[Feature] PVC Expansion Support for StarRocks Kubernetes Operator #655

dengliu · 2025-06-17T06:19:52Z

Description

This PR implements comprehensive PVC (Persistent Volume Claim) expansion support for the StarRocks Kubernetes operator, enabling users to expand storage volumes for FE, BE, and CN components without data loss.

✨ Key Features

🔧 Core Functionality

Automatic PVC Expansion: Detects storage size increases and expands PVCs automatically
Storage Class Validation: Validates that storage classes support volume expansion (allowVolumeExpansion: true)
Conservative Safety: Defaults to offline expansion for unknown storage classes to prevent data corruption
Smart StatefulSet Management: Minimizes disruption by intelligently handling StatefulSet updates

🛡️ Safety Features

Size Reduction Prevention: Validates against storage size decreases
Data Preservation: All data is preserved during expansion (PVCs are never deleted)
Detachment Detection: Automatically detects when storage classes require PVC detachment
Comprehensive Validation: Multiple validation layers prevent dangerous operations

⚡ Performance Optimizations

Zero-Downtime Expansion: For size-only changes with online-capable storage classes
Minimal Disruption: Only recreates StatefulSets when absolutely necessary
Intelligent Decision Making: Chooses optimal expansion strategy based on change scope and storage capabilities

🔄 Expansion Strategies

The operator implements three intelligent expansion strategies:

Scenario	Strategy	Downtime	Description
Size-only + Online Storage	Direct PVC expansion	None	Expands PVCs without touching StatefulSet
Size-only + Offline Storage	Offline expansion	Minimal	Deletes StatefulSet → Expands PVCs → Recreates StatefulSet
Mixed Changes	Safe recreation	Necessary	Deletes StatefulSet → Expands PVCs → Recreates with all changes

🧪 Testing

Comprehensive Test Coverage

Unit Tests: 15+ test cases covering all expansion scenarios
Integration Tests: Automated test script for real cluster validation
E2E Tests: End-to-end testing with actual Kubernetes resources
Edge Case Testing: Storage class validation, size reduction prevention, detachment scenarios

Test Results

$ go test ./pkg/k8sutils/... -v
=== RUN   TestDetectPVCExpansion
=== RUN   TestExpandPVCs  
=== RUN   TestValidateStorageClassExpansion
=== RUN   TestCheckStorageClassRequiresDetachment
--- PASS: All tests (0.366s)

🔍 Technical Implementation

Key Components

PVC Expansion Detection

type PVCExpansionResult struct {
    NeedsExpansion             bool
    NeedsStatefulSetRecreation bool
    RequiresDetachment         bool
    OnlyPVCSizeChanged         bool
    PVCsToExpand               []PVCExpansionInfo
    ValidationErrors           []string
}

Storage Class Validation

Validates allowVolumeExpansion: true before attempting expansion
Maintains whitelist of known-safe online expansion provisioners
Conservative default: unknown storage classes use offline expansion

Smart StatefulSet Management

Detects scope of changes (size-only vs. mixed)
Avoids VolumeClaimTemplate immutability errors
Reuses existing StatefulSet recreation logic for consistency

🛡️ Safety Guarantees

Data Protection

✅ PVCs are never deleted - only expanded
✅ Size reduction prevention - validates against dangerous operations
✅ Storage class validation - ensures expansion is supported
✅ Conservative defaults - prefers safety over convenience

Operational Safety

✅ Graceful StatefulSet recreation - proper pod termination and PVC detachment
✅ Comprehensive error handling - clear error messages and recovery guidance
✅ Rollback safety - failed expansions don't corrupt existing data

📖 Documentation

Please list any related issues and link them here.

#121

Checklist

For operator, please complete the following checklist:

run make generate to generate the code.
run golangci-lint run to check the code style.
run make test to run UT.
run make manifests to update the yaml files of CRD.

For helm chart, please complete the following checklist:

make sure you have updated the values.yaml
file of starrocks chart.
In scripts directory, run bash create-parent-chart-values.sh to update the values.yaml file of the parent
chart( kube-starrocks chart).

Signed-off-by: Deng Liu <[email protected]>

yandongxiao · 2025-06-30T11:42:51Z

Thank you very much for submitting such an important Feature again. If this feature can be used as a switch option, I think it would be better for existing users.

yandongxiao · 2025-06-27T07:01:45Z

doc/pvc_expansion_howto.md

+
+1. **Storage Class Support**: Your storage class must support volume expansion
+2. **Kubernetes Version**: Kubernetes 1.11+ (for PVC expansion support)
+3. **Operator Version**: StarRocks operator v1.9.9+ (with PVC expansion feature)


Now the newest version is v1.10.2.

yandongxiao · 2025-06-30T10:59:34Z

pkg/k8sutils/k8sutils.go

+				return nil
+			} else {
+				// PVC sizes + other changes - delete StatefulSet first, then expand PVCs, then recreate
+				logger.Info("PVC expansion with other StatefulSet changes, will delete StatefulSet first for safe expansion", "count", len(expansionResult.PVCsToExpand))


The are some errors reported by golangci-lint, please see https://github.com/StarRocks/starrocks-kubernetes-operator/actions/runs/15699899736/job/44232198023?pr=655

yandongxiao · 2025-06-30T11:04:13Z

pkg/k8sutils/k8sutils.go


+// ApplyStatefulSetWithPVCExpansion applies a StatefulSet with support for PVC expansion.
+// It detects when PVC sizes need to be expanded and handles the expansion process.
+func ApplyStatefulSetWithPVCExpansion(ctx context.Context, k8sClient client.Client, expect *appv1.StatefulSet,


Can we provide a command - line argument for the operator as an optional feature? That is, by default, the operator still directly calls ApplyStatefulSet. When the operator is launched with a certain parameter, for example, --with- pvc-expansion, then the operator calls ApplyStatefulSetWithPVCExpansion.

yandongxiao · 2025-06-30T11:14:43Z

pkg/k8sutils/k8sutils.go

+}
+
+// waitForStatefulSetDeletion waits for a StatefulSet to be fully deleted
+func waitForStatefulSetDeletion(ctx context.Context, k8sClient client.Client, namespace, name string) error {


According to my tests, deleting a StatefulSet is a very quick action and does not require loop waiting. If you need to wait for the POD to be deleted, the logic of waiting for five minutes is a bit imprecise. If it returns due to timeout, the operator will fail before Step 3: Wait for PVCs to be fully detached

yandongxiao · 2025-06-30T11:29:20Z

pkg/k8sutils/pvc_expansion.go

+	}
+
+	// Step 3: Wait for PVCs to be fully detached
+	err = waitForPVCsDetached(ctx, k8sClient, expansionInfos)


If waitForPVCsDetached fails, it will cause the expansion of PVC to fail and the creation of the Statefulset object to fail. Then, the Operator will rebuild the Statefulset object in the subsequent reconciliation. However, there will be the following error: The storage size set in StarRocksCluster is equal to the storage size set in the Statefulset. But the value set in the PVC has not changed at all.

yandongxiao · 2025-06-30T11:32:13Z

pkg/k8sutils/pvc_expansion.go

+	err := k8sClient.Get(ctx, types.NamespacedName{
+		Namespace: namespace,
+		Name:      statefulSetName,
+	}, &sts)


There will be an situation: The storage size set in StarRocksCluster is equal to the storage size set in the Statefulset. But the value set in the PVC has not changed at all.
So I think check the existing Statefulset is not enough.

yandongxiao · 2025-06-30T11:34:45Z

pkg/k8sutils/pvc_expansion.go

+	}
+
+	// Step 5: Wait for PVC expansion to complete
+	err = waitForPVCExpansionComplete(ctx, k8sClient, expansionInfos)


If the PVC Expansion has not been completed and a timeout occurs, what problems will occur if the newly created POD is attached to the PVC?

In addition, there is a situation where although the Operator has executed the ExpandPVCs operation, Kubernetes has not started the Expansion, and the Operator may mistakenly think that the Expand has been successful.

yandongxiao · 2025-06-30T11:39:20Z

helm-charts/charts/kube-starrocks/charts/starrocks/templates/_helpers.tpl

+{{- fail (printf "Log storage size cannot be zero for %s component: %s" $component $logStorageSize) -}}
+{{- end -}}
+{{- if and $spillStorageSize (regexMatch "^0" $spillStorageSize) -}}
+{{- fail (printf "Spill storage size cannot be zero for %s component: %s" $component $spillStorageSize) -}}


Setting the storage size to 0 is no longer allowed here. This conflicts with the behavior of the Operator. Please refer to

starrocks-kubernetes-operator/helm-charts/charts/kube-starrocks/values.yaml

Line 481 in b1153db

# If you set it to 0Gi, the related PVC will not be created, and the log will not be persisted.

yandongxiao · 2025-06-30T11:40:09Z

pkg/k8sutils/k8sutils.go

+	// Delete the StatefulSet immediately since VolumeClaimTemplates are immutable
+	// This is more efficient than scaling to 0 first
+	logger.Info("deleting StatefulSet to update VolumeClaimTemplates")
+	err = k8sClient.Delete(ctx, &current)


Do we need to adjust the RBAC configuration of Operator?

CLAassistant · 2025-09-17T22:44:50Z

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.

Deng Liu seems not to be a GitHub user. You need a GitHub account to be able to sign the CLA. If you have already a GitHub account, please add the email address used for this commit to your account.
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dengliu changed the title ~~[Feature] PVC expansion~~ [Feature] PVC Expansion Support for StarRocks Kubernetes Operator Jun 17, 2025

Deng Liu added 2 commits June 16, 2025 23:30

[Feature] PVC expansion

c44a23b

Signed-off-by: Deng Liu <[email protected]>

update

888632e

Signed-off-by: Deng Liu <[email protected]>

dengliu force-pushed the dliu/pvcexpansion branch from 2543e60 to 888632e Compare June 17, 2025 06:30

kevincai self-requested a review June 17, 2025 09:21

yandongxiao requested changes Jun 30, 2025

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[Feature] PVC Expansion Support for StarRocks Kubernetes Operator #655

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Description

✨ Key Features

🔧 Core Functionality

🛡️ Safety Features

⚡ Performance Optimizations

🔄 Expansion Strategies

🧪 Testing

Comprehensive Test Coverage

Test Results

🔍 Technical Implementation

Key Components

PVC Expansion Detection

Storage Class Validation

Smart StatefulSet Management

🛡️ Safety Guarantees

Data Protection

Operational Safety

📖 Documentation

Checklist

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yandongxiao commented Jun 30, 2025

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CLAassistant commented Sep 17, 2025

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dengliu commented Jun 17, 2025 •

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