hadoop MultipleDestinationMountTableResolver 源码

haddop MultipleDestinationMountTableResolver 代码

文件路径：/hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/resolver/MultipleDestinationMountTableResolver.java

/**
 * 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.hadoop.hdfs.server.federation.resolver;

import java.io.IOException;
import java.util.EnumMap;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hdfs.server.federation.resolver.order.AvailableSpaceResolver;
import org.apache.hadoop.hdfs.server.federation.resolver.order.DestinationOrder;
import org.apache.hadoop.hdfs.server.federation.resolver.order.HashFirstResolver;
import org.apache.hadoop.hdfs.server.federation.resolver.order.HashResolver;
import org.apache.hadoop.hdfs.server.federation.resolver.order.LocalResolver;
import org.apache.hadoop.hdfs.server.federation.resolver.order.OrderedResolver;
import org.apache.hadoop.hdfs.server.federation.resolver.order.RandomResolver;
import org.apache.hadoop.hdfs.server.federation.router.Router;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.hadoop.classification.VisibleForTesting;

/**
 * Mount table resolver that supports multiple locations for each mount entry.
 * The returned location contains prioritized remote paths from highest priority
 * to the lowest priority. Multiple locations for a mount point are optional.
 * When multiple locations are specified, both will be checked for the presence
 * of a file and the nameservice for a new file/dir is chosen based on the
 * results of a consistent hashing algorithm.
 * <p>
 * Does the Mount table entry for this path have multiple destinations?
 * <ul>
 * <li>No: Return the location
 * <li>Yes: Return all locations, prioritizing the best guess from the
 * consistent hashing algorithm.
 * </ul>
 * <p>
 * It has multiple options to order the locations: HASH (default), LOCAL,
 * RANDOM, and HASH_ALL.
 * <p>
 * The consistent hashing result is dependent on the number and combination of
 * nameservices that are registered for particular mount point. The order of
 * nameservices/locations in the mount table is not prioritized. Each consistent
 * hash calculation considers only the set of unique nameservices present for
 * the mount table location.
 */
public class MultipleDestinationMountTableResolver extends MountTableResolver {

  private static final Logger LOG =
      LoggerFactory.getLogger(MultipleDestinationMountTableResolver.class);


  /** Resolvers that use a particular order for multiple destinations. */
  private EnumMap<DestinationOrder, OrderedResolver> orderedResolvers =
      new EnumMap<>(DestinationOrder.class);


  public MultipleDestinationMountTableResolver(
      Configuration conf, Router router) {
    super(conf, router);

    // Initialize the ordered resolvers
    addResolver(DestinationOrder.HASH, new HashFirstResolver());
    addResolver(DestinationOrder.LOCAL, new LocalResolver(conf, router));
    addResolver(DestinationOrder.RANDOM, new RandomResolver());
    addResolver(DestinationOrder.HASH_ALL, new HashResolver());
    addResolver(DestinationOrder.SPACE,
        new AvailableSpaceResolver(conf, router));
  }

  @Override
  public PathLocation getDestinationForPath(String path) throws IOException {
    PathLocation mountTableResult = super.getDestinationForPath(path);
    if (mountTableResult == null) {
      LOG.error("The {} cannot find a location for {}",
          super.getClass().getSimpleName(), path);
    } else if (mountTableResult.hasMultipleDestinations()) {
      DestinationOrder order = mountTableResult.getDestinationOrder();
      OrderedResolver orderedResolver = orderedResolvers.get(order);
      if (orderedResolver == null) {
        LOG.error("Cannot find resolver for order {}", order);
      } else {
        String firstNamespace =
            orderedResolver.getFirstNamespace(path, mountTableResult);

        // Change the order of the name spaces according to the policy
        if (firstNamespace != null) {
          // Create our own prioritized copy based on the entity in the tree.
          mountTableResult = PathLocation.prioritizeDestination(
              mountTableResult, firstNamespace);
          LOG.debug("Ordered locations following {} are {}",
              order, mountTableResult);
        } else {
          LOG.error("Cannot get main namespace for path {} with order {}",
              path, order);
        }
      }
    }
    return mountTableResult;
  }

  @VisibleForTesting
  public void addResolver(DestinationOrder order, OrderedResolver resolver) {
    orderedResolvers.put(order, resolver);
  }
}

相关信息

hadoop 源码目录

相关文章

hadoop ActiveNamenodeResolver 源码

hadoop FederationNamenodeContext 源码

hadoop FederationNamenodeServiceState 源码

hadoop FederationNamespaceInfo 源码

hadoop FileSubclusterResolver 源码

hadoop MembershipNamenodeResolver 源码

hadoop MountTableManager 源码

hadoop MountTableResolver 源码

hadoop NamenodePriorityComparator 源码

hadoop NamenodeStatusReport 源码