| /** |
| * 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.net; |
| |
| import java.util.ArrayList; |
| import java.util.List; |
| import java.util.Map; |
| import java.util.concurrent.ConcurrentHashMap; |
| |
| /** |
| * A cached implementation of DNSToSwitchMapping that takes an |
| * raw DNSToSwitchMapping and stores the resolved network location in |
| * a cache. The following calls to a resolved network location |
| * will get its location from the cache. |
| * |
| */ |
| public class CachedDNSToSwitchMapping implements DNSToSwitchMapping { |
| private Map<String, String> cache = new ConcurrentHashMap<String, String>(); |
| protected DNSToSwitchMapping rawMapping; |
| |
| public CachedDNSToSwitchMapping(DNSToSwitchMapping rawMapping) { |
| this.rawMapping = rawMapping; |
| } |
| |
| public List<String> resolve(List<String> names) { |
| // normalize all input names to be in the form of IP addresses |
| names = NetUtils.normalizeHostNames(names); |
| |
| List <String> result = new ArrayList<String>(names.size()); |
| if (names.isEmpty()) { |
| return result; |
| } |
| |
| |
| // find out all names without cached resolved location |
| List<String> unCachedHosts = new ArrayList<String>(names.size()); |
| for (String name : names) { |
| if (cache.get(name) == null) { |
| unCachedHosts.add(name); |
| } |
| } |
| |
| // Resolve those names |
| List<String> rNames = rawMapping.resolve(unCachedHosts); |
| |
| // Cache the result |
| if (rNames != null) { |
| for (int i=0; i<unCachedHosts.size(); i++) { |
| cache.put(unCachedHosts.get(i), rNames.get(i)); |
| } |
| } |
| |
| // Construct the result |
| for (String name : names) { |
| //now everything is in the cache |
| String networkLocation = cache.get(name); |
| if (networkLocation != null) { |
| result.add(networkLocation); |
| } else { //resolve all or nothing |
| return null; |
| } |
| } |
| return result; |
| } |
| } |