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Use a copy of the new best possible assignment for measuring baseline divergence #542

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Merged
jiajunwang merged 1 commit into from
Oct 31, 2019
Merged

Use a copy of the new best possible assignment for measuring baseline divergence #542

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8 changes: 7 additions & 1 deletion helix-core/src/main/java/org/apache/helix/controller/rebalancer/waged/WagedRebalancer.java
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Original file line number Diff line number Diff line change
Expand Up @@ -401,11 +401,17 @@ private Map<String, ResourceAssignment> partialRebalance(

// Asynchronously report baseline divergence metric before persisting to metadata store,
// just in case if persisting fails, we still have the metric.
// To avoid changes of the new assignment and make it safe when being used to measure baseline
// divergence, use a deep copy of the new assignment.
Map<String, ResourceAssignment> newAssignmentCopy = new HashMap<>();
for (Map.Entry<String, ResourceAssignment> entry : newAssignment.entrySet()) {
newAssignmentCopy.put(entry.getKey(), new ResourceAssignment(entry.getValue().getRecord()));
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@huizhilu huizhilu Oct 29, 2019

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Luckily we have

new ResourceAssignment(ZNRecord)

which is creating a deep copy of a resource assignment.

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@huizhilu huizhilu Oct 29, 2019 •
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ZNRecord has mapFields which is a nested map: Map<String, Map<String, String>>. Caling putAll doesn't do deep copy. Still have to do deep copy manually.
If we can do deep copy for #549, we can keep this code.

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@narendly narendly Oct 29, 2019

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Using a copy constructor works.

}
BaselineDivergenceGauge baselineDivergenceGauge = _metricCollector.getMetric(
WagedRebalancerMetricCollector.WagedRebalancerMetricNames.BaselineDivergenceGauge.name(),
BaselineDivergenceGauge.class);
baselineDivergenceGauge.asyncMeasureAndUpdateValue(clusterData.getAsyncTasksThreadPool(),
currentBaseline, newAssignment);
currentBaseline, newAssignmentCopy);

if (_assignmentMetadataStore != null) {
try {
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