content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.worker.block;
  
  import alluxio.ClientContext;
  import alluxio.conf.Configuration;
  import alluxio.conf.PropertyKey;
  import alluxio.master.MasterClientContext;
  import alluxio.resource.ResourcePool;
  
  import com.google.common.annotations.VisibleForTesting;
  import com.google.common.io.Closer;
  
  import java.io.IOException;
  import java.net.InetSocketAddress;
  import java.util.Queue;
  import java.util.concurrent.ConcurrentLinkedQueue;
  import javax.annotation.Nullable;
  import javax.annotation.concurrent.ThreadSafe;
  
  /**
   * Class for managing block master clients. After obtaining a client with
   * {@link ResourcePool#acquire()}, {@link ResourcePool#release(Object)} must be called when the
   * thread is done using the client.
   */
  @ThreadSafe
  public class BlockMasterClientPool extends ResourcePool<BlockMasterClient> {
    private final Queue<BlockMasterClient> mClientList;
    private final MasterClientContext mMasterContext;
  
    /** If not specified, the client pool will create clients connecting to the primary master. **/
    @Nullable
    private final InetSocketAddress mMasterAddress;
  
    /**
     * A factory class for testing purpose.
     */
    @VisibleForTesting
    static class Factory {
      BlockMasterClientPool create() {
        return new BlockMasterClientPool();
      }
  
      BlockMasterClientPool create(@Nullable InetSocketAddress address) {
        return new BlockMasterClientPool(address);
      }
    }
  
    /**
     * Creates a new block master client pool.
     */
    public BlockMasterClientPool() {
      this(null);
    }
  
    /**
     * Creates a new block master client pool.
     * @param address the block master address
     */
    public BlockMasterClientPool(@Nullable InetSocketAddress address) {
      super(Configuration.getInt(PropertyKey.WORKER_BLOCK_MASTER_CLIENT_POOL_SIZE));
      mClientList = new ConcurrentLinkedQueue<>();
      mMasterContext = MasterClientContext
          .newBuilder(ClientContext.create(Configuration.global())).build();
      mMasterAddress = address;
    }
  
    @Override
    public void close() throws IOException {
      BlockMasterClient client;
      Closer closer = Closer.create();
      while ((client = mClientList.poll()) != null) {
        closer.register(client);
      }
      closer.close();
    }
  
    @Override
    public BlockMasterClient createNewResource() {
      final BlockMasterClient client;
      if (mMasterAddress != null) {
        // If an address is specified, that means all clients in this pool connect
        // to the specific master no matter it is a primary or standby
        client = new BlockMasterClient(mMasterContext, mMasterAddress);
      } else {
        client = new BlockMasterClient(mMasterContext);
      }
      mClientList.add(client);
      return client;
    }
  }
  