/*
* Copyright 1999-2015 dangdang.com.
* <p>
* 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.
* </p>
*/
package com.dangdang.ddframe.job.lite.api.strategy.impl;
import com.dangdang.ddframe.job.lite.api.strategy.JobInstance;
import com.dangdang.ddframe.job.lite.api.strategy.JobShardingStrategy;
import java.util.Collections;
import java.util.List;
import java.util.Map;
/**
* 根据作业名的哈希值奇偶数决定IP升降序算法的分片策略.
*
* <p>
* 作业名的哈希值为奇数则IP升序.
* 作业名的哈希值为偶数则IP降序.
* 用于不同的作业平均分配负载至不同的服务器.
* 如:
* 1. 如果有3台服务器, 分成2片, 作业名称的哈希值为奇数, 则每台服务器分到的分片是: 1=[0], 2=[1], 3=[].
* 2. 如果有3台服务器, 分成2片, 作业名称的哈希值为偶数, 则每台服务器分到的分片是: 3=[0], 2=[1], 1=[].
* </p>
*
* @author zhangliang
*/
public final class OdevitySortByNameJobShardingStrategy implements JobShardingStrategy {
private AverageAllocationJobShardingStrategy averageAllocationJobShardingStrategy = new AverageAllocationJobShardingStrategy();
@Override
public Map<JobInstance, List<Integer>> sharding(final List<JobInstance> jobInstances, final String jobName, final int shardingTotalCount) {
long jobNameHash = jobName.hashCode();
if (0 == jobNameHash % 2) {
Collections.reverse(jobInstances);
}
return averageAllocationJobShardingStrategy.sharding(jobInstances, jobName, shardingTotalCount);
}
}