starter

An example Python/starlette-based web application, deployable to Kubernetes with all the essentials.

Problem Definition

Develop a webservice and implement the following methods:

1. /add
   • It will take two numbers and add them together.
   • Return the result of adding them.
2. /substract
   • It will take two real numbers and return the result of subtracting them.
3. /division
   • Divide two numbers, return the result.
4. /random
   • Optional argument Count.
   • It will return by default 10 random numbers if Count provided, return the amount of random numbers requested.
5. /metrics
   • Provide prometheus metrics that you see fit.
6. /readiness
   • 200 if service is ready to take requests.
7. /liveness
   • 200 if the service is alive.

Also:

• Include unit tests
• Dockerize the above webservice.
• Employ the best practices you are aware of to create a good container image.
• Create Kubernetes manifests to deploy this web service into Kubernetes.
  • Use the nginx ingress class.

Getting Started - Locally

A Makefile is provided with various utility targets to help you get going. A good place to start is to try running the tests:

# From root of project...
make build
# Output from docker build here...
make test
# Test output here...

While developing the application locally, the easiest way to run the server is to use the make run target:

make build
make run

This will start the application in an auto-reload mode where if you make any changes to your local files, the server will automatically restart.

Deployment - Minikube

This application was developed to deploy against minikube with its nginx ingress addon configured. Please see the make deploy_to_minikube target and associated script for how this deployment works.

Pre-requisites

1. Have kapp installed. This is used to deploy the application's manifest to the cluster, grouping its resources.
2. Have built and published the Dockerfile to Docker Hub. (Hint: use make publish_image)
3. Change out the image field in the Deployment's pod spec to match where you pushed your image

Notes on the Kubernetes Manifest

Typically I would use a Helm chart here but for this small example, I went for a simpler bare YAML approach with kapp to take care of the application management side of things. In the past I have also used ArgoCD successfully to complete this responsiblity of deployment lifecycle management in a GitOps pattern.

When it comes to the task of templating itself, an alternative I have been exploring recently would be to use ytt to template and patch the manifest as required before then using kapp or ArgoCD to deploy.

Monitoring

As far as monitoring, Prometheus has been integrated to provide a standard set of generic HTTP server-relevant and Python-specific metrics. This along with a log collection solution integrated at cluster level would be sufficient for managing the service in production.

If I were to take this further, I would also integrate Honeycomb to introduce an event-based observability tool with distributed tracing too.