jiajunwang commented on a change in pull request #651: Improve the algorithm so
it prioritizes the assignment to the idle nodes when the constraint evaluation
results are the same
URL: https://github.com/apache/helix/pull/651#discussion_r356812688
##########
File path:
helix-core/src/main/java/org/apache/helix/controller/rebalancer/waged/constraints/ConstraintBasedAlgorithm.java
##########
@@ -113,8 +112,24 @@ public OptimalAssignment calculate(ClusterModel
clusterModel) throws HelixRebala
return candidateNodes.parallelStream().map(node -> new
HashMap.SimpleEntry<>(node,
getAssignmentNormalizedScore(node, replica, clusterContext)))
- .max(Comparator.comparingDouble((scoreEntry) -> scoreEntry.getValue()))
- .map(Map.Entry::getKey);
+ .max((nodeEntry1, nodeEntry2) -> {
+ int scoreCompareResult =
nodeEntry1.getValue().compareTo(nodeEntry2.getValue());
+ if (scoreCompareResult == 0) {
+ // If the evaluation scores of 2 nodes are the same, the algorithm
assigns the replica
+ // to the idle node first.
+ boolean isNodeOneIdle =
Review comment:
That logic will be different, note that the score is still the most
important thing. If I change it as you suggested, the busy node will always win
regardless of the score. As I explained to you earlier, this should only change
the behavior when the evaluation cannot tell the difference between 2 nodes.
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