Launch a Simple Flask App on DOKs

This codebase contains all of the necessary files required to launch a simple Flask application on Digital Ocean Kubernetes (DOKs).

Required Packages

• Doctl
• Docker Desktop

Prequisites

• DigitalOcean Container Registry (DOCR) is already created.
• DigitalOcean Kubernetes (DOKs) cluster is already provisioned.
• DOCR + DOks are already integrated.

Assumptions

Any environment variable configurations will be handled via python-dotenv or kubectl secrets.

Getting Started

Create a new directory in a location of your choice on your local machine and clone this repository into it.

git clone https://github.com/codyfishman/doks-resources/

Dockerize Application

Build the image locally with Docker.

docker build -t my-python-app .

Confirm the image is available in your local Docker registry.

docker images

Run the image locally with Docker.

docker run -ti -p 80:80 my-python-app

Push Docker Image to DOCR

Run doctl’s login command for registries.

docker registry login

Tag your image locally with the DigitalOcean registry name.

docker tag my-python-app registry.digitalocean.com/<your-registry-name>/my-python-app

Push your image from the local Docker registry to the DigitalOcean registry.

docker push registry.digitalocean.com/<your-registry-name>/my-python-app

Deploy Application to DOKs Cluster

Deploy your application to your DOKs cluster by submitting a deployment object.

kubectl create deployment my-python-app --image=registry.digitalocean.com/<your-registry-name>/my-python-app

Check the replica set configuration.

kubectl get rs

Check the state of your pods (containers running your application).

kubectl get pods

Create a Load Balancer Service

Expose your application to the internet via a load balancer.

kubectl expose deployment my-python-app --type=LoadBalancer --port=80 --target-port=80

Confirm that the load balancer is activated.

doctl compute load-balancer list --format Name,Created,IP,Status

Troubleshooting

Confirm that the image exists on DOCR.

doctl registry repository list-tags <your-registry-name>/my-python-app

Check for warnings and error messages in the event log for a particular pod.

• You can get the pod name by running kubectl get pods and copying the name value listed for a degraded pod.

kubectl describe pod <pod_name>

Restart a deployment after fixes have been implemented.

kubectl rollout restart deployment my-python-app