| /** |
| * 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.HashMap; |
| import java.util.List; |
| import java.util.Map; |
| import java.util.concurrent.ConcurrentHashMap; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
| |
| /** |
| * 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. |
| * |
| */ |
| @InterfaceAudience.Public |
| @InterfaceStability.Evolving |
| public class CachedDNSToSwitchMapping extends AbstractDNSToSwitchMapping { |
| private Map<String, String> cache = new ConcurrentHashMap<String, String>(); |
| |
| /** |
| * The uncached mapping |
| */ |
| protected final DNSToSwitchMapping rawMapping; |
| |
| /** |
| * cache a raw DNS mapping |
| * @param rawMapping the raw mapping to cache |
| */ |
| public CachedDNSToSwitchMapping(DNSToSwitchMapping rawMapping) { |
| this.rawMapping = rawMapping; |
| } |
| |
| /** |
| * @param names a list of hostnames to probe for being cached |
| * @return the hosts from 'names' that have not been cached previously |
| */ |
| private List<String> getUncachedHosts(List<String> names) { |
| // 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); |
| } |
| } |
| return unCachedHosts; |
| } |
| |
| /** |
| * Caches the resolved host:rack mappings. The two list |
| * parameters must be of equal size. |
| * |
| * @param uncachedHosts a list of hosts that were uncached |
| * @param resolvedHosts a list of resolved host entries where the element |
| * at index(i) is the resolved value for the entry in uncachedHosts[i] |
| */ |
| private void cacheResolvedHosts(List<String> uncachedHosts, |
| List<String> resolvedHosts) { |
| // Cache the result |
| if (resolvedHosts != null) { |
| for (int i=0; i<uncachedHosts.size(); i++) { |
| cache.put(uncachedHosts.get(i), resolvedHosts.get(i)); |
| } |
| } |
| } |
| |
| /** |
| * @param names a list of hostnames to look up (can be be empty) |
| * @return the cached resolution of the list of hostnames/addresses. |
| * or null if any of the names are not currently in the cache |
| */ |
| private List<String> getCachedHosts(List<String> names) { |
| List<String> result = new ArrayList<String>(names.size()); |
| // Construct the result |
| for (String name : names) { |
| String networkLocation = cache.get(name); |
| if (networkLocation != null) { |
| result.add(networkLocation); |
| } else { |
| return null; |
| } |
| } |
| return result; |
| } |
| |
| @Override |
| 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; |
| } |
| |
| List<String> uncachedHosts = getUncachedHosts(names); |
| |
| // Resolve the uncached hosts |
| List<String> resolvedHosts = rawMapping.resolve(uncachedHosts); |
| //cache them |
| cacheResolvedHosts(uncachedHosts, resolvedHosts); |
| //now look up the entire list in the cache |
| return getCachedHosts(names); |
| |
| } |
| |
| /** |
| * Get the (host x switch) map. |
| * @return a copy of the cached map of hosts to rack |
| */ |
| @Override |
| public Map<String, String> getSwitchMap() { |
| Map<String, String > switchMap = new HashMap<String, String>(cache); |
| return switchMap; |
| } |
| |
| |
| @Override |
| public String toString() { |
| return "cached switch mapping relaying to " + rawMapping; |
| } |
| |
| /** |
| * Delegate the switch topology query to the raw mapping, via |
| * {@link AbstractDNSToSwitchMapping#isMappingSingleSwitch(DNSToSwitchMapping)} |
| * @return true iff the raw mapper is considered single-switch. |
| */ |
| @Override |
| public boolean isSingleSwitch() { |
| return isMappingSingleSwitch(rawMapping); |
| } |
| |
| @Override |
| public void reloadCachedMappings() { |
| cache.clear(); |
| } |
| |
| @Override |
| public void reloadCachedMappings(List<String> names) { |
| for (String name : names) { |
| cache.remove(name); |
| } |
| } |
| } |