Support direct reply-to in RPC client support class

.github/workflows/test-pr.yml

@@ -1,4 +1,4 @@
-name: Test against RabbitMQ 4.1 (PR)
+name: Test against RabbitMQ stable (PR)
 
 on:
   pull_request:

.github/workflows/test.yml

@@ -1,4 +1,4 @@
-name: Test against RabbitMQ 4.0
+name: Test against RabbitMQ stable
 
 on:
   push:

src/docs/asciidoc/usage.adoc

@@ -235,7 +235,7 @@ This behavior is hardcoded but it is possible to cancel it thanks to a reply pos
 
 The RPC client uses the following defaults:
 
-* it creates and waits for replies on an auto-delete, exclusive queue if no reply-to queue is set.
+* it uses https://www.rabbitmq.com/docs/direct-reply-to[direct reply-to] if available (RabbitMQ 4.2 or more) for replies if no reply-to queue is set (it falls back to an auto-delete, exclusive queue if direct reply-to is not available)
 * it uses a string-based correlation ID generator, with a fixed random UUID prefix and a strictly monotonic increasing sequence suffix (`{UUID}-{sequence}`, e.g. `6f839461-6b19-47e1-80b3-6be10d899d85-42`).
 The prefix is different for each `RpcClient` instance and the suffix is incremented by one for each request.
 * it sets the _request_ https://docs.oasis-open.org/amqp/core/v1.0/os/amqp-core-messaging-v1.0-os.html#type-properties[`reply-to` property] to the reply-to queue address (defined by the user or created automatically, see above).

src/main/java/com/rabbitmq/client/amqp/Publisher.java

@@ -32,8 +32,8 @@ public interface Publisher extends AutoCloseable, Resource {
   /**
    * Create a message meant to be published by the publisher instance.
    *
-   * <p>Once published with the {@link #publish(Message, Callback)} the message instance should be
-   * not be modified or even reused.
+   * <p>Once published with the {@link #publish(Message, Callback)} the message instance should not
+   * be modified or even reused.
    *
    * @return a message
    */
@@ -42,8 +42,8 @@ public interface Publisher extends AutoCloseable, Resource {
   /**
    * Create a message meant to be published by the publisher instance.
    *
-   * <p>Once published with the {@link #publish(Message, Callback)} the message instance should be
-   * not be modified or even reused.
+   * <p>Once published with the {@link #publish(Message, Callback)} the message instance should not
+   * be modified or even reused.
    *
    * @param body message body
    * @return a message with the provided body

src/main/java/com/rabbitmq/client/amqp/RpcClient.java

@@ -29,7 +29,7 @@ public interface RpcClient extends AutoCloseable {
   /**
    * Create a message meant to be published by the underlying publisher instance.
    *
-   * <p>Once published with the {@link #publish(Message)} the message instance should be not be
+   * <p>Once published with the {@link #publish(Message)} the message instance should not be
    * modified or even reused.
    *
    * @return a message
@@ -39,7 +39,7 @@ public interface RpcClient extends AutoCloseable {
   /**
    * Create a message meant to be published by the underlying publisher instance.
    *
-   * <p>Once published with the {@link #publish(Message)} the message instance should be not be
+   * <p>Once published with the {@link #publish(Message)} the message instance should not be
    * modified or even reused.
    *
    * @param body message body

src/main/java/com/rabbitmq/client/amqp/RpcServer.java

@@ -41,6 +41,20 @@ interface Handler {
   /** Request processing context. */
   interface Context {
 
+    /**
+     * Tell whether the requester is still able to receive the response.
+     *
+     * <p>The call assumes a reply-to queue address has been set on the request message and checks
+     * whether this queue still exists or not.
+     *
+     * <p>A time-consuming request handler can use this call from time to time to make sure it still
+     * worth keeping processing the request.
+     *
+     * @param request the incoming request
+     * @return true if the requester is still considered alive, false otherwise
+     */
+    boolean isRequesterAlive(Message request);
+
     /**
      * Create a message meant to be published by the underlying publisher instance.
      *

src/main/java/com/rabbitmq/client/amqp/impl/AmqpConnection.java

@@ -24,6 +24,7 @@
 import static com.rabbitmq.client.amqp.Resource.State.RECOVERING;
 import static com.rabbitmq.client.amqp.impl.ExceptionUtils.convert;
 import static com.rabbitmq.client.amqp.impl.Tuples.pair;
+import static com.rabbitmq.client.amqp.impl.Utils.supportDirectReplyTo;
 import static com.rabbitmq.client.amqp.impl.Utils.supportFilterExpressions;
 import static com.rabbitmq.client.amqp.impl.Utils.supportSetToken;
 import static com.rabbitmq.client.amqp.impl.Utils.supportSqlFilterExpressions;
@@ -118,7 +119,8 @@ final class AmqpConnection extends ResourceBase implements Connection {
   private final Lock instanceLock = new ReentrantLock();
   private final boolean filterExpressionsSupported,
       setTokenSupported,
-      sqlFilterExpressionsSupported;
+      sqlFilterExpressionsSupported,
+      directReplyToSupported;
   private volatile ConsumerWorkService consumerWorkService;
   private volatile Executor dispatchingExecutor;
   private final boolean privateDispatchingExecutor;
@@ -216,6 +218,7 @@ final class AmqpConnection extends ResourceBase implements Connection {
     this.filterExpressionsSupported = supportFilterExpressions(brokerVersion);
     this.setTokenSupported = supportSetToken(brokerVersion);
     this.sqlFilterExpressionsSupported = supportSqlFilterExpressions(brokerVersion);
+    this.directReplyToSupported = supportDirectReplyTo(brokerVersion);
     LOGGER.debug("Opened connection '{}' on node '{}'.", this.name(), this.connectionNodename());
     this.state(OPEN);
     this.environment.metricsCollector().openConnection();
@@ -868,6 +871,10 @@ boolean setTokenSupported() {
     return this.setTokenSupported;
   }
 
+  boolean directReplyToSupported() {
+    return this.directReplyToSupported;
+  }
+
   long id() {
     return this.id;
   }

src/main/java/com/rabbitmq/client/amqp/impl/AmqpConsumer.java

@@ -65,6 +65,7 @@ final class AmqpConsumer extends ResourceBase implements Consumer {
   private final int initialCredits;
   private final Long id;
   private final String address;
+  private volatile String directReplyToAddress;
   private final String queue;
   private final Map<String, DescribedType> filters;
   private final Map<String, Object> linkProperties;
@@ -96,10 +97,15 @@ final class AmqpConsumer extends ResourceBase implements Consumer {
             .connection()
             .observationCollector()
             .subscribe(builder.queue(), builder.messageHandler());
-    DefaultAddressBuilder<?> addressBuilder = Utils.addressBuilder();
-    addressBuilder.queue(builder.queue());
-    this.address = addressBuilder.address();
-    this.queue = builder.queue();
+    if (builder.directReplyTo()) {
+      this.address = null;
+      this.queue = null;
+    } else {
+      DefaultAddressBuilder<?> addressBuilder = Utils.addressBuilder();
+      addressBuilder.queue(builder.queue());
+      this.address = addressBuilder.address();
+      this.queue = builder.queue();
+    }
     this.filters = Map.copyOf(builder.filters());
     this.linkProperties = Map.copyOf(builder.properties());
     this.subscriptionListener =
@@ -120,18 +126,19 @@ final class AmqpConsumer extends ResourceBase implements Consumer {
     this.consumerWorkService = connection.consumerWorkService();
     this.consumerWorkService.register(this);
     this.nativeReceiver =
-        this.createNativeReceiver(
+        createNativeReceiver(
             this.sessionHandler.session(),
             this.address,
             this.linkProperties,
             this.filters,
             this.subscriptionListener,
             this.nativeHandler,
             this.nativeCloseHandler);
-    this.initStateFromNativeReceiver(this.nativeReceiver);
-    this.metricsCollector = this.connection.metricsCollector();
-    this.state(OPEN);
     try {
+      this.directReplyToAddress = nativeReceiver.address();
+      this.initStateFromNativeReceiver(this.nativeReceiver);
+      this.metricsCollector = this.connection.metricsCollector();
+      this.state(OPEN);
       this.nativeReceiver.addCredit(this.initialCredits);
     } catch (ClientException e) {
       AmqpException ex = ExceptionUtils.convert(e);
@@ -189,7 +196,7 @@ public void close() {
 
   // internal API
 
-  private ClientReceiver createNativeReceiver(
+  private static ClientReceiver createNativeReceiver(
       Session nativeSession,
       String address,
       Map<String, Object> properties,
@@ -201,24 +208,47 @@ private ClientReceiver createNativeReceiver(
       filters = new LinkedHashMap<>(filters);
       StreamOptions streamOptions = AmqpConsumerBuilder.streamOptions(filters);
       subscriptionListener.preSubscribe(() -> streamOptions);
-      ReceiverOptions receiverOptions =
-          new ReceiverOptions()
-              .deliveryMode(DeliveryMode.AT_LEAST_ONCE)
-              .autoAccept(false)
-              .autoSettle(false)
-              .handler(nativeHandler)
-              .closeHandler(closeHandler)
-              .creditWindow(0)
-              .properties(properties);
+      boolean directReplyTo = address == null;
+      ReceiverOptions receiverOptions = new ReceiverOptions();
+
+      if (directReplyTo) {
+        receiverOptions
+            .deliveryMode(DeliveryMode.AT_MOST_ONCE)
+            .autoAccept(true)
+            .autoSettle(true)
+            .sourceOptions()
+            .capabilities("rabbitmq:volatile-queue")
+            .expiryPolicy(ExpiryPolicy.LINK_CLOSE)
+            .durabilityMode(DurabilityMode.NONE);
+      } else {
+        receiverOptions
+            .deliveryMode(DeliveryMode.AT_LEAST_ONCE)
+            .autoAccept(false)
+            .autoSettle(false);
+      }
+      receiverOptions
+          .handler(nativeHandler)
+          .closeHandler(closeHandler)
+          .creditWindow(0)
+          .properties(properties);
       Map<String, Object> localSourceFilters = Collections.emptyMap();
       if (!filters.isEmpty()) {
         localSourceFilters = Map.copyOf(filters);
         receiverOptions.sourceOptions().filters(localSourceFilters);
       }
-      ClientReceiver receiver =
-          (ClientReceiver)
-              ExceptionUtils.wrapGet(
-                  nativeSession.openReceiver(address, receiverOptions).openFuture());
+      ClientReceiver receiver;
+      if (directReplyTo) {
+        receiver =
+            (ClientReceiver)
+                ExceptionUtils.wrapGet(
+                    nativeSession.openDynamicReceiver(receiverOptions).openFuture());
+      } else {
+        receiver =
+            (ClientReceiver)
+                ExceptionUtils.wrapGet(
+                    nativeSession.openReceiver(address, receiverOptions).openFuture());
+      }
+
       boolean filterOk = true;
       if (!filters.isEmpty()) {
         Map<String, String> remoteSourceFilters = receiver.source().filters();
@@ -298,10 +328,11 @@ void recoverAfterConnectionFailure() {
             List.of(ofSeconds(1), ofSeconds(2), ofSeconds(3), BackOffDelayPolicy.TIMEOUT),
             "Create AMQP receiver to address '%s'",
             this.address);
-    this.initStateFromNativeReceiver(this.nativeReceiver);
-    this.pauseStatus.set(PauseStatus.UNPAUSED);
-    this.unsettledMessageCount.set(0);
     try {
+      this.directReplyToAddress = this.nativeReceiver.address();
+      this.initStateFromNativeReceiver(this.nativeReceiver);
+      this.pauseStatus.set(PauseStatus.UNPAUSED);
+      this.unsettledMessageCount.set(0);
       this.nativeReceiver.addCredit(this.initialCredits);
     } catch (ClientException e) {
       throw ExceptionUtils.convert(e);
@@ -493,6 +524,10 @@ private void settle(
     }
   }
 
+  String directReplyToAddress() {
+    return this.directReplyToAddress;
+  }
+
   @Override
   public String toString() {
     return "AmqpConsumer{" + "id=" + id + ", queue='" + queue + '\'' + '}';

src/main/java/com/rabbitmq/client/amqp/impl/AmqpConsumerBuilder.java

@@ -33,6 +33,7 @@ class AmqpConsumerBuilder implements ConsumerBuilder {
 
   private final AmqpConnection connection;
   private String queue;
+  private boolean directReplyTo = false;
   private Consumer.MessageHandler messageHandler;
   private int initialCredits = 100;
   private final List<Resource.StateListener> listeners = new ArrayList<>();
@@ -48,6 +49,19 @@ class AmqpConsumerBuilder implements ConsumerBuilder {
   @Override
   public ConsumerBuilder queue(String queue) {
     this.queue = queue;
+    if (this.queue == null) {
+      this.directReplyTo = true;
+    } else {
+      this.directReplyTo = false;
+    }
+    return this;
+  }
+
+  ConsumerBuilder directReplyTo(boolean directReplyTo) {
+    this.directReplyTo = directReplyTo;
+    if (this.directReplyTo) {
+      this.queue = null;
+    }
     return this;
   }
 
@@ -102,6 +116,10 @@ String queue() {
     return queue;
   }
 
+  boolean directReplyTo() {
+    return this.directReplyTo;
+  }
+
   Consumer.MessageHandler messageHandler() {
     return messageHandler;
   }
@@ -124,7 +142,7 @@ Map<String, DescribedType> filters() {
 
   @Override
   public Consumer build() {
-    if (this.queue == null || this.queue.isBlank()) {
+    if ((this.queue == null || this.queue.isBlank()) && !this.directReplyTo) {
       throw new IllegalArgumentException("A queue must be specified");
     }
     if (this.messageHandler == null) {
@@ -442,7 +460,7 @@ public StreamFilterOptions propertySymbol(String key, String value) {
 
     @Override
     public StreamFilterOptions sql(String sql) {
-      if (!this.streamOptions.builder.connection.filterExpressionsSupported()) {
+      if (!this.streamOptions.builder.connection.sqlFilterExpressionsSupported()) {
         throw new IllegalArgumentException(
             "AMQP SQL filter expressions requires at least RabbitMQ 4.2.0");
       }

src/main/java/com/rabbitmq/client/amqp/impl/AmqpManagement.java

@@ -713,11 +713,18 @@ private static class DefaultQueueInfo implements QueueInfo {
 
     @SuppressWarnings("unchecked")
     private DefaultQueueInfo(Map<String, Object> response) {
+      QueueType queueType;
       this.name = (String) response.get("name");
       this.durable = (Boolean) response.get("durable");
       this.autoDelete = (Boolean) response.get("auto_delete");
       this.exclusive = (Boolean) response.get("exclusive");
-      this.type = QueueType.valueOf(((String) response.get("type")).toUpperCase(Locale.ENGLISH));
+      try {
+        queueType = QueueType.valueOf(((String) response.get("type")).toUpperCase(Locale.ENGLISH));
+      } catch (Exception e) {
+        // this happens for reply-to queues, no need to make the type public
+        queueType = null;
+      }
+      this.type = queueType;
       this.arguments = Map.copyOf((Map<String, Object>) response.get("arguments"));
       this.leader = (String) response.get("leader");
       String[] members = (String[]) response.get("replicas");