Opamp client implementation (#2021)

Author: LikeTheSalad

dependencyManagement/build.gradle.kts

@@ -17,6 +17,7 @@ dependencies {
   api(enforcedPlatform("io.opentelemetry.instrumentation:opentelemetry-instrumentation-bom-alpha:${otelInstrumentationVersion}"))
   api(enforcedPlatform("com.fasterxml.jackson:jackson-bom:2.19.2"))
   api(enforcedPlatform("com.google.protobuf:protobuf-bom:4.31.1"))
+  api(enforcedPlatform("com.squareup.okhttp3:okhttp-bom:5.1.0"))
 
   constraints {
     api("io.opentelemetry.semconv:opentelemetry-semconv:${semconvVersion}")
@@ -44,7 +45,6 @@ dependencies {
 
     api("com.google.code.findbugs:annotations:3.0.1u2")
     api("com.google.code.findbugs:jsr305:3.0.2")
-    api("com.squareup.okhttp3:okhttp:5.1.0")
     api("com.uber.nullaway:nullaway:0.12.7")
     api("org.assertj:assertj-core:3.27.3")
     api("org.awaitility:awaitility:4.3.0")
@@ -58,5 +58,6 @@ dependencies {
     api("tools.profiler:async-profiler:4.0")
     api("com.blogspot.mydailyjava:weak-lock-free:0.18")
     api("org.agrona:agrona:1.22.0")
+    api("com.github.f4b6a3:uuid-creator:6.0.0")
   }
 }

opamp-client/build.gradle.kts

@@ -13,10 +13,13 @@ otelJava.moduleName.set("io.opentelemetry.contrib.opamp.client")
 
 dependencies {
   implementation("com.squareup.okhttp3:okhttp")
+  implementation("com.github.f4b6a3:uuid-creator")
   annotationProcessor("com.google.auto.value:auto-value")
   compileOnly("com.google.auto.value:auto-value-annotations")
   testImplementation("org.mockito:mockito-inline")
   testImplementation("com.google.protobuf:protobuf-java-util")
+  testImplementation("com.squareup.okhttp3:mockwebserver3")
+  testImplementation("com.squareup.okhttp3:mockwebserver3-junit5")
 }
 
 val opampProtos = tasks.register<DownloadOpampProtos>("opampProtoDownload", download)

opamp-client/src/main/java/io/opentelemetry/opamp/client/internal/OpampClient.java

@@ -6,17 +6,21 @@
 package io.opentelemetry.opamp.client.internal;
 
 import io.opentelemetry.opamp.client.internal.response.MessageData;
+import javax.annotation.Nullable;
 import opamp.proto.AgentDescription;
 import opamp.proto.RemoteConfigStatus;
 import opamp.proto.ServerErrorResponse;
 
 public interface OpampClient {
 
+  static OpampClientBuilder builder() {
+    return new OpampClientBuilder();
+  }
+
   /**
    * Starts the client and begin attempts to connect to the Server. Once connection is established
    * the client will attempt to maintain it by reconnecting if the connection is lost. All failed
-   * connection attempts will be reported via {@link Callbacks#onConnectFailed(OpampClient,
-   * Throwable)} callback.
+   * connection attempts will be reported via {@link Callbacks#onConnectFailed(Throwable)} callback.
    *
    * <p>This method does not wait until the connection to the Server is established and will likely
    * return before the connection attempts are even made.
@@ -40,7 +44,7 @@ public interface OpampClient {
    * the Server. When called after {@link #start(Callbacks)}, the attributes will be included in the
    * next outgoing status report. This is typically used by Agents which allow their
    * AgentDescription to change dynamically while the OpAMPClient is started. May be also called
-   * from {@link Callbacks#onMessage(OpampClient, MessageData)}.
+   * from {@link Callbacks#onMessage(MessageData)}.
    *
    * @param agentDescription The new agent description.
    */
@@ -59,31 +63,27 @@ interface Callbacks {
      * {@link #start(Callbacks)} is called and every time a connection is established to the Server.
      * For WebSocket clients this is called after the handshake is completed without any error. For
      * HTTP clients this is called for any request if the response status is OK.
-     *
-     * @param client The relevant {@link OpampClient} instance.
      */
-    void onConnect(OpampClient client);
+    void onConnect();
 
     /**
      * Called when the connection to the Server cannot be established. May be called after {@link
      * #start(Callbacks)} is called and tries to connect to the Server. May also be called if the
      * connection is lost and reconnection attempt fails.
      *
-     * @param client The relevant {@link OpampClient} instance.
      * @param throwable The exception.
      */
-    void onConnectFailed(OpampClient client, Throwable throwable);
+    void onConnectFailed(@Nullable Throwable throwable);
 
     /**
      * Called when the Server reports an error in response to some previously sent request. Useful
      * for logging purposes. The Agent should not attempt to process the error by reconnecting or
      * retrying previous operations. The client handles the ErrorResponse_UNAVAILABLE case
      * internally by performing retries as necessary.
      *
-     * @param client The relevant {@link OpampClient} instance.
      * @param errorResponse The error returned by the Server.
      */
-    void onErrorResponse(OpampClient client, ServerErrorResponse errorResponse);
+    void onErrorResponse(ServerErrorResponse errorResponse);
 
     /**
      * Called when the Agent receives a message that needs processing. See {@link MessageData}
@@ -94,9 +94,8 @@ interface Callbacks {
      * onMessage returns. This is advisable if processing can take a long time. In that case
      * returning quickly is preferable to avoid blocking the {@link OpampClient}.
      *
-     * @param client The relevant {@link OpampClient} instance.
      * @param messageData The server response data that needs processing.
      */
-    void onMessage(OpampClient client, MessageData messageData);
+    void onMessage(MessageData messageData);
   }
 }