code: /*
   * 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.skywalking.oap.server.core.storage;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.locks.Condition;
  import java.util.concurrent.locks.ReentrantLock;
  import lombok.Getter;
  import lombok.RequiredArgsConstructor;
  import org.apache.skywalking.oap.server.library.util.CollectionUtils;
  
  @RequiredArgsConstructor
  public class BlockingBatchQueueWithReentrantLock<E> implements BlockingBatchQueue<E> {
  
      @Getter
      private final int maxBatchSize;
  
      @Getter
      private volatile boolean inAppendingMode = true;
  
      private final List<E> elementData = new ArrayList<>(50000);
  
      private ReentrantLock reentrantLock = new ReentrantLock();
      private Condition condition = this.reentrantLock.newCondition();
  
      public void offer(List<E> elements) {
          reentrantLock.lock();
          try {
              elementData.addAll(elements);
              if (elementData.size() >= maxBatchSize) {
                  condition.signalAll();
              }
          } finally {
              reentrantLock.unlock();
          }
      }
  
      public List<E> poll() throws InterruptedException {
          reentrantLock.lock();
          try {
              while (this.elementData.size() < maxBatchSize && inAppendingMode) {
                  condition.await(1000, TimeUnit.MILLISECONDS);
              }
              if (CollectionUtils.isEmpty(elementData)) {
                  return Collections.EMPTY_LIST;
              }
              List<E> sublist = this.elementData.subList(
                  0, Math.min(maxBatchSize, this.elementData.size()));
              List<E> partition = new ArrayList<>(sublist);
              sublist.clear();
              return partition;
          } finally {
              reentrantLock.unlock();
          }
      }
  
      public void noFurtherAppending() {
          reentrantLock.lock();
          try {
              inAppendingMode = false;
              condition.signalAll();
          } finally {
              reentrantLock.unlock();
          }
      }
  
      public void furtherAppending() {
          reentrantLock.lock();
          try {
              inAppendingMode = true;
              condition.signalAll();
          } finally {
              reentrantLock.unlock();
          }
      }
  
      @Override
      public int size() {
          return elementData.size();
      }
  }
  