RoundRobinPartitionSelector.java

/*
 * (C) 2007-2012 Alibaba Group Holding Limited.
 * 
 * Licensed 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.
 * Authors:
 *   wuhua <wq163@163.com> , boyan <killme2008@gmail.com>
 */
package com.taobao.metamorphosis.client.producer;

import java.util.List;

import com.taobao.gecko.core.util.PositiveAtomicCounter;
import com.taobao.metamorphosis.Message;
import com.taobao.metamorphosis.cluster.Partition;
import com.taobao.metamorphosis.exception.MetaClientException;


/**
 * ��ѯ�ķ���ѡ������Ĭ��ʹ�ô�ѡ����
 * 
 * @author boyan
 * @Date 2011-4-26
 * 
 */
public class RoundRobinPartitionSelector extends AbstractPartitionSelector {

    private final PositiveAtomicCounter sets = new PositiveAtomicCounter();


    @Override
    public Partition getPartition0(final String topic, final List<Partition> partitions, final Message message)
            throws MetaClientException {
        try {
            return partitions.get(this.sets.incrementAndGet() % partitions.size());
        }
        catch (final Throwable t) {
            throw new MetaClientException(t);
        }
    }

}