| /** |
| * 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.balancer; |
| |
| /** |
| * A stream chooser that can only choose limited number of streams. |
| */ |
| public class LimitedStreamChooser implements StreamChooser { |
| |
| /** |
| * Create a limited stream chooser by {@code limit}. |
| * |
| * @param underlying the underlying stream chooser. |
| * @param limit the limit of number of streams to choose. |
| * @return the limited stream chooser. |
| */ |
| public static LimitedStreamChooser of(StreamChooser underlying, int limit) { |
| return new LimitedStreamChooser(underlying, limit); |
| } |
| |
| final StreamChooser underlying; |
| int limit; |
| |
| LimitedStreamChooser(StreamChooser underlying, int limit) { |
| this.underlying = underlying; |
| this.limit = limit; |
| } |
| |
| @Override |
| public synchronized String choose() { |
| if (limit <= 0) { |
| return null; |
| } |
| String s = underlying.choose(); |
| if (s == null) { |
| limit = 0; |
| return null; |
| } |
| --limit; |
| return s; |
| } |
| } |