[improve][broker] Replace String.intern() with Guava Interner (#20432)

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

@@ -34,6 +34,7 @@
 import org.apache.pulsar.client.impl.PulsarClientImpl;
 import org.apache.pulsar.common.naming.TopicName;
 import org.apache.pulsar.common.util.FutureUtil;
+import org.apache.pulsar.common.util.StringInterner;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -73,9 +74,9 @@ public AbstractReplicator(String localCluster, String localTopicName, String rem
         this.brokerService = brokerService;
         this.localTopicName = localTopicName;
         this.replicatorPrefix = replicatorPrefix;
-        this.localCluster = localCluster.intern();
+        this.localCluster = StringInterner.intern(localCluster);
         this.remoteTopicName = remoteTopicName;
-        this.remoteCluster = remoteCluster.intern();
+        this.remoteCluster = StringInterner.intern(remoteCluster);
         this.replicationClient = replicationClient;
         this.client = (PulsarClientImpl) brokerService.pulsar().getClient();
         this.producer = null;
@@ -228,7 +229,7 @@ public static String getRemoteCluster(String remoteCursor) {
     }
 
     public static String getReplicatorName(String replicatorPrefix, String cluster) {
-        return (replicatorPrefix + "." + cluster).intern();
+        return StringInterner.intern(replicatorPrefix + "." + cluster);
     }
 
     /**

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

@@ -164,6 +164,7 @@
 import org.apache.pulsar.common.schema.SchemaType;
 import org.apache.pulsar.common.topics.TopicList;
 import org.apache.pulsar.common.util.FutureUtil;
+import org.apache.pulsar.common.util.StringInterner;
 import org.apache.pulsar.common.util.collections.ConcurrentLongHashMap;
 import org.apache.pulsar.common.util.netty.NettyChannelUtil;
 import org.apache.pulsar.common.util.netty.NettyFutureUtil;
@@ -717,7 +718,7 @@ private void completeConnect(int clientProtoVersion, String clientVersion) {
         }
         setRemoteEndpointProtocolVersion(clientProtoVersion);
         if (isNotBlank(clientVersion)) {
-            this.clientVersion = clientVersion.intern();
+            this.clientVersion = StringInterner.intern(clientVersion);
         }
         if (!service.isAuthenticationEnabled()) {
             log.info("[{}] connected with clientVersion={}, clientProtocolVersion={}, proxyVersion={}", remoteAddress,

pulsar-common/src/main/java/org/apache/pulsar/common/util/StringInterner.java

@@ -0,0 +1,46 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.pulsar.common.util;
+
+import com.google.common.collect.Interner;
+import com.google.common.collect.Interners;
+
+/**
+ * Deduplicates String instances by interning them using Guava's Interner
+ * which is more efficient than String.intern().
+ */
+public class StringInterner {
+    private static final StringInterner INSTANCE = new StringInterner();
+    private final Interner<String> interner;
+
+    public static String intern(String sample) {
+        return INSTANCE.doIntern(sample);
+    }
+
+    private StringInterner() {
+        this.interner = Interners.newWeakInterner();
+    }
+
+    String doIntern(String sample) {
+        if (sample == null) {
+            return null;
+        }
+        return interner.intern(sample);
+    }
+}