rhauch commented on a change in pull request #9780: URL: https://github.com/apache/kafka/pull/9780#discussion_r570657028
########## File path: connect/runtime/src/main/java/org/apache/kafka/connect/util/SharedTopicAdmin.java ########## @@ -0,0 +1,145 @@ +/* + * 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.kafka.connect.util; + +import java.time.Duration; +import java.util.Map; +import java.util.Objects; +import java.util.concurrent.atomic.AtomicBoolean; +import java.util.concurrent.atomic.AtomicReference; +import java.util.function.Function; +import java.util.function.Supplier; +import java.util.function.UnaryOperator; + +import org.apache.kafka.clients.admin.AdminClientConfig; +import org.apache.kafka.connect.errors.ConnectException; + +/** + * A holder of a {@link TopicAdmin} object that is lazily and atomically created when needed by multiple callers. + * As soon as one of the getters is called, all getters will return the same shared {@link TopicAdmin} + * instance until this SharedAdmin is closed via {@link #close()} or {@link #close(Duration)}. + * + * <p>The owner of this object is responsible for ensuring that either {@link #close()} or {@link #close(Duration)} + * is called when the {@link TopicAdmin} instance is no longer needed. Consequently, once this + * {@link SharedTopicAdmin} instance has been closed, the {@link #get()} and {@link #topicAdmin()} methods, + * nor any previously returned {@link TopicAdmin} instances may be used. + * + * <p>This class is thread-safe. It also appears as immutable to callers that obtain the {@link TopicAdmin} object, + * until this object is closed, at which point it cannot be used anymore + */ +public class SharedTopicAdmin implements AutoCloseable, Supplier<TopicAdmin> { + + // Visible for testing + static final Duration DEFAULT_CLOSE_DURATION = Duration.ofMillis(Long.MAX_VALUE); + + private final Map<String, Object> adminProps; + private final AtomicReference<TopicAdmin> admin = new AtomicReference<>(); + private final AtomicBoolean closed = new AtomicBoolean(false); + private final Function<Map<String, Object>, TopicAdmin> factory; + + public SharedTopicAdmin(Map<String, Object> adminProps) { + this(adminProps, TopicAdmin::new); + } + + // Visible for testing + SharedTopicAdmin(Map<String, Object> adminProps, Function<Map<String, Object>, TopicAdmin> factory) { + this.adminProps = Objects.requireNonNull(adminProps); + this.factory = Objects.requireNonNull(factory); + } + + /** + * Get the shared {@link TopicAdmin} instance. + * + * @return the shared instance; never null + * @throws ConnectException if this object has already been closed + */ + @Override + public TopicAdmin get() { + return topicAdmin(); + } + + /** + * Get the shared {@link TopicAdmin} instance. + * + * @return the shared instance; never null + * @throws ConnectException if this object has already been closed + */ + public TopicAdmin topicAdmin() { + return admin.updateAndGet(this::createAdmin); Review comment: I'm not sure there is much advantage either way, considering these methods are not called frequently and `synchronized` would indeed work. I personally like the simplicity of using `AtomicReference`, which to me seemed natural and straightforward, avoided having to synchronize the entire methods, and needed no if-checks in this method. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
