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Manage KubeDB objects using CLIs

KubeDB CLI

KubeDB comes with its own cli. It is called kubedb cli. kubedb can be used to manage any KubeDB object. kubedb cli also performs various validations to improve ux. To install KubeDB cli on your workstation, follow the steps here.

How to Create objects

kubectl create creates a database CRD object in default namespace by default. Following command will create a Memcached object as specified in memcached.yaml.

$ kubectl create -f memcached-demo.yaml
memcached.kubedb.com/memcached-demo created

You can provide namespace as a flag --namespace. Provided namespace should match with namespace specified in input file.

$ kubectl create -f memcached-demo.yaml --namespace=kube-system
memcached.kubedb.com/memcached-demo created

kubectl create command also considers stdin as input.

cat memcached-demo.yaml | kubectl create -f -

How to List Objects

kubectl get command allows users to list or find any KubeDB object. To list all Memcached objects in default namespace, run the following command:

$ kubectl get memcached
NAME             VERSION    STATUS    AGE
memcached-demo   1.5.4-v1   Running   40s
memcached-dev    1.5.4-v1   Running   40s
memcached-prod   1.5.4-v1   Running   40s
memcached-qa     1.5.4-v1   Running   40s

To get YAML of an object, use --output=yaml flag.

$ kubectl get memcached memcached-demo --output=yaml
apiVersion: kubedb.com/v1alpha2
kind: Memcached
metadata:
  creationTimestamp: 2018-10-04T05:58:57Z
  finalizers:
  - kubedb.com
  generation: 1
  labels:
    kubedb: cli-demo
  name: memcached-demo
  namespace: demo
  resourceVersion: "6883"
  selfLink: /apis/kubedb.com/v1alpha2/namespaces/default/memcacheds/memcached-demo
  uid: 953df4d1-c79a-11e8-bb11-0800272ad446
spec:
  podTemplate:
    controller: {}
    metadata: {}
    spec:
      resources:
        limits:
          cpu: 500m
          memory: 128Mi
        requests:
          cpu: 250m
          memory: 64Mi
  replicas: 3
  terminationPolicy: Halt
  version: 1.5.4-v1
status:
  observedGeneration: 1$7916315637361465932
  phase: Running

To get JSON of an object, use --output=json flag.

kubectl get memcached memcached-demo --output=json

To list all KubeDB objects, use following command:

$ kubectl get all -o wide
NAME                    VERSION     STATUS   AGE
mc/memcached-demo       1.5.4-v1    Running  3h
mc/memcached-dev        1.5.4-v1    Running  3h
mc/memcached-prod       1.5.4-v1    Running  3h
mc/memcached-qa         1.5.4-v1    Running  3h

Flag --output=wide is used to print additional information.

List command supports short names for each object types. You can use it like kubectl get <short-name>. Below are the short name for KubeDB objects:

  • Memcached: mc
  • DormantDatabase: drmn

You can print labels with objects. The following command will list all Memcached with their corresponding labels.

$ kubectl get mc --show-labels
NAME             VERSION    STATUS    AGE       LABELS
memcached-demo   1.5.4-v1   Running   2m        kubedb=cli-demo

To print only object name, run the following command:

$ kubectl get all -o name
memcached/memcached-demo
memcached/memcached-dev
memcached/memcached-prod
memcached/memcached-qa

How to Describe Objects

kubectl dba describe command allows users to describe any KubeDB object. The following command will describe Memcached server memcached-demo with relevant information.

$ kubectl dba describe mc memcached-demo
Name:               memcached-demo
Namespace:          default
CreationTimestamp:  Thu, 04 Oct 2018 11:58:57 +0600
Labels:             kubedb=cli-demo
Annotations:        <none>
Replicas:           3  total
Status:             Running

Deployment:
  Name:               memcached-demo
  CreationTimestamp:  Thu, 04 Oct 2018 11:58:59 +0600
  Labels:               kubedb=cli-demo
                        app.kubernetes.io/name=memcacheds.kubedb.com
                        app.kubernetes.io/instance=memcached-demo
  Annotations:          deployment.kubernetes.io/revision=1
  Replicas:           3 desired | 3 updated | 3 total | 3 available | 0 unavailable
  Pods Status:        3 Running / 0 Waiting / 0 Succeeded / 0 Failed

Service:
  Name:         memcached-demo
  Labels:         kubedb=cli-demo
                  app.kubernetes.io/name=memcacheds.kubedb.com
                  app.kubernetes.io/instance=memcached-demo
  Annotations:  <none>
  Type:         ClusterIP
  IP:           10.102.208.191
  Port:         db  11211/TCP
  TargetPort:   db/TCP
  Endpoints:    172.17.0.4:11211,172.17.0.5:11211,172.17.0.6:11211

No Snapshots.

Events:
  Type    Reason      Age   From                Message
  ----    ------      ----  ----                -------
  Normal  Successful  2m    Memcached operator  Successfully created Service
  Normal  Successful  2m    Memcached operator  Successfully created StatefulSet
  Normal  Successful  2m    Memcached operator  Successfully created Memcached
  Normal  Successful  2m    Memcached operator  Successfully patched StatefulSet
  Normal  Successful  2m    Memcached operator  Successfully patched Memcached

kubectl dba describe command provides following basic information about a Memcached server.

  • Deployment
  • Service
  • Monitoring system (If available)

To hide events on KubeDB object, use flag --show-events=false

To describe all Memcached objects in default namespace, use following command

kubectl dba describe mc

To describe all Memcached objects from every namespace, provide --all-namespaces flag.

kubectl dba describe mc --all-namespaces

To describe all KubeDB objects from every namespace, use the following command:

kubectl dba describe all --all-namespaces

You can also describe KubeDB objects with matching labels. The following command will describe all Memcached objects with specified labels from every namespace.

kubectl dba describe mc --all-namespaces --selector='group=dev'

To learn about various options of describe command, please visit here.

How to Edit Objects

kubectl edit command allows users to directly edit any KubeDB object. It will open the editor defined by KUBEDB_EDITOR, or EDITOR environment variables, or fall back to nano.

Let’s edit an existing running Memcached object to setup Monitoring. The following command will open Memcached memcached-demo in editor.

$ kubectl edit mc memcached-demo

#spec:
#  monitor:
#    agent: prometheus.io/builtin

memcached "memcached-demo" edited

Edit Restrictions

Various fields of a KubeDB object can’t be edited using edit command. The following fields are restricted from updates for all KubeDB objects:

  • apiVersion
  • kind
  • metadata.name
  • metadata.namespace
  • status

If Deployment exists for a Memcached server, following fields can’t be modified as well.

  • spec.nodeSelector
  • spec.podTemplate.spec.nodeSelector
  • spec.podTemplate.spec.env

For DormantDatabase, spec.origin can’t be edited using kubectl edit

How to Delete Objects

kubectl delete command will delete an object in default namespace by default unless namespace is provided. The following command will delete a Memcached memcached-dev in default namespace

$ kubectl delete memcached memcached-dev
memcached.kubedb.com "memcached-dev" deleted

You can also use YAML files to delete objects. The following command will delete a memcached using the type and name specified in memcached.yaml.

$ kubectl delete -f memcached-demo.yaml
memcached.kubedb.com "memcached-dev" deleted

kubectl delete command also takes input from stdin.

cat memcached-demo.yaml | kubectl delete -f -

To delete database with matching labels, use --selector flag. The following command will delete memcached with label memcached.app.kubernetes.io/instance=memcached-demo.

kubectl delete memcached -l memcached.app.kubernetes.io/instance=memcached-demo

Using Kubectl

You can use Kubectl with KubeDB objects like any other CRDs. Below are some common examples of using Kubectl with KubeDB objects.

# List objects
$ kubectl get memcached
$ kubectl get memcached.kubedb.com

# Delete objects
$ kubectl delete memcached <name>

Next Steps