MLBParks App

In this lab, we’re going to deploy a complete backend application, consisting of a REST API backend and a MongoDB database. The complete application will already be wired together and described as a backend for the map visualization tool, so that once the application is built and deployed, you will be able to see the new map.

Background: Templates

Running all these individual commands can be tedious and error prone. Fortunately for you, all of this configuration can be put together into a single Template which can then be processed to create a full set of resources. As you saw with MongoDB, a Template may define parameters for certain values, such as DB username or password, and they can be automatically generated by OpenShift at processing time.

Administrators can load Templates into OpenShift and make them available to all users. Users can create Templates and load them into their own Projects for other users (with access) to share and use.

The great thing about Templates is that they can speed up the deployment workflow for application development by providing a "recipe" of sorts that can be deployed with a single command. Not only that, they can be loaded into OpenShift from an external URL, which will allow you to keep your templates in a version control system.

Let’s combine all of the exercises we have performed in the last several labs by using a Template that we can instantiate with a single command. While we could have used templates to deploy everything in the workshop today, remember that it is important for you to understand how to create, deploy, and wire resources together.

Exercise: Instantiate a Template

The front end application we’ve been working with this whole time will display as many back end services' data as are created. Adding more stuff with the right Label will make more stuff show up on the map.

Now you will deploy a map of Major League Baseball stadiums in the US by using a template. It is pre-configured to build the back end Java application, and deploy the MongoDB database. It also uses a Hook to call the /ws/data/load endpoint to cause the data to be loaded into the database from a JSON file in the source code repository. Execute the following command:

oc create -f https://raw.githubusercontent.com/openshift-roadshow/mlbparks/master/ose3/application-template-eap.json -n workshop

What just happened? What did you just create? The item that we passed to the create command is a Template. create simply makes the template available in your Project. You can see this with the following command:

oc get template

You will see output like the following:

mlbparks      Application template MLBParks backend running on Wildfly and using mongodb   12 (2 blank)   8

Run the following command to instantiate the template:

oc new-app mlbparks -p APPLICATION_NAME=mlbparks

You will see some output similar to this:

--> Deploying template "workshop/mlbparks" to project workshop

     MLBparks
     ---------
     Application template MLBParks backend running on Wildfly and using mongodb

     * With parameters:
        * Application Name=mlbparks
        * Application route=
        * Mongodb App=mongodb-mlbparks
        * Git source repository=https://github.com/openshift-roadshow/mlbparks.git
        * Git branch/tag reference=master
        * Maven mirror url=
        * Database name=mongodb
        * Database user name=userW3n # generated
        * Database user password=4PmSfXWL # generated
        * Database admin password=cBQ4RGJf # generated
        * GitHub Trigger=TOR1p3wO # generated
        * Generic Trigger=NUlqyK54 # generated

--> Creating resources ...
    configmap "mlbparks" created
    service "mongodb-mlbparks" created
    deploymentconfig.apps.openshift.io "mongodb-mlbparks" created
    imagestream.image.openshift.io "mlbparks" created
    buildconfig.build.openshift.io "mlbparks" created
    deploymentconfig.apps.openshift.io "mlbparks" created
    service "mlbparks" created
    route.route.openshift.io "mlbparks" created
--> Success
    Build scheduled, use 'oc logs -f bc/mlbparks' to track its progress.
    Access your application via route 'mlbparks-workshop.apps.cluster-1d43.1d43.openshiftworkshop.com'
    Run 'oc status' to view your app.

OpenShift will now:

Configure and start a build
- Using the supplied Maven mirror URL (if you have specified the parameter)
- From the supplied source code repository
Configure and deploy MongoDB
- Using auto-generated user, password, and database name
Configure environment variables for the app to connect to the DB
Create the correct services
Label the app service with type=parksmap-backend

All with one command!

When the build is complete, visit the parks map. Does it work? Think about how this could be used in your environment. For example, a template could define a large set of resources that make up a "reference application", complete with several app servers, databases, and more. You could deploy the entire set of resources with one command, and then hack on them to develop new features, microservices, fix bugs, and more.

You’ll notice apps are already inside workshop application group and they have a nice EAP and MongoDB icon. This is thanks to the label app.kubernetes.io/part-of and app.kubernetes.io/name that the template already setup for both DeploymentConfigs

In addition to being able to instantiate templates from the command line as we did above, templates can also be instantiated from the Developer Perspective in the web console. Click +Add, then From Catalog and search for mlb. You should see a result for MLBparks.

If you click on MLBparks and then click the Instantiate Template button, you’ll see a form that guides you through the different required and optional parameters needed to instantiate this template.

Do not actually instantiate the template from the web console now, since you have already done so via the command line.

As a final exercise, look at the template that was used to create the resources for our mlbparks application.

oc get template mlbparks -o yaml

But as always, you can use the OpenShift web console to do the same. In the Developer Perspective, click Advanced → Search in the left navigation, then select Template from the dropdown, and click mlbparks.

On the next page, click YAML to see/edit the YAML from here.