johnny2002 commented on issue #1720:
URL:
https://github.com/apache/shardingsphere-elasticjob/issues/1720#issuecomment-727561219
Here is my sample strategy :
```java
/**
* @author WeiZhou
*
* shardingTotalCount should be as same as JobInstances count.
* Neighbor 2 JobInstances backup eachother.
* Each partition will be assigned to same Jobinstance number or its backup.
* shardingTotalCount和jobInstances数量要一样.
* 相邻两个JobInstances互相备份.
* 每个作业分片要分配给相同号码的JobInstance或是它的备份单元
*/
@Slf4j
public class UnitizedAllocationJobShardingStrategy implements
JobShardingStrategy {
int[] backupMap = new int[] { 2, 1, 4, 3, 6, 5, 8, 7 };//Unit 1<>2,
3<>4, 5<>6, 7<>8 backup eachother
@Override
public Map<JobInstance, List<Integer>> sharding(final List<JobInstance>
jobInstances, final String jobName, final int shardingTotalCount) {
if (jobInstances.isEmpty()) {
return Collections.emptyMap();
}
JobInstance[] instArray = new JobInstance[shardingTotalCount];
for (JobInstance jobInst : jobInstances) {
//Job instance IDs like xxx@-@001, xxx@-@002, xxx@-@003 ...
String jobInstanceId = jobInst.getJobInstanceId();
jobInstanceId =
jobInstanceId.substring(jobInstanceId.indexOf(JobInstance.DELIMITER) +
JobInstance.DELIMITER.length());
int jobInstNum = Integer.parseInt(jobInstanceId);
instArray[jobInstNum - 1] = jobInst;
}
Map<JobInstance, List<Integer>> result = new
LinkedHashMap<>(jobInstances.size(), 1);
for (int i = 0; i < shardingTotalCount; i++) {
//looup same number JobInstance
JobInstance locatedJobInst = instArray[i];
log.debug("master of {} is {}", i, locatedJobInst);
if (locatedJobInst == null) {
//lookup backup JobInstance
if (backupMap[i] - 1 >= instArray.length ||
instArray[backupMap[i] - 1] == null) {
throw new RuntimeException("No main or backup job
executor found for unit:" + (i + 1) + ", backup unit:" + backupMap[i]);
}
locatedJobInst = instArray[backupMap[i] - 1];
log.debug("backup of {} is {}", i, locatedJobInst);
}
List<Integer> parts = result.get(locatedJobInst);
if (parts == null) {
parts = new ArrayList<>(2);
result.put(locatedJobInst, parts);
}
parts.add(i);
}
return result;
}
@Override
public String getType() {
return "UNIT_ALLOCATION";
}
}
```
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