Merge pull request #103414 from ravisantoshgudimetla/fix-pdb-status

[disruptioncontroller] Don't error for unmanaged pods

pkg/controller/disruption/disruption.go

@@ -595,11 +595,16 @@ func (dc *DisruptionController) trySync(pdb *policy.PodDisruptionBudget) error {
 		dc.recorder.Eventf(pdb, v1.EventTypeNormal, "NoPods", "No matching pods found")
 	}
 
-	expectedCount, desiredHealthy, err := dc.getExpectedPodCount(pdb, pods)
+	expectedCount, desiredHealthy, unmanagedPods, err := dc.getExpectedPodCount(pdb, pods)
 	if err != nil {
 		dc.recorder.Eventf(pdb, v1.EventTypeWarning, "CalculateExpectedPodCountFailed", "Failed to calculate the number of expected pods: %v", err)
 		return err
 	}
+	// We have unmamanged pods, instead of erroring and hotlooping in disruption controller, log and continue.
+	if len(unmanagedPods) > 0 {
+		klog.V(4).Infof("found unmanaged pods associated with this PDB: %v",
+			strings.Join(unmanagedPods, ",'"))
+	}
 
 	currentTime := time.Now()
 	disruptedPods, recheckTime := dc.buildDisruptedPodMap(pods, pdb, currentTime)
@@ -615,7 +620,7 @@ func (dc *DisruptionController) trySync(pdb *policy.PodDisruptionBudget) error {
 	return err
 }
 
-func (dc *DisruptionController) getExpectedPodCount(pdb *policy.PodDisruptionBudget, pods []*v1.Pod) (expectedCount, desiredHealthy int32, err error) {
+func (dc *DisruptionController) getExpectedPodCount(pdb *policy.PodDisruptionBudget, pods []*v1.Pod) (expectedCount, desiredHealthy int32, unmanagedPods []string, err error) {
 	err = nil
 	// TODO(davidopp): consider making the way expectedCount and rules about
 	// permitted controller configurations (specifically, considering it an error
@@ -623,7 +628,7 @@ func (dc *DisruptionController) getExpectedPodCount(pdb *policy.PodDisruptionBud
 	// handled the same way for integer and percentage minAvailable
 
 	if pdb.Spec.MaxUnavailable != nil {
-		expectedCount, err = dc.getExpectedScale(pdb, pods)
+		expectedCount, unmanagedPods, err = dc.getExpectedScale(pdb, pods)
 		if err != nil {
 			return
 		}
@@ -641,7 +646,7 @@ func (dc *DisruptionController) getExpectedPodCount(pdb *policy.PodDisruptionBud
 			desiredHealthy = pdb.Spec.MinAvailable.IntVal
 			expectedCount = int32(len(pods))
 		} else if pdb.Spec.MinAvailable.Type == intstr.String {
-			expectedCount, err = dc.getExpectedScale(pdb, pods)
+			expectedCount, unmanagedPods, err = dc.getExpectedScale(pdb, pods)
 			if err != nil {
 				return
 			}
@@ -657,7 +662,7 @@ func (dc *DisruptionController) getExpectedPodCount(pdb *policy.PodDisruptionBud
 	return
 }
 
-func (dc *DisruptionController) getExpectedScale(pdb *policy.PodDisruptionBudget, pods []*v1.Pod) (expectedCount int32, err error) {
+func (dc *DisruptionController) getExpectedScale(pdb *policy.PodDisruptionBudget, pods []*v1.Pod) (expectedCount int32, unmanagedPods []string, err error) {
 	// When the user specifies a fraction of pods that must be available, we
 	// use as the fraction's denominator
 	// SUM_{all c in C} scale(c)
@@ -672,13 +677,19 @@ func (dc *DisruptionController) getExpectedScale(pdb *policy.PodDisruptionBudget
 	// A mapping from controllers to their scale.
 	controllerScale := map[types.UID]int32{}
 
-	// 1. Find the controller for each pod.  If any pod has 0 controllers,
-	// that's an error. With ControllerRef, a pod can only have 1 controller.
+	// 1. Find the controller for each pod.
+
+	// As of now, we allow PDBs to be applied to pods via selectors, so there
+	// can be unmanaged pods(pods that don't have backing controllers) but still have PDBs associated.
+	// Such pods are to be collected and PDB backing them should be enqueued instead of immediately throwing
+	// a sync error. This ensures disruption controller is not frequently updating the status subresource and thus
+	// preventing excessive and expensive writes to etcd.
+	// With ControllerRef, a pod can only have 1 controller.
 	for _, pod := range pods {
 		controllerRef := metav1.GetControllerOf(pod)
 		if controllerRef == nil {
-			err = fmt.Errorf("found no controller ref for pod %q", pod.Name)
-			return
+			unmanagedPods = append(unmanagedPods, pod.Name)
+			continue
 		}
 
 		// If we already know the scale of the controller there is no need to do anything.

pkg/controller/disruption/disruption_test.go

@@ -22,6 +22,7 @@ import (
 	"fmt"
 	"os"
 	"runtime/debug"
+	"strings"
 	"sync"
 	"testing"
 	"time"
@@ -115,6 +116,15 @@ func (ps *pdbStates) VerifyDisruptionAllowed(t *testing.T, key string, disruptio
 	}
 }
 
+func (ps *pdbStates) VerifyNoStatusError(t *testing.T, key string) {
+	pdb := ps.Get(key)
+	for _, condition := range pdb.Status.Conditions {
+		if strings.Contains(condition.Message, "found no controller ref") && condition.Reason == policy.SyncFailedReason {
+			t.Fatalf("PodDisruption Controller should not error when unmanaged pods are found but it failed for %q", key)
+		}
+	}
+}
+
 type disruptionController struct {
 	*DisruptionController
 
@@ -534,6 +544,47 @@ func TestNakedPod(t *testing.T) {
 	ps.VerifyDisruptionAllowed(t, pdbName, 0)
 }
 
+// Verify that disruption controller is not erroring when unmanaged pods are found
+func TestStatusForUnmanagedPod(t *testing.T) {
+	dc, ps := newFakeDisruptionController()
+
+	pdb, pdbName := newMinAvailablePodDisruptionBudget(t, intstr.FromString("28%"))
+	add(t, dc.pdbStore, pdb)
+	dc.sync(pdbName)
+	// This verifies that when a PDB has 0 pods, disruptions are not allowed.
+	ps.VerifyDisruptionAllowed(t, pdbName, 0)
+
+	pod, _ := newPod(t, "unmanaged")
+	add(t, dc.podStore, pod)
+	dc.sync(pdbName)
+
+	ps.VerifyNoStatusError(t, pdbName)
+
+}
+
+// Check if the unmanaged pods are correctly collected or not
+func TestTotalUnmanagedPods(t *testing.T) {
+	dc, ps := newFakeDisruptionController()
+
+	pdb, pdbName := newMinAvailablePodDisruptionBudget(t, intstr.FromString("28%"))
+	add(t, dc.pdbStore, pdb)
+	dc.sync(pdbName)
+	// This verifies that when a PDB has 0 pods, disruptions are not allowed.
+	ps.VerifyDisruptionAllowed(t, pdbName, 0)
+
+	pod, _ := newPod(t, "unmanaged")
+	add(t, dc.podStore, pod)
+	dc.sync(pdbName)
+	var pods []*v1.Pod
+	pods = append(pods, pod)
+	_, unmanagedPods, _ := dc.getExpectedScale(pdb, pods)
+	if len(unmanagedPods) != 1 {
+		t.Fatalf("expected one pod to be unmanaged pod but found %d", len(unmanagedPods))
+	}
+	ps.VerifyNoStatusError(t, pdbName)
+
+}
+
 // Verify that we count the scale of a ReplicaSet even when it has no Deployment.
 func TestReplicaSet(t *testing.T) {
 	dc, ps := newFakeDisruptionController()
@@ -752,7 +803,7 @@ func TestReplicationController(t *testing.T) {
 	rogue, _ := newPod(t, "rogue")
 	add(t, dc.podStore, rogue)
 	dc.sync(pdbName)
-	ps.VerifyDisruptionAllowed(t, pdbName, 0)
+	ps.VerifyDisruptionAllowed(t, pdbName, 2)
 }
 
 func TestStatefulSetController(t *testing.T) {

test/e2e/apps/disruption.go

@@ -19,6 +19,8 @@ package apps
 import (
 	"context"
 	"fmt"
+	"github.com/onsi/gomega"
+	"strings"
 	"time"
 
 	jsonpatch "github.com/evanphx/json-patch"
@@ -185,6 +187,25 @@ var _ = SIGDescribe("DisruptionController", func() {
 		framework.ExpectEmpty(patched.Status.DisruptedPods, "Expecting the PodDisruptionBudget's be empty")
 	})
 
+	// PDB shouldn't error out when there are unmanaged pods
+	ginkgo.It("should observe that the PodDisruptionBudget status is not updated for unmanaged pods",
+		func() {
+			createPDBMinAvailableOrDie(cs, ns, defaultName, intstr.FromInt(1), defaultLabels)
+
+			createPodsOrDie(cs, ns, 3)
+			waitForPodsOrDie(cs, ns, 3)
+
+			// Since we allow unmanaged pods to be associated with a PDB, we should not see any error
+			gomega.Consistently(func() (bool, error) {
+				pdb, err := cs.PolicyV1().PodDisruptionBudgets(ns).Get(context.TODO(), defaultName, metav1.GetOptions{})
+				if err != nil {
+					return false, err
+				}
+				return isPDBErroring(pdb), nil
+			}, 1*time.Minute, 1*time.Second).ShouldNot(gomega.BeTrue(), "pod shouldn't error for "+
+				"unmanaged pod")
+		})
+
 	evictionCases := []struct {
 		description        string
 		minAvailable       intstr.IntOrString
@@ -677,3 +698,15 @@ func unstructuredToPDB(obj *unstructured.Unstructured) (*policyv1.PodDisruptionB
 	pdb.APIVersion = ""
 	return pdb, err
 }
+
+// isPDBErroring checks if the PDB is erroring on when there are unmanaged pods
+func isPDBErroring(pdb *policyv1.PodDisruptionBudget) bool {
+	hasFailed := false
+	for _, condition := range pdb.Status.Conditions {
+		if strings.Contains(condition.Reason, "SyncFailed") &&
+			strings.Contains(condition.Message, "found no controller ref for pod") {
+			hasFailed = true
+		}
+	}
+	return hasFailed
+}