org.apache.hadoop.metrics2.lib.UniqueNames 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.hadoop.metrics2.lib;
import java.util.Map;
import org.apache.hadoop.thirdparty.com.google.common.base.Joiner;
import org.apache.hadoop.thirdparty.com.google.common.collect.Maps;
import org.apache.hadoop.classification.InterfaceAudience;
/**
* Generates predictable and user-friendly unique names
*/
@InterfaceAudience.Private
public class UniqueNames {
static class Count {
final String baseName;
int value;
Count(String name, int value) {
baseName = name;
this.value = value;
}
}
static final Joiner joiner = Joiner.on('-');
final Map map = Maps.newHashMap();
public synchronized String uniqueName(String name) {
Count c = map.get(name);
if (c == null) {
c = new Count(name, 0);
map.put(name, c);
return name;
}
if (!c.baseName.equals(name)) c = new Count(name, 0);
do {
String newName = joiner.join(name, ++c.value);
Count c2 = map.get(newName);
if (c2 == null) {
map.put(newName, c);
return newName;
}
// handle collisons, assume to be rare cases,
// eg: people explicitly passed in name-\d+ names.
} while (true);
}
}