org.apache.bookkeeper.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.bookkeeper.net;
import java.util.ArrayList;
import java.util.HashMap;
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 extends AbstractDNSToSwitchMapping {
private Map cache = new ConcurrentHashMap();
/**
* 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;
}
// we'll use IP Address for these mappings.
@Override
public boolean useHostName() {
return false;
}
/**
* @param names a list of hostnames to probe for being cached
* @return the hosts from 'names' that have not been cached previously
*/
private List getUncachedHosts(List names) {
// 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);
}
}
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 uncachedHosts,
List 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 getCachedHosts(List names) {
List result = new ArrayList(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 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;
}
List uncachedHosts = getUncachedHosts(names);
// Resolve the uncached hosts
List 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 getSwitchMap() {
Map switchMap = new HashMap(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();
}
}