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.client.block.policy;
  
  import alluxio.client.block.BlockWorkerInfo;
  import alluxio.client.block.policy.options.GetWorkerOptions;
  import alluxio.client.block.util.BlockLocationUtils;
  import alluxio.collections.Pair;
  import alluxio.conf.AlluxioConfiguration;
  import alluxio.network.TieredIdentityFactory;
  import alluxio.wire.TieredIdentity;
  import alluxio.wire.WorkerNetAddress;
  
  import com.google.common.annotations.VisibleForTesting;
  import com.google.common.collect.Lists;
  
  import java.util.Collections;
  import java.util.List;
  import java.util.Objects;
  import java.util.Optional;
  import java.util.stream.Collectors;
  import javax.annotation.concurrent.ThreadSafe;
  
  /**
   * A policy that returns the local worker first, and if the local worker doesn't
   * exist or doesn't have enough capacity, will select the nearest worker from the active
   * workers list with sufficient capacity.
   *
   * The definition of 'nearest worker' is based on {@link alluxio.wire.TieredIdentity}.
   * @see alluxio.util.TieredIdentityUtils#nearest
   *
   * The calculation of which worker gets selected is done for each block write.
   */
  @ThreadSafe
  public final class LocalFirstPolicy implements BlockLocationPolicy {
    private final TieredIdentity mTieredIdentity;
    private final AlluxioConfiguration mConf;
  
    /**
     * Constructs a new {@link LocalFirstPolicy}.
     *
     * @param conf Alluxio configuration
     */
    public LocalFirstPolicy(AlluxioConfiguration conf) {
      mTieredIdentity = TieredIdentityFactory.localIdentity(conf);
      mConf = conf;
    }
  
    static LocalFirstPolicy create(AlluxioConfiguration conf) {
      return new LocalFirstPolicy(conf);
    }
  
    @VisibleForTesting
    LocalFirstPolicy(TieredIdentity identity, AlluxioConfiguration conf) {
      mTieredIdentity = identity;
      mConf = conf;
    }
  
    @Override
    public Optional<WorkerNetAddress> getWorker(GetWorkerOptions options) {
      List<BlockWorkerInfo> shuffledWorkers = Lists.newArrayList(options.getBlockWorkerInfos());
      Collections.shuffle(shuffledWorkers);
      // Workers must have enough capacity to hold the block.
      List<BlockWorkerInfo> candidateWorkers = shuffledWorkers.stream()
          .filter(worker -> worker.getCapacityBytes() >= options.getBlockInfo().getLength())
          .collect(Collectors.toList());
  
      // Try finding the nearest worker.
      List<WorkerNetAddress> addresses = candidateWorkers.stream()
          .map(BlockWorkerInfo::getNetAddress)
          .filter(Objects::nonNull)
          .collect(Collectors.toList());
      Optional<Pair<WorkerNetAddress, Boolean>> nearest =
          BlockLocationUtils.nearest(mTieredIdentity, addresses, mConf);
      return nearest.map(Pair::getFirst);
    }
  
    @Override
    public boolean equals(Object o) {
      if (this == o) {
        return true;
      }
      if (!(o instanceof LocalFirstPolicy)) {
        return false;
      }
      LocalFirstPolicy that = (LocalFirstPolicy) o;
      return Objects.equals(mTieredIdentity, that.mTieredIdentity);
    }
  
    @Override
    public int hashCode() {
      return Objects.hash(mTieredIdentity);
    }
  
    @Override
    public String toString() {
      return com.google.common.base.MoreObjects.toStringHelper(this)
          .add("tieredIdentity", mTieredIdentity)
          .toString();
    }
  }
  