fix: using our own pod template hashing (#1809)

* fix: implement pod template hash calculate function Signed-off-by: Andrii Perenesenko <[email protected]> * fix: using new hashing for FindNewReplicaSet and other places Signed-off-by: Andrii Perenesenko <[email protected]> * fix tests Signed-off-by: Andrii Perenesenko <[email protected]> * fix tests with deprecated hash Signed-off-by: Andrii Perenesenko <[email protected]> * test TestFindNewReplicaSet, TestHashUtils Signed-off-by: Andrii Perenesenko <[email protected]> * fix the doc for ComputePodTemplateHash Signed-off-by: Andrii Perenesenko <[email protected]> * test for ComputePodTemplateHash with collisionCount Signed-off-by: Andrii Perenesenko <[email protected]> * refactoring avoid double FindNewReplicaSet call: pass newRS as a parameter to the FindOldReplicaSets as it using only right after the FindNewReplicaSet Signed-off-by: Andrii Perenesenko <[email protected]> * fix time dependent flaky test Signed-off-by: Andrii Perenesenko <[email protected]>
argoproj · Feb 2, 2022 · e79296a · e79296a
1 parent f388937
commit e79296a
Show file tree

Hide file tree

Showing 15 changed files with 175 additions and 53 deletions.
diff --git a/experiments/replicaset.go b/experiments/replicaset.go
@@ -13,13 +13,13 @@ import (
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/labels"
 	patchtypes "k8s.io/apimachinery/pkg/types"
-	"k8s.io/kubernetes/pkg/controller"
 	labelsutil "k8s.io/kubernetes/pkg/util/labels"
 
 	"github.com/argoproj/argo-rollouts/pkg/apis/rollouts/v1alpha1"
 	"github.com/argoproj/argo-rollouts/utils/conditions"
 	"github.com/argoproj/argo-rollouts/utils/defaults"
 	experimentutil "github.com/argoproj/argo-rollouts/utils/experiment"
+	"github.com/argoproj/argo-rollouts/utils/hash"
 	logutil "github.com/argoproj/argo-rollouts/utils/log"
 	"github.com/argoproj/argo-rollouts/utils/record"
 	replicasetutil "github.com/argoproj/argo-rollouts/utils/replicaset"
@@ -161,7 +161,7 @@ func newReplicaSetFromTemplate(experiment *v1alpha1.Experiment, template v1alpha
 			delete(newRSTemplate.Labels, v1alpha1.DefaultRolloutUniqueLabelKey)
 		}
 	}
-	podHash := controller.ComputeHash(&newRSTemplate, collisionCount)
+	podHash := hash.ComputePodTemplateHash(&newRSTemplate, collisionCount)
 
 	newRSTemplate.Labels = labelsutil.CloneAndAddLabel(newRSTemplate.Labels, v1alpha1.DefaultRolloutUniqueLabelKey, podHash)
 	// Add podTemplateHash label to selector.

diff --git a/rollout/analysis_test.go b/rollout/analysis_test.go
@@ -8,13 +8,13 @@ import (
 	"testing"
 	"time"
 
+	"github.com/argoproj/argo-rollouts/utils/hash"
 	timeutil "github.com/argoproj/argo-rollouts/utils/time"
 
 	"github.com/stretchr/testify/assert"
 	corev1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/util/intstr"
-	"k8s.io/kubernetes/pkg/controller"
 	"k8s.io/utils/pointer"
 
 	"github.com/argoproj/argo-rollouts/pkg/apis/rollouts/v1alpha1"
@@ -58,7 +58,7 @@ func clusterAnalysisTemplate(name string) *v1alpha1.ClusterAnalysisTemplate {
 
 func clusterAnalysisRun(cat *v1alpha1.ClusterAnalysisTemplate, analysisRunType string, r *v1alpha1.Rollout) *v1alpha1.AnalysisRun {
 	labels := map[string]string{}
-	podHash := controller.ComputeHash(&r.Spec.Template, r.Status.CollisionCount)
+	podHash := hash.ComputePodTemplateHash(&r.Spec.Template, r.Status.CollisionCount)
 	var name string
 	if analysisRunType == v1alpha1.RolloutTypeStepLabel {
 		labels = analysisutil.StepLabels(*r.Status.CurrentStepIndex, podHash, "")
@@ -89,7 +89,7 @@ func clusterAnalysisRun(cat *v1alpha1.ClusterAnalysisTemplate, analysisRunType s
 
 func analysisRun(at *v1alpha1.AnalysisTemplate, analysisRunType string, r *v1alpha1.Rollout) *v1alpha1.AnalysisRun {
 	labels := map[string]string{}
-	podHash := controller.ComputeHash(&r.Spec.Template, r.Status.CollisionCount)
+	podHash := hash.ComputePodTemplateHash(&r.Spec.Template, r.Status.CollisionCount)
 	var name string
 	if analysisRunType == v1alpha1.RolloutTypeStepLabel {
 		labels = analysisutil.StepLabels(*r.Status.CurrentStepIndex, podHash, "")

diff --git a/rollout/bluegreen_test.go b/rollout/bluegreen_test.go
@@ -11,12 +11,12 @@ import (
 	corev1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	core "k8s.io/client-go/testing"
-	"k8s.io/kubernetes/pkg/controller"
 	"k8s.io/utils/pointer"
 
 	"github.com/argoproj/argo-rollouts/pkg/apis/rollouts/v1alpha1"
 	"github.com/argoproj/argo-rollouts/utils/annotations"
 	"github.com/argoproj/argo-rollouts/utils/conditions"
+	"github.com/argoproj/argo-rollouts/utils/hash"
 	rolloututil "github.com/argoproj/argo-rollouts/utils/rollout"
 	timeutil "github.com/argoproj/argo-rollouts/utils/time"
 )
@@ -34,7 +34,7 @@ func newBlueGreenRollout(name string, replicas int, revisionHistoryLimit *int32,
 		AbortScaleDownDelaySeconds: &abortScaleDownDelaySeconds,
 	}
 	rollout.Status.CurrentStepHash = conditions.ComputeStepHash(rollout)
-	rollout.Status.CurrentPodHash = controller.ComputeHash(&rollout.Spec.Template, rollout.Status.CollisionCount)
+	rollout.Status.CurrentPodHash = hash.ComputePodTemplateHash(&rollout.Spec.Template, rollout.Status.CollisionCount)
 	return rollout
 }
 

diff --git a/rollout/canary_test.go b/rollout/canary_test.go
@@ -15,13 +15,13 @@ import (
 	"k8s.io/apimachinery/pkg/util/intstr"
 	k8sinformers "k8s.io/client-go/informers"
 	k8sfake "k8s.io/client-go/kubernetes/fake"
-	"k8s.io/kubernetes/pkg/controller"
 	"k8s.io/utils/pointer"
 
 	"github.com/argoproj/argo-rollouts/pkg/apis/rollouts/v1alpha1"
 	"github.com/argoproj/argo-rollouts/pkg/client/clientset/versioned/fake"
 	"github.com/argoproj/argo-rollouts/utils/annotations"
 	"github.com/argoproj/argo-rollouts/utils/conditions"
+	"github.com/argoproj/argo-rollouts/utils/hash"
 	logutil "github.com/argoproj/argo-rollouts/utils/log"
 	"github.com/argoproj/argo-rollouts/utils/record"
 	replicasetutil "github.com/argoproj/argo-rollouts/utils/replicaset"
@@ -39,7 +39,7 @@ func newCanaryRollout(name string, replicas int, revisionHistoryLimit *int32, st
 	}
 	rollout.Status.CurrentStepIndex = stepIndex
 	rollout.Status.CurrentStepHash = conditions.ComputeStepHash(rollout)
-	rollout.Status.CurrentPodHash = controller.ComputeHash(&rollout.Spec.Template, rollout.Status.CollisionCount)
+	rollout.Status.CurrentPodHash = hash.ComputePodTemplateHash(&rollout.Spec.Template, rollout.Status.CollisionCount)
 	rollout.Status.Selector = metav1.FormatLabelSelector(rollout.Spec.Selector)
 	rollout.Status.Phase, rollout.Status.Message = rolloututil.CalculateRolloutPhase(rollout.Spec, rollout.Status)
 	return rollout
@@ -54,7 +54,7 @@ func bumpVersion(rollout *v1alpha1.Rollout) *v1alpha1.Rollout {
 	newRevisionStr := strconv.FormatInt(int64(newRevision), 10)
 	annotations.SetRolloutRevision(newRollout, newRevisionStr)
 	newRollout.Spec.Template.Spec.Containers[0].Image = "foo/bar" + newRevisionStr
-	newRollout.Status.CurrentPodHash = controller.ComputeHash(&newRollout.Spec.Template, newRollout.Status.CollisionCount)
+	newRollout.Status.CurrentPodHash = hash.ComputePodTemplateHash(&newRollout.Spec.Template, newRollout.Status.CollisionCount)
 	newRollout.Status.CurrentStepHash = conditions.ComputeStepHash(newRollout)
 	newRollout.Status.Phase, newRollout.Status.Message = rolloututil.CalculateRolloutPhase(newRollout.Spec, newRollout.Status)
 	return newRollout
@@ -841,7 +841,7 @@ func TestRollBackToStable(t *testing.T) {
 		}
 	}`
 	newConditions := generateConditionsPatch(true, conditions.ReplicaSetUpdatedReason, rs1, false, "")
-	expectedPatch := fmt.Sprintf(expectedPatchWithoutSub, controller.ComputeHash(&r2.Spec.Template, r2.Status.CollisionCount), newConditions)
+	expectedPatch := fmt.Sprintf(expectedPatchWithoutSub, hash.ComputePodTemplateHash(&r2.Spec.Template, r2.Status.CollisionCount), newConditions)
 	patch := f.getPatchedRollout(patchIndex)
 	assert.Equal(t, calculatePatch(r2, expectedPatch), patch)
 }
@@ -929,7 +929,7 @@ func TestRollBackToStableAndStepChange(t *testing.T) {
 			"conditions": %s
 		}
 	}`
-	newPodHash := controller.ComputeHash(&r2.Spec.Template, r2.Status.CollisionCount)
+	newPodHash := hash.ComputePodTemplateHash(&r2.Spec.Template, r2.Status.CollisionCount)
 	newStepHash := conditions.ComputeStepHash(r2)
 	newConditions := generateConditionsPatch(true, conditions.ReplicaSetUpdatedReason, rs1, false, "")
 	expectedPatch := fmt.Sprintf(expectedPatchWithoutSub, newPodHash, newStepHash, newConditions)

diff --git a/rollout/controller.go b/rollout/controller.go
@@ -433,7 +433,7 @@ func (c *Controller) newRolloutContext(rollout *v1alpha1.Rollout) (*rolloutConte
 	}
 
 	newRS := replicasetutil.FindNewReplicaSet(rollout, rsList)
-	olderRSs := replicasetutil.FindOldReplicaSets(rollout, rsList)
+	olderRSs := replicasetutil.FindOldReplicaSets(rollout, rsList, newRS)
 	stableRS := replicasetutil.GetStableRS(rollout, newRS, olderRSs)
 	otherRSs := replicasetutil.GetOtherRSs(rollout, newRS, stableRS, rsList)
 

diff --git a/rollout/controller_test.go b/rollout/controller_test.go
@@ -34,7 +34,6 @@ import (
 	"k8s.io/client-go/tools/cache"
 	"k8s.io/client-go/util/workqueue"
 	corev1defaults "k8s.io/kubernetes/pkg/apis/core/v1"
-	"k8s.io/kubernetes/pkg/controller"
 	"k8s.io/utils/pointer"
 
 	"github.com/argoproj/argo-rollouts/controller/metrics"
@@ -47,6 +46,7 @@ import (
 	"github.com/argoproj/argo-rollouts/utils/annotations"
 	"github.com/argoproj/argo-rollouts/utils/conditions"
 	"github.com/argoproj/argo-rollouts/utils/defaults"
+	"github.com/argoproj/argo-rollouts/utils/hash"
 	ingressutil "github.com/argoproj/argo-rollouts/utils/ingress"
 	istioutil "github.com/argoproj/argo-rollouts/utils/istio"
 	"github.com/argoproj/argo-rollouts/utils/queue"
@@ -401,7 +401,7 @@ func updateBaseRolloutStatus(r *v1alpha1.Rollout, availableReplicas, updatedRepl
 }
 
 func newReplicaSet(r *v1alpha1.Rollout, replicas int) *appsv1.ReplicaSet {
-	podHash := controller.ComputeHash(&r.Spec.Template, r.Status.CollisionCount)
+	podHash := hash.ComputePodTemplateHash(&r.Spec.Template, r.Status.CollisionCount)
 	rsLabels := map[string]string{
 		v1alpha1.DefaultRolloutUniqueLabelKey: podHash,
 	}
@@ -1300,7 +1300,7 @@ func TestPodTemplateHashEquivalence(t *testing.T) {
 	var err error
 	// NOTE: This test will fail on every k8s library upgrade.
 	// To fix it, update expectedReplicaSetName to match the new hash.
-	expectedReplicaSetName := "guestbook-859fc5d686"
+	expectedReplicaSetName := "guestbook-6c5667f666"
 
 	r1 := newBlueGreenRollout("guestbook", 1, nil, "active", "")
 	r1Resources := `

diff --git a/rollout/experiment.go b/rollout/experiment.go
@@ -4,19 +4,20 @@ import (
 	"context"
 	"fmt"
 
+	appsv1 "k8s.io/api/apps/v1"
+	"k8s.io/apimachinery/pkg/api/errors"
+	k8serrors "k8s.io/apimachinery/pkg/api/errors"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/labels"
+
 	"github.com/argoproj/argo-rollouts/pkg/apis/rollouts/v1alpha1"
 	analysisutil "github.com/argoproj/argo-rollouts/utils/analysis"
 	"github.com/argoproj/argo-rollouts/utils/annotations"
 	"github.com/argoproj/argo-rollouts/utils/defaults"
 	experimentutil "github.com/argoproj/argo-rollouts/utils/experiment"
+	"github.com/argoproj/argo-rollouts/utils/hash"
 	"github.com/argoproj/argo-rollouts/utils/record"
 	replicasetutil "github.com/argoproj/argo-rollouts/utils/replicaset"
-	appsv1 "k8s.io/api/apps/v1"
-	"k8s.io/apimachinery/pkg/api/errors"
-	k8serrors "k8s.io/apimachinery/pkg/api/errors"
-	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
-	"k8s.io/apimachinery/pkg/labels"
-	"k8s.io/kubernetes/pkg/controller"
 )
 
 // GetExperimentFromTemplate takes the canary experiment step and converts it to an experiment
@@ -25,7 +26,7 @@ func GetExperimentFromTemplate(r *v1alpha1.Rollout, stableRS, newRS *appsv1.Repl
 	if step == nil {
 		return nil, nil
 	}
-	podHash := controller.ComputeHash(&r.Spec.Template, r.Status.CollisionCount)
+	podHash := hash.ComputePodTemplateHash(&r.Spec.Template, r.Status.CollisionCount)
 	currentStep := int32(0)
 	if r.Status.CurrentStepIndex != nil {
 		currentStep = *r.Status.CurrentStepIndex

diff --git a/rollout/sync.go b/rollout/sync.go
@@ -23,6 +23,7 @@ import (
 	"github.com/argoproj/argo-rollouts/utils/defaults"
 	"github.com/argoproj/argo-rollouts/utils/diff"
 	experimentutil "github.com/argoproj/argo-rollouts/utils/experiment"
+	"github.com/argoproj/argo-rollouts/utils/hash"
 	logutil "github.com/argoproj/argo-rollouts/utils/log"
 	"github.com/argoproj/argo-rollouts/utils/record"
 	replicasetutil "github.com/argoproj/argo-rollouts/utils/replicaset"
@@ -139,7 +140,7 @@ func (c *rolloutContext) createDesiredReplicaSet() (*appsv1.ReplicaSet, error) {
 	newRSTemplate := *c.rollout.Spec.Template.DeepCopy()
 	// Add default anti-affinity rule if antiAffinity bool set and RSTemplate meets requirements
 	newRSTemplate.Spec.Affinity = replicasetutil.GenerateReplicaSetAffinity(*c.rollout)
-	podTemplateSpecHash := controller.ComputeHash(&c.rollout.Spec.Template, c.rollout.Status.CollisionCount)
+	podTemplateSpecHash := hash.ComputePodTemplateHash(&c.rollout.Spec.Template, c.rollout.Status.CollisionCount)
 	newRSTemplate.Labels = labelsutil.CloneAndAddLabel(c.rollout.Spec.Template.Labels, v1alpha1.DefaultRolloutUniqueLabelKey, podTemplateSpecHash)
 	// Add podTemplateHash label to selector.
 	newRSSelector := labelsutil.CloneSelectorAndAddLabel(c.rollout.Spec.Selector, v1alpha1.DefaultRolloutUniqueLabelKey, podTemplateSpecHash)
@@ -378,7 +379,7 @@ func (c *rolloutContext) calculateBaseStatus() v1alpha1.RolloutStatus {
 		// newRS potentially might be nil when called by syncReplicasOnly(). For this
 		// to happen, the user would have had to simultaneously change the number of replicas, and
 		// the pod template spec at the same time.
-		currentPodHash = controller.ComputeHash(&c.rollout.Spec.Template, c.rollout.Status.CollisionCount)
+		currentPodHash = hash.ComputePodTemplateHash(&c.rollout.Spec.Template, c.rollout.Status.CollisionCount)
 		c.log.Infof("Assuming %s for new replicaset pod hash", currentPodHash)
 	} else {
 		currentPodHash = c.newRS.Labels[v1alpha1.DefaultRolloutUniqueLabelKey]

diff --git a/utils/conditions/rollouts_test.go b/utils/conditions/rollouts_test.go
@@ -8,10 +8,10 @@ import (
 	"github.com/stretchr/testify/assert"
 	v1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
-	"k8s.io/kubernetes/pkg/controller"
 	"k8s.io/utils/pointer"
 
 	"github.com/argoproj/argo-rollouts/pkg/apis/rollouts/v1alpha1"
+	"github.com/argoproj/argo-rollouts/utils/hash"
 )
 
 var (
@@ -363,7 +363,7 @@ func TestRolloutComplete(t *testing.T) {
 			},
 		}
 		r.Generation = 123
-		podHash := controller.ComputeHash(&r.Spec.Template, r.Status.CollisionCount)
+		podHash := hash.ComputePodTemplateHash(&r.Spec.Template, r.Status.CollisionCount)
 		r.Status.CurrentPodHash = podHash
 		return r
 	}
@@ -411,13 +411,13 @@ func TestRolloutComplete(t *testing.T) {
 		{
 			name: "BlueGreen complete",
 			// update hash to status.CurrentPodHash after k8s library update
-			r:        blueGreenRollout(5, 5, 5, 5, true, "78957574d7", "78957574d7"),
+			r:        blueGreenRollout(5, 5, 5, 5, true, "76bbb58f74", "76bbb58f74"),
 			expected: true,
 		},
 		{
 			name: "BlueGreen complete with extra old replicas",
 			// update hash to status.CurrentPodHash after k8s library update
-			r:        blueGreenRollout(5, 6, 5, 5, true, "78957574d7", "78957574d7"),
+			r:        blueGreenRollout(5, 6, 5, 5, true, "76bbb58f74", "76bbb58f74"),
 			expected: true,
 		},
 		{

diff --git a/utils/experiment/experiment.go b/utils/experiment/experiment.go
@@ -8,11 +8,11 @@ import (
 
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	patchtypes "k8s.io/apimachinery/pkg/types"
-	"k8s.io/kubernetes/pkg/controller"
 
 	"github.com/argoproj/argo-rollouts/pkg/apis/rollouts/v1alpha1"
 	rolloutsclient "github.com/argoproj/argo-rollouts/pkg/client/clientset/versioned/typed/rollouts/v1alpha1"
 	"github.com/argoproj/argo-rollouts/utils/defaults"
+	"github.com/argoproj/argo-rollouts/utils/hash"
 	timeutil "github.com/argoproj/argo-rollouts/utils/time"
 )
 
@@ -131,8 +131,9 @@ func GetCollisionCountForTemplate(experiment *v1alpha1.Experiment, template v1al
 
 // ReplicasetNameFromExperiment gets the replicaset name based off of the experiment and the template
 func ReplicasetNameFromExperiment(experiment *v1alpha1.Experiment, template v1alpha1.TemplateSpec) string {
+	// todo: review this method for deletion as it's not using
 	collisionCount := GetCollisionCountForTemplate(experiment, template)
-	podTemplateSpecHash := controller.ComputeHash(&template.Template, collisionCount)
+	podTemplateSpecHash := hash.ComputePodTemplateHash(&template.Template, collisionCount)
 	return fmt.Sprintf("%s-%s-%s", experiment.Name, template.Name, podTemplateSpecHash)
 }
 

diff --git a/utils/experiment/experiment_test.go b/utils/experiment/experiment_test.go
@@ -5,13 +5,14 @@ import (
 	"testing"
 	"time"
 
-	"github.com/argoproj/argo-rollouts/pkg/apis/rollouts/v1alpha1"
-	"github.com/argoproj/argo-rollouts/pkg/client/clientset/versioned/fake"
 	"github.com/stretchr/testify/assert"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
 	kubetesting "k8s.io/client-go/testing"
 	"k8s.io/utils/pointer"
+
+	"github.com/argoproj/argo-rollouts/pkg/apis/rollouts/v1alpha1"
+	"github.com/argoproj/argo-rollouts/pkg/client/clientset/versioned/fake"
 )
 
 func TestHasFinished(t *testing.T) {
@@ -90,6 +91,7 @@ func TestGetTemplateStatusMapping(t *testing.T) {
 	assert.Equal(t, int32(1), mapping["test"].Replicas)
 	assert.Equal(t, int32(2), mapping["test2"].Replicas)
 }
+
 func TestReplicaSetNameFromExperiment(t *testing.T) {
 	templateName := "template"
 	template := v1alpha1.TemplateSpec{
@@ -100,14 +102,14 @@ func TestReplicaSetNameFromExperiment(t *testing.T) {
 			Name: "foo",
 		},
 	}
-	assert.Equal(t, "foo-template-78957574d7", ReplicasetNameFromExperiment(e, template))
+	assert.Equal(t, "foo-template-76bbb58f74", ReplicasetNameFromExperiment(e, template))
 
 	newTemplateStatus := v1alpha1.TemplateStatus{
 		Name:           templateName,
 		CollisionCount: pointer.Int32Ptr(1),
 	}
 	e.Status.TemplateStatuses = append(e.Status.TemplateStatuses, newTemplateStatus)
-	assert.Equal(t, "foo-template-db98f55f8", ReplicasetNameFromExperiment(e, template))
+	assert.Equal(t, "foo-template-688c48b575", ReplicasetNameFromExperiment(e, template))
 }
 
 func TestExperimentByCreationTimestamp(t *testing.T) {

diff --git a/utils/hash/hash.go b/utils/hash/hash.go
@@ -0,0 +1,34 @@
+package hash
+
+import (
+	"encoding/binary"
+	"encoding/json"
+	"fmt"
+	"hash/fnv"
+
+	corev1 "k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/util/rand"
+)
+
+// ComputePodTemplateHash returns a hash value calculated from pod template.
+// The hash will be safe encoded to avoid bad words.
+func ComputePodTemplateHash(template *corev1.PodTemplateSpec, collisionCount *int32) string {
+	podTemplateSpecHasher := fnv.New32a()
+	stepsBytes, err := json.Marshal(template)
+	if err != nil {
+		panic(err)
+	}
+	_, err = podTemplateSpecHasher.Write(stepsBytes)
+	if err != nil {
+		panic(err)
+	}
+	if collisionCount != nil {
+		collisionCountBytes := make([]byte, 8)
+		binary.LittleEndian.PutUint32(collisionCountBytes, uint32(*collisionCount))
+		_, err = podTemplateSpecHasher.Write(collisionCountBytes)
+		if err != nil {
+			panic(err)
+		}
+	}
+	return rand.SafeEncodeString(fmt.Sprint(podTemplateSpecHasher.Sum32()))
+}