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Sample 'Programming Jokes' Application Deployment and Update Guide on OpenShift

This README provides a comprehensive guide on deploying a simple Flask application, which serves extremely cheesy and randomly selected programming jokes, on OpenShift, and also outlines how to update the application with new content and versioning.

Prerequisites

  • Access to an OpenShift cluster
  • OpenShift CLI (oc) installed
  • Podman or Docker installed
  • Git installed

Initial Setup

Log Into Your OpenShift Cluster

Authenticate via CLI:

oc login --token=<your-token> --server=<your-cluster-api-url>

Expose the Internal OpenShift Registry

Ensure the internal registry is externally accessible:

oc patch configs.imageregistry.operator.openshift.io/cluster --patch '{"spec":{"defaultRoute":true}}' --type=merge

Clone the Repository

Clone the application's repository:

git clone https://github.com/bstrauss84/programming-jokes-demo.git
cd ./programming-jokes-demo

Define Environment Variables

To simplify the rest of this excercise, let's go ahead and define some environment variables for our OpenShift internal registry route, as well as the namespace, and initial image tag for our sample application:

OPENSHIFT_REGISTRY_ROUTE=$(oc get route default-route -n openshift-image-registry --template='{{ .spec.host }}')
NAMESPACE="demo-$(oc whoami)"

Create your Application Namespace

Create your namespace:

oc new-project $NAMESPACE

Application Structure

  • app.py: The main Flask application file containing the server logic and joke list.
  • requirements.txt: Specifies Python package dependencies for the application.
  • templates/index.html: HTML template for rendering the jokes in a web browser.
  • Containerfile: Used to build the container image of the application.

Deploying the Application

Build the Container Image

Build your image using Podman or Docker:

podman build -t $OPENSHIFT_REGISTRY_ROUTE/$NAMESPACE/programming-jokes:latest .

Tag and Push the Image to the OpenShift Registry

Authenticate with the OpenShift registry:

podman login -u $(oc whoami) -p $(oc whoami -t) $OPENSHIFT_REGISTRY_ROUTE

Push your image to the internal OpenShift registry:

podman push $OPENSHIFT_REGISTRY_ROUTE/$NAMESPACE/programming-jokes:latest

Deploy and Expose the Application

Deploy your application on OpenShift:

oc new-app $NAMESPACE/programming-jokes:latest --name=programming-jokes-app
oc create route edge programming-jokes-app --service=programming-jokes-app --insecure-policy=Redirect

Accessing Your Deployed Application

After deploying your application and exposing it via a route, you can easily find the URL to access it with the following command:

echo "Application URL: https://$(oc get route programming-jokes-app -o jsonpath='{.spec.host}')"

Next Steps:

  1. Navigate to the Application URL: Open a web browser and go to the URL output by the previous command.
  2. Explore the Application: Click the "Get Another Joke" button a few times to see different programming jokes displayed. This verifies that your application is running successfully and serving content dynamically.

Updating the Application

To update your application (e.g., adding new jokes), follow these steps:

  1. Edit app.py:

    Add a new joke to the end of the joke list. For example...

    "I've been using Vim for a long time now, mainly because I can't figure out how to exit it."

IMPORTANT: Remember, when adding a new joke, ensure you place a comma at the end of the preceding line to maintain valid Python list syntax.

  1. (Optional) Update the Containerfile:

    Modify the ENV variable APP_VERSION in the Containerfile from 1.0 to 2.0.

  2. Rebuild and Push the Updated Image:

    Rebuild the image with the new content:

    podman build -t $OPENSHIFT_REGISTRY_ROUTE/$NAMESPACE/programming-jokes:latest .

    Push the updated image to the registry:

    podman push $OPENSHIFT_REGISTRY_ROUTE/$NAMESPACE/programming-jokes:latest

Verifying Application Updates

Ensure the deployment has rolled out the new version:

oc rollout status deployment/programming-jokes-app
oc get pods -n $NAMESPACE

After updating your application, pushing the new image, and ensuring your deployment is using this latest version, repeat the process to access your application:

echo "Application URL: https://$(oc get route programming-jokes-app -o jsonpath='{.spec.host}')"

Next Steps:

  1. Visit the Application Again: Use the URL provided by the command to open your application in a web browser.
  2. Check for New Content: Press the "Get Another Joke" button multiple times until you see the new jokes appear. This confirms that the update was successful and the new version of your application is live. If you did the optional step earlier, where you updated the Containerfile, you should notice that the "Current Version:" listed beneath the button has been updated as well.

Updated Application

Conclusion

This guide walked us through the process of deploying a simple Flask application on OpenShift, making updates to the application, and managing deployment updates. It covered everything from initial setup to deploying and updating the application.

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