Ability to trigger auto rebalance on imbalance feature by ShubhamRwt · Pull Request #13037 · strimzi/strimzi-kafka-operator

ShubhamRwt · 2026-08-07T09:15:58Z

Type of change

New feature

Description

This PR implements the proposal auto-rebalance-on-imbalance. This feature allows the operator to trigger rebalance automatically in case their are some imbalance in the cluster

Checklist

Please go through this checklist and make sure all applicable tasks have been done

Update documentation
Update CHANGELOG.md (if present)
Reference relevant issue(s) and close them after merging
Write tests
Make sure all tests pass
Try your changes inside a Kubernetes cluster, not just from unit tests
AI assistance was used to create this PR (see the Strimzi AI policy)

Signed-off-by: ShubhamRwt <[email protected]>

snyk-io · 2026-08-07T09:16:06Z

✅ Snyk checks have passed. No issues have been found so far.

Status	Scan Engine	Critical	High	Medium	Low	Total (0)
✅	Open Source Security	0	0	0	0	0 issues
✅	Licenses	0	0	0	0	0 issues
✅	Code Security	0	0	0	0	0 issues

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Signed-off-by: ShubhamRwt <[email protected]>

ppatierno · 2026-08-10T11:37:15Z

@ShubhamRwt can we get a green build before starting for an early review please? Failure are around the CruiseControlReconciler so maybe something to fix in the logic before taking a look. Thanks :-)

Signed-off-by: ShubhamRwt <[email protected]>

codecov · 2026-08-10T12:40:28Z

Codecov Report

❌ Patch coverage is 62.32295% with 133 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.05%. Comparing base (8721743) to head (d2bb3e8).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
.../assembly/KafkaAutoRebalanceImbalanceDetector.java	53.91%	38 Missing and 15 partials ⚠️
...rator/assembly/KafkaAutoRebalancingReconciler.java	76.22%	25 Missing and 9 partials ⚠️
...r/resource/cruisecontrol/CruiseControlApiImpl.java	50.00%	19 Missing and 12 partials ⚠️
...imzi/operator/common/metrics/AnomalyMetricKey.java	0.00%	10 Missing ⚠️
...urce/cruisecontrol/CruiseControlStateResponse.java	50.00%	1 Missing and 1 partial ⚠️
.../strimzi/operator/cluster/model/CruiseControl.java	50.00%	0 Missing and 1 partial ⚠️
...uster/operator/assembly/KafkaAssemblyOperator.java	0.00%	1 Missing ⚠️
...strimzi/operator/common/metrics/MetricsHolder.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #13037      +/-   ##
============================================
- Coverage     80.35%   80.05%   -0.31%     
- Complexity     6532     6594      +62     
============================================
  Files           343      346       +3     
  Lines         22731    23024     +293     
  Branches       3085     3117      +32     
============================================
+ Hits          18265    18431     +166     
- Misses         3253     3340      +87     
- Partials       1213     1253      +40

Files with missing lines	Coverage Δ
...r/assembly/KafkaAssemblyOperatorMetricsHolder.java	`100.00% <100.00%> (ø)`
...rator/assembly/KafkaRebalanceAssemblyOperator.java	`82.13% <ø> (ø)`
...perator/assembly/KafkaRebalanceConfigMapUtils.java	`83.33% <100.00%> (ø)`
...ator/resource/cruisecontrol/GoalViolationInfo.java	`100.00% <100.00%> (ø)`
.../strimzi/operator/cluster/model/CruiseControl.java	`91.92% <50.00%> (-0.89%)`	⬇️
...uster/operator/assembly/KafkaAssemblyOperator.java	`84.11% <0.00%> (-0.37%)`	⬇️
...strimzi/operator/common/metrics/MetricsHolder.java	`30.18% <0.00%> (-0.59%)`	⬇️
...urce/cruisecontrol/CruiseControlStateResponse.java	`71.42% <50.00%> (-28.58%)`	⬇️
...imzi/operator/common/metrics/AnomalyMetricKey.java	`0.00% <0.00%> (ø)`
...r/resource/cruisecontrol/CruiseControlApiImpl.java	`69.25% <50.00%> (-6.06%)`	⬇️
... and 2 more

... and 5 files with indirect coverage changes

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ShubhamRwt · 2026-08-10T12:52:24Z

@ppatierno All the tests seems to be passing now

ppatierno

@ShubhamRwt I had a first quick pass but it needs more detailed review.

ppatierno · 2026-08-13T12:28:28Z

-                    "been changed to match the specified default goals.");
+        // If the user has not explicitly configured anomaly detection goals, default them to the default anomaly detection goals
+        if (configuration.getConfigOption(CruiseControlConfigurationParameters.ANOMALY_DETECTION_CONFIG_KEY.toString()) == null) {
+            configuration.setConfigOption(CruiseControlConfigurationParameters.ANOMALY_DETECTION_CONFIG_KEY.toString(), CRUISE_CONTROL_DEFAULT_ANOMALY_DETECTION_GOALS);


why the previous logic changed so heavily. Weren't we checking that anomaly detection goals should be in the default goals as well otherwise CC fails on startup? I see this logic now removed.

ppatierno · 2026-08-13T12:29:33Z

        private Map<String, ResourceRequirements> kafkaBrokerResources;
        // needed to take information for the auto-rebalancing on scaling via Cruise Control
-        private Set<Integer> scalingDownBlockedNodes;
+        Set<Integer> scalingDownBlockedNodes;


why not private anymore?

ppatierno · 2026-08-13T13:33:30Z

+     * @return Future with boolean indicating if rebalance should be triggered
+     */
+    public CompletionStage<Boolean> shouldTriggerRebalance(Instant detectionDate) {
+        String configMapName = reconciliation.name() + KafkaAutoRebalancingReconciler.AUTO_REBALANCE_IMBALANCE_TRACKER_SUFFIX;


we can avoid this additional variable.

ppatierno · 2026-08-13T13:35:25Z

+                "RackAwareGoal",
+                "MinTopicLeadersPerBrokerGoal",
+                "ReplicaCapacityGoal",
+                "DiskCapacityGoal"


why do we have these hard-coded here, should we have them somewhere in the Cruise Control api classes, IIRC we have some default constants there?

I was referring to CruiseControlConfiguration.CRUISE_CONTROL_DEFAULT_ANOMALY_DETECTION_GOALS

ppatierno · 2026-08-13T13:41:45Z

+                    .onComplete(v -> kafkaStatus.setAutoRebalance(kafkaAutoRebalanceStatus));
+        }
+
+        return Future.<Boolean>fromCompletionStage(imbalanceDetector.validateTemplateGoals())


I see this pattern of using fromCompletionStage motsly everywhere when you have calls coming from the detector. I think it means that all detector methods are badly declared returning a CompletionStage while they should return a CompletableFuture instead.

ppatierno · 2026-08-13T13:43:29Z

        return kafkaRebalance.getStatus();
    }

+


remove this blank line, so this file won't change :-)

ppatierno · 2026-08-13T13:44:43Z

-                        .withParameter(CruiseControlParameters.JSON, "true")
-                        .withParameter(CruiseControlParameters.FETCH_COMPLETE, "true");
+                .withParameter(CruiseControlParameters.JSON, "true")
+                .withParameter(CruiseControlParameters.FETCH_COMPLETE, "true");


why this change? Even for the others below, why changing the indentation? I think something different in your IDE?

Yeah, I have some formatting filter in my IDE, I will fix these

ppatierno · 2026-08-14T12:57:48Z

+        } else if (ex.getCause() instanceof RuntimeException) {
            return (RuntimeException) ex.getCause();
+        } else {
+            // Wrap checked exceptions (like IOException) in RuntimeException


the comment says wrapping into RuntimeException but the code is wrapping into CruiseControlRetriableConnectionException.

ppatierno · 2026-08-14T13:05:54Z

+     *
+     * @return  Future which completes when the check is done
+     */
+    private Future<Void> maybeCheckForImbalance(ScalingNodes scalingNodes, KafkaStatus kafkaStatus) {


I don't get why the check for imbalance method needs the scalingNodes. I think this could be handled outside of it within the reconcile? I don't expect this method to call maybeRebalance internally by providing the scalingNodes. I don't have a solution right now to provide but maybe we could re-arrange the code to be more understandable.

ppatierno · 2026-08-14T13:09:43Z

+                "RackAwareGoal",
+                "MinTopicLeadersPerBrokerGoal",
+                "ReplicaCapacityGoal",
+                "DiskCapacityGoal"


I was referring to CruiseControlConfiguration.CRUISE_CONTROL_DEFAULT_ANOMALY_DETECTION_GOALS

Added auto rebalance on imbalance feature

54f8672

Signed-off-by: ShubhamRwt <[email protected]>

scholzj added this to the 1.3.0 milestone Aug 7, 2026

Fix tests

f2b73d5

Signed-off-by: ShubhamRwt <[email protected]>

Fix tests

d2bb3e8

Signed-off-by: ShubhamRwt <[email protected]>

ppatierno reviewed Aug 13, 2026

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ppatierno reviewed Aug 14, 2026

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ShubhamRwt commented Aug 7, 2026

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ppatierno commented Aug 10, 2026

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codecov Bot commented Aug 10, 2026

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ShubhamRwt commented Aug 10, 2026

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snyk-io Bot commented Aug 7, 2026 •

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