| /* |
| * 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 com.google.common.base.Joiner; |
| import 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<String, Count> 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); |
| } |
| } |