GH-9743: Add observation to the SourcePollingChannelAdapter

Fixes: #9743

Spring Integration provides observation for the `MessageChannel`, `MessageHandler`
and `MessageProducerSupport`.
The `SourcePollingChannelAdapter` is missing, and it is that only special endpoint which
deals with `MessageSource` implementations via scheduled tasks in the poller.
Essentially, this endpoint is a start of the flow, but it still is a consumer of data from the source system.

* Add an `Observation` logic to the `SourcePollingChannelAdapter`.
* Divide it into two phases: start (and open scope) when message is received; stop (and close scope) when the whole polling task for a message is done.
We need this separation because of transaction scope for the polling task.
At the same time we don't want to emit an observation for a void polling task.
* Change `MessageReceiverContext` to accept a `handlerType`.
The `MessageHandler` contributes a `handler`.
The new support in the `SourcePollingChannelAdapter` - `message-source`.
And change `MessageProducerSupport` to contribute a `message-producer`
* Verify the single trace is supported for the whole flow (including transaction synchronization) starting from a `SourcePollingChannelAdapter` in a new `SourcePollingChannelAdapterObservationTests`
* Document this new feature

spring-integration-core/src/main/java/org/springframework/integration/endpoint/AbstractPollingEndpoint.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -51,6 +51,7 @@
 import org.springframework.integration.transaction.TransactionSynchronizationFactory;
 import org.springframework.integration.util.ErrorHandlingTaskExecutor;
 import org.springframework.jmx.export.annotation.ManagedAttribute;
+import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageChannel;
 import org.springframework.messaging.MessagingException;
@@ -416,10 +417,12 @@ private Flux<Message<?>> createFluxGenerator() {
 	}
 
 	private Message<?> pollForMessage() {
+		Exception pollingTaskError = null;
 		try {
 			return this.pollingTask.call();
 		}
 		catch (Exception ex) {
+			pollingTaskError = ex;
 			if (ex instanceof MessagingException) { // NOSONAR
 				throw (MessagingException) ex;
 			}
@@ -441,6 +444,7 @@ private Message<?> pollForMessage() {
 					TransactionSynchronizationManager.unbindResource(resource);
 				}
 			}
+			donePollingTask(pollingTaskError);
 		}
 	}
 
@@ -471,7 +475,7 @@ private Message<?> doPoll() {
 		return message;
 	}
 
-	private void messageReceived(IntegrationResourceHolder holder, Message<?> message) {
+	protected void messageReceived(@Nullable IntegrationResourceHolder holder, Message<?> message) {
 		this.logger.debug(() -> "Poll resulted in Message: " + message);
 		if (holder != null) {
 			holder.setMessage(message);
@@ -490,6 +494,10 @@ private void messageReceived(IntegrationResourceHolder holder, Message<?> messag
 		}
 	}
 
+	protected void donePollingTask(@Nullable Exception pollingTaskError) {
+
+	}
+
 	@Override // guarded by super#lifecycleLock
 	protected void doStop() {
 		if (this.runningTask != null) {
@@ -536,6 +544,7 @@ protected String getResourceKey() {
 		return null;
 	}
 
+	@Nullable
 	private IntegrationResourceHolder bindResourceHolderIfNecessary(String key, Object resource) {
 		if (this.transactionSynchronizationFactory != null && resource != null &&
 				TransactionSynchronizationManager.isActualTransactionActive()) {

spring-integration-core/src/main/java/org/springframework/integration/endpoint/MessageProducerSupport.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -256,7 +256,7 @@ protected void sendMessage(Message<?> message) {
 			IntegrationObservation.HANDLER.observation(
 							this.observationConvention,
 							DefaultMessageReceiverObservationConvention.INSTANCE,
-							() -> new MessageReceiverContext(message, getComponentName()),
+							() -> new MessageReceiverContext(message, getComponentName(), "message-producer"),
 							this.observationRegistry)
 					.observe(() -> this.messagingTemplate.send(getRequiredOutputChannel(), trackMessageIfAny(message)));
 		}

spring-integration-core/src/main/java/org/springframework/integration/endpoint/SourcePollingChannelAdapter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -19,8 +19,12 @@
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 
+import io.micrometer.observation.Observation;
+import io.micrometer.observation.ObservationRegistry;
+
 import org.springframework.aop.framework.Advised;
 import org.springframework.beans.factory.BeanCreationException;
+import org.springframework.beans.factory.BeanFactory;
 import org.springframework.context.Lifecycle;
 import org.springframework.integration.StaticMessageHeaderAccessor;
 import org.springframework.integration.acks.AckUtils;
@@ -31,16 +35,21 @@
 import org.springframework.integration.core.MessagingTemplate;
 import org.springframework.integration.history.MessageHistory;
 import org.springframework.integration.support.context.NamedComponent;
+import org.springframework.integration.support.management.IntegrationManagement;
 import org.springframework.integration.support.management.TrackableComponent;
+import org.springframework.integration.support.management.observation.DefaultMessageReceiverObservationConvention;
+import org.springframework.integration.support.management.observation.IntegrationObservation;
+import org.springframework.integration.support.management.observation.MessageReceiverContext;
+import org.springframework.integration.support.management.observation.MessageReceiverObservationConvention;
 import org.springframework.integration.transaction.IntegrationResourceHolder;
+import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageChannel;
 import org.springframework.messaging.MessagingException;
 import org.springframework.util.Assert;
 
 /**
- * A Channel Adapter implementation for connecting a
- * {@link MessageSource} to a {@link MessageChannel}.
+ * A Channel Adapter implementation for connecting a {@link MessageSource} to a {@link MessageChannel}.
  *
  * @author Mark Fisher
  * @author Oleg Zhurakousky
@@ -49,12 +58,16 @@
  * @author Christian Tzolov
  */
 public class SourcePollingChannelAdapter extends AbstractPollingEndpoint
-		implements TrackableComponent {
+		implements TrackableComponent, IntegrationManagement {
 
 	private final MessagingTemplate messagingTemplate = new MessagingTemplate();
 
 	private MessageSource<?> originalSource;
 
+	private ObservationRegistry observationRegistry = ObservationRegistry.NOOP;
+
+	private MessageReceiverObservationConvention observationConvention;
+
 	private volatile MessageSource<?> source;
 
 	private volatile MessageChannel outputChannel;
@@ -67,7 +80,6 @@ public class SourcePollingChannelAdapter extends AbstractPollingEndpoint
 
 	/**
 	 * Specify the source to be polled for Messages.
-	 *
 	 * @param source The message source.
 	 */
 	public void setSource(MessageSource<?> source) {
@@ -76,14 +88,13 @@ public void setSource(MessageSource<?> source) {
 		Object target = extractProxyTarget(source);
 		this.originalSource = target != null ? (MessageSource<?>) target : source;
 
-		if (source instanceof ExpressionCapable) {
-			setPrimaryExpression(((ExpressionCapable) source).getExpression());
+		if (source instanceof ExpressionCapable expressionCapable) {
+			setPrimaryExpression(expressionCapable.getExpression());
 		}
 	}
 
 	/**
 	 * Specify the {@link MessageChannel} where Messages should be sent.
-	 *
 	 * @param outputChannel The output channel.
 	 */
 	public void setOutputChannel(MessageChannel outputChannel) {
@@ -105,9 +116,7 @@ public void setOutputChannelName(String outputChannelName) {
 	}
 
 	/**
-	 * Specify the maximum time to wait for a Message to be sent to the
-	 * output channel.
-	 *
+	 * Specify the maximum time to wait for a Message to be sent to the output channel.
 	 * @param sendTimeout The send timeout.
 	 */
 	public void setSendTimeout(long sendTimeout) {
@@ -116,18 +125,38 @@ public void setSendTimeout(long sendTimeout) {
 
 	/**
 	 * Specify whether this component should be tracked in the Message History.
-	 *
 	 * @param shouldTrack true if the component should be tracked.
 	 */
 	@Override
 	public void setShouldTrack(boolean shouldTrack) {
 		this.shouldTrack = shouldTrack;
 	}
 
+	@Override
+	public void registerObservationRegistry(ObservationRegistry observationRegistry) {
+		this.observationRegistry = observationRegistry;
+	}
+
+	/**
+	 * Set a custom {@link MessageReceiverObservationConvention} for {@link IntegrationObservation#HANDLER}.
+	 * Ignored if an {@link ObservationRegistry} is not configured for this component.
+	 * @param observationConvention the {@link MessageReceiverObservationConvention} to use.
+	 * @since 6.5
+	 */
+	public void setObservationConvention(@Nullable MessageReceiverObservationConvention observationConvention) {
+		this.observationConvention = observationConvention;
+	}
+
+	@Override
+	public boolean isObserved() {
+		return !ObservationRegistry.NOOP.equals(this.observationRegistry);
+	}
+
 	@Override
 	public String getComponentType() {
-		return (this.source instanceof NamedComponent) ?
-				((NamedComponent) this.source).getComponentType() : "inbound-channel-adapter";
+		return (this.source instanceof NamedComponent namedComponent)
+				? namedComponent.getComponentType()
+				: "inbound-channel-adapter";
 	}
 
 	@Override
@@ -147,8 +176,8 @@ protected final void setReceiveMessageSource(Object source) {
 
 	@Override
 	protected void doStart() {
-		if (this.source instanceof Lifecycle) {
-			((Lifecycle) this.source).start();
+		if (this.source instanceof Lifecycle lifecycle) {
+			lifecycle.start();
 		}
 		super.doStart();
 
@@ -160,8 +189,8 @@ protected void doStart() {
 	@Override
 	protected void doStop() {
 		super.doStop();
-		if (this.source instanceof Lifecycle) {
-			((Lifecycle) this.source).stop();
+		if (this.source instanceof Lifecycle lifecycle) {
+			lifecycle.stop();
 		}
 	}
 
@@ -172,8 +201,9 @@ protected void onInit() {
 						|| (this.outputChannelName != null && this.outputChannel == null),
 				"One and only one of 'outputChannelName' or 'outputChannel' is required.");
 		super.onInit();
-		if (this.getBeanFactory() != null) {
-			this.messagingTemplate.setBeanFactory(this.getBeanFactory());
+		BeanFactory beanFactory = getBeanFactory();
+		if (beanFactory != null) {
+			this.messagingTemplate.setBeanFactory(beanFactory);
 		}
 	}
 
@@ -204,13 +234,13 @@ protected void handleMessage(Message<?> messageArg) {
 			this.messagingTemplate.send(getOutputChannel(), message);
 			AckUtils.autoAck(ackCallback);
 		}
-		catch (Exception e) {
+		catch (Exception ex) {
 			AckUtils.autoNack(ackCallback);
-			if (e instanceof MessagingException) { // NOSONAR
-				throw (MessagingException) e;
+			if (ex instanceof MessagingException messagingException) { // NOSONAR
+				throw messagingException;
 			}
 			else {
-				throw new MessagingException(message, "Failed to send Message", e);
+				throw new MessagingException(message, "Failed to send Message", ex);
 			}
 		}
 	}
@@ -220,6 +250,41 @@ protected Message<?> receiveMessage() {
 		return this.source.receive();
 	}
 
+	/**
+	 * Start an observation (and open scope) for the received message.
+	 * @param holder the resource holder for this component.
+	 * @param message the received message.
+	 */
+	@Override
+	protected void messageReceived(@Nullable IntegrationResourceHolder holder, Message<?> message) {
+		Observation observation =
+				IntegrationObservation.HANDLER.observation(this.observationConvention,
+						DefaultMessageReceiverObservationConvention.INSTANCE,
+						() -> new MessageReceiverContext(message, getComponentName(), "message-source"),
+						this.observationRegistry);
+
+		observation.start().openScope();
+		super.messageReceived(holder, message);
+	}
+
+	/**
+	 * Stop an observation (and close its scope) previously started
+	 * from the {@link #messageReceived(IntegrationResourceHolder, Message)}.
+	 * @param pollingTaskError an optional error as a result of the polling task.
+	 */
+	@Override
+	protected void donePollingTask(@Nullable Exception pollingTaskError) {
+		Observation.Scope currentObservationScope = this.observationRegistry.getCurrentObservationScope();
+		if (currentObservationScope != null) {
+			currentObservationScope.close();
+			Observation currentObservation = currentObservationScope.getCurrentObservation();
+			if (pollingTaskError != null) {
+				currentObservation.error(pollingTaskError);
+			}
+			currentObservation.stop();
+		}
+	}
+
 	@Override
 	protected Object getResourceToBind() {
 		return this.originalSource;
@@ -230,16 +295,16 @@ protected String getResourceKey() {
 		return IntegrationResourceHolder.MESSAGE_SOURCE;
 	}
 
+	@Nullable
 	private static Object extractProxyTarget(Object target) {
-		if (!(target instanceof Advised)) {
+		if (!(target instanceof Advised advised)) {
 			return target;
 		}
-		Advised advised = (Advised) target;
 		try {
 			return extractProxyTarget(advised.getTargetSource().getTarget());
 		}
-		catch (Exception e) {
-			throw new BeanCreationException("Could not extract target", e);
+		catch (Exception ex) {
+			throw new BeanCreationException("Could not extract target", ex);
 		}
 	}
 

spring-integration-core/src/main/java/org/springframework/integration/support/management/observation/DefaultMessageReceiverObservationConvention.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022 the original author or authors.
+ * Copyright 2022-2025 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.
@@ -40,7 +40,7 @@ public KeyValues getLowCardinalityKeyValues(MessageReceiverContext context) {
 				// See IntegrationObservation.HandlerTags.COMPONENT_NAME - to avoid class tangle
 				.of("spring.integration.name", context.getHandlerName())
 				// See IntegrationObservation.HandlerTags.COMPONENT_TYPE - to avoid class tangle
-				.and("spring.integration.type", "handler");
+				.and("spring.integration.type", context.getHandlerType());
 	}
 
 }

spring-integration-core/src/main/java/org/springframework/integration/support/management/observation/MessageReceiverContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022-2024 the original author or authors.
+ * Copyright 2022-2025 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.
@@ -36,10 +36,24 @@ public class MessageReceiverContext extends ReceiverContext<Message<?>> {
 
 	private final String handlerName;
 
+	private final String handlerType;
+
 	public MessageReceiverContext(Message<?> message, @Nullable String handlerName) {
+		this(message, handlerName, "handler");
+	}
+
+	/**
+	 * Construct an instance based on the message, the handler (or source, producer) bean name and handler type.
+	 * @param message the received message for this context.
+	 * @param handlerName the handler (or source, producer) bean name processing the message.
+	 * @param handlerType the handler type: {@code handler}, or {@code message-source}, or {@code message-producer}.
+	 * @since 6.5
+	 */
+	public MessageReceiverContext(Message<?> message, @Nullable String handlerName, String handlerType) {
 		super(MessageReceiverContext::getHeader);
 		this.message = message;
 		this.handlerName = handlerName != null ? handlerName : "unknown";
+		this.handlerType = handlerType;
 	}
 
 	@Override
@@ -51,6 +65,10 @@ public String getHandlerName() {
 		return this.handlerName;
 	}
 
+	public String getHandlerType() {
+		return this.handlerType;
+	}
+
 	@Nullable
 	private static String getHeader(Message<?> message, String key) {
 		Object value = message.getHeaders().get(key);