Add opamp client

custom/build.gradle.kts

@@ -17,6 +17,7 @@ dependencies {
 
   implementation("io.opentelemetry.contrib:opentelemetry-samplers")
   implementation("io.opentelemetry.contrib:opentelemetry-resource-providers")
+  implementation("io.opentelemetry.contrib:opentelemetry-opamp-client")
 
   testImplementation(project(":testing:common"))
   testImplementation("io.opentelemetry:opentelemetry-sdk")

custom/src/main/java/com/splunk/opentelemetry/opamp/OpampActivator.java

@@ -0,0 +1,91 @@
+/*
+ * Copyright Splunk Inc.
+ *
+ * Licensed 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 com.splunk.opentelemetry.opamp;
+
+import static io.opentelemetry.sdk.autoconfigure.AutoConfigureUtil.getConfig;
+import static io.opentelemetry.sdk.autoconfigure.AutoConfigureUtil.getResource;
+import static java.util.logging.Level.WARNING;
+
+import com.google.auto.service.AutoService;
+import io.opentelemetry.javaagent.extension.AgentListener;
+import io.opentelemetry.opamp.client.internal.OpampClient;
+import io.opentelemetry.opamp.client.internal.OpampClientBuilder;
+import io.opentelemetry.opamp.client.internal.connectivity.http.OkHttpSender;
+import io.opentelemetry.opamp.client.internal.request.service.HttpRequestService;
+import io.opentelemetry.opamp.client.internal.response.MessageData;
+import io.opentelemetry.sdk.autoconfigure.AutoConfiguredOpenTelemetrySdk;
+import io.opentelemetry.sdk.autoconfigure.spi.ConfigProperties;
+import io.opentelemetry.sdk.resources.Resource;
+import io.opentelemetry.semconv.ServiceAttributes;
+import java.util.logging.Logger;
+import opamp.proto.ServerErrorResponse;
+import org.jetbrains.annotations.Nullable;
+
+@AutoService(AgentListener.class)
+public class OpampActivator implements AgentListener {
+  private static final Logger logger = Logger.getLogger(OpampActivator.class.getName());
+
+  private static final String OP_AMP_ENABLED_PROPERTY = "splunk.opamp.enabled";
+  private static final String OP_AMP_ENDPOINT = "splunk.opamp.endpoint";
+
+  @Override
+  public void afterAgent(AutoConfiguredOpenTelemetrySdk autoConfiguredOpenTelemetrySdk) {
+    ConfigProperties config = getConfig(autoConfiguredOpenTelemetrySdk);
+    if (!config.getBoolean(OP_AMP_ENABLED_PROPERTY, false)) {
+      return;
+    }
+
+    Resource resource = getResource(autoConfiguredOpenTelemetrySdk);
+    String serviceName = resource.getAttribute(ServiceAttributes.SERVICE_NAME);
+
+    String endpoint = config.getString(OP_AMP_ENDPOINT);
+    startOpampClient(
+        endpoint,
+        serviceName,
+        new OpampClient.Callbacks() {
+          @Override
+          public void onConnect() {}
+
+          @Override
+          public void onConnectFailed(@Nullable Throwable throwable) {
+            logger.log(WARNING, "Connection to OpAMP server failed", throwable);
+          }
+
+          @Override
+          public void onErrorResponse(ServerErrorResponse errorResponse) {
+            logger.log(WARNING, "OpAMP server returned error " + errorResponse);
+          }
+
+          @Override
+          public void onMessage(MessageData messageData) {}
+        });
+  }
+
+  static OpampClient startOpampClient(
+      String endpoint, String serviceName, OpampClient.Callbacks callbacks) {
+    OpampClientBuilder builder = OpampClient.builder();
+    builder.enableRemoteConfig();
+    if (endpoint != null) {
+      builder.setRequestService(HttpRequestService.create(OkHttpSender.create(endpoint)));
+    }
+    if (serviceName != null) {
+      builder.putIdentifyingAttribute("service.name", serviceName);
+    }
+
+    return builder.build(callbacks);
+  }
+}

custom/src/test/java/com/splunk/opentelemetry/opamp/OpampActivatorTest.java

@@ -0,0 +1,116 @@
+/*
+ * Copyright Splunk Inc.
+ *
+ * Licensed 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 com.splunk.opentelemetry.opamp;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import io.opentelemetry.instrumentation.testing.internal.AutoCleanupExtension;
+import io.opentelemetry.opamp.client.internal.OpampClient;
+import io.opentelemetry.opamp.client.internal.response.MessageData;
+import io.opentelemetry.testing.internal.armeria.common.HttpResponse;
+import io.opentelemetry.testing.internal.armeria.common.HttpStatus;
+import io.opentelemetry.testing.internal.armeria.common.MediaType;
+import io.opentelemetry.testing.internal.armeria.testing.junit5.server.mock.MockWebServerExtension;
+import java.util.Collections;
+import java.util.Map;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.TimeUnit;
+import okio.ByteString;
+import opamp.proto.AgentConfigFile;
+import opamp.proto.AgentConfigMap;
+import opamp.proto.AgentRemoteConfig;
+import opamp.proto.ServerErrorResponse;
+import opamp.proto.ServerToAgent;
+import org.jetbrains.annotations.Nullable;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+
+class OpampActivatorTest {
+  private static final MockWebServerExtension server = new MockWebServerExtension();
+
+  @RegisterExtension static final AutoCleanupExtension cleanup = AutoCleanupExtension.create();
+
+  @BeforeAll
+  static void setUp() {
+    server.start();
+  }
+
+  @BeforeEach
+  void reset() {
+    server.beforeTestExecution(null);
+  }
+
+  @AfterAll
+  static void cleanUp() {
+    server.stop();
+  }
+
+  @Test
+  void testOpamp() throws Exception {
+    // given
+    Map<String, AgentConfigFile> configMap =
+        Collections.singletonMap(
+            "test-key",
+            new AgentConfigFile.Builder().body(ByteString.encodeUtf8("test-value")).build());
+    ServerToAgent response =
+        new ServerToAgent.Builder()
+            .remote_config(
+                new AgentRemoteConfig.Builder()
+                    .config(new AgentConfigMap.Builder().config_map(configMap).build())
+                    .build())
+            .build();
+    server.enqueue(HttpResponse.of(HttpStatus.OK, MediaType.X_PROTOBUF, response.encode()));
+
+    CompletableFuture<MessageData> result = new CompletableFuture<>();
+    OpampClient client =
+        OpampActivator.startOpampClient(
+            server.httpUri().toString(),
+            "test",
+            new OpampClient.Callbacks() {
+              @Override
+              public void onConnect() {}
+
+              @Override
+              public void onConnectFailed(@Nullable Throwable throwable) {
+                result.completeExceptionally(throwable);
+              }
+
+              @Override
+              public void onErrorResponse(ServerErrorResponse serverErrorResponse) {
+                result.completeExceptionally(
+                    new IllegalStateException(serverErrorResponse.toString()));
+              }
+
+              @Override
+              public void onMessage(MessageData messageData) {
+                result.complete(messageData);
+              }
+            });
+    cleanup.deferCleanup(client);
+
+    // when
+    MessageData message = result.get(5, TimeUnit.SECONDS);
+    AgentRemoteConfig remoteConfig = message.getRemoteConfig();
+
+    // then
+    assertThat(remoteConfig).isNotNull();
+    assertThat(remoteConfig.config.config_map.get("test-key").body.utf8()).isEqualTo("test-value");
+  }
+}

dependencyManagement/build.gradle.kts

@@ -55,6 +55,7 @@ dependencies {
 
     api("io.opentelemetry.contrib:opentelemetry-samplers:$otelContribAlphaVersion")
     api("io.opentelemetry.contrib:opentelemetry-resource-providers:$otelContribAlphaVersion")
+    api("io.opentelemetry.contrib:opentelemetry-opamp-client:${otelContribAlphaVersion}")
     api("io.opentelemetry.proto:opentelemetry-proto:1.8.0-alpha")
 
     api("org.apache.commons:commons-jexl3:3.5.0")