Reproduce out-of-order delivery issue in PR 12456

pulsar-broker/src/test/java/org/apache/pulsar/client/api/MultiTopicsConsumerTest.java

@@ -16,6 +16,7 @@
  * specific language governing permissions and limitations
  * under the License.
  */
+
 package org.apache.pulsar.client.api;
 
 import static org.mockito.ArgumentMatchers.any;
@@ -24,16 +25,24 @@
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import com.google.common.collect.Lists;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.ExecutionException;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+import java.util.concurrent.atomic.AtomicLong;
 import lombok.Cleanup;
+import org.apache.pulsar.client.admin.PulsarAdminException;
 import org.apache.pulsar.client.impl.ClientBuilderImpl;
 import org.apache.pulsar.client.impl.PulsarClientImpl;
 import org.apache.pulsar.client.impl.conf.ClientConfigurationData;
 import org.mockito.AdditionalAnswers;
 import org.mockito.Mockito;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+import org.testng.Assert;
 import org.testng.annotations.AfterMethod;
 import org.testng.annotations.BeforeMethod;
 import org.testng.annotations.Test;
@@ -70,6 +79,7 @@ protected PulsarClient createNewPulsarClient(ClientBuilder clientBuilder) throws
                         // method calls on the interface.
                         Mockito.withSettings().defaultAnswer(AdditionalAnswers.delegatesTo(internalExecutorService)));
             }
+
             @Override
             public ExecutorService getInternalExecutorService() {
                 return internalExecutorServiceDelegate;
@@ -119,4 +129,69 @@ public void testMultiTopicsConsumerCloses() throws Exception {
         verify(internalExecutorServiceDelegate, times(0))
                 .schedule(any(Runnable.class), anyLong(), any());
     }
+
+    // test that reproduces the issue that PR https://github.com/apache/pulsar/pull/12456 fixes
+    // where MultiTopicsConsumerImpl has a data race that causes out-of-order delivery of messages
+    @Test
+    public void testShouldMaintainOrderForIndividualTopicInMultiTopicsConsumer()
+            throws PulsarAdminException, PulsarClientException, ExecutionException, InterruptedException,
+            TimeoutException {
+        String topicName = newTopicName();
+        int numPartitions = 2;
+        int numMessages = 100000;
+        admin.topics().createPartitionedTopic(topicName, numPartitions);
+
+        Producer<Long>[] producers = new Producer[numPartitions];
+
+        for (int i = 0; i < numPartitions; i++) {
+            producers[i] = pulsarClient.newProducer(Schema.INT64)
+                    // produce to each partition directly so that order can be maintained in sending
+                    .topic(topicName + "-partition-" + i)
+                    .enableBatching(true)
+                    .maxPendingMessages(30000)
+                    .maxPendingMessagesAcrossPartitions(60000)
+                    .batchingMaxMessages(10000)
+                    .batchingMaxPublishDelay(5, TimeUnit.SECONDS)
+                    .batchingMaxBytes(4 * 1024 * 1024)
+                    .blockIfQueueFull(true)
+                    .create();
+        }
+
+        @Cleanup
+        Consumer<Long> consumer = pulsarClient
+                .newConsumer(Schema.INT64)
+                // consume on the partitioned topic
+                .topic(topicName)
+                .subscriptionInitialPosition(SubscriptionInitialPosition.Earliest)
+                .receiverQueueSize(numMessages)
+                .subscriptionName(methodName)
+                .subscribe();
+
+        // produce sequence numbers to each partition topic
+        long sequenceNumber = 1L;
+        for (int i = 0; i < numMessages; i++) {
+            for (Producer<Long> producer : producers) {
+                producer.newMessage()
+                        .value(sequenceNumber)
+                        .sendAsync();
+            }
+            sequenceNumber++;
+        }
+        for (Producer<Long> producer : producers) {
+            producer.close();
+        }
+
+        // receive and validate sequences in the partitioned topic
+        Map<String, AtomicLong> receivedSequences = new HashMap<>();
+        int receivedCount = 0;
+        while (receivedCount < numPartitions * numMessages) {
+            Message<Long> message = consumer.receiveAsync().get(5, TimeUnit.SECONDS);
+            consumer.acknowledge(message);
+            receivedCount++;
+            AtomicLong receivedSequenceCounter =
+                    receivedSequences.computeIfAbsent(message.getTopicName(), k -> new AtomicLong(1L));
+            Assert.assertEquals(message.getValue().longValue(), receivedSequenceCounter.getAndIncrement());
+        }
+        Assert.assertEquals(numPartitions * numMessages, receivedCount);
+    }
 }