[120] | 1 | /** |
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| 2 | * Licensed to the Apache Software Foundation (ASF) under one |
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| 3 | * or more contributor license agreements. See the NOTICE file |
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| 4 | * distributed with this work for additional information |
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| 5 | * regarding copyright ownership. The ASF licenses this file |
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| 6 | * to you under the Apache License, Version 2.0 (the |
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| 7 | * "License"); you may not use this file except in compliance |
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| 8 | * with the License. You may obtain a copy of the License at |
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| 9 | * |
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| 10 | * http://www.apache.org/licenses/LICENSE-2.0 |
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| 11 | * |
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| 12 | * Unless required by applicable law or agreed to in writing, software |
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| 13 | * distributed under the License is distributed on an "AS IS" BASIS, |
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| 14 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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| 15 | * See the License for the specific language governing permissions and |
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| 16 | * limitations under the License. |
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| 17 | */ |
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| 18 | package org.apache.hadoop.net; |
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| 19 | |
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| 20 | import java.util.ArrayList; |
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| 21 | import java.util.List; |
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| 22 | import java.util.Map; |
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| 23 | import java.util.concurrent.ConcurrentHashMap; |
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| 24 | |
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| 25 | /** |
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| 26 | * A cached implementation of DNSToSwitchMapping that takes an |
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| 27 | * raw DNSToSwitchMapping and stores the resolved network location in |
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| 28 | * a cache. The following calls to a resolved network location |
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| 29 | * will get its location from the cache. |
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| 30 | * |
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| 31 | */ |
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| 32 | public class CachedDNSToSwitchMapping implements DNSToSwitchMapping { |
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| 33 | private Map<String, String> cache = new ConcurrentHashMap<String, String>(); |
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| 34 | protected DNSToSwitchMapping rawMapping; |
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| 35 | |
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| 36 | public CachedDNSToSwitchMapping(DNSToSwitchMapping rawMapping) { |
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| 37 | this.rawMapping = rawMapping; |
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| 38 | } |
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| 39 | |
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| 40 | public List<String> resolve(List<String> names) { |
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| 41 | // normalize all input names to be in the form of IP addresses |
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| 42 | names = NetUtils.normalizeHostNames(names); |
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| 43 | |
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| 44 | List <String> result = new ArrayList<String>(names.size()); |
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| 45 | if (names.isEmpty()) { |
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| 46 | return result; |
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| 47 | } |
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| 48 | |
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| 49 | |
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| 50 | // find out all names without cached resolved location |
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| 51 | List<String> unCachedHosts = new ArrayList<String>(names.size()); |
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| 52 | for (String name : names) { |
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| 53 | if (cache.get(name) == null) { |
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| 54 | unCachedHosts.add(name); |
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| 55 | } |
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| 56 | } |
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| 57 | |
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| 58 | // Resolve those names |
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| 59 | List<String> rNames = rawMapping.resolve(unCachedHosts); |
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| 60 | |
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| 61 | // Cache the result |
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| 62 | if (rNames != null) { |
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| 63 | for (int i=0; i<unCachedHosts.size(); i++) { |
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| 64 | cache.put(unCachedHosts.get(i), rNames.get(i)); |
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| 65 | } |
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| 66 | } |
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| 67 | |
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| 68 | // Construct the result |
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| 69 | for (String name : names) { |
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| 70 | //now everything is in the cache |
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| 71 | String networkLocation = cache.get(name); |
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| 72 | if (networkLocation != null) { |
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| 73 | result.add(networkLocation); |
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| 74 | } else { //resolve all or nothing |
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| 75 | return null; |
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| 76 | } |
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| 77 | } |
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| 78 | return result; |
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| 79 | } |
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| 80 | } |
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