[OpAMP client] Added health reporting support

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

@@ -9,6 +9,7 @@
 import java.io.Closeable;
 import javax.annotation.Nullable;
 import opamp.proto.AgentDescription;
+import opamp.proto.ComponentHealth;
 import opamp.proto.RemoteConfigStatus;
 import opamp.proto.ServerErrorResponse;
 
@@ -35,6 +36,13 @@ static OpampClientBuilder builder() {
    */
   void setRemoteConfigStatus(RemoteConfigStatus remoteConfigStatus);
 
+  /**
+   * Sets the current Agent health which will be sent in the next agent to server request.
+   *
+   * @param health The new component health.
+   */
+  void setHealth(ComponentHealth health);
+
   interface Callbacks {
     /**
      * Called when the connection is successfully established to the Server. For WebSocket clients

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

@@ -19,12 +19,15 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.UUID;
+import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import opamp.proto.AgentCapabilities;
 import opamp.proto.AgentDescription;
 import opamp.proto.AnyValue;
 import opamp.proto.ArrayValue;
+import opamp.proto.ComponentHealth;
 import opamp.proto.KeyValue;
 import opamp.proto.RemoteConfigStatus;
 
@@ -37,6 +40,7 @@ public final class OpampClientBuilder {
       HttpRequestService.create(OkHttpSender.create("http://localhost:4320/v1/opamp"));
   @Nullable private byte[] instanceUid;
   @Nullable private State.EffectiveConfig effectiveConfigState;
+  @Nullable private ComponentHealth initialHealth;
 
   OpampClientBuilder() {}
 
@@ -341,10 +345,8 @@ public OpampClientBuilder putNonIdentifyingAttribute(String key, double... value
    */
   @CanIgnoreReturnValue
   public OpampClientBuilder enableRemoteConfig() {
-    capabilities =
-        capabilities
-            | AgentCapabilities.AgentCapabilities_AcceptsRemoteConfig.getValue()
-            | AgentCapabilities.AgentCapabilities_ReportsRemoteConfig.getValue();
+    enableCapability(AgentCapabilities.AgentCapabilities_AcceptsRemoteConfig);
+    enableCapability(AgentCapabilities.AgentCapabilities_ReportsRemoteConfig);
     return this;
   }
 
@@ -357,8 +359,7 @@ public OpampClientBuilder enableRemoteConfig() {
    */
   @CanIgnoreReturnValue
   public OpampClientBuilder enableEffectiveConfigReporting() {
-    capabilities =
-        capabilities | AgentCapabilities.AgentCapabilities_ReportsEffectiveConfig.getValue();
+    enableCapability(AgentCapabilities.AgentCapabilities_ReportsEffectiveConfig);
     return this;
   }
 
@@ -376,6 +377,20 @@ public OpampClientBuilder setEffectiveConfigState(State.EffectiveConfig effectiv
     return this;
   }
 
+  /**
+   * Enables health reporting and sets the initial health object that is then passed to the
+   * corresponding state implementation.
+   *
+   * @param initialHealth The component health
+   * @return this
+   */
+  @CanIgnoreReturnValue
+  public OpampClientBuilder enableHealthReporting(@Nonnull ComponentHealth initialHealth) {
+    this.initialHealth = Objects.requireNonNull(initialHealth);
+    enableCapability(AgentCapabilities.AgentCapabilities_ReportsHealth);
+    return this;
+  }
+
   public OpampClient build(OpampClient.Callbacks callbacks) {
     List<KeyValue> protoIdentifyingAttributes = new ArrayList<>();
     List<KeyValue> protoNonIdentifyingAttributes = new ArrayList<>();
@@ -399,12 +414,17 @@ public OpampClient build(OpampClient.Callbacks callbacks) {
                     .non_identifying_attributes(protoNonIdentifyingAttributes)
                     .build()),
             new State.Capabilities(capabilities),
+            new State.Health(initialHealth),
             new State.InstanceUid(instanceUid),
             new State.Flags(0L),
             effectiveConfigState);
     return OpampClientImpl.create(service, state, callbacks);
   }
 
+  private void enableCapability(AgentCapabilities capability) {
+    capabilities = capabilities | capability.getValue();
+  }
+
   private static State.EffectiveConfig createEffectiveConfigNoop() {
     return new State.EffectiveConfig() {
       @Nullable

opamp-client/src/main/java/io/opentelemetry/opamp/client/internal/impl/OpampClientImpl.java

@@ -14,6 +14,7 @@
 import io.opentelemetry.opamp.client.internal.impl.recipe.appenders.CapabilitiesAppender;
 import io.opentelemetry.opamp.client.internal.impl.recipe.appenders.EffectiveConfigAppender;
 import io.opentelemetry.opamp.client.internal.impl.recipe.appenders.FlagsAppender;
+import io.opentelemetry.opamp.client.internal.impl.recipe.appenders.HealthAppender;
 import io.opentelemetry.opamp.client.internal.impl.recipe.appenders.InstanceUidAppender;
 import io.opentelemetry.opamp.client.internal.impl.recipe.appenders.RemoteConfigStatusAppender;
 import io.opentelemetry.opamp.client.internal.impl.recipe.appenders.SequenceNumberAppender;
@@ -32,8 +33,10 @@
 import java.util.function.Supplier;
 import javax.annotation.Nonnull;
 import okio.ByteString;
+import opamp.proto.AgentCapabilities;
 import opamp.proto.AgentDescription;
 import opamp.proto.AgentToServer;
+import opamp.proto.ComponentHealth;
 import opamp.proto.RemoteConfigStatus;
 import opamp.proto.ServerErrorResponse;
 import opamp.proto.ServerToAgent;
@@ -76,6 +79,7 @@ public final class OpampClientImpl
     // Compressable fields init
     List<Field> compressableFields = new ArrayList<>();
     compressableFields.add(Field.AGENT_DESCRIPTION);
+    compressableFields.add(Field.HEALTH);
     compressableFields.add(Field.EFFECTIVE_CONFIG);
     compressableFields.add(Field.REMOTE_CONFIG_STATUS);
     COMPRESSABLE_FIELDS = Collections.unmodifiableList(compressableFields);
@@ -90,6 +94,7 @@ public static OpampClientImpl create(
             RemoteConfigStatusAppender.create(state.remoteConfigStatus),
             SequenceNumberAppender.create(state.sequenceNum),
             CapabilitiesAppender.create(state.capabilities),
+            HealthAppender.create(state.health),
             InstanceUidAppender.create(state.instanceUid),
             FlagsAppender.create(state.flags),
             AgentDisconnectAppender.create());
@@ -130,20 +135,27 @@ public void close() {
 
   @Override
   public void setAgentDescription(@Nonnull AgentDescription agentDescription) {
-    if (!state.agentDescription.get().equals(agentDescription)) {
-      state.agentDescription.set(agentDescription);
+    if (state.agentDescription.set(agentDescription)) {
       addFieldAndSend(Field.AGENT_DESCRIPTION);
     }
   }
 
   @Override
   public void setRemoteConfigStatus(@Nonnull RemoteConfigStatus remoteConfigStatus) {
-    if (!state.remoteConfigStatus.get().equals(remoteConfigStatus)) {
-      state.remoteConfigStatus.set(remoteConfigStatus);
+    verifyCapability(AgentCapabilities.AgentCapabilities_ReportsRemoteConfig);
+    if (state.remoteConfigStatus.set(remoteConfigStatus)) {
       addFieldAndSend(Field.REMOTE_CONFIG_STATUS);
     }
   }
 
+  @Override
+  public void setHealth(@Nonnull ComponentHealth health) {
+    verifyCapability(AgentCapabilities.AgentCapabilities_ReportsHealth);
+    if (state.health.set(health)) {
+      addFieldAndSend(Field.HEALTH);
+    }
+  }
+
   @Override
   public void onConnectionSuccess() {
     callbacks.onConnect(this);
@@ -252,4 +264,11 @@ private void addFieldAndSend(Field field) {
     recipeManager.next().addField(field);
     requestService.sendRequest();
   }
+
+  private void verifyCapability(AgentCapabilities capabilityToCheck) {
+    if ((state.capabilities.mustGet() & capabilityToCheck.getValue()) == 0) {
+      throw new IllegalStateException(
+          "Required capability " + capabilityToCheck + " is not enabled");
+    }
+  }
 }

opamp-client/src/main/java/io/opentelemetry/opamp/client/internal/impl/OpampClientState.java

@@ -19,6 +19,7 @@ public final class OpampClientState {
   public final State.SequenceNum sequenceNum;
   public final State.AgentDescription agentDescription;
   public final State.Capabilities capabilities;
+  public final State.Health health;
   public final State.InstanceUid instanceUid;
   public final State.Flags flags;
   public final State.EffectiveConfig effectiveConfig;
@@ -29,13 +30,15 @@ public OpampClientState(
       State.SequenceNum sequenceNum,
       State.AgentDescription agentDescription,
       State.Capabilities capabilities,
+      State.Health health,
       State.InstanceUid instanceUid,
       State.Flags flags,
       State.EffectiveConfig effectiveConfig) {
     this.remoteConfigStatus = remoteConfigStatus;
     this.sequenceNum = sequenceNum;
     this.agentDescription = agentDescription;
     this.capabilities = capabilities;
+    this.health = health;
     this.instanceUid = instanceUid;
     this.flags = flags;
     this.effectiveConfig = effectiveConfig;
@@ -45,6 +48,7 @@ public OpampClientState(
     providedItems.add(sequenceNum);
     providedItems.add(agentDescription);
     providedItems.add(capabilities);
+    providedItems.add(health);
     providedItems.add(instanceUid);
     providedItems.add(flags);
     providedItems.add(effectiveConfig);

opamp-client/src/main/java/io/opentelemetry/opamp/client/internal/impl/recipe/AgentToServerAppenders.java

@@ -11,6 +11,7 @@
 import io.opentelemetry.opamp.client.internal.impl.recipe.appenders.CapabilitiesAppender;
 import io.opentelemetry.opamp.client.internal.impl.recipe.appenders.EffectiveConfigAppender;
 import io.opentelemetry.opamp.client.internal.impl.recipe.appenders.FlagsAppender;
+import io.opentelemetry.opamp.client.internal.impl.recipe.appenders.HealthAppender;
 import io.opentelemetry.opamp.client.internal.impl.recipe.appenders.InstanceUidAppender;
 import io.opentelemetry.opamp.client.internal.impl.recipe.appenders.RemoteConfigStatusAppender;
 import io.opentelemetry.opamp.client.internal.impl.recipe.appenders.SequenceNumberAppender;
@@ -29,17 +30,20 @@ public final class AgentToServerAppenders {
   public final RemoteConfigStatusAppender remoteConfigStatusAppender;
   public final SequenceNumberAppender sequenceNumberAppender;
   public final CapabilitiesAppender capabilitiesAppender;
+  public final HealthAppender healthAppender;
   public final InstanceUidAppender instanceUidAppender;
   public final FlagsAppender flagsAppender;
   public final AgentDisconnectAppender agentDisconnectAppender;
   private final Map<Field, AgentToServerAppender> allAppenders;
 
+  @SuppressWarnings("TooManyParameters")
   public AgentToServerAppenders(
       AgentDescriptionAppender agentDescriptionAppender,
       EffectiveConfigAppender effectiveConfigAppender,
       RemoteConfigStatusAppender remoteConfigStatusAppender,
       SequenceNumberAppender sequenceNumberAppender,
       CapabilitiesAppender capabilitiesAppender,
+      HealthAppender healthAppender,
       InstanceUidAppender instanceUidAppender,
       FlagsAppender flagsAppender,
       AgentDisconnectAppender agentDisconnectAppender) {
@@ -48,6 +52,7 @@ public AgentToServerAppenders(
     this.remoteConfigStatusAppender = remoteConfigStatusAppender;
     this.sequenceNumberAppender = sequenceNumberAppender;
     this.capabilitiesAppender = capabilitiesAppender;
+    this.healthAppender = healthAppender;
     this.instanceUidAppender = instanceUidAppender;
     this.flagsAppender = flagsAppender;
     this.agentDisconnectAppender = agentDisconnectAppender;
@@ -58,6 +63,7 @@ public AgentToServerAppenders(
     appenders.put(Field.REMOTE_CONFIG_STATUS, remoteConfigStatusAppender);
     appenders.put(Field.SEQUENCE_NUM, sequenceNumberAppender);
     appenders.put(Field.CAPABILITIES, capabilitiesAppender);
+    appenders.put(Field.HEALTH, healthAppender);
     appenders.put(Field.INSTANCE_UID, instanceUidAppender);
     appenders.put(Field.FLAGS, flagsAppender);
     appenders.put(Field.AGENT_DISCONNECT, agentDisconnectAppender);

opamp-client/src/main/java/io/opentelemetry/opamp/client/internal/impl/recipe/appenders/HealthAppender.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.opamp.client.internal.impl.recipe.appenders;
+
+import java.util.function.Supplier;
+import opamp.proto.AgentToServer;
+import opamp.proto.ComponentHealth;
+
+/**
+ * This class is internal and is hence not for public use. Its APIs are unstable and can change at
+ * any time.
+ */
+public final class HealthAppender implements AgentToServerAppender {
+  private final Supplier<ComponentHealth> health;
+
+  public static HealthAppender create(Supplier<ComponentHealth> health) {
+    return new HealthAppender(health);
+  }
+
+  private HealthAppender(Supplier<ComponentHealth> health) {
+    this.health = health;
+  }
+
+  @Override
+  public void appendTo(AgentToServer.Builder builder) {
+    ComponentHealth currentHealth = health.get();
+    if (currentHealth != null) {
+      builder.health(currentHealth);
+    }
+  }
+}

opamp-client/src/main/java/io/opentelemetry/opamp/client/internal/request/Field.java

@@ -18,6 +18,7 @@ public enum Field {
   SEQUENCE_NUM,
   AGENT_DESCRIPTION,
   CAPABILITIES,
+  HEALTH,
   EFFECTIVE_CONFIG,
   REMOTE_CONFIG_STATUS,
   AGENT_DISCONNECT,

opamp-client/src/main/java/io/opentelemetry/opamp/client/internal/state/InMemoryState.java

@@ -5,10 +5,9 @@
 
 package io.opentelemetry.opamp.client.internal.state;
 
-import static java.util.Objects.requireNonNull;
-
+import java.util.Objects;
 import java.util.concurrent.atomic.AtomicReference;
-import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 
 /**
  * This class is internal and is hence not for public use. Its APIs are unstable and can change at
@@ -17,23 +16,28 @@
 abstract class InMemoryState<T> implements State<T> {
   private final AtomicReference<T> state = new AtomicReference<>();
 
-  public InMemoryState(T initialValue) {
-    if (initialValue == null) {
-      throw new IllegalArgumentException("The value must not be null");
-    }
+  public InMemoryState(@Nullable T initialValue) {
     state.set(initialValue);
   }
 
-  public void set(T value) {
+  /**
+   * Set a new state's value in a thread safe way.
+   *
+   * @param value a new value stored in the state
+   * @return <code>true</code> if new value is different that the previous one, <code>false</code>
+   *     otherwise.
+   */
+  public boolean set(T value) {
     if (value == null) {
       throw new IllegalArgumentException("The value must not be null");
     }
-    state.set(value);
+    T previousValue = state.getAndSet(value);
+    return !Objects.equals(previousValue, value);
   }
 
-  @Nonnull
+  @Nullable
   @Override
   public T get() {
-    return requireNonNull(state.get());
+    return state.get();
   }
 }

opamp-client/src/main/java/io/opentelemetry/opamp/client/internal/state/State.java

@@ -9,6 +9,8 @@
 import java.util.Objects;
 import java.util.function.Supplier;
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import opamp.proto.ComponentHealth;
 
 /**
  * This class is internal and is hence not for public use. Its APIs are unstable and can change at
@@ -75,6 +77,17 @@ public Field getFieldType() {
     }
   }
 
+  final class Health extends InMemoryState<ComponentHealth> {
+    public Health(@Nullable ComponentHealth initialValue) {
+      super(initialValue);
+    }
+
+    @Override
+    public Field getFieldType() {
+      return Field.HEALTH;
+    }
+  }
+
   final class RemoteConfigStatus extends InMemoryState<opamp.proto.RemoteConfigStatus> {
 
     public RemoteConfigStatus(opamp.proto.RemoteConfigStatus initialValue) {