| /** |
| * 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 com.twitter.distributedlog.service.streamset; |
| |
| import java.util.concurrent.ConcurrentHashMap; |
| import java.util.concurrent.ConcurrentMap; |
| |
| public abstract class CacheableStreamPartitionConverter implements StreamPartitionConverter { |
| |
| private final ConcurrentMap<String, Partition> partitions; |
| |
| protected CacheableStreamPartitionConverter() { |
| this.partitions = new ConcurrentHashMap<String, Partition>(); |
| } |
| |
| @Override |
| public Partition convert(String streamName) { |
| Partition p = partitions.get(streamName); |
| if (null != p) { |
| return p; |
| } |
| // not found |
| Partition newPartition = newPartition(streamName); |
| Partition oldPartition = partitions.putIfAbsent(streamName, newPartition); |
| if (null == oldPartition) { |
| return newPartition; |
| } else { |
| return oldPartition; |
| } |
| } |
| |
| /** |
| * Create the partition from <code>streamName</code>. |
| * |
| * @param streamName |
| * stream name |
| * @return partition id of the stream |
| */ |
| protected abstract Partition newPartition(String streamName); |
| } |