org.apache.activemq.artemis.core.server.balancing.policies.ConsistentHashPolicy Maven / Gradle / Ivy
/**
* 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.activemq.artemis.core.server.balancing.policies;
import org.apache.activemq.artemis.core.server.balancing.targets.Target;
import java.util.List;
import java.util.Map;
import java.util.NavigableMap;
import java.util.TreeMap;
public class ConsistentHashPolicy extends AbstractPolicy {
public static final String NAME = "CONSISTENT_HASH";
public ConsistentHashPolicy() {
super(NAME);
}
protected ConsistentHashPolicy(String name) {
super(name);
}
@Override
public Target selectTarget(List targets, String key) {
if (targets.size() > 1) {
NavigableMap consistentTargets = new TreeMap<>();
for (Target target : targets) {
consistentTargets.put(getHash(target.getNodeID()), target);
}
if (consistentTargets.size() > 0) {
Map.Entry consistentEntry = consistentTargets.floorEntry(getHash(key));
if (consistentEntry == null) {
consistentEntry = consistentTargets.firstEntry();
}
return consistentEntry.getValue();
}
} else if (targets.size() > 0) {
return targets.get(0);
}
return null;
}
private int getHash(String str) {
final int FNV_INIT = 0x811c9dc5;
final int FNV_PRIME = 0x01000193;
int hash = FNV_INIT;
for (int i = 0; i < str.length(); i++) {
hash = (hash ^ str.charAt(i)) * FNV_PRIME;
}
return hash;
}
}