Backport "Fix batch listener error handling" (1.1.x) (#1006)

* Fix batch listener error handling

Updates the batch listener error handler code to handle
the case where there is only a single outstanding
message in the batch list when retries are expired.

Fixes #998

Signed-off-by: darshimo <[email protected]>
(cherry picked from commit fddc711)

* Polish "Fix batch listener error handling"

Updates the error handler logic to only use `List.remove`
in the special case when 1 item in batch.

Also adds a test for the special case when 1 item in
batch.

See #998

(cherry picked from commit 16e0c9e)

---------

Co-authored-by: darshimo <[email protected]>

Author: onobc

spring-pulsar/src/main/java/org/springframework/pulsar/listener/DefaultPulsarMessageListenerContainer.java

@@ -748,12 +748,11 @@ private List<Message<T>> invokeBatchListenerErrorHandler(AtomicBoolean inRetryMo
 						pulsarBatchListenerFailedException);
 				handleAck(pulsarMessage, txn);
 				if (messageList.size() == 1) {
+					messageList.remove(0);
 					messagesPendingInBatch.set(false);
 				}
 				else {
 					messageList = messageList.subList(1, messageList.size());
-				}
-				if (!messageList.isEmpty()) {
 					messagesPendingInBatch.set(true);
 				}
 				this.pulsarConsumerErrorHandler.clearMessage();

spring-pulsar/src/test/java/org/springframework/pulsar/listener/DefaultPulsarConsumerErrorHandlerTests.java

@@ -38,6 +38,7 @@
 import org.apache.pulsar.client.api.Schema;
 import org.junit.jupiter.api.Test;
 
+import org.springframework.core.log.LogAccessor;
 import org.springframework.pulsar.core.DefaultPulsarConsumerFactory;
 import org.springframework.pulsar.core.DefaultPulsarProducerFactory;
 import org.springframework.pulsar.core.PulsarOperations;
@@ -51,6 +52,8 @@
  */
 public class DefaultPulsarConsumerErrorHandlerTests implements PulsarTestContainerSupport {
 
+	private final LogAccessor logger = new LogAccessor(this.getClass());
+
 	@Test
 	@SuppressWarnings("unchecked")
 	void happyPathErrorHandlingForRecordMessageListener() throws Exception {
@@ -564,4 +567,78 @@ else if (message.getValue() == 7) {
 		pulsarClient.close();
 	}
 
+	@Test
+	@SuppressWarnings("unchecked")
+	void whenBatchRecordListenerOneMessageBatchFailsThenSentToDltProperly() throws Exception {
+		var topicName = "default-error-handler-tests-9";
+		var pulsarClient = PulsarClient.builder().serviceUrl(PulsarTestContainerSupport.getPulsarBrokerUrl()).build();
+		var pulsarConsumerFactory = new DefaultPulsarConsumerFactory<Integer>(pulsarClient,
+				List.of((consumerBuilder) -> {
+					consumerBuilder.topic(topicName);
+					consumerBuilder.subscriptionName("%s-sub".formatted(topicName));
+				}));
+		// Prepare container for batch consume
+		var pulsarContainerProperties = new PulsarContainerProperties();
+		pulsarContainerProperties.setSchema(Schema.INT32);
+		pulsarContainerProperties.setAckMode(AckMode.MANUAL);
+		pulsarContainerProperties.setBatchListener(true);
+		pulsarContainerProperties.setMaxNumMessages(1);
+		pulsarContainerProperties.setBatchTimeoutMillis(60_000);
+		PulsarBatchAcknowledgingMessageListener<?> pulsarBatchMessageListener = mock();
+		doAnswer(invocation -> {
+			List<Message<Integer>> message = invocation.getArgument(1);
+			Message<Integer> integerMessage = message.get(0);
+			Integer value = integerMessage.getValue();
+			if (value == 0) {
+				throw new PulsarBatchListenerFailedException("failed", integerMessage);
+			}
+			Acknowledgement acknowledgment = invocation.getArgument(2);
+			List<MessageId> messageIds = new ArrayList<>();
+			for (Message<Integer> integerMessage1 : message) {
+				messageIds.add(integerMessage1.getMessageId());
+			}
+			acknowledgment.acknowledge(messageIds);
+			return new Object();
+		}).when(pulsarBatchMessageListener).received(any(Consumer.class), any(List.class), any(Acknowledgement.class));
+		pulsarContainerProperties.setMessageListener(pulsarBatchMessageListener);
+		var container = new DefaultPulsarMessageListenerContainer<>(pulsarConsumerFactory, pulsarContainerProperties);
+
+		// Set error handler to recover after 2 retries
+		PulsarTemplate<Integer> mockPulsarTemplate = mock(RETURNS_DEEP_STUBS);
+		PulsarOperations.SendMessageBuilder<Integer> sendMessageBuilderMock = mock();
+		when(mockPulsarTemplate.newMessage(any(Integer.class))
+			.withTopic(any(String.class))
+			.withMessageCustomizer(any(TypedMessageBuilderCustomizer.class))).thenReturn(sendMessageBuilderMock);
+		container.setPulsarConsumerErrorHandler(new DefaultPulsarConsumerErrorHandler<>(
+				new PulsarDeadLetterPublishingRecoverer<>(mockPulsarTemplate), new FixedBackOff(100, 2)));
+		try {
+			container.start();
+			// Send single message in batch
+			var pulsarProducerFactory = new DefaultPulsarProducerFactory<Integer>(pulsarClient, topicName);
+			var pulsarTemplate = new PulsarTemplate<>(pulsarProducerFactory);
+			pulsarTemplate.sendAsync(0);
+			// Initial call should fail
+			// Next 2 calls should fail (retries 2)
+			// No more calls after that - msg should go to DLT
+			await().atMost(Duration.ofSeconds(30))
+				.untilAsserted(() -> verify(pulsarBatchMessageListener, times(3)).received(any(Consumer.class),
+						any(List.class), any(Acknowledgement.class)));
+			await().atMost(Duration.ofSeconds(30))
+				.untilAsserted(() -> verify(sendMessageBuilderMock, times(1)).sendAsync());
+		}
+		finally {
+			safeStopContainer(container);
+		}
+		pulsarClient.close();
+	}
+
+	private void safeStopContainer(PulsarMessageListenerContainer container) {
+		try {
+			container.stop();
+		}
+		catch (Exception ex) {
+			logger.warn(ex, "Failed to stop container %s: %s".formatted(container, ex.getMessage()));
+		}
+	}
+
 }