMPLE_RATIO);
+
+  public static void setRatio(double ratio) {
+    delegate = newSampler(ratio);
+  }
+
+  @Override
+  public SamplingResult shouldSample(
+      Context parentContext,
+      String traceId,
+      String name,
+      SpanKind spanKind,
+      Attributes attributes,
+      List<LinkData> parentLinks) {
+    return delegate.shouldSample(parentContext, traceId, name, spanKind, attributes, parentLinks);
+  }
+
+  @Override
+  public String getDescription() {
+    return INSTANCE.getDescription();
+  }
+
+  private static Sampler newSampler(double ratio) {
+    return ConsistentSampler.parentBased(ConsistentSampler.probabilityBased(ratio));
+  }
+}

gradle/libs.versions.toml

@@ -31,6 +31,7 @@ opentelemetryInstrumentationAlphaBom = { group = "io.opentelemetry.instrumentati
 
 opentelemetryProto = { group = "io.opentelemetry.proto", name = "opentelemetry-proto", version.ref = "opentelemetryProto" }
 
+contribConsistentSampling = { group = "io.opentelemetry.contrib", name = "opentelemetry-consistent-sampling", version.ref = "opentelemetryContribAlpha" }
 contribResources = { group = "io.opentelemetry.contrib", name = "opentelemetry-resource-providers", version.ref = "opentelemetryContribAlpha" }
 contribSpanStacktrace = { group = "io.opentelemetry.contrib", name = "opentelemetry-span-stacktrace", version.ref = "opentelemetryContribAlpha" }
 contribInferredSpans = { group = "io.opentelemetry.contrib", name = "opentelemetry-inferred-spans", version.ref = "opentelemetryContribAlpha" }