Change:
<!-- Please use this template while reporting a bug and provide as much info as possible. Not doing so may result in your bug not being addressed in a timely manner. Thanks! If the matter is security related, please disclose it privately via --What happened: There are too many pdb update operations compared with other resources. ! That is, there are many "Put" operations for pdb periodically in kube-apiserver log. In my view, the amount of pdb operations is connected with disruption controller's resyncPeriod and pdb's quantity in cluster. For example: disruption-controlle's default resyncPeriod is 30s, and there are 100 pdbs in cluster. We can find that the update operation times per minute is about 200. The data is reasonable, explanation is as follows: According to disruption-controlle's design, there is one resync every 30s. One resync means to call updatePdbStatus function for every pdb, so there are 200 times updatePdbStatus. Function updatePdbStatus judges whether the pdb is changed. If changed, call apiserver to update the pdb' status. When no eviction happens, disruptedPods is empty. In this situation, disruptedPods is an empty map, but pdb.Status.DisruptedPods is nil, empty map is not equal to nil. So reflect.DeepEqual(pdb.Status.DisruptedPods, disruptedPods) returns false. The pdb is thought to has be changed, then apiserver is called to update the pdb' status. In fact, there is no change for the pdb when disruptedPods is an empty map and pdb.Status.DisruptedPods is nil. What you expected to happen: There shouldn't be so many pdb update operations. That is, when pdb has no change, apiserver shouldn't be called to update its status. How to reproduce it (as minimally and precisely as possible): Create some pdbs in cluster, you will see many "Put" operations for pdb periodically in kube-apiserver log. Anything else we need to know?: Environment: kubernetes v1.13.2 Fix suggestions: The bug is caused by the mixed usage of empty and nil for disruptedPods, the type of which is map[string]metav1.Time. There are two fix suggestions for it: one of empty map and nil for disruptedPods, use it consistently and refuse to mix empty map and nil. For example, when disruptedPods is empty or nil, save it as an empty map in etcd. Then every client gets pdb from etcd, the pdb.Status.DisruptedPods is an empty map. get pdb for etcd, assign an empty map to it if pdb.Status.DisruptedPods is nil. Maybe the mixed usage of empty and nil for map is a common problem in k8s design, not just for disruptedPods. I will propose a work around solution for the problem. If the solution has any problem, please let me know and I can modify the code.
/sig apps
/assign Morten can you PTAL and the open PR. I reviewed as well.
ref

Discussion:
"//staging/src/k8s.io/api/core/v1:go_default_library", "//staging/src/k8s.io/api/extensions/v1beta1:go_default_library", "//staging/src/k8s.io/api/policy/v1beta1:go_default_library", <ins> "//staging/src/k8s.io/apimachinery/pkg/api/equality:go_default_library", </ins> "//staging/src/k8s.io/apimachinery/pkg/api/errors:go_default_library", "//staging/src/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library", "//staging/src/k8s.io/apimachinery/pkg/types:go_default_library",

"//staging/src/k8s.io/api/apps/v1:go_default_library", "//staging/src/k8s.io/api/core/v1:go_default_library", "//staging/src/k8s.io/api/policy/v1beta1:go_default_library", <ins> "//staging/src/k8s.io/apimachinery/pkg/api/equality:go_default_library", </ins> "//staging/src/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library", "//staging/src/k8s.io/apimachinery/pkg/util/intstr:go_default_library", "//staging/src/k8s.io/apimachinery/pkg/util/uuid:go_default_library",

import ( "fmt" <del> "reflect" </del> "time" apps "k8s.io/api/apps/v1beta1" "k8s.io/api/core/v1" "k8s.io/api/extensions/v1beta1" policy "k8s.io/api/policy/v1beta1" <ins> apiequality "k8s.io/apimachinery/pkg/api/equality" </ins> "k8s.io/apimachinery/pkg/api/errors" metav1 "k8s.io/apimachinery/pkg/apis/meta/v1" "k8s.io/apimachinery/pkg/types"

pdb.Status.DesiredHealthy == desiredHealthy && pdb.Status.ExpectedPods == expectedCount && pdb.Status.PodDisruptionsAllowed == disruptionsAllowed && <del> reflect.DeepEqual(pdb.Status.DisruptedPods, disruptedPods) && </del> <ins> apiequality.Semantic.DeepEqual(pdb.Status.DisruptedPods, disruptedPods) && </ins> pdb.Status.ObservedGeneration == pdb.Generation { return nil }

import ( "fmt" <del> "reflect" </del> "runtime/debug" "testing" "time"

apps "k8s.io/api/apps/v1" "k8s.io/api/core/v1" policy "k8s.io/api/policy/v1beta1" <ins> apiequality "k8s.io/apimachinery/pkg/api/equality" </ins> metav1 "k8s.io/apimachinery/pkg/apis/meta/v1" "k8s.io/apimachinery/pkg/util/intstr" "k8s.io/apimachinery/pkg/util/uuid"

ObservedGeneration:    actualPDB.Generation, } actualStatus := actualPDB.Status <del> if !reflect.DeepEqual(actualStatus, expectedStatus) { </del> <ins> if !apiequality.Semantic.DeepEqual(actualStatus, expectedStatus) { </ins> debug.PrintStack() t.Fatalf("PDB %q status mismatch.  Expected %+v but got %+v.", key, expectedStatus, actualStatus) }