dasahcc commented on a change in pull request #1078:
URL: https://github.com/apache/helix/pull/1078#discussion_r442418714
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File path:
helix-core/src/main/java/org/apache/helix/controller/rebalancer/waged/constraints/PartitionMovementConstraint.java
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@@ -40,31 +40,53 @@
class PartitionMovementConstraint extends SoftConstraint {
private static final double MAX_SCORE = 1f;
private static final double MIN_SCORE = 0f;
- //TODO: these factors will be tuned based on user's preference
- // This factor indicates the default score that is evaluated if only
partition allocation matches
- // (states are different).
- private static final double ALLOCATION_MATCH_FACTOR = 0.5;
+ // The scale factor to adjust score when the proposed allocation partially
matches the assignment
+ // plan but will require a state transition (with partition movement).
+ // TODO: these factors will be tuned based on user's preference
+ private static final double STATE_TRANSITION_COST_FACTOR = 0.5;
+ private static final double MOVEMENT_COST_FACTOR = 0.25;
PartitionMovementConstraint() {
super(MAX_SCORE, MIN_SCORE);
}
+ /**
+ * @return 1 if the proposed assignment completely matches the previous best
possible assignment
+ * (or baseline assignment if the replica is newly added).
+ * STATE_TRANSITION_COST_FACTOR if the proposed assignment's
allocation matches the
+ * previous Best Possible assignment (or baseline assignment if the
replica is newly
+ * added) but state does not match.
+ * MOVEMENT_COST_FACTOR if the proposed assignment's allocation
matches the baseline
+ * assignment only, but not matches the previous best possible
assignment.
+ * 0 if the proposed assignment is a pure random movement.
+ */
@Override
protected double getAssignmentScore(AssignableNode node, AssignableReplica
replica,
ClusterContext clusterContext) {
- // Prioritize the previous Best Possible assignment
Map<String, String> bestPossibleAssignment =
getStateMap(replica, clusterContext.getBestPossibleAssignment());
- if (!bestPossibleAssignment.isEmpty()) {
- return calculateAssignmentScale(node, replica, bestPossibleAssignment);
- }
- // else, compare the baseline only if the best possible assignment does
not contain the replica
Map<String, String> baselineAssignment =
getStateMap(replica, clusterContext.getBaselineAssignment());
- if (!baselineAssignment.isEmpty()) {
- return calculateAssignmentScale(node, replica, baselineAssignment);
+ String nodeName = node.getInstanceName();
+ String state = replica.getReplicaState();
+
+ if (bestPossibleAssignment.isEmpty()) {
+ // If bestPossibleAssignment of the replica is empty, indicating this is
a new replica.
+ // Then the baseline is the only reference.
+ return calculateAssignmentScore(nodeName, state, baselineAssignment);
+ } else {
+ // Else, for minimizing partition movements or state transitions,
prioritize the proposed
+ // assignment that matches the previous Best Possible assignment.
+ double score = calculateAssignmentScore(nodeName, state,
bestPossibleAssignment);
+ // If no Best Possible assignment matches, check the baseline assignment.
+ if (score == 0 && baselineAssignment.containsKey(nodeName)) {
Review comment:
If I understand it correctly, when score == 0, should this be same as
bestpossible is Empty()? Then score should be
calculateAssignmentScore(nodeName, state, baselineAssignment);
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