PVC在K8S集群迁移或恢复需注意地方
目前在做同城双活，每个机房都有一个k8s集群，其中一些共享卷需要做到双活的2个集群上都可用。
比如我们现在在主机房的集群上有一个PVC：
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
annotations:
pv.kubernetes.io/bind-completed: "yes"
pv.kubernetes.io/bound-by-controller: "yes"
volume.beta.kubernetes.io/storage-provisioner: com.tencent.cloud.csi.cfs
creationTimestamp: "2020-11-25T07:24:15Z"
name: public-devops-teststatefulset-nginx-online-pvc
namespace: test
uid: 3d65a636-f4c3-4c49-b957-c45673f48bc6
spec:
accessModes:
- ReadWriteMany
resources:
requests:
storage: 30Gi
storageClassName: cfs-hp
volumeMode: Filesystem
volumeName: pvc-3d65a636-f4c3-4c49-b957-c45673f48bc6
以及对应的PV：
apiVersion: v1
kind: PersistentVolume
metadata:
annotations:
pv.kubernetes.io/provisioned-by: com.tencent.cloud.csi.cfs
creationTimestamp: "2020-11-25T07:24:22Z"
name: pvc-3d65a636-f4c3-4c49-b957-c45673f48bc6
uid: 301c903e-10fc-40ee-98e1-0655948425fc
spec:
accessModes:
- ReadWriteMany
capacity:
storage: 30Gi
claimRef:
apiVersion: v1
kind: PersistentVolumeClaim
name: public-devops-teststatefulset-nginx-online-pvc
namespace: test
resourceVersion: "657951844"
uid: 3d65a636-f4c3-4c49-b957-c45673f48bc6
csi:
driver: com.tencent.cloud.csi.cfs
fsType: ext4
volumeAttributes:
fsid: cfs-3c7e956f6
host: 10.10.144.12
storage.kubernetes.io/csiProvisionerIdentity: 1597949457398-8081-com.tencent.cloud.csi.cfs
storagetype: HP
subnetid: subnet-mg9pp5o5
vpcid: vpc-aqpp2l40
zone: ap-shanghai-4
volumeHandle: cfs-3c7e956f6
persistentVolumeReclaimPolicy: Delete
storageClassName: cfs-hp
volumeMode: Filesystem
如果我们将上面的yaml直接导到备机房的集群上，会发现其实有问题：
[root@sh5-saas-k8scs1-master-online-01 ~]# kubectl get pvc -n test -o wide
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE VOLUMEMODE
data1-public-devops-teststatefulset-nginx-online-0 Bound pvc-ad9a8bad-f9e6-4968-a633-d786a1925b38 30Gi RWO cbs-ssd-prepaid 123d Filesystem
data1-public-devops-teststatefulset-nginx-online-1 Bound pvc-67df7b6f-d5a1-47a3-9239-bc5173b1eb36 30Gi RWO cbs-ssd-prepaid 75d Filesystem
public-devops-teststatefulset-nginx-online-pvc Bound pvc-3d65a636-f4c3-4c49-b957-c45673f48bc6 30Gi RWX cfs-hp 19s Filesystem
[root@sh5-saas-k8scs1-master-online-01 ~]# kubectl get pvc -n test -o wide
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE VOLUMEMODE
data1-public-devops-teststatefulset-nginx-online-0 Bound pvc-ad9a8bad-f9e6-4968-a633-d786a1925b38 30Gi RWO cbs-ssd-prepaid 123d Filesystem
data1-public-devops-teststatefulset-nginx-online-1 Bound pvc-67df7b6f-d5a1-47a3-9239-bc5173b1eb36 30Gi RWO cbs-ssd-prepaid 75d Filesystem
public-devops-teststatefulset-nginx-online-pvc Lost pvc-3d65a636-f4c3-4c49-b957-c45673f48bc6 0 cfs-hp 3m57s Filesystem
[root@sh5-saas-k8scs1-master-online-01 ~]# kubectl describe pvc -n test public-devops-teststatefulset-nginx-online-pvc
Name: public-devops-teststatefulset-nginx-online-pvc
Namespace: test
StorageClass: cfs-hp
Status: Lost
Volume: pvc-3d65a636-f4c3-4c49-b957-c45673f48bc6
Labels: app=public-devops-teststatefulset-nginx-online
Annotations: pv.kubernetes.io/bind-completed: yes
pv.kubernetes.io/bound-by-controller: yes
volume.beta.kubernetes.io/storage-provisioner: com.tencent.cloud.csi.cfs
Finalizers: [kubernetes.io/pvc-protection]
Capacity: 0
Access Modes:
VolumeMode: Filesystem
Mounted By: <none>
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Warning ClaimMisbound 4m19s persistentvolume-controller Two claims are bound to the same volume, this one is bound incorrectly
pvc的状态是lost的，查看事件，发现报错：Two claims are bound to the same volume, this one is bound incorrectly。
根据报错查找kubernetes的源码，发现在pkg/controller/volume/persistentvolume/pv_controller.go:
// syncBoundClaim is the main controller method to decide what to do with a
// bound claim.
func (ctrl *PersistentVolumeController) syncBoundClaim(claim *v1.PersistentVolumeClaim) error {
// HasAnnotation(pvc, pvutil.AnnBindCompleted)
// This PVC has previously been bound
// OBSERVATION: pvc is not "Pending"
// [Unit test set 3]
if claim.Spec.VolumeName == "" {
// Claim was bound before but not any more.
if _, err := ctrl.updateClaimStatusWithEvent(claim, v1.ClaimLost, nil, v1.EventTypeWarning, "ClaimLost", "Bound claim has lost reference to PersistentVolume. Data on the volume is lost!"); err != nil {
return err
}
return nil
}
obj, found, err := ctrl.volumes.store.GetByKey(claim.Spec.VolumeName)
if err != nil {
return err
}
if !found {
// Claim is bound to a non-existing volume.
if _, err = ctrl.updateClaimStatusWithEvent(claim, v1.ClaimLost, nil, v1.EventTypeWarning, "ClaimLost", "Bound claim has lost its PersistentVolume. Data on the volume is lost!"); err != nil {
return err
}
return nil
} else {
volume, ok := obj.(*v1.PersistentVolume)
if !ok {
return fmt.Errorf("Cannot convert object from volume cache to volume %q!?: %#v", claim.Spec.VolumeName, obj)
}
klog.V(4).Infof("synchronizing bound PersistentVolumeClaim[%s]: volume %q found: %s", claimToClaimKey(claim), claim.Spec.VolumeName, getVolumeStatusForLogging(volume))
if volume.Spec.ClaimRef == nil {
// Claim is bound but volume has come unbound.
// Or, a claim was bound and the controller has not received updated
// volume yet. We can't distinguish these cases.
// Bind the volume again and set all states to Bound.
klog.V(4).Infof("synchronizing bound PersistentVolumeClaim[%s]: volume is unbound, fixing", claimToClaimKey(claim))
if err = ctrl.bind(volume, claim); err != nil {
// Objects not saved, next syncPV or syncClaim will try again
return err
}
return nil
} else if volume.Spec.ClaimRef.UID == claim.UID {
// All is well
// NOTE: syncPV can handle this so it can be left out.
// NOTE: bind() call here will do nothing in most cases as
// everything should be already set.
klog.V(4).Infof("synchronizing bound PersistentVolumeClaim[%s]: claim is already correctly bound", claimToClaimKey(claim))
if err = ctrl.bind(volume, claim); err != nil {
// Objects not saved, next syncPV or syncClaim will try again
return err
}
return nil
} else {
// Claim is bound but volume has a different claimant.
// Set the claim phase to 'Lost', which is a terminal
// phase.
if _, err = ctrl.updateClaimStatusWithEvent(claim, v1.ClaimLost, nil, v1.EventTypeWarning, "ClaimMisbound", "Two claims are bound to the same volume, this one is bound incorrectly"); err != nil {
return err
}
return nil
}
}
}
通过查看源码，可以发现是pv中的claimRef存在，且claimRef.UID与pvc的UID对应不上(if elseif的条件)导致的。主要原因是虽然yaml内有uid，但是apply到一个新的集群内，UID会重新生成，跟yaml内的不一样了。
那我们去掉UID和claimRef，PVC的yaml如下：
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
annotations:
pv.kubernetes.io/bind-completed: "yes"
pv.kubernetes.io/bound-by-controller: "yes"
volume.beta.kubernetes.io/storage-provisioner: com.tencent.cloud.csi.cfs
name: public-devops-teststatefulset-nginx-online-pvc
namespace: test
spec:
accessModes:
- ReadWriteMany
resources:
requests:
storage: 30Gi
storageClassName: cfs-hp
volumeMode: Filesystem
volumeName: pvc-3d65a636-f4c3-4c49-b957-c45673f48bc6
pv的yaml如下：
apiVersion: v1
kind: PersistentVolume
metadata:
annotations:
pv.kubernetes.io/provisioned-by: com.tencent.cloud.csi.cfs
name: pvc-3d65a636-f4c3-4c49-b957-c45673f48bc6
spec:
accessModes:
- ReadWriteMany
capacity:
storage: 30Gi
csi:
driver: com.tencent.cloud.csi.cfs
fsType: ext4
volumeAttributes:
fsid: cfs-3c7e956f6
host: 10.10.144.12
storage.kubernetes.io/csiProvisionerIdentity: 1597949457398-8081-com.tencent.cloud.csi.cfs
storagetype: HP
subnetid: subnet-mg9pp5o5
vpcid: vpc-aqpp2l40
zone: ap-shanghai-4
volumeHandle: cfs-3c7e956f6
persistentVolumeReclaimPolicy: Delete
storageClassName: cfs-hp
volumeMode: Filesystem
将上面的yaml apply后，发现正常了：
[root@sh5-saas-k8scs1-master-online-01 ~]# kubectl get pv pvc-3d65a636-f4c3-4c49-b957-c45673f48bc6
NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
pvc-3d65a636-f4c3-4c49-b957-c45673f48bc6 30Gi RWX Delete Bound test/public-devops-teststatefulset-nginx-online-pvc cfs-hp 4h2m
[root@sh5-saas-k8scs1-master-online-01 ~]# kubectl get pvc -n test public-devops-teststatefulset-nginx-online-pvc -o wide
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE VOLUMEMODE
public-devops-teststatefulset-nginx-online-pvc Bound pvc-3d65a636-f4c3-4c49-b957-c45673f48bc6 30Gi RWX cfs-hp 3h53m Filesystem
