| /** |
| * 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 com.google.common.annotations.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); |
| } |
| } |