Shulou(Shulou.com)06/02 Report--

Why can't k8s pv and PVC be bound?

Using statefuset to deploy stateful applications, applications are always in pending state. Before starting, introduce what is statefuset. In K8s, deployment is generally used to manage stateless applications. Statefuset is used to manage stateful applications, such as redis, mysql, zookper and other distributed applications. These applications will be started and stopped in a strict order.

1. Statefulset

Headless (headless service), without cluserIP, resource identifier, used to generate parsable dns records

StatefulSet is used to manage pod resources

VolumeClaimTemplates provides storage

II. Statefulset deployment

Using nfs for Network Storage

Set up nfs

Configure shared storage directory

Create pv

Choreographed yaml

Set up nfs

Yum install nfs-utils-y

Mkdir-p / usr/local/k8s/redis/pv {7.. 12} # create a mount directory

Cat / etc/exports / usr/local/k8s/redis/pv7 172.16.0 rw,sync,no_root_squash 16 (rw,sync,no_root_squash) / usr/local/k8s/redis/pv8 172.16.0 Universe 16 (rw,sync,no_root_squash) / usr/local/k8s/redis/pv9 172.16.0 Universe 16 (rw,sync,no_root_squash) / usr/local/k8s/redis/pv10 172.16.0.0 Universe 16 (rw,sync) No_root_squash) / usr/local/k8s/redis/pv11 172.16.0.0 no_root_squash 16 (rw,sync,no_root_squash exportfs-avr)

Create pv

Cat nfs_pv2.yaml

ApiVersion: v1kind: PersistentVolumemetadata: name: nfs-pv7spec: capacity: storage: 500m accessModes:-ReadWriteMany persistentVolumeReclaimPolicy: Retain storageClassName: slow nfs: server: 172.16.0.59 path: "/ usr/local/k8s/redis/pv7"-apiVersion: v1kind: PersistentVolumemetadata: name: nfs-pv8spec: capacity: storage: 500m accessModes:-ReadWriteMany storageClassName: slow persistentVolumeReclaimPolicy: Retain nfs: server: 172.16.0.59 path: "/ usr/local / k8s/redis/pv8 "--apiVersion: v1kind: PersistentVolumemetadata: name: nfs-pv9spec: capacity: storage: 500m accessModes:-ReadWriteMany storageClassName: slow persistentVolumeReclaimPolicy: Retain nfs: server: 172.16.0.59 path:" / usr/local/k8s/redis/pv9 "--apiVersion: v1kind: PersistentVolumemetadata: name: nfs-pv10spec: capacity: storage: 500m accessModes:-ReadWriteMany storageClassName: slow persistentVolumeReclaimPolicy: Retain nfs: server: 172.16.0. 59 path: "/ usr/local/k8s/redis/pv10"-apiVersion: v1kind: PersistentVolumemetadata: name: nfs-pv11spec: capacity: storage: 500m accessModes:-ReadWriteMany storageClassName: slow persistentVolumeReclaimPolicy: Retain nfs: server: 172.16.0.59 path: "/ usr/local/k8s/redis/pv11"-- apiVersion: v1kind: PersistentVolumemetadata: name: nfs-pv12spec: capacity: storage: 500m accessModes:-ReadWriteMany storageClassName: slow persistentVolumeReclaimPolicy: Retain nfs: Server: 172.16.0.59 path: "/ usr/local/k8s/redis/pv12"

Kubectl apply-f nfs_pv2.yaml

View # created successfully

Write yaml choreography application

ApiVersion: v1kind: Servicemetadata: name: myapp labels: app: myappspec: ports:-port: 80 name: web clusterIP: None selector: app: myapp-pod---apiVersion: apps/v1kind: StatefulSetmetadata: name: myappspec: serviceName: myapp replicas: 3 selector: matchLabels: app: myapp-pod template: metadata: labels: app: myapp-pod spec: containers:-name: myapp image: ikubernetes / myapp:v1 resources: requests: cpu: "500m" memory: "500Mi" ports:-containerPort: 80 name: web volumeMounts:-name: myappdata mountPath: / usr/share/nginx/html volumeClaimTemplates:-metadata: name: myappdata spec: accessModes: ["ReadWriteOnce"] storageClassName: "slow" resources: requests: storage: 400Mi

Kubectl create-f new-stateful.yaml

Check whether the headless is created successfully

Check whether the pod is created successfully

Check whether the pvc is created successfully

Pod startup is not successful, depends on pvc, check the log of pvc, did not find the corresponding pvc, obviously wrote ah

To view the associated information, there is the following property

StorageClassName: "slow"

III. Statefulset troubleshooting

Pvc could not be created, so pod could not start properly, and the yaml file was rechecked several times.

Direction of thinking: how pvc binds pv, disassociates through storageClassName, pv is also created successfully, and there is also the attribute storageClassName: slow, but I can't find it.

.

.

Later, check whether the permissions of pv and pvc have been

Discover permissions set by pv

VolumeClaimTemplates: declared pvc permissions

The permissions of both sides are not the same.

Operation

Delete pvc kubectl delete pvc myappdata-myapp-0-n daemon

Delete the yaml file, kubectl delete-f new-stateful.yaml-n daemon

Try to modify accessModes: ["ReadWriteMany"]

Check again

Tip: pv and PVC set permission notes

4. Statefulset testing and domain name resolution

Kubectl exec-it myapp-0 sh-n daemon

Nslookup myapp-0.myapp.daemon.svc.cluster.local

The rules for parsing are as follows

Myapp-0 myapp daemon

FQDN: $(podname). (headless server name). Namespace.svc.cluster.local

If there is no nsllokup in the container, you need to install the corresponding package. Busybox can provide similar functions.

Provide yaml files

ApiVersion: v1kind: Podmetadata: name: busybox namespace: daemonspec: containers:-name: busybox image: busybox:1.28.4 command:-sleep-"7600" resources: requests: memory: "200Mi" cpu: "250m" imagePullPolicy: IfNotPresent restartPolicy: Never

5. Expansion and reduction of statefulset

Capacity expansion:

The expansion and reduction of Statefulset resources is similar to that of Deployment resources, that is, by modifying the number of copies, the expansion process of Statefulset resources is similar to the creation process, and the index number of the application name is increased in turn.

You can use kubectl scale

Kubectl patch

Practice: kubectl scale statefulset myapp-replicas=4

Scale down:

Downsizing only needs to reduce the number of pod copies.

Kubectl patch statefulset myapp-p'{"spec": {"replicas": 3}'- n daemon

Tip: to expand and scale up resources, you need to dynamically create a binding relationship between pv and pvc. Here, nfs is used for persistent storage, and how much of pv is created in advance.

VI. Rolling updates of statefulset

Scrolling update

Canary release

Scrolling update

Rolling update starts with the largest index pod number, terminates one resource and starts the next pod. Rolling update is the default update policy of statefulset.

Kubectl set image statefulset/myapp myapp=ikubernetes/myapp:v2-n daemon

Upgrade process

View pod status

Kubectl get pods-n daemon

Check whether the image is updated after the upgrade

Kubectl describe pod myapp-0-n daemon

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