[fix] [broker] Fix configurationMetadataSyncEventTopic is marked supporting dynamic setting, but not implemented (apache#22684)

(cherry picked from commit ff4853e)

Author: poorbarcode

pulsar-broker/src/main/java/org/apache/pulsar/broker/PulsarService.java

@@ -607,13 +607,12 @@ public CompletableFuture<Void> closeAsync() {
                 }
             }
 
-            closeLocalMetadataStore();
+            asyncCloseFutures.add(closeLocalMetadataStore());
+            if (configMetadataSynchronizer != null) {
+                asyncCloseFutures.add(configMetadataSynchronizer.closeAsync());
+            }
             if (configurationMetadataStore != null && shouldShutdownConfigurationMetadataStore) {
                 configurationMetadataStore.close();
-                if (configMetadataSynchronizer != null) {
-                    configMetadataSynchronizer.close();
-                    configMetadataSynchronizer = null;
-                }
             }
 
             if (transactionExecutorProvider != null) {
@@ -1160,14 +1159,16 @@ public MetadataStoreExtended createLocalMetadataStore(PulsarMetadataEventSynchro
                         .build());
     }
 
-    protected void closeLocalMetadataStore() throws Exception {
+    protected CompletableFuture<Void> closeLocalMetadataStore() throws Exception {
         if (localMetadataStore != null) {
             localMetadataStore.close();
         }
         if (localMetadataSynchronizer != null) {
-            localMetadataSynchronizer.close();
+            CompletableFuture<Void> closeSynchronizer = localMetadataSynchronizer.closeAsync();
             localMetadataSynchronizer = null;
+            return closeSynchronizer;
         }
+        return CompletableFuture.completedFuture(null);
     }
 
     protected void startLeaderElectionService() {
@@ -1928,4 +1929,69 @@ public CompletableFuture<TopicCompactionService> newTopicCompactionService(Strin
             return CompletableFuture.failedFuture(e);
         }
     }
+
+    public void initConfigMetadataSynchronizerIfNeeded() {
+        mutex.lock();
+        try {
+            final String newTopic = config.getConfigurationMetadataSyncEventTopic();
+            final PulsarMetadataEventSynchronizer oldSynchronizer = configMetadataSynchronizer;
+            // Skip if not support.
+            if (!(configurationMetadataStore instanceof MetadataStoreExtended)) {
+                LOG.info(
+                        "Skip to update Metadata Synchronizer because of the Configuration Metadata Store using[{}]"
+                                + " does not support.", configurationMetadataStore.getClass().getName());
+                return;
+            }
+            // Skip if no changes.
+            //   case-1: both null.
+            //   case-2: both topics are the same.
+            if ((oldSynchronizer == null && StringUtils.isBlank(newTopic))) {
+                LOG.info("Skip to update Metadata Synchronizer because the topic[null] does not changed.");
+            }
+            if (StringUtils.isNotBlank(newTopic) && oldSynchronizer != null) {
+                TopicName newTopicName = TopicName.get(newTopic);
+                TopicName oldTopicName = TopicName.get(oldSynchronizer.getTopicName());
+                if (newTopicName.equals(oldTopicName)) {
+                    LOG.info("Skip to update Metadata Synchronizer because the topic[{}] does not changed.",
+                            oldTopicName);
+                }
+            }
+            // Update(null or not null).
+            //   1.set the new one.
+            //   2.close the old one.
+            //   3.async start the new one.
+            if (StringUtils.isBlank(newTopic)) {
+                configMetadataSynchronizer = null;
+            } else {
+                configMetadataSynchronizer = new PulsarMetadataEventSynchronizer(this, newTopic);
+            }
+            // close the old one and start the new one.
+            PulsarMetadataEventSynchronizer newSynchronizer = configMetadataSynchronizer;
+            MetadataStoreExtended metadataStoreExtended = (MetadataStoreExtended) configurationMetadataStore;
+            metadataStoreExtended.updateMetadataEventSynchronizer(newSynchronizer);
+            Runnable startNewSynchronizer = () -> {
+                if (newSynchronizer == null) {
+                    return;
+                }
+                try {
+                    newSynchronizer.start();
+                } catch (Exception e) {
+                    // It only occurs when get internal client fails.
+                    LOG.error("Start Metadata Synchronizer with topic {} failed.",
+                            newTopic, e);
+                }
+            };
+            executor.submit(() -> {
+                if (oldSynchronizer != null) {
+                    oldSynchronizer.closeAsync().whenComplete((ignore, ex) -> {
+                        startNewSynchronizer.run();
+                    });
+                } else {
+                    startNewSynchronizer.run();
+                }
+            });
+        } finally {
+            mutex.unlock();
+        }
+    }
 }

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

@@ -2806,6 +2806,11 @@ private void updateConfigurationAndRegisterListeners() {
             pulsar.getWebService().updateHttpRequestsFailOnUnknownPropertiesEnabled((boolean) enabled);
         });
 
+        // add listener to notify web service httpRequestsFailOnUnknownPropertiesEnabled changed.
+        registerConfigurationListener("configurationMetadataSyncEventTopic", enabled -> {
+            pulsar.initConfigMetadataSynchronizerIfNeeded();
+        });
+
         // add more listeners here
 
         // (3) create dynamic-config if not exist.