Exercise 1.1 - OpenShift Templates | Red Hat

What are OpenShift Templates

A template describes a set of objects that can be parameterized and processed to produce a list of objects for creation by OpenShift Container Platform. A template can be processed to create anything you have permission to create within a project, for example services, build configurations, and deployment configurations. A template may also define a set of labels to apply to every object defined in the template.

You can create a list of objects from a template using the CLI or, if a template has been uploaded to your project or the global template library, using the web console. For a curated set of templates, see the OpenShift Image Streams and Templates library OpenShift Image Streams and Templates library.

Exploring OpenShift Templates

Step 1:

First lets create a new name space to work in. Namespaces are a way to get your own space of computing on a OpenShift cluster where you can deploy applications.

See Template Parameters

oc new-project template --description="Exploring Templates" --display-name="Templates"

Now lets look at a default template for the Nodejs & MongoDB template.

See Template Parameters

oc process --parameters -n openshift nodejs-mongo-persistent

Results

Table 1. Windtrainer workouts
NAME	DESCRIPTION	GENERATOR	VALUE
NAME	The name assigned to all of the frontend objects defined in this template.
NAMESPACE	The OpenShift Namespace where the ImageStream resides.		openshift
MEMORY_LIMIT	Maximum amount of memory the Node.js container can use.		512Mi
MEMORY_MONGODB_LIMIT	Maximum amount of memory the MongoDB container can use.		512Mi
VOLUME_CAPACITY	Volume space available for data, e.g. 512Mi, 2Gi		1Gi
SOURCE_REPOSITORY_URL	The URL of the repository with your application source code.
SOURCE_REPOSITORY_REF	Set this to a branch name, tag or other ref of your repository if you are not using the default branch.
CONTEXT_DIR	Set this to the relative path to your project if it is not in the root of your repository.
APPLICATION_DOMAIN	The exposed hostname that will route to the Node.js service, if left blank a value will be defaulted.
GITHUB_WEBHOOK_SECRET	Github trigger secret. A difficult to guess string encoded as part of the webhook URL. Not encrypted.	expression	[a-zA-Z0-9]{40}
GENERIC_WEBHOOK_SECRET	A secret string used to configure the Generic webhook.	expression	[a-zA-Z0-9]{40}
DATABASE_SERVICE_NAME			mongodb
DATABASE_USER	Username for MongoDB user that will be used for accessing the database.	expression	user[A-Z0-9]{3}
DATABASE_PASSWORD	Password for the MongoDB user.	expression	[a-zA-Z0-9]{16}
DATABASE_NAME			sampledb
DATABASE_ADMIN_PASSWORD	Password for the database admin user.	expression	[a-zA-Z0-9]{16}

In this example we see that we can, from a security angle control exactly what we want to run in our container environment. The Template is how we can configure what source code repositories we want to allow a end user run or developer to develop against. Templates define what the application limits can be for further constraining an applications memory, or storage. This is alo a place where we can pass environmental variables to the application as well.

Step 2:

Lets take a deeper look at Templates by switching over to a higher privileged user to be able to edit the Template with your built in editor of choice, (it’s VIM).

oc login -u system:admin

OpenShift provides the ability to quickly make changes to templates for users with correct permissions.

View/Edit Template Parameters

oc edit -n openshift template nodejs-mongo-persistent

Exit by esc + : + q

esc + : + q

Step 3:

Lets go ahead and launch a template from the commandline

Launch the Template

oc process -n openshift nodejs-mongo-persistent | oc create -f -

Multiple OpenShift objects created

secret "nodejs-mongo-persistent" created
service "nodejs-mongo-persistent" created
route "nodejs-mongo-persistent" created
imagestream "nodejs-mongo-persistent" created
buildconfig "nodejs-mongo-persistent" created
deploymentconfig "nodejs-mongo-persistent" created
persistentvolumeclaim "mongodb" created
service "mongodb" created
deploymentconfig "mongodb" created

You should be able to login to the web UI (EXAMPLE: http://nodejs-mongo-persistent-myproject.apps.ocp.0.redhatgov.io/) and in your Templates project and see the Nodejs application.

Click the Nodejs route;