backend: loading: Fix in-cluster kubeconfig panic and errors by dibyanshu-pal-kushwaha · Pull Request #4428 · kubernetes-sigs/headlamp

dibyanshu-pal-kushwaha · 2026-01-23T09:56:47Z

This PR fixes a bug where running Headlamp in-cluster caused a panic and generated misleading "no such file or directory" error logs when no kubeconfig was present.

Related Issue
related #4401

Changes
1.backend/cmd/headlamp.go:
-Added a nil check for the in-cluster context to prevent a panic when context loading fails (e.g. missing environment variables).
-Added a fileExists check before loading the dynamic cluster config file to suppress error logs on fresh installations where this file does not yet exist.
2.backend/pkg/kubeconfig/kubeconfig.go
-Updated LoadContextsFromMultipleFiles to skip empty strings in the kubeconfig path list, preventing errors like open : no such file.
3.backend/pkg/kubeconfig/kubeconfig_test.go :
-added regression for empty kubeconfig string and fix ClusterID MD5 in TestLoadContextsFromFile

Steps to Test
1.Build the backend binary: cd backend && go build -o headlamp ./cmd
2.Simulate an in-cluster environment (locally): Run: HOME=/tmp/fakehome KUBECONFIG="" timeout 5s ./headlamp -in-cluster

Screenshots (if applicable)

Notes for the Reviewer
-I verified this locally by running the binary in a clean environment as described in the testing steps.

Copilot

Pull request overview

Fixes in-cluster startup robustness by avoiding panics when in-cluster context loading fails and by reducing noisy kubeconfig “file not found” errors (especially on fresh installs without persisted dynamic kubeconfigs).

Changes:

Add nil-guard around in-cluster context setup to prevent panic when GetInClusterContext fails.
Skip loading dynamic kubeconfig persistence file when it doesn’t exist to avoid misleading error logs.
Ignore empty kubeconfig path entries when loading multiple kubeconfig files; add/adjust tests accordingly.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 5 comments.

File	Description
backend/cmd/headlamp.go	Prevents in-cluster panic and suppresses dynamic kubeconfig load errors when the persistence file is absent.
backend/pkg/kubeconfig/kubeconfig.go	Skips empty kubeconfig path entries during multi-file loading; also changes ClusterID generation logic.
backend/pkg/kubeconfig/kubeconfig_test.go	Adds regression coverage for empty kubeconfig strings and updates ClusterID expectations.

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backend/pkg/kubeconfig/kubeconfig.go

backend/pkg/kubeconfig/kubeconfig_test.go

backend/cmd/headlamp.go

illume · 2026-01-24T19:49:54Z

Please try to run the backend test locally? Its failing in the GitHub check.

dibyanshu-pal-kushwaha · 2026-01-25T10:55:15Z

@illume , I ran the all the backend tests thoroughly , It ran correctly sir for the latest changes....and I also took care of the Copilot instruction sir

Copilot

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

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Copilot · 2026-01-25T13:12:52Z

backend/cmd/headlamp.go

 // returns True if a file exists.
 func fileExists(filename string) bool {
 	info, err := os.Stat(filename)
-	if os.IsNotExist(err) {
+	if err != nil {
 		return false


PR description mentions adding a fileExists guard to avoid logging errors when the dynamic kubeconfig persistence file is missing, but this change isn’t present in createHeadlampHandler (it still unconditionally calls LoadAndStoreKubeConfigs for the persistence file). Consider either adding the existence check where the persistence file is loaded, or updating the PR description to match the actual behavior.

Agreed, this would make it easier for reviewers to understand. Or it could be a bug?

Copilot · 2026-01-25T13:12:52Z

backend/pkg/kubeconfig/kubeconfig.go

 	kubeConfigPaths := splitKubeConfigPath(kubeConfigs)
 	for _, kubeConfigPath := range kubeConfigPaths {
+		if strings.TrimSpace(kubeConfigPath) == "" {
+			continue
+		}
+
 		kubeConfigContexts, errs, err := LoadContextsFromFile(kubeConfigPath, source)
 		if err != nil {


LoadContextsFromMultipleFiles checks TrimSpace(kubeConfigPath) for emptiness, but then passes the untrimmed value to LoadContextsFromFile. If the path list contains entries with leading/trailing whitespace, this will still fail to open the file. Consider trimming once (e.g., assign kubeConfigPath = strings.TrimSpace(kubeConfigPath)) and using the trimmed value for both the emptiness check and the subsequent load.

This is a good point. Can you please consider?

Copilot · 2026-01-25T13:12:53Z

backend/pkg/kubeconfig/kubeconfig_test.go

+	t.Run("empty_file_string", func(t *testing.T) {
+		kubeConfigFile := ""
+		err := kubeconfig.LoadAndStoreKubeConfigs(contextStore, kubeConfigFile, kubeconfig.KubeConfig, nil)
+		require.NoError(t, err)
+	})


This subtest shares contextStore state with the earlier valid_file run. That makes the subtests order-dependent and doesn’t verify that the empty-string input leaves the store unchanged. Consider creating a fresh ContextStore per subtest (or clearing it) and asserting expected store contents after the call.

Agreed. It's not clear to me how this tests the issue being fixed?

Does the test fail without your other changes as it should fail?

illume

Thanks for those changes. I appreciate it.

Please run the backend:format and backend:lint checks locally? There is an error in CI with the backend lint job

I left some other comments with the copilot review. Can you please have a look?

illume · 2026-01-25T13:08:33Z

backend/pkg/kubeconfig/kubeconfig_test.go

 	require.NoError(t, err, "Expected no error for valid file")
 	require.Empty(t, contextErrors, "Expected no context errors for valid file")
-	require.Equal(t, 2, len(contexts), "Expected 3 contexts from valid file")
+	require.Equal(t, 2, len(contexts), "Expected 2 contexts from valid file")


Do you know why this is changed? Can you please add an explanation to the commit message?

Take a look at this good explanation of what to include in the commit body message:
https://chris.beams.io/git-commit#why-not-how

illume · 2026-01-25T13:16:07Z

backend/cmd/headlamp.go

 // returns True if a file exists.
 func fileExists(filename string) bool {
 	info, err := os.Stat(filename)
-	if os.IsNotExist(err) {
+	if err != nil {
 		return false


Agreed, this would make it easier for reviewers to understand. Or it could be a bug?

illume · 2026-01-25T13:17:03Z

backend/pkg/kubeconfig/kubeconfig.go

 	kubeConfigPaths := splitKubeConfigPath(kubeConfigs)
 	for _, kubeConfigPath := range kubeConfigPaths {
+		if strings.TrimSpace(kubeConfigPath) == "" {
+			continue
+		}
+
 		kubeConfigContexts, errs, err := LoadContextsFromFile(kubeConfigPath, source)
 		if err != nil {


This is a good point. Can you please consider?

illume · 2026-01-25T13:18:24Z

backend/pkg/kubeconfig/kubeconfig_test.go

+	t.Run("empty_file_string", func(t *testing.T) {
+		kubeConfigFile := ""
+		err := kubeconfig.LoadAndStoreKubeConfigs(contextStore, kubeConfigFile, kubeconfig.KubeConfig, nil)
+		require.NoError(t, err)
+	})


Agreed. It's not clear to me how this tests the issue being fixed?

Does the test fail without your other changes as it should fail?

k8s-ci-robot · 2026-02-01T10:08:17Z

PR needs rebase.

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k8s-ci-robot · 2026-02-01T10:15:51Z

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: dibyanshu-pal-kushwaha

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k8s-ci-robot requested review from skoeva and yolossn January 23, 2026 09:56

k8s-ci-robot added size/M Denotes a PR that changes 30-99 lines, ignoring generated files. cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. labels Jan 23, 2026

illume requested a review from Copilot January 24, 2026 19:33

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dibyanshu-pal-kushwaha force-pushed the fix/in-cluster-kubeconfig-loading branch 2 times, most recently from dc6fd00 to e1e1294 Compare January 25, 2026 09:16

k8s-ci-robot added size/L Denotes a PR that changes 100-499 lines, ignoring generated files. and removed size/M Denotes a PR that changes 30-99 lines, ignoring generated files. labels Jan 25, 2026

dibyanshu-pal-kushwaha force-pushed the fix/in-cluster-kubeconfig-loading branch 2 times, most recently from 2ee9444 to 5058670 Compare January 25, 2026 10:49

k8s-ci-robot added size/M Denotes a PR that changes 30-99 lines, ignoring generated files. and removed size/L Denotes a PR that changes 100-499 lines, ignoring generated files. labels Jan 25, 2026

illume requested a review from Copilot January 25, 2026 13:06

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k8s-ci-robot added needs-rebase Indicates a PR cannot be merged because it has merge conflicts with HEAD. size/XXL Denotes a PR that changes 1000+ lines, ignoring generated files. and removed size/M Denotes a PR that changes 30-99 lines, ignoring generated files. labels Feb 1, 2026

dibyanshu-pal-kushwaha closed this Feb 1, 2026

dibyanshu-pal-kushwaha force-pushed the fix/in-cluster-kubeconfig-loading branch from 0d4832a to 022469e Compare February 1, 2026 10:15

k8s-ci-robot added size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. and removed size/XXL Denotes a PR that changes 1000+ lines, ignoring generated files. labels Feb 1, 2026

dibyanshu-pal-kushwaha deleted the fix/in-cluster-kubeconfig-loading branch February 1, 2026 10:23

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dibyanshu-pal-kushwaha commented Jan 23, 2026 •

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