Add links based sample option to config (#903)

Co-authored-by: Trask Stalnaker <[email protected]>

samplers/build.gradle.kts

@@ -9,4 +9,6 @@ otelJava.moduleName.set("io.opentelemetry.contrib.sampler")
 dependencies {
   api("io.opentelemetry:opentelemetry-sdk")
   api("io.opentelemetry:opentelemetry-semconv")
+  testImplementation("io.opentelemetry:opentelemetry-sdk-extension-autoconfigure")
+  api("io.opentelemetry:opentelemetry-sdk-extension-autoconfigure-spi")
 }

samplers/src/main/java/io/opentelemetry/contrib/sampler/LinksParentAlwaysOnSamplerProvider.java

@@ -0,0 +1,22 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.contrib.sampler;
+
+import io.opentelemetry.sdk.autoconfigure.spi.ConfigProperties;
+import io.opentelemetry.sdk.autoconfigure.spi.traces.ConfigurableSamplerProvider;
+import io.opentelemetry.sdk.trace.samplers.Sampler;
+
+public class LinksParentAlwaysOnSamplerProvider implements ConfigurableSamplerProvider {
+  @Override
+  public Sampler createSampler(ConfigProperties config) {
+    return LinksBasedSampler.create(Sampler.parentBased(Sampler.alwaysOn()));
+  }
+
+  @Override
+  public String getName() {
+    return "linksbased_parentbased_always_on";
+  }
+}

samplers/src/main/resources/META-INF/services/io.opentelemetry.sdk.autoconfigure.spi.traces.ConfigurableSamplerProvider

@@ -0,0 +1 @@
+io.opentelemetry.contrib.sampler.LinksParentAlwaysOnSamplerProvider

samplers/src/test/java/io/opentelemetry/contrib/sampler/LinksBasedSamplerTest.java

@@ -14,10 +14,14 @@
 import io.opentelemetry.api.trace.TraceFlags;
 import io.opentelemetry.api.trace.TraceState;
 import io.opentelemetry.context.Context;
+import io.opentelemetry.sdk.autoconfigure.AutoConfiguredOpenTelemetrySdkBuilder;
+import io.opentelemetry.sdk.autoconfigure.spi.ConfigProperties;
+import io.opentelemetry.sdk.autoconfigure.spi.internal.DefaultConfigProperties;
 import io.opentelemetry.sdk.trace.IdGenerator;
 import io.opentelemetry.sdk.trace.data.LinkData;
 import io.opentelemetry.sdk.trace.samplers.Sampler;
 import io.opentelemetry.sdk.trace.samplers.SamplingDecision;
+import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
@@ -185,4 +189,25 @@ void testTwoUnsampled() {
                 .getDecision())
         .isEqualTo(SamplingDecision.DROP);
   }
+
+  @Test
+  void testProvider() throws Exception {
+    Method method =
+        Class.forName("io.opentelemetry.sdk.autoconfigure.TracerProviderConfiguration")
+            .getDeclaredMethod(
+                "configureSampler", String.class, ConfigProperties.class, ClassLoader.class);
+    method.setAccessible(true);
+
+    Sampler sampler =
+        (Sampler)
+            method.invoke(
+                null,
+                "linksbased_parentbased_always_on",
+                DefaultConfigProperties.createForTest(Collections.emptyMap()),
+                AutoConfiguredOpenTelemetrySdkBuilder.class.getClassLoader());
+
+    assertThat(sampler.getDescription())
+        .isEqualTo(
+            LinksBasedSampler.create(Sampler.parentBased(Sampler.alwaysOn())).getDescription());
+  }
 }