GH-10624: PartitionedChannel: customize worker queue size (#10647)

Fixes: #10624

* Expose `workerQueueSize` from the `PartitionedDispatcher`
and respective delegates from the `PartitionedChannel` and `PartitionedChannelSpec`

**Auto-cherry-pick to `6.5.x` & `6.4.x`**

Author: artembilan

spring-integration-core/src/main/java/org/springframework/integration/channel/PartitionedChannel.java

@@ -36,7 +36,7 @@
  * The {@code partitionKeyFunction} is used to determine to which partition the message
  * has to be dispatched.
  * By default, the {@link IntegrationMessageHeaderAccessor#CORRELATION_ID} message header is used
- * for partition key.
+ * for a partition key.
  * <p>
  * The actual dispatching and threading logic is implemented in the {@link PartitionedDispatcher}.
  * <p>
@@ -71,7 +71,7 @@ public PartitionedChannel(int partitionCount) {
 	}
 
 	/**
-	 * Instantiate based on a provided number of partitions and function for partition key against
+	 * Instantiate based on a provided number of partitions and function for a partition key against
 	 * the message.
 	 * @param partitionCount the number of partitions in this channel.
 	 * @param partitionKeyFunction the function to resolve a partition key against the message
@@ -123,6 +123,16 @@ public void setLoadBalancingStrategy(@Nullable LoadBalancingStrategy loadBalanci
 		getDispatcher().setLoadBalancingStrategy(loadBalancingStrategy);
 	}
 
+	/**
+	 * Provide a size of the queue in the partition executor's worker.
+	 * Default to zero.
+	 * @param workerQueueSize the size of the partition executor's worker queue.
+	 * @since 6.4.10
+	 */
+	public void setWorkerQueueSize(int workerQueueSize) {
+		getDispatcher().setWorkerQueueSize(workerQueueSize);
+	}
+
 	@Override
 	protected PartitionedDispatcher getDispatcher() {
 		return (PartitionedDispatcher) this.dispatcher;

spring-integration-core/src/main/java/org/springframework/integration/dispatcher/PartitionedDispatcher.java

@@ -19,17 +19,22 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Set;
+import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.Executor;
 import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.SynchronousQueue;
 import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 import java.util.function.Function;
 import java.util.function.Predicate;
 
 import org.jspecify.annotations.Nullable;
 
+import org.springframework.integration.util.CallerBlocksPolicy;
 import org.springframework.integration.util.ErrorHandlingTaskExecutor;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageHandler;
@@ -78,6 +83,8 @@ public class PartitionedDispatcher extends AbstractDispatcher {
 
 	private final Lock lock = new ReentrantLock();
 
+	private int workerQueueSize;
+
 	/**
 	 * Instantiate based on a provided number of partitions and function for a partition key against
 	 * the message to dispatch.
@@ -153,6 +160,17 @@ public void setMessageHandlingTaskDecorator(MessageHandlingTaskDecorator message
 		this.messageHandlingTaskDecorator = messageHandlingTaskDecorator;
 	}
 
+	/**
+	 * Provide a size of the queue in the partition executor's worker.
+	 * Default to zero.
+	 * @param workerQueueSize the size of the partition executor's worker queue.
+	 * @since 6.4.10
+	 */
+	public void setWorkerQueueSize(int workerQueueSize) {
+		Assert.isTrue(workerQueueSize >= 0, "'workerQueueSize' must be greater than or equal to 0.");
+		this.workerQueueSize = workerQueueSize;
+	}
+
 	/**
 	 * Shutdown this dispatcher on application close.
 	 * The partition executors are shutdown and the internal state of this instance is cleared.
@@ -188,7 +206,16 @@ private void populatedPartitions() {
 	}
 
 	private UnicastingDispatcher newPartition() {
-		ExecutorService executor = Executors.newSingleThreadExecutor(this.threadFactory);
+		BlockingQueue<Runnable> workQueue =
+				this.workerQueueSize == 0
+						? new SynchronousQueue<>()
+						: new LinkedBlockingQueue<>(this.workerQueueSize);
+		ExecutorService executor =
+				new ThreadPoolExecutor(1, 1,
+						0L, TimeUnit.MILLISECONDS,
+						workQueue,
+						this.threadFactory,
+						new CallerBlocksPolicy(Long.MAX_VALUE));
 		this.executors.add(executor);
 
 		Executor effectiveExecutor = this.errorHandler != null

spring-integration-core/src/main/java/org/springframework/integration/dsl/PartitionedChannelSpec.java

@@ -39,6 +39,8 @@ public class PartitionedChannelSpec extends LoadBalancingChannelSpec<Partitioned
 
 	private @Nullable ThreadFactory threadFactory;
 
+	private int workerQueueSize;
+
 	protected PartitionedChannelSpec(int partitionCount) {
 		this.partitionCount = partitionCount;
 	}
@@ -53,6 +55,18 @@ public PartitionedChannelSpec threadFactory(ThreadFactory threadFactory) {
 		return this;
 	}
 
+	/**
+	 * Provide a size of the queue in the partition executor's worker.
+	 * Default to zero.
+	 * @param workerQueueSize the size of the partition executor's worker queue.
+	 * @return the spec.
+	 * @since 6.4.10
+	 */
+	public PartitionedChannelSpec workerQueueSize(int workerQueueSize) {
+		this.workerQueueSize = workerQueueSize;
+		return this;
+	}
+
 	@Override
 	protected PartitionedChannel doGet() {
 		if (this.partitionKeyFunction != null) {
@@ -62,6 +76,7 @@ protected PartitionedChannel doGet() {
 			this.channel = new PartitionedChannel(this.partitionCount);
 		}
 		this.channel.setLoadBalancingStrategy(this.loadBalancingStrategy);
+		this.channel.setWorkerQueueSize(this.workerQueueSize);
 		if (this.failoverStrategy != null) {
 			this.channel.setFailoverStrategy(this.failoverStrategy);
 		}

spring-integration-core/src/test/java/org/springframework/integration/channel/PartitionedChannelTests.java

@@ -18,8 +18,13 @@
 
 import java.util.Collection;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Set;
+import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.SynchronousQueue;
+import java.util.concurrent.ThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
@@ -36,6 +41,7 @@
 import org.springframework.integration.config.EnableIntegration;
 import org.springframework.integration.dsl.IntegrationFlow;
 import org.springframework.integration.support.MessageBuilder;
+import org.springframework.integration.test.util.TestUtils;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageChannel;
 import org.springframework.messaging.MessageHandler;
@@ -48,6 +54,7 @@
 import org.springframework.util.MultiValueMap;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.InstanceOfAssertFactories.type;
 import static org.mockito.Mockito.mock;
 
 /**
@@ -128,6 +135,11 @@ public void afterMessageHandled(Message<?> message, MessageChannel ch, MessageHa
 		String partitionForLastMessage = partitionedMessages.keySet().iterator().next();
 		assertThat(partitionForLastMessage).isIn(allocatedPartitions);
 
+		List<?> partitionExecutors = TestUtils.getPropertyValue(partitionedChannel, "dispatcher.executors", List.class);
+		BlockingQueue<?> workQueue = ((ThreadPoolExecutor) partitionExecutors.get(0)).getQueue();
+
+		assertThat(workQueue).isInstanceOf(SynchronousQueue.class);
+
 		partitionedChannel.destroy();
 	}
 
@@ -138,6 +150,9 @@ public void afterMessageHandled(Message<?> message, MessageChannel ch, MessageHa
 	@Autowired
 	PollableChannel resultChannel;
 
+	@Autowired
+	PartitionedChannel testChannel;
+
 	@Test
 	void messagesArePartitionedByCorrelationId() {
 		this.inputChannel.send(new GenericMessage<>(IntStream.range(0, 5).toArray()));
@@ -153,6 +168,14 @@ void messagesArePartitionedByCorrelationId() {
 		Set<String> strings = new HashSet<>((Collection<? extends String>) receive.getPayload());
 		assertThat(strings).hasSize(1)
 				.allMatch(value -> value.startsWith("testChannel-partition-thread-"));
+
+		List<?> partitionExecutors = TestUtils.getPropertyValue(this.testChannel, "dispatcher.executors", List.class);
+		BlockingQueue<?> workQueue = ((ThreadPoolExecutor) partitionExecutors.get(0)).getQueue();
+
+		assertThat(workQueue)
+				.asInstanceOf(type(LinkedBlockingQueue.class))
+				.extracting(LinkedBlockingQueue::remainingCapacity)
+				.isEqualTo(1);
 	}
 
 	@Configuration
@@ -163,7 +186,7 @@ public static class TestConfiguration {
 		IntegrationFlow someFlow() {
 			return f -> f
 					.split()
-					.channel(c -> c.partitioned("testChannel", 10))
+					.channel(c -> c.partitioned("testChannel", 10).workerQueueSize(1))
 					.transform(p -> Thread.currentThread().getName())
 					.aggregate()
 					.channel(c -> c.queue("resultChannel"));