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.conf.AlluxioConfiguration;
  import alluxio.wire.TieredIdentity;
  import alluxio.wire.WorkerNetAddress;
  
  import com.google.common.annotations.VisibleForTesting;
  import com.google.common.base.MoreObjects;
  import com.google.common.base.Objects;
  import com.google.common.collect.Lists;
  
  import java.util.List;
  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 availability, will select the nearest worker from the active
   * workers list with sufficient availability.
   *
   * 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.
   *
   * The {@link alluxio.conf.PropertyKey.USER_BLOCK_AVOID_EVICTION_POLICY_RESERVED_BYTES}
   * (alluxio.user.block.avoid.eviction.policy.reserved.size.bytes)
   * is used as buffer space on each worker when calculating available space
   * to store each block.
   */
  @ThreadSafe
  public final class LocalFirstAvoidEvictionPolicy implements BlockLocationPolicy {
    private final LocalFirstPolicy mPolicy;
    private final long mBlockCapacityReserved;
  
    /**
     * Constructs a new {@link LocalFirstAvoidEvictionPolicy}.
     *
     * @param conf Alluxio configuration
     */
    public LocalFirstAvoidEvictionPolicy(AlluxioConfiguration conf) {
      this(conf.getBytes(alluxio.conf.PropertyKey.USER_BLOCK_AVOID_EVICTION_POLICY_RESERVED_BYTES),
          conf);
    }
  
    LocalFirstAvoidEvictionPolicy(long blockCapacityReserved,
        AlluxioConfiguration conf) {
      mPolicy = LocalFirstPolicy.create(conf);
      mBlockCapacityReserved = blockCapacityReserved;
    }
  
    @VisibleForTesting
    LocalFirstAvoidEvictionPolicy(long blockCapacityReserved, TieredIdentity identity,
        AlluxioConfiguration conf) {
      mPolicy = new LocalFirstPolicy(identity, conf);
      mBlockCapacityReserved = blockCapacityReserved;
    }
  
    @Override
    public Optional<WorkerNetAddress> getWorker(GetWorkerOptions options) {
      List<BlockWorkerInfo> allWorkers = Lists.newArrayList(options.getBlockWorkerInfos());
      // Prefer workers with enough availability.
      List<BlockWorkerInfo> workers = allWorkers.stream()
          .filter(worker -> getAvailableBytes(worker) >= options.getBlockInfo().getLength())
          .collect(Collectors.toList());
      if (workers.isEmpty()) {
        workers = allWorkers;
      }
      GetWorkerOptions filteredWorkers = GetWorkerOptions.defaults()
          .setBlockInfo(options.getBlockInfo())
          .setBlockWorkerInfos(workers);
      return mPolicy.getWorker(filteredWorkers);
    }
  
    /**
     * Calculate the available bytes for a worker with the added buffer of
     * {@link alluxio.conf.PropertyKey.USER_BLOCK_AVOID_EVICTION_POLICY_RESERVED_BYTES}
     * (alluxio.user.block.avoid.eviction.policy.reserved.size.bytes)
     *
     * Since the information of BlockWorkerInfo is updated <em>after</em> a file
     * completes a write, mCapacityBytes minus mUsedBytes may not be the true available bytes.
     *
     * @param workerInfo BlockWorkerInfo of the worker
     * @return the available bytes of the worker
     */
    private long getAvailableBytes(BlockWorkerInfo workerInfo) {
      long capacityBytes = workerInfo.getCapacityBytes();
      long usedBytes = workerInfo.getUsedBytes();
      return capacityBytes - usedBytes - mBlockCapacityReserved;
    }
  
    @Override
    public boolean equals(Object o) {
      if (this == o) {
        return true;
      }
      if (!(o instanceof LocalFirstAvoidEvictionPolicy)) {
        return false;
      }
      LocalFirstAvoidEvictionPolicy that = (LocalFirstAvoidEvictionPolicy) o;
      return Objects.equal(mPolicy, that.mPolicy)
          && Objects.equal(mBlockCapacityReserved, that.mBlockCapacityReserved);
    }
  
    @Override
    public int hashCode() {
      return Objects.hashCode(mPolicy);
    }
  
    @Override
    public String toString() {
      return MoreObjects.toStringHelper(this)
          .add("policy", mPolicy)
          .add("blockCapacityReservered", mBlockCapacityReserved)
          .toString();
    }
  }
  