WaitForFirstConsumer PersistentVolumeClaim waiting for first consumer to be created before binding

Question

I setup a new k8s in a single node, which is tainted. But the PersistentVolume can not be created successfully, when I am trying to create a simple PostgreSQL.

There is some detail information below.

---

The StorageClass is copied from the official page: https://kubernetes.io/docs/concepts/storage/storage-classes/#local

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: local-storage
provisioner: kubernetes.io/no-provisioner
volumeBindingMode: WaitForFirstConsumer

The StatefulSet is:

kind: StatefulSet
apiVersion: apps/v1beta1
metadata:
  name: postgres
spec:
  serviceName: postgres
  replicas: 1
  ...
  volumeClaimTemplates:
    - metadata:
        name: postgres-data
      spec:
        storageClassName: local-storage
        accessModes:
          - ReadWriteOnce
        resources:
          requests:
            storage: 1Gi

About the running StorageClass:

$ kubectl describe storageclasses.storage.k8s.io
Name:            local-storage
IsDefaultClass:  No
Annotations:     kubectl.kubernetes.io/last-applied-configuration={"apiVersion":"storage.k8s.io/v1","kind":"StorageClass","metadata":{"annotations":{},"name":"local-storage"},"provisioner":"kubernetes.io/no-provisioner","volumeBindingMode":"WaitForFirstConsumer"}

Provisioner:           kubernetes.io/no-provisioner
Parameters:            <none>
AllowVolumeExpansion:  <unset>
MountOptions:          <none>
ReclaimPolicy:         Delete
VolumeBindingMode:     WaitForFirstConsumer
Events:                <none>

About the running PersistentVolumeClaim:

$ kubectl describe pvc
Name:          postgres-data-postgres-0
Namespace:     default
StorageClass:  local-storage
Status:        Pending
Volume:
Labels:        app=postgres
Annotations:   <none>
Finalizers:    [kubernetes.io/pvc-protection]
Capacity:
Access Modes:
VolumeMode:    Filesystem
Events:
  Type       Reason                Age                            From                         Message
  ----       ------                ----                           ----                         -------
  Normal     WaitForFirstConsumer  <invalid> (x2 over <invalid>)  persistentvolume-controller  waiting for first consumer to be created before binding

K8s versions:

$ kubectl version
Client Version: version.Info{Major:"1", Minor:"13", GitVersion:"v1.13.4", GitCommit:"c27b913fddd1a6c480c229191a087698aa92f0b1", GitTreeState:"clean", BuildDate:"2019-02-28T13:37:52Z", GoVersion:"go1.11.5", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"13", GitVersion:"v1.13.1", GitCommit:"eec55b9ba98609a46fee712359c7b5b365bdd920", GitTreeState:"clean", BuildDate:"2018-12-13T10:31:33Z", GoVersion:"go1.11.2", Compiler:"gc", Platform:"linux/amd64"}

Answer 1

The app is waiting for the Pod, while the Pod is waiting for a PersistentVolume by a PersistentVolumeClaim. However, the PersistentVolume should be prepared by the user before using.

My previous YAMLs are lack of a PersistentVolume like this:

kind: PersistentVolume
apiVersion: v1
metadata:
  name: postgres-data
  labels:
    type: local
spec:
  storageClassName: local-storage
  capacity:
    storage: 1Gi
  local:
    path: /data/postgres
  persistentVolumeReclaimPolicy: Retain
  accessModes:
    - ReadWriteOnce
  storageClassName: local-storage
  nodeAffinity:
    required:
      nodeSelectorTerms:
        - matchExpressions:
          - key: app
            operator: In
            values:
              - postgres

The local path /data/postgres should be prepared before using. Kubernetes will not create it automatically.