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.connect.storage;
  
  import org.apache.kafka.common.utils.ThreadUtils;
  import org.apache.kafka.connect.runtime.WorkerConfig;
  import org.apache.kafka.connect.util.Callback;
  
  import java.nio.ByteBuffer;
  import java.util.Collection;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Set;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Executors;
  import java.util.concurrent.Future;
  import java.util.concurrent.TimeUnit;
  
  /**
   * Implementation of OffsetBackingStore that doesn't actually persist any data. To ensure this
   * behaves similarly to a real backing store, operations are executed asynchronously on a
   * background thread.
   */
  public abstract class MemoryOffsetBackingStore implements OffsetBackingStore {
  
      protected Map<ByteBuffer, ByteBuffer> data = new HashMap<>();
      protected ExecutorService executor;
  
      public MemoryOffsetBackingStore() {
  
      }
  
      @Override
      public void configure(WorkerConfig config) {
      }
  
      @Override
      public void start() {
          executor = Executors.newFixedThreadPool(1, ThreadUtils.createThreadFactory(
                  this.getClass().getSimpleName() + "-%d", false));
      }
  
      @Override
      public void stop() {
          if (executor != null) {
              ThreadUtils.shutdownExecutorServiceQuietly(executor, 30, TimeUnit.SECONDS);
              executor = null;
          }
      }
  
      @Override
      public Future<Map<ByteBuffer, ByteBuffer>> get(final Collection<ByteBuffer> keys) {
          return executor.submit(() -> {
              Map<ByteBuffer, ByteBuffer> result = new HashMap<>();
              for (ByteBuffer key : keys) {
                  result.put(key, data.get(key));
              }
              return result;
          });
      }
  
      @Override
      public Future<Void> set(final Map<ByteBuffer, ByteBuffer> values,
                              final Callback<Void> callback) {
          return executor.submit(() -> {
              data.putAll(values);
              save();
              if (callback != null)
                  callback.onCompletion(null, null);
              return null;
          });
      }
  
      // Hook to allow subclasses to persist data
      protected void save() {
  
      }
  
      @Override
      public abstract Set<Map<String, Object>> connectorPartitions(String connectorName);
  }
  