Adding opamp builder

Author: LikeTheSalad

dependencyManagement/build.gradle.kts

@@ -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

@@ -13,6 +13,7 @@ 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")

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

@@ -0,0 +1,189 @@
+package io.opentelemetry.opamp.client.internal;
+
+import com.github.f4b6a3.uuid.UuidCreator;
+import io.opentelemetry.opamp.client.internal.impl.OpampClientImpl;
+import io.opentelemetry.opamp.client.internal.impl.OpampClientState;
+import io.opentelemetry.opamp.client.internal.request.service.HttpRequestService;
+import io.opentelemetry.opamp.client.internal.request.service.RequestService;
+import io.opentelemetry.opamp.client.internal.request.service.WebSocketRequestService;
+import io.opentelemetry.opamp.client.internal.state.State;
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.UUID;
+import opamp.proto.AgentCapabilities;
+import opamp.proto.AgentDescription;
+import opamp.proto.AnyValue;
+import opamp.proto.KeyValue;
+import opamp.proto.RemoteConfigStatus;
+
+/**
+ * This class is internal and is hence not for public use. Its APIs are unstable and can change at
+ * any time.
+ *
+ * <p>Builds an {@link OpampClient} instance.
+ */
+public final class OpampClientBuilder {
+  private final Map<String, String> identifyingAttributes = new HashMap<>();
+  private final Map<String, String> nonIdentifyingAttributes = new HashMap<>();
+  private byte[] instanceUid;
+  private long capabilities = 0;
+  private State.EffectiveConfig effectiveConfigState;
+  private RequestService service;
+
+  OpampClientBuilder() {}
+
+  /**
+   * Sets an implementation of a {@link RequestService} to handle the request's sending process.
+   * There are 2 possible options, either {@link HttpRequestService} to use HTTP, or {@link
+   * WebSocketRequestService} to use WebSocket.
+   *
+   * @param service The request service implementation.
+   * @return this
+   */
+  public OpampClientBuilder setRequestService(RequestService service) {
+    this.service = service;
+    return this;
+  }
+
+  /**
+   * Sets the Agent's <a
+   * href="https://github.com/open-telemetry/opamp-spec/blob/main/specification.md#agenttoserverinstance_uid">instance_uid</a>
+   * value. A random one is generated by default.
+   *
+   * @param value The AgentToServer.instance_uid value.
+   * @return this
+   */
+  public OpampClientBuilder setInstanceUid(byte[] value) {
+    this.instanceUid = value;
+    return this;
+  }
+
+  /**
+   * Sets a string attribute into the <a
+   * href="https://github.com/open-telemetry/opamp-spec/blob/main/specification.md#agentdescriptionidentifying_attributes">identifying_attributes</a>
+   * field.
+   *
+   * @param key The attribute key.
+   * @param value The attribute value.
+   * @return this
+   */
+  public OpampClientBuilder setIdentifyingAttribute(String key, String value) {
+    identifyingAttributes.put(key, value);
+    return this;
+  }
+
+  /**
+   * Sets an attribute into the <a
+   * href="https://github.com/open-telemetry/opamp-spec/blob/main/specification.md#agentdescriptionnon_identifying_attributes">non_identifying_attributes</a>
+   * field.
+   *
+   * @param key The attribute key
+   * @param value The attribute value.
+   * @return this
+   */
+  public OpampClientBuilder setNonIdentifyingAttribute(String key, String value) {
+    nonIdentifyingAttributes.put(key, value);
+    return this;
+  }
+
+  /**
+   * Adds the AcceptsRemoteConfig and ReportsRemoteConfig capabilities to the Client so that the
+   * Server can offer remote config values as explained <a
+   * href="https://github.com/open-telemetry/opamp-spec/blob/main/specification.md#agentdescriptionidentifying_attributes">here</a>.
+   *
+   * @return this
+   */
+  public OpampClientBuilder enableRemoteConfig() {
+    capabilities =
+        capabilities
+            | AgentCapabilities.AgentCapabilities_AcceptsRemoteConfig.getValue()
+            | AgentCapabilities.AgentCapabilities_ReportsRemoteConfig.getValue();
+    return this;
+  }
+
+  /**
+   * Adds the ReportsEffectiveConfig capability to the Client so that the Server expects the
+   * Client's effective config report, as explained <a
+   * href="https://github.com/open-telemetry/opamp-spec/blob/main/specification.md#agentdescriptionidentifying_attributes">here</a>.
+   *
+   * @return this
+   */
+  public OpampClientBuilder enableEffectiveConfigReporting() {
+    capabilities =
+        capabilities | AgentCapabilities.AgentCapabilities_ReportsEffectiveConfig.getValue();
+    return this;
+  }
+
+  /**
+   * Sets the effective config state implementation. It should call {@link
+   * State.EffectiveConfig#notifyUpdate()} whenever it has changes that have not been sent to the
+   * server.
+   *
+   * @param effectiveConfigState The state implementation.
+   * @return this
+   */
+  public OpampClientBuilder setEffectiveConfigState(State.EffectiveConfig effectiveConfigState) {
+    this.effectiveConfigState = effectiveConfigState;
+    return this;
+  }
+
+  public OpampClient build() {
+    if (service == null) {
+      throw new NullPointerException(
+          "The request service is not set. You must provide it by calling setRequestService()");
+    }
+    List<KeyValue> protoIdentifyingAttributes = new ArrayList<>();
+    List<KeyValue> protoNonIdentifyingAttributes = new ArrayList<>();
+    identifyingAttributes.forEach(
+        (key, value) -> protoIdentifyingAttributes.add(createKeyValue(key, value)));
+    nonIdentifyingAttributes.forEach(
+        (key, value) -> protoNonIdentifyingAttributes.add(createKeyValue(key, value)));
+    if (instanceUid == null) {
+      instanceUid = createRandomInstanceUid();
+    }
+    if (effectiveConfigState == null) {
+      effectiveConfigState = createEffectiveConfigNoop();
+    }
+    OpampClientState state =
+        new OpampClientState(
+            new State.RemoteConfigStatus(new RemoteConfigStatus.Builder().build()),
+            new State.SequenceNum(1L),
+            new State.AgentDescription(
+                new AgentDescription.Builder()
+                    .identifying_attributes(protoIdentifyingAttributes)
+                    .non_identifying_attributes(protoNonIdentifyingAttributes)
+                    .build()),
+            new State.Capabilities(capabilities),
+            new State.InstanceUid(instanceUid),
+            new State.Flags(0L),
+            effectiveConfigState);
+    return OpampClientImpl.create(service, state);
+  }
+
+  private State.EffectiveConfig createEffectiveConfigNoop() {
+    return new State.EffectiveConfig() {
+      @Override
+      public opamp.proto.EffectiveConfig get() {
+        return null;
+      }
+    };
+  }
+
+  private KeyValue createKeyValue(String key, String value) {
+    return new KeyValue.Builder()
+        .key(key)
+        .value(new AnyValue.Builder().string_value(value).build())
+        .build();
+  }
+
+  public static byte[] createRandomInstanceUid() {
+    UUID uuid = UuidCreator.getTimeOrderedEpoch();
+    ByteBuffer buffer = ByteBuffer.allocate(16);
+    buffer.putLong(uuid.getMostSignificantBits());
+    buffer.putLong(uuid.getLeastSignificantBits());
+    return buffer.array();
+  }
+}