Introduce PartitionedChannel (#8617)

* Introduce `PartitionedChannel`

* Implement a `PartitionedChannel` as an extension of the `AbstractExecutorChannel`
* Supply this channel with a `PartitionedDispatcher` which is an extension of the `AbstractDispatcher`
* The target partition is essentially a `UnicastingDispatcher` with a single thead executor

* * Fix language in Javadocs
* Add docs for `PartitionedChannel` into `channel.adoc`
* Pre-populate partitions in the `PartitionedDispatcher`
to ensure a thread number reflection of the partition it is used for (for default `ThreadFactory`)
* Add Javadocs to `public` methods
* Add Java DSL `PartitionedChannelSpec` and respective factory methods into `Channels`
* Use `IntegrationMessageHeaderAccessor.CORRELATION_ID` header as a default partition key

* * Fix language in Javadocs
* Fix Checkstyle violations
* Mark `PartitionedDispatcher.prePopulatedPartitions()` with `synchronized`

* * Populate partitions from `PartitionedDispatcher` ctor
and when a custom `ThreadFactory` is set

* * Clear `executors` in `populatedPartitions()`

* * Bring back `synchronized populatedPartitions()` and use it in the `dispatch()`

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

@@ -0,0 +1,148 @@
+/*
+ * Copyright 2023 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.integration.channel;
+
+import java.util.concurrent.ThreadFactory;
+import java.util.function.Function;
+
+import org.springframework.integration.IntegrationMessageHeaderAccessor;
+import org.springframework.integration.dispatcher.LoadBalancingStrategy;
+import org.springframework.integration.dispatcher.PartitionedDispatcher;
+import org.springframework.lang.Nullable;
+import org.springframework.messaging.Message;
+import org.springframework.scheduling.concurrent.CustomizableThreadFactory;
+import org.springframework.util.Assert;
+
+/**
+ * An {@link AbstractExecutorChannel} implementation for partitioned message dispatching.
+ * Requires a number of partitions where each of them is backed by a dedicated thread.
+ * 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.
+ * <p>
+ * The actual dispatching and threading logic is implemented in the {@link PartitionedDispatcher}.
+ * <p>
+ * The default {@link ThreadFactory} is based on the bean name of this channel plus {@code -partition-thread-}.
+ * Thus, every thread name will reflect a partition it belongs to.
+ * <p>
+ * The rest of the logic is similar to the {@link ExecutorChannel}, which includes:
+ * - load balancing for subscribers;
+ * - fail-over and error handling;
+ * - channel operations intercepting.
+ *
+ * @author Artem Bilan
+ *
+ * @since 6.1
+ *
+ * @see PartitionedDispatcher
+ */
+public class PartitionedChannel extends AbstractExecutorChannel {
+
+	@Nullable
+	private ThreadFactory threadFactory;
+
+	/**
+	 * Instantiate based on a provided number of partitions and function resolving a partition key from
+	 * the {@link IntegrationMessageHeaderAccessor#CORRELATION_ID} message header.
+	 * @param partitionCount the number of partitions in this channel.
+	 * sent to this channel.
+	 */
+	public PartitionedChannel(int partitionCount) {
+		this(partitionCount, (message) -> message.getHeaders().get(IntegrationMessageHeaderAccessor.CORRELATION_ID));
+	}
+
+	/**
+	 * Instantiate based on a provided number of partitions and function for 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
+	 * sent to this channel.
+	 */
+	public PartitionedChannel(int partitionCount, Function<Message<?>, Object> partitionKeyFunction) {
+		super(null);
+		this.dispatcher = new PartitionedDispatcher(partitionCount, partitionKeyFunction);
+	}
+
+	/**
+	 * Set a {@link ThreadFactory} for executors per partitions.
+	 * Propagated down to the {@link PartitionedDispatcher}.
+	 * Defaults to the {@link CustomizableThreadFactory} based on the bean name
+	 * of this channel plus {@code -partition-thread-}.
+	 * @param threadFactory the {@link ThreadFactory} to use.
+	 */
+	public void setThreadFactory(ThreadFactory threadFactory) {
+		Assert.notNull(threadFactory, "'threadFactory' must not be null");
+		this.threadFactory = threadFactory;
+	}
+
+	/**
+	 * Specify whether the channel's dispatcher should have failover enabled.
+	 * By default, it will. Set this value to 'false' to disable it.
+	 * @param failover The failover boolean.
+	 */
+	public void setFailover(boolean failover) {
+		getDispatcher().setFailover(failover);
+	}
+
+	/**
+	 * Provide a {@link LoadBalancingStrategy} for the {@link PartitionedDispatcher}.
+	 * @param loadBalancingStrategy The load balancing strategy implementation.
+	 */
+	public void setLoadBalancingStrategy(@Nullable LoadBalancingStrategy loadBalancingStrategy) {
+		getDispatcher().setLoadBalancingStrategy(loadBalancingStrategy);
+	}
+
+	@Override
+	protected PartitionedDispatcher getDispatcher() {
+		return (PartitionedDispatcher) this.dispatcher;
+	}
+
+	@Override
+	protected void onInit() {
+		super.onInit();
+
+		if (this.threadFactory == null) {
+			this.threadFactory = new CustomizableThreadFactory(getComponentName() + "-partition-thread-");
+		}
+		PartitionedDispatcher partitionedDispatcher = getDispatcher();
+		partitionedDispatcher.setThreadFactory(this.threadFactory);
+
+		if (this.maxSubscribers == null) {
+			partitionedDispatcher.setMaxSubscribers(getIntegrationProperties().getChannelsMaxUnicastSubscribers());
+		}
+
+		partitionedDispatcher.setErrorHandler(ChannelUtils.getErrorHandler(getBeanFactory()));
+
+		partitionedDispatcher.setMessageHandlingTaskDecorator(task -> {
+			if (this.executorInterceptorsSize > 0) {
+				return new MessageHandlingTask(task);
+			}
+			else {
+				return task;
+			}
+		});
+
+	}
+
+	@Override
+	public void destroy() {
+		super.destroy();
+		getDispatcher().shutdown();
+	}
+
+}

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

@@ -0,0 +1,191 @@
+/*
+ * Copyright 2023 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.integration.dispatcher;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.Executor;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ThreadFactory;
+import java.util.function.Function;
+
+import org.springframework.integration.util.ErrorHandlingTaskExecutor;
+import org.springframework.lang.Nullable;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.MessageHandler;
+import org.springframework.scheduling.concurrent.CustomizableThreadFactory;
+import org.springframework.util.Assert;
+import org.springframework.util.ErrorHandler;
+
+/**
+ * An {@link AbstractDispatcher} implementation for distributing messages to
+ * dedicated threads according to the key determined by the provided function against
+ * the message to dispatch.
+ * <p>
+ * Every partition, created by this class, is a {@link UnicastingDispatcher}
+ * delegate based on a single thread {@link Executor}.
+ * <p>
+ * The number of partitions should be a reasonable value for the application environment
+ * since every partition is based on a dedicated thread for message processing.
+ * <p>
+ * The rest of the logic is similar to {@link UnicastingDispatcher} behavior.
+ *
+ * @author Artem Bilan
+ *
+ * @since 6.1
+ */
+public class PartitionedDispatcher extends AbstractDispatcher {
+
+	private final Map<Integer, UnicastingDispatcher> partitions = new HashMap<>();
+
+	private final List<ExecutorService> executors = new ArrayList<>();
+
+	private final int partitionCount;
+
+	private final Function<Message<?>, Object> partitionKeyFunction;
+
+	private ThreadFactory threadFactory = new CustomizableThreadFactory("partition-thread-");
+
+	private boolean failover = true;
+
+	@Nullable
+	private LoadBalancingStrategy loadBalancingStrategy;
+
+	private ErrorHandler errorHandler;
+
+	private MessageHandlingTaskDecorator messageHandlingTaskDecorator = task -> task;
+
+	/**
+	 * Instantiate based on a provided number of partitions and function for partition key against
+	 * the message to dispatch.
+	 * @param partitionCount the number of partitions in this channel.
+	 * @param partitionKeyFunction the function to resolve a partition key against the message
+	 * to dispatch.
+	 */
+	public PartitionedDispatcher(int partitionCount, Function<Message<?>, Object> partitionKeyFunction) {
+		Assert.isTrue(partitionCount > 0, "'partitionCount' must be greater than 0");
+		Assert.notNull(partitionKeyFunction, "'partitionKeyFunction' must not be null");
+		this.partitionKeyFunction = partitionKeyFunction;
+		this.partitionCount = partitionCount;
+	}
+
+	/**
+	 * Set a {@link ThreadFactory} for executors per partitions.
+	 * Defaults to the {@link CustomizableThreadFactory} based on a {@code partition-thread-} prefix.
+	 * @param threadFactory the {@link ThreadFactory} to use.
+	 */
+	public void setThreadFactory(ThreadFactory threadFactory) {
+		Assert.notNull(threadFactory, "'threadFactory' must not be null");
+		this.threadFactory = threadFactory;
+	}
+
+	/**
+	 * Specify whether partition dispatchers should have failover enabled.
+	 * By default, it will. Set this value to 'false' to disable it.
+	 * @param failover The failover boolean.
+	 */
+	public void setFailover(boolean failover) {
+		this.failover = failover;
+	}
+
+	/**
+	 * Provide a {@link LoadBalancingStrategy} for partition dispatchers.
+	 * @param loadBalancingStrategy The load balancing strategy implementation.
+	 */
+	public void setLoadBalancingStrategy(@Nullable LoadBalancingStrategy loadBalancingStrategy) {
+		this.loadBalancingStrategy = loadBalancingStrategy;
+	}
+
+	/**
+	 * Provide a {@link ErrorHandler} for wrapping partition {@link Executor}
+	 * to the {@link ErrorHandlingTaskExecutor}.
+	 * @param errorHandler the {@link ErrorHandler} to use.
+	 */
+	public void setErrorHandler(ErrorHandler errorHandler) {
+		this.errorHandler = errorHandler;
+	}
+
+	/**
+	 * Set a {@link MessageHandlingTaskDecorator} to wrap a message handling task into some
+	 * addition logic, e.g. message channel may provide an interception for its operations.
+	 * @param messageHandlingTaskDecorator the {@link MessageHandlingTaskDecorator} to use.
+	 */
+	public void setMessageHandlingTaskDecorator(MessageHandlingTaskDecorator messageHandlingTaskDecorator) {
+		Assert.notNull(messageHandlingTaskDecorator, "'messageHandlingTaskDecorator' must not be null.");
+		this.messageHandlingTaskDecorator = messageHandlingTaskDecorator;
+	}
+
+	/**
+	 * Shutdown this dispatcher on application close.
+	 * The partition executors are shutdown and internal state of this instance is cleared.
+	 */
+	public void shutdown() {
+		this.executors.forEach(ExecutorService::shutdown);
+		this.executors.clear();
+		this.partitions.clear();
+	}
+
+	@Override
+	public boolean dispatch(Message<?> message) {
+		populatedPartitions();
+		int partition = Math.abs(this.partitionKeyFunction.apply(message).hashCode()) % this.partitionCount;
+		UnicastingDispatcher partitionDispatcher = this.partitions.get(partition);
+		return partitionDispatcher.dispatch(message);
+	}
+
+	private synchronized void populatedPartitions() {
+		if (this.partitions.isEmpty()) {
+			for (int i = 0; i < this.partitionCount; i++) {
+				this.partitions.put(i, newPartition());
+			}
+		}
+	}
+
+	private UnicastingDispatcher newPartition() {
+		ExecutorService executor = Executors.newSingleThreadExecutor(this.threadFactory);
+		this.executors.add(executor);
+		DelegateDispatcher delegateDispatcher =
+				new DelegateDispatcher(new ErrorHandlingTaskExecutor(executor, this.errorHandler));
+		delegateDispatcher.setFailover(this.failover);
+		delegateDispatcher.setLoadBalancingStrategy(this.loadBalancingStrategy);
+		delegateDispatcher.setMessageHandlingTaskDecorator(this.messageHandlingTaskDecorator);
+		return delegateDispatcher;
+	}
+
+	private final class DelegateDispatcher extends UnicastingDispatcher {
+
+		DelegateDispatcher(Executor executor) {
+			super(executor);
+		}
+
+		@Override
+		protected Set<MessageHandler> getHandlers() {
+			return PartitionedDispatcher.this.getHandlers();
+		}
+
+		@Override
+		protected boolean tryOptimizedDispatch(Message<?> message) {
+			return PartitionedDispatcher.this.tryOptimizedDispatch(message);
+		}
+
+	}
+
+}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2021 the original author or authors.
+ * Copyright 2016-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -147,6 +147,27 @@ public final class Channels {
 		return MessageChannels.flux(id);
 	}
 
+	/**
+	 * Create a {@link PartitionedChannelSpec}.
+	 * @param partitionCount the number of partitions in the channel.
+	 * @return the {@link PartitionedChannelSpec}.
+	 * @since 6.1
+	 */
+	public PartitionedChannelSpec partitioned(int partitionCount) {
+		return MessageChannels.partitioned(partitionCount);
+	}
+
+	/**
+	 * Create a {@link PartitionedChannelSpec}.
+	 * @param id the bean name for the channel.
+	 * @param partitionCount the number of partitions in the channel.
+	 * @return the {@link PartitionedChannelSpec}.
+	 * @since 6.1
+	 */
+	public PartitionedChannelSpec partitioned(String id, int partitionCount) {
+		return MessageChannels.partitioned(id, partitionCount);
+	}
+
 	private Channels() {
 	}
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2021 the original author or authors.
+ * Copyright 2016-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -149,6 +149,27 @@ public final class MessageChannels {
 		return flux().id(id);
 	}
 
+	/**
+	 * Create a {@link PartitionedChannelSpec}.
+	 * @param partitionCount the number of partitions in the channel.
+	 * @return the {@link PartitionedChannelSpec}.
+	 * @since 6.1
+	 */
+	public static PartitionedChannelSpec partitioned(int partitionCount) {
+		return new PartitionedChannelSpec(partitionCount);
+	}
+
+	/**
+	 * Create a {@link PartitionedChannelSpec}.
+	 * @param id the bean name for the channel.
+	 * @param partitionCount the number of partitions in the channel.
+	 * @return the {@link PartitionedChannelSpec}.
+	 * @since 6.1
+	 */
+	public static PartitionedChannelSpec partitioned(String id, int partitionCount) {
+		return new PartitionedChannelSpec(partitionCount).id(id);
+	}
+
 	private MessageChannels() {
 	}
 

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

@@ -0,0 +1,78 @@
+/*
+ * Copyright 2023 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.integration.dsl;
+
+import java.util.concurrent.ThreadFactory;
+import java.util.function.Function;
+
+import org.springframework.integration.channel.PartitionedChannel;
+import org.springframework.lang.Nullable;
+import org.springframework.messaging.Message;
+
+/**
+ * A {@link LoadBalancingChannelSpec} implementation for the {@link PartitionedChannel}.
+ *
+ * @author Artem Bilan
+ *
+ * @since 6.1
+ */
+public class PartitionedChannelSpec extends LoadBalancingChannelSpec<PartitionedChannelSpec, PartitionedChannel> {
+
+	private final int partitionCount;
+
+	@Nullable
+	private Function<Message<?>, Object> partitionKeyFunction;
+
+	@Nullable
+	private ThreadFactory threadFactory;
+
+	protected PartitionedChannelSpec(int partitionCount) {
+		this.partitionCount = partitionCount;
+	}
+
+	public PartitionedChannelSpec partitionKey(Function<Message<?>, Object> partitionKeyFunction) {
+		this.partitionKeyFunction = partitionKeyFunction;
+		return this;
+	}
+
+	public PartitionedChannelSpec threadFactory(ThreadFactory threadFactory) {
+		this.threadFactory = threadFactory;
+		return this;
+	}
+
+	@Override
+	protected PartitionedChannel doGet() {
+		if (this.partitionKeyFunction != null) {
+			this.channel = new PartitionedChannel(this.partitionCount, this.partitionKeyFunction);
+		}
+		else {
+			this.channel = new PartitionedChannel(this.partitionCount);
+		}
+		this.channel.setLoadBalancingStrategy(this.loadBalancingStrategy);
+		if (this.failover != null) {
+			this.channel.setFailover(this.failover);
+		}
+		if (this.maxSubscribers != null) {
+			this.channel.setMaxSubscribers(this.maxSubscribers);
+		}
+		if (this.threadFactory != null) {
+			this.channel.setThreadFactory(this.threadFactory);
+		}
+		return super.doGet();
+	}
+
+}

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

@@ -0,0 +1,161 @@
+/*
+ * Copyright 2023 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.integration.channel;
+
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.IntStream;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.beans.factory.BeanFactory;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Qualifier;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.integration.config.EnableIntegration;
+import org.springframework.integration.dsl.IntegrationFlow;
+import org.springframework.integration.support.MessageBuilder;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.MessageChannel;
+import org.springframework.messaging.MessageHandler;
+import org.springframework.messaging.PollableChannel;
+import org.springframework.messaging.support.ExecutorChannelInterceptor;
+import org.springframework.messaging.support.GenericMessage;
+import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;
+import org.springframework.util.LinkedMultiValueMap;
+import org.springframework.util.MultiValueMap;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
+
+/**
+ * @author Artem Bilan
+ *
+ * @since 6.1
+ */
+@SpringJUnitConfig
+public class PartitionedChannelTests {
+
+	@Test
+	void messagesAreProperlyPartitioned() throws InterruptedException {
+		PartitionedChannel partitionedChannel =
+				new PartitionedChannel(2, (message) -> message.getHeaders().get("partitionKey"));
+		partitionedChannel.setBeanFactory(mock(BeanFactory.class));
+		partitionedChannel.setBeanName("testPartitionedChannel");
+
+		CountDownLatch handleLatch = new CountDownLatch(4);
+
+		partitionedChannel.addInterceptor(new ExecutorChannelInterceptor() {
+
+			@Override
+			public void afterMessageHandled(Message<?> message, MessageChannel ch, MessageHandler h, Exception ex) {
+				handleLatch.countDown();
+			}
+
+		});
+		partitionedChannel.afterPropertiesSet();
+
+		MultiValueMap<String, Message<?>> partitionedMessages = new LinkedMultiValueMap<>();
+
+		partitionedChannel.subscribe((message) -> partitionedMessages.add(Thread.currentThread().getName(), message));
+
+		partitionedChannel.send(MessageBuilder.withPayload("test1").setHeader("partitionKey", "1").build());
+		partitionedChannel.send(MessageBuilder.withPayload("test2").setHeader("partitionKey", "2").build());
+		partitionedChannel.send(MessageBuilder.withPayload("test3").setHeader("partitionKey", "2").build());
+		partitionedChannel.send(MessageBuilder.withPayload("test4").setHeader("partitionKey", "1").build());
+
+		assertThat(handleLatch.await(10, TimeUnit.SECONDS)).isTrue();
+
+		assertThat(partitionedMessages).hasSize(2);
+		partitionedMessages.values()
+				.forEach(messagesInPartition -> {
+					assertThat(messagesInPartition).hasSize(2);
+					assertThat(messagesInPartition.get(0).getHeaders().get("partitionKey"))
+							.isEqualTo(messagesInPartition.get(1).getHeaders().get("partitionKey"));
+				});
+
+
+		HashSet<String> allocatedPartitions = new HashSet<>(partitionedMessages.keySet());
+		partitionedMessages.clear();
+
+		CountDownLatch anotherHandleLatch = new CountDownLatch(1);
+
+		partitionedChannel.addInterceptor(new ExecutorChannelInterceptor() {
+
+			@Override
+			public void afterMessageHandled(Message<?> message, MessageChannel ch, MessageHandler h, Exception ex) {
+				anotherHandleLatch.countDown();
+			}
+
+		});
+
+		partitionedChannel.send(MessageBuilder.withPayload("test4").setHeader("partitionKey", "3").build());
+
+		assertThat(anotherHandleLatch.await(10, TimeUnit.SECONDS)).isTrue();
+
+		assertThat(partitionedMessages).hasSize(1);
+		String partitionForLastMessage = partitionedMessages.keySet().iterator().next();
+		assertThat(partitionForLastMessage).isIn(allocatedPartitions);
+
+		partitionedChannel.destroy();
+	}
+
+	@Autowired
+	@Qualifier("someFlow.input")
+	MessageChannel inputChannel;
+
+	@Autowired
+	PollableChannel resultChannel;
+
+	@Test
+	void messagesArePartitionedByCorrelationId() {
+		this.inputChannel.send(new GenericMessage<>(IntStream.range(0, 5).toArray()));
+
+		Message<?> receive = this.resultChannel.receive(10_000);
+
+		assertThat(receive).isNotNull()
+				.extracting(Message::getPayload)
+				.asList()
+				.hasSize(5);
+
+		@SuppressWarnings("unchecked")
+		Set<String> strings = new HashSet<>((Collection<? extends String>) receive.getPayload());
+		assertThat(strings).hasSize(1)
+				.allMatch(value -> value.startsWith("testChannel-partition-thread-"));
+	}
+
+	@Configuration
+	@EnableIntegration
+	public static class TestConfiguration {
+
+		@Bean
+		IntegrationFlow someFlow() {
+			return f -> f
+					.split()
+					.channel(c -> c.partitioned("testChannel", 10))
+					.transform(p -> Thread.currentThread().getName())
+					.aggregate()
+					.channel(c -> c.queue("resultChannel"));
+		}
+
+	}
+
+}