[fix] [broker] Topics failed to delete after remove cluster from repl…

…icated clusters set and caused OOM (apache#23360)

(cherry picked from commit d9bc7af)
(cherry picked from commit 187e6d4)

pulsar-broker/src/main/java/org/apache/pulsar/broker/service/SystemTopicBasedTopicPoliciesService.java

@@ -127,7 +127,16 @@ public CompletableFuture<Void> deleteTopicPoliciesAsync(TopicName topicName) {
         if (NamespaceService.isHeartbeatNamespace(topicName.getNamespaceObject())) {
             return CompletableFuture.completedFuture(null);
         }
-        return sendTopicPolicyEvent(topicName, ActionType.DELETE, null);
+        TopicName changeEvents = NamespaceEventsSystemTopicFactory.getEventsTopicName(topicName.getNamespaceObject());
+        return pulsarService.getNamespaceService().checkTopicExists(changeEvents).thenCompose(topicExistsInfo -> {
+            // If the system topic named "__change_events" has been deleted, it means all the data in the topic have
+            // been deleted, so we do not need to delete the message that we want to delete again.
+            if (!topicExistsInfo.isExists()) {
+                log.info("Skip delete topic-level policies because {} has been removed before", changeEvents);
+                return CompletableFuture.completedFuture(null);
+            }
+            return sendTopicPolicyEvent(topicName, ActionType.DELETE, null);
+        });
     }
 
     @Override

pulsar-broker/src/main/java/org/apache/pulsar/broker/systopic/NamespaceEventsSystemTopicFactory.java

@@ -37,12 +37,16 @@ public NamespaceEventsSystemTopicFactory(PulsarClient client) {
     }
 
     public TopicPoliciesSystemTopicClient createTopicPoliciesSystemTopicClient(NamespaceName namespaceName) {
-        TopicName topicName = TopicName.get(TopicDomain.persistent.value(), namespaceName,
-                SystemTopicNames.NAMESPACE_EVENTS_LOCAL_NAME);
+        TopicName topicName = getEventsTopicName(namespaceName);
         log.info("Create topic policies system topic client {}", topicName.toString());
         return new TopicPoliciesSystemTopicClient(client, topicName);
     }
 
+    public static TopicName getEventsTopicName(NamespaceName namespaceName) {
+        return TopicName.get(TopicDomain.persistent.value(), namespaceName,
+                SystemTopicNames.NAMESPACE_EVENTS_LOCAL_NAME);
+    }
+
     public <T> TransactionBufferSnapshotBaseSystemTopicClient<T> createTransactionBufferSystemTopicClient(
             TopicName systemTopicName, SystemTopicTxnBufferSnapshotService<T>
             systemTopicTxnBufferSnapshotService, Class<T> schemaType) {

pulsar-broker/src/test/java/org/apache/pulsar/broker/service/OneWayReplicatorUsingGlobalZKTest.java

@@ -19,17 +19,25 @@
 package org.apache.pulsar.broker.service;
 
 import static org.testng.Assert.assertEquals;
+import static org.testng.Assert.assertFalse;
 import static org.testng.Assert.assertNotNull;
+import static org.testng.Assert.assertTrue;
+import java.time.Duration;
 import java.util.Arrays;
 import java.util.HashSet;
+import java.util.Optional;
 import java.util.UUID;
+import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.TimeUnit;
 import lombok.extern.slf4j.Slf4j;
 import org.apache.pulsar.broker.BrokerTestUtil;
 import org.apache.pulsar.client.api.Message;
 import org.apache.pulsar.client.api.MessageId;
+import org.apache.pulsar.client.api.Producer;
 import org.apache.pulsar.client.api.Schema;
+import org.apache.pulsar.common.naming.TopicName;
 import org.apache.pulsar.common.policies.data.RetentionPolicies;
+import org.apache.pulsar.common.util.collections.ConcurrentOpenHashMap;
 import org.awaitility.Awaitility;
 import org.testng.annotations.AfterClass;
 import org.testng.annotations.BeforeClass;
@@ -173,4 +181,42 @@ public void testDifferentTopicCreationRule(ReplicationMode replicationMode) thro
     public void testReplicationCountMetrics() throws Exception {
         super.testReplicationCountMetrics();
     }
+
+    @Test
+    public void testRemoveCluster() throws Exception {
+        // Initialize.
+        final String ns1 = defaultTenant + "/" + "ns_73b1a31afce34671a5ddc48fe5ad7fc8";
+        final String topic = "persistent://" + ns1 + "/___tp-5dd50794-7af8-4a34-8a0b-06188052c66a";
+        final String topicChangeEvents = "persistent://" + ns1 + "/__change_events";
+        admin1.namespaces().createNamespace(ns1);
+        admin1.namespaces().setNamespaceReplicationClusters(ns1, new HashSet<>(Arrays.asList(cluster1, cluster2)));
+        admin1.topics().createNonPartitionedTopic(topic);
+
+        // Wait for loading topic up.
+        Producer<String> p = client1.newProducer(Schema.STRING).topic(topic).create();
+        Awaitility.await().untilAsserted(() -> {
+            ConcurrentOpenHashMap<String, CompletableFuture<Optional<Topic>>> tps
+                    = pulsar1.getBrokerService().getTopics();
+            assertTrue(tps.containsKey(topic));
+            assertTrue(tps.containsKey(topicChangeEvents));
+        });
+
+        // The topics under the namespace of the cluster-1 will be deleted.
+        // Verify the result.
+        admin1.namespaces().setNamespaceReplicationClusters(ns1, new HashSet<>(Arrays.asList(cluster2)));
+        Awaitility.await().atMost(Duration.ofSeconds(120)).untilAsserted(() -> {
+            ConcurrentOpenHashMap<String, CompletableFuture<Optional<Topic>>> tps
+                    = pulsar1.getBrokerService().getTopics();
+            assertFalse(tps.containsKey(topic));
+            assertFalse(tps.containsKey(topicChangeEvents));
+            assertFalse(pulsar1.getNamespaceService().checkTopicExists(TopicName.get(topic)).join().isExists());
+            assertFalse(pulsar1.getNamespaceService()
+                    .checkTopicExists(TopicName.get(topicChangeEvents)).join().isExists());
+        });
+
+        // cleanup.
+        p.close();
+        admin2.topics().delete(topic);
+        admin2.namespaces().deleteNamespace(ns1);
+    }
 }