dongzhonghua opened a new pull request, #24954:
URL: https://github.com/apache/pulsar/pull/24954
### Motivation
AvgShedder encounter Exception when sort broker by scores.
```
2025-11-05T17:11:24,894+0800 [pulsar-load-manager-1-1] WARN
org.apache.pulsar.broker.loadbalance.LoadSheddingTask.run(LoadSheddingTask.java:59)
- Error during the load shedding
java.lang.IllegalArgumentException: Comparison method violates its general
contract!
at java.base/java.util.TimSort.mergeHi(TimSort.java:903) ~[?:?]
at java.base/java.util.TimSort.mergeAt(TimSort.java:520) ~[?:?]
at java.base/java.util.TimSort.mergeForceCollapse(TimSort.java:461)
~[?:?]
at java.base/java.util.TimSort.sort(TimSort.java:254) ~[?:?]
at java.base/java.util.Arrays.sort(Arrays.java:1307) ~[?:?]
at
java.base/java.util.stream.SortedOps$SizedRefSortingSink.end(SortedOps.java:353)
~[?:?]
at
java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:510)
~[?:?]
at
java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499)
~[?:?]
at
java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:575)
~[?:?]
at
java.base/java.util.stream.AbstractPipeline.evaluateToArrayNode(AbstractPipeline.java:260)
~[?:?]
at
java.base/java.util.stream.ReferencePipeline.toArray(ReferencePipeline.java:616)
~[?:?]
at
java.base/java.util.stream.ReferencePipeline.toArray(ReferencePipeline.java:622)
~[?:?]
at
java.base/java.util.stream.ReferencePipeline.toList(ReferencePipeline.java:627)
~[?:?]
at
org.apache.pulsar.broker.loadbalance.impl.AvgShedder.calculateScoresAndSort(AvgShedder.java:228)
~[org.apache.pulsar-pulsar-broker-3.3.6.13-kwai.jar:3.3.6.13-kwai]
at
org.apache.pulsar.broker.loadbalance.impl.AvgShedder.findBundlesForUnloading(AvgShedder.java:79)
~[org.apache.pulsar-pulsar-broker-3.3.6.13-kwai.jar:3.3.6.13-kwai]
at
org.apache.pulsar.broker.loadbalance.impl.ModularLoadManagerImpl.doLoadShedding(ModularLoadManagerImpl.java:652)
~[org.apache.pulsar-pulsar-broker-3.3.6.13-kwai.jar:3.3.6.13-kwai]
at
org.apache.pulsar.broker.loadbalance.impl.ModularLoadManagerWrapper.doLoadShedding(ModularLoadManagerWrapper.java:52)
~[org.apache.pulsar-pulsar-broker-3.3.6.13-kwai.jar:3.3.6.13-kwai]
at
org.apache.pulsar.broker.loadbalance.LoadSheddingTask.run(LoadSheddingTask.java:57)
~[org.apache.pulsar-pulsar-broker-3.3.6.13-kwai.jar:3.3.6.13-kwai]
at
java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:539)
~[?:?]
at
java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264) ~[?:?]
at
java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:304)
~[?:?]
at
java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
~[?:?]
at
java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
~[?:?]
at
io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
~[io.netty-netty-common-4.1.119.Final.jar:4.1.119.Final]
at java.base/java.lang.Thread.run(Thread.java:833) [?:?]
```
```
private List<String> calculateScoresAndSort(LoadData loadData,
ServiceConfiguration conf) {
brokerScoreMap.clear();
// calculate scores of brokers.
for (Map.Entry<String, BrokerData> entry :
loadData.getBrokerData().entrySet()) {
LocalBrokerData localBrokerData =
entry.getValue().getLocalData();
String broker = entry.getKey();
Double score = calculateScores(localBrokerData, conf);
brokerScoreMap.put(broker, score);
if (log.isDebugEnabled()) {
log.info("broker:{}, scores:{}, throughput:{},
messageRate:{}", broker, score,
localBrokerData.getMsgThroughputIn() +
localBrokerData.getMsgThroughputOut(),
localBrokerData.getMsgRateIn() +
localBrokerData.getMsgRateOut());
}
}
// sort brokers by scores.
return brokerScoreMap.entrySet().stream().sorted((o1, o2) -> (int)
(o1.getValue() - o2.getValue()))
.map(Map.Entry::getKey).toList();
}
```
There is why:
Double value `o1.getValue() - o2.getValue()` cast to int wil loss precision
and break violation of transitivity.
For example:
brokerScoreMap.put("X", 0.999);
brokerScoreMap.put("Y", 1.0);
brokerScoreMap.put("Z", 1.999);
(int)(0.999 - 1.0) = (int)(-0.001) = 0 → X == Y
(int)(1.0 - 1.999) = (int)(-0.999) = 0 → Y == Z
(int)(0.999 - 1.999) = (int)(-1.0) = -1 → X < Z
### Modifications
Fix double cost to int. Use `Comparator.comparingDouble`
### Documentation
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