backend: k8cache/cacheInvalidation: filter gvrList to reduce the number of go routines for informers

currently the number of go routines is spawning is around 400, because
in CheckForChanges, there are 54 informers are there so because of it
it is spawning to much go routines per context. so through this PR it
is now filtering out the resources which are important or widely used
such as secrets, nodes, pods etc.

Author: upsaurav12

backend/cmd/headlamp_test.go

@@ -1769,6 +1769,44 @@ func TestCacheMiddleware_CacheHitAndCacheMiss_RealK8s(t *testing.T) {
 	assert.Equal(t, "true", secondFromCache, "second request should be from cache")
 }
 
+// Integration test to verify CacheMiddleware does not cause excessive goroutine usage with a real Kubernetes API server.
+func TestCacheMiddleware_GoRoutines(t *testing.T) {
+	if os.Getenv("HEADLAMP_RUN_INTEGRATION_TESTS") != strconv.FormatBool(istrue) {
+		t.Skip("skipping integration test")
+	}
+
+	start := runtime.NumGoroutine()
+
+	c, clusterName := newRealK8sHeadlampConfig(t)
+	handler := createHeadlampHandler(c)
+	ts := httptest.NewServer(handler)
+	defer ts.Close()
+
+	apiPath := "/clusters/" + clusterName + "/api/v1/pods"
+	ctx := context.Background()
+
+	_, err := httpRequestWithContext(ctx, ts.URL+apiPath, "GET")
+	require.NoError(t, err)
+
+	time.Sleep(3 * time.Second)
+
+	running := runtime.NumGoroutine()
+
+	time.Sleep(3 * time.Second)
+
+	after := runtime.NumGoroutine()
+
+	expected := false
+	afterExpected := false
+	if (running >= 50 && running < 200) && (after >= 50 && after < 200) {
+		expected = true
+		afterExpected = true
+	}
+	assert.Equal(t, 3, start)
+	assert.Equal(t, running >= 50 && running < 200, expected)
+	assert.Equal(t, after >= 50 && after < 200, afterExpected)
+}
+
 // TestCacheMiddleware_CacheInvalidation_RealK8s tests cache invalidation with a
 // real Kubernetes API server. Creates a ConfigMap, invalidates via DELETE, then
 // verifies the next GET fetches fresh data. Requires HEADLAMP_RUN_INTEGRATION_TESTS=true

backend/pkg/k8cache/cacheInvalidation.go

@@ -135,7 +135,43 @@ func returnGVRList(apiResourceLists []*metav1.APIResourceList) []schema.GroupVer
 		}
 	}
 
-	return gvrList
+	// filtering the gvrList to make sure spawning go routines for only important
+	// resources which are required to be watched and cached,
+	// this will help to reduce the performance issue and resource utilization.
+	filtered := filterImportantResources(gvrList)
+
+	return filtered
+}
+
+// filterImportantResources filters the provided list of GroupVersionResources to
+// include only those that are deemed important for caching and watching.
+// This helps reduce the number of resources we watch and cache,
+// improving performance and resource utilization.
+func filterImportantResources(gvrList []schema.GroupVersionResource) []schema.GroupVersionResource {
+	allowed := map[string]struct{}{
+		"pods":         {},
+		"services":     {},
+		"deployments":  {},
+		"replicasets":  {},
+		"statefulsets": {},
+		"daemonsets":   {},
+		"nodes":        {},
+		"configmaps":   {},
+		"secrets":      {},
+		"jobs":         {},
+		"cronjobs":     {},
+	}
+
+	filtered := make([]schema.GroupVersionResource, 0, len(allowed))
+
+	for _, gvr := range gvrList {
+		if _, ok := allowed[gvr.Resource]; ok {
+			filtered = append(filtered, gvr)
+		}
+	}
+
+	// return the filtered list of GroupVersionResources that are important for caching and watching
+	return filtered
 }
 
 // Corrected CheckForChanges.