View source for OpenShift Create an Application from a Docker Image

=Internal=

* [[Oc_new-app#Modes|oc new-app]]
* [[OpenShift_Application_Operations#Create_a_New_Application|Application Operations]]

=Overview=

A Docker image repository URL can be provided to oc new-app to create an application based on that image. 

 oc new-app <''[[Docker_Concepts#URL|docker-repository-URL]]''>

Example:

 oc new-app docker.io/sonatype/nexus3:latest

This is roughly what happens during the application creation process:

=Primitives=

The utility creates an image stream, a deployment configuration and a service in the ''current project'', and associate all of them with a single application by annotating them with the "app=<''application-name''>" label, where the application name is inferred from - and equal to - the name of the image repository given as argument.

1. '''Image Stream'''. The [[OpenShift_Concepts#Image_Stream|image stream]] name is set to the application name, and the object is associated with the application by the "app=<''app-name''> label. 

 apiVersion: v1
 '''kind''': <font color='teal'>ImageStream</font>
 metadata:
  '''labels''':
    '''app''': <font color='teal'>nexus3</font>
  '''name''': <font color='teal'>nexus3</font>
 '''spec''':
  lookupPolicy:
    local: false
  '''tags''':
    '''name''': <font color='teal'>latest</font>
    '''from''':
      '''kind''': <font color='teal'>DockerImage</font>
      '''name''': <font color='teal'>docker.io/sonatype/nexus3:latest</font>
    referencePolicy:
      type: Source

{{Internal|OpenShift_Concepts#Image_Stream|Image Streams}}

2. '''Deployment Configuration''' The [[OpenShift Concepts#Deployment_Configuration|deployment configuration]] defines a [[OpenShift_DeploymentConfig_Definition#selector|selector that applied over pods, returns the number of pods that should match the replica count]].  It also defines a "rolling" deployment strategy by default. You may want to change that after the application primitives are first created. The deployment configuration includes the labels applied to the pod and pod's specification. The pod will consist of one container, which will be instantiated from the image specified as argument.

OpenShift performs an introspection of the image metadata and extracts the ports that should be exposed and the Docker data volumes needed, which are declaratively associated with persistent volumes:

 "Id": "sha256:0b6b1bc88ccb767d128d87002d164ca1bd90ca0b7775aed3864504dcf8f968d8",
 "Config": {
     ...
     "'''ExposedPorts'''": {
         <font color='teal'>"8081/tcp"</font>: {}
     },
     ...
     "'''Volumes'''": {
         <font color='teal'>"/nexus-data"</font>: {}
     },
      ...
 }

By default, the deployment configuration declares an "emptyDir" volume, which is a temporary directory whose content will be lost upon pod recycling, so this is probably something you may want to change.

Finally, the deployment configuration contains metadata that says the redeployment will be attempted on configuration change and image change.

 apiVersion: v1
 '''kind''': <font color='teal'>DeploymentConfig</font>
 metadata:
  '''name''': <font color='teal'>nexus3</font>
  '''labels''':
    '''app''': <font color='teal'>nexus3</font>
 spec:
  '''selector''':
    '''app''': <font color='teal'>nexus3</font>
    deploymentconfig: nexus3
  '''strategy''':
    '''type''': <font color='teal'>Rolling</font>
    rollingParams:
      ...
    activeDeadlineSeconds: 21600
  '''template''':
    '''metadata''':
      '''labels''':
        '''app''': <font color='teal'>nexus3</font>
        deploymentconfig: nexus3
    '''spec''':
      '''containers''':
      - '''name''': <font color='teal'>nexus3</font>
        '''image''': docker.io/sonatype/nexus3@sha256:1b1a581c76bf2a43112d4eea0077a73aadf234bb34a7b56f76fd5f3c1634dcaf
        imagePullPolicy: Always
        '''ports''':
        - '''containerPort''': <font color='teal'>8081</font>
          protocol: TCP
        '''volumeMounts''':
        - '''name''': <font color='teal'>nexus3-volume-1</font>
          '''mountPath''': <font color='teal'>/nexus-data</font>
      dnsPolicy: ClusterFirst
      restartPolicy: Always
      schedulerName: default-scheduler
      terminationGracePeriodSeconds: 30
      '''volumes''':
      - '''name''': <font color='teal'>nexus3-volume-1</font>
        emptyDir: {}
  test: false
  '''triggers''':
  - '''type''': <font color='teal'>ConfigChange</font>
  - '''type''': <font color='teal'>ImageChange</font>
    imageChangeParams:
      automatic: true
      containerNames:
      - nexus3
      from:
        kind: ImageStreamTag
        name: nexus3:latest
        namespace: production-nexus
    
{{Internal|OpenShift_Concepts#Deployment_Configuration|Deployment Configuration}}

3. '''Service'''

 apiVersion: v1
 '''kind''': <font color='teal'>Service</font>
 metadata:
  '''name''': <font color='teal'>nexus3</font>
  labels:
    app: nexus3
 spec:
  clusterIP: 172.30.73.18
  ports:
  - name: 8081-tcp
    port: 8081
    protocol: TCP
    targetPort: 8081
  selector:
    app: nexus3
    deploymentconfig: nexus3
  sessionAffinity: None
  type: ClusterIP

{{Internal|OpenShift_Concepts#Service|Service}}

=Post-Creation Operations=

Simply creating the application triggers a deployment, while the application is not ready yet to be deployed, so we disable the automatic deployment and drop what has already been deployed:

 [[OpenShift_Application_Operations#pause|oc rollout pause]] dc nexus3
 oc delete rc <''rc-name''>

Deleting the replication controller will also terminate the pod it started.

==Change the Deployment Strategy==

 [[oc patch]] dc nexus3 --patch='{ "spec": { "strategy": { "type": "Recreate" }}}'

<font color=red>Don't I need to also change configuration?</font>

==Attach a Valid Persistence Volume==

For this to work, a 2Gi or more persistent volume must be already provisioned and available.

Create the persistent volume claim:

 echo "apiVersion: v1
 kind: PersistentVolumeClaim
 metadata:
  name: production-nexus-pvc
 spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 2Gi" | oc create -f -

If an appropriate persistent volume exists, it will be immediately bound after the persistent volume claim creation.

Modify the deployment configuration to use the persistent volume claim:

 [[Oc_set#Delete_the_Definition_of_a_Volume|oc set volumes]] dc/nexus3 [[Oc_set#Delete_the_Definition_of_a_Volume|--remove]] --name=nexus3-volume-1

 [[Oc_set#Adding_the_Definition_of_a_New_Volume|oc set volumes]] dc/nexus3 [[Oc_set#Adding_the_Definition_of_a_New_Volume|--add]] --name=nexus-data --mount-path=/nexus-data/ --type persistentVolumeClaim --claim-name=production-nexus-pvc

==Setup Resources==

 [[Oc_set#resources|oc set resources]] dc/nexus3 --limits=memory=2Gi --requests=memory=1Gi

==Setup the Readiness and Liveness Probes==

 [[Oc_set#probe|oc set probe]] dc/nexus3 --readiness \
 --failure-threshold 3 --initial-delay-seconds 120 \
 --get-url=http&#58;//:8081/repository/maven-public/

 [[Oc_set#probe|oc set probe]] dc/nexus3 --liveness \
 --failure-threshold 3 --initial-delay-seconds 120 \
 -- echo ok

==Expose the Service==

 [[OpenShift_Route_Operations#Expose_a_Service|oc expose service]] nexus3 --hostname=maven.apps.openshift.novaordis.io

==Resume Rollout==

 [[OpenShift_Application_Operations#resume|oc rollout resume]] dc nexus3

=Example=

For more details on how to deploy a production-ready Nexus instance starting with oc new-app <''nexus-image-url''>, go to:

{{Internal|OpenShift_Nexus#Deploy_Nexus_Based_on_a_Standard_Sonatype_Docker_Image|Deploy Nexus Based on a Standard Sonatype Docker Image}}