content: /*
   * 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.raft.internals;
  
  import org.apache.kafka.common.errors.InterruptException;
  import org.apache.kafka.common.protocol.ApiMessage;
  import org.apache.kafka.raft.RaftMessage;
  import org.apache.kafka.raft.RaftMessageQueue;
  
  import java.util.concurrent.BlockingQueue;
  import java.util.concurrent.LinkedBlockingQueue;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicInteger;
  
  public class BlockingMessageQueue implements RaftMessageQueue {
      private static final RaftMessage WAKEUP_MESSAGE = new RaftMessage() {
          @Override
          public int correlationId() {
              return 0;
          }
  
          @Override
          public ApiMessage data() {
              return null;
          }
      };
  
      private final BlockingQueue<RaftMessage> queue = new LinkedBlockingQueue<>();
      private final AtomicInteger size = new AtomicInteger(0);
  
      @Override
      public RaftMessage poll(long timeoutMs) {
          try {
              RaftMessage message = queue.poll(timeoutMs, TimeUnit.MILLISECONDS);
              if (message == null || message == WAKEUP_MESSAGE) {
                  return null;
              } else {
                  size.decrementAndGet();
                  return message;
              }
          } catch (InterruptedException e) {
              throw new InterruptException(e);
          }
      }
  
      @Override
      public void add(RaftMessage message) {
          queue.add(message);
          size.incrementAndGet();
      }
  
      @Override
      public boolean isEmpty() {
          return size.get() == 0;
      }
  
      @Override
      public void wakeup() {
          queue.add(WAKEUP_MESSAGE);
      }
  
  }
  