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Posted to dev@eventmesh.apache.org by GitBox <gi...@apache.org> on 2021/11/23 03:07:45 UTC
[GitHub] [incubator-eventmesh] lrhkobe opened a new pull request #605: Develop
lrhkobe opened a new pull request #605:
URL: https://github.com/apache/incubator-eventmesh/pull/605
Fixes **ISSUE#<>.**
### Motivation
As to the follow scene:
The cluster has 2 eventmesh instance: {EventMesh-01, EventMesh-02}
There are 100 eventmesh-client with same group distributed in eventmesh, and the distributed data is: {EventMesh-01: 75 , EventMesh-02: 25}
**The current algorithm:**
```
int sum = 0;
for(Integer item : clientDistributionMap.values()){
sum += item.intValue();
}
int currentNum = 0;
if(clientDistributionMap.get(eventMeshTCPServer.getEventMeshTCPConfiguration().eventMeshName) != null){
currentNum = clientDistributionMap.get(eventMeshTCPServer.getEventMeshTCPConfiguration().eventMeshName);
}
int avgNum = sum / clientDistributionMap.size();
int judge = avgNum >= 2 ? avgNum/2 : 1;
if(currentNum - avgNum > judge) {
...
}
```
In this scene, rebalance will not happen, because the rebalance condition is not satisfied.
As to EventMesh-01, currentNum =75, avgNum=50, judge=25 --> currentNum - avgNum > judge : false
As to EventMesh-02, currentNum =25, avgNum=50, judge=25 --> currentNum - avgNum > judge : false
Obviously, the rebalance result is not proper.
Expected Rebalance Result：{EventMesh-01: 50, EventMesh-02: 50}
**Improved algorithm:**
```
public int caculateRedirectNum(String eventMeshName, String group, String purpose, Map<String, Integer> clientDistributionMap) throws Exception{
int sum = 0;
for(Integer item : clientDistributionMap.values()){
sum += item.intValue();
}
int currentNum = 0;
if(clientDistributionMap.get(eventMeshName) != null){
currentNum = clientDistributionMap.get(eventMeshName);
}
int avgNum = sum / clientDistributionMap.size();
int modNum = sum % clientDistributionMap.size();
List<String> eventMeshList = new ArrayList<>(clientDistributionMap.keySet());
Collections.sort(eventMeshList);
int index = -1;
for(int i=0; i < Math.min(modNum, eventMeshList.size()); i++){
if(StringUtils.equals(eventMeshName, eventMeshList.get(i))){
index = i;
break;
}
}
int rebalanceResult = 0;
if(avgNum == 0){
rebalanceResult = 1;
}else {
rebalanceResult = (modNum != 0 && index < modNum && index >= 0) ? avgNum + 1 : avgNum;
}
logger.info("rebalance caculateRedirectNum,group:{}, purpose:{},sum:{},avgNum:{},modNum:{},index:{}, currentNum:{},rebalanceResult:{}", group, purpose, sum, avgNum, modNum, index, currentNum, rebalanceResult);
return currentNum - rebalanceResult;
}
```
if the num of client is less than the num of eventmesh, then choose eventmesh randomly with the same num of client;
otherwise, calculate the accurate num which current eventmesh should be allocated.
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[GitHub] [incubator-eventmesh] xwm1992 merged pull request #605: [ISSUE #604]Improve the rebalance algorithm
Posted by GitBox <gi...@apache.org>.
xwm1992 merged pull request #605:
URL: https://github.com/apache/incubator-eventmesh/pull/605
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