org.apache.hadoop.net.CachedDNSToSwitchMapping Maven / Gradle / Ivy
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/**
* 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;
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 implements DNSToSwitchMapping {
private Map cache = new ConcurrentHashMap();
protected DNSToSwitchMapping rawMapping;
public CachedDNSToSwitchMapping(DNSToSwitchMapping rawMapping) {
this.rawMapping = rawMapping;
}
public List resolve(List names) {
// normalize all input names to be in the form of IP addresses
names = NetUtils.normalizeHostNames(names);
List result = new ArrayList(names.size());
if (names.isEmpty()) {
return result;
}
// find out all names without cached resolved location
List unCachedHosts = new ArrayList(names.size());
for (String name : names) {
if (cache.get(name) == null) {
unCachedHosts.add(name);
}
}
// Resolve those names
List rNames = rawMapping.resolve(unCachedHosts);
// Cache the result
if (rNames != null) {
for (int i=0; i