jiajunwang commented on a change in pull request #535: Adjust the replica
rebalance calculating ordering method to avoid a static order.
URL: https://github.com/apache/helix/pull/535#discussion_r339178844
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File path:
helix-core/src/main/java/org/apache/helix/controller/rebalancer/waged/constraints/ConstraintBasedAlgorithm.java
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@@ -159,12 +159,19 @@ private float
getAssignmentNormalizedScore(AssignableNode node, AssignableReplic
int statePriority1 = replica1.getStatePriority();
int statePriority2 = replica2.getStatePriority();
if (statePriority1 == statePriority2) {
- // If state prioritizes are the same, compare the names.
- if (resourceName1.equals(resourceName2)) {
- return
replica1.getPartitionName().compareTo(replica2.getPartitionName());
- } else {
- return resourceName1.compareTo(resourceName2);
- }
+ // If state prioritizes are the same, try to randomize the
replicas order. Otherwise,
+ // the same replicas might always be moved in the rebalance. This
is because their
+ // rebalance calculating will always happen at the critical moment
while the cluster is
+ // almost full.
+ //
+ // Note that to ensure the algorithm is deterministic with the
same inputs, do not use
+ // Random functions here. Use hashcode based on the cluster
topology information to get
+ // a controlled randomized order is good enough.
+ long replicaHash1 = Objects
Review comment:
It is java hashing based. Just a wrapper.
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