Python REST API Test Application

2020-10-30 509 words 3 minutes

Contents

When you work in platform engineering focused on infrastructure, you sometimes need to create prototypes specifically built for platform testing purposes. I needed a backend that could simulate real API behavior without coupling to any actual business logic — something I could abuse freely.

Two goals:

Function as a REST API
Run in Kubernetes

Running Locally

Build the image and run it:

docker build --tag pytbak:0.1 .
docker run -t -p 5000:5000 pytbak:0.1

Access the application at localhost:5000/api/

Kubernetes Deployment

From the main folder, apply the configurations:

kubectl apply -f kubernetes/

Verify it’s running:

$ kubectl get pods -n pytbak
NAME                             READY   STATUS    RESTARTS   AGE
pytbak-stable-5dfb4fbfd4-n64kx   1/1     Running   0          40m

Ingress Configuration

You need to change the host in the Ingress file to match your environment:

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: pytbak-ingress
  namespace: pytbak
  annotations:
    ingress.kubernetes.io/proxy-connect-timeout: "10"
    ingress.kubernetes.io/proxy-read-timeout: "30"
    ingress.kubernetes.io/proxy-send-timeout: "30"
spec:
  rules:
  - host: pytbak.ing.h4x0r3d.lan
    http:
      paths:
      - path: /
        backend:
          serviceName: pytbak-svc
          servicePort: 5000

The example uses pytbak.ing.h4x0r3d.lan — that’s my homelab ingress DNS.

DNS Strategy

My home DNS is h4x0r3d.lan with *.ing.h4x0r3d.lan as a wildcard A record pointing to the Kubernetes ingress. This means I don’t need to add DNS entries per service — whatever namespace I create automatically becomes accessible at <namespace>.ing.h4x0r3d.lan. Create a namespace called “pippo” and it’s immediately at pippo.ing.h4x0r3d.lan.

Simple, and it eliminates the DNS management overhead entirely.

API Endpoints

The application responds on /api/ with an HTML interface documenting available methods:

HTTP Method	URI	Action
GET	/api/get/context	Retrieve list of contexts
GET	/api/get/context/[context_id]	Retrieve a specific context
POST	/api/post/context	Create a new context
PUT	/api/put/context/[context_id]	Update an existing context
DELETE	/api/delete/context/[context_id]	Delete a context

Examples

GET all contexts:

$ curl -i http://pytbak.ing.h4x0r3d.lan/api/get/context
HTTP/1.1 200 OK
Server: openresty/1.15.8.1
Content-Type: application/json

{
  "context": [
    {
      "description": "RHEL 6 based",
      "done": false,
      "title": "Cento 6",
      "uri": "http://pytbak.ing.h4x0r3d.lan/api/get/context/1"
    },
    {
      "description": "RHEL 7 based",
      "done": false,
      "title": "Centos 7",
      "uri": "http://pytbak.ing.h4x0r3d.lan/api/get/context/2"
    },
    {
      "description": "RHEL 8 based",
      "done": false,
      "title": "Centos 8",
      "uri": "http://pytbak.ing.h4x0r3d.lan/api/get/context/3"
    },
    {
      "description": "Fedora + RHEL based",
      "done": false,
      "title": "Centos stream",
      "uri": "http://pytbak.ing.h4x0r3d.lan/api/get/context/4"
    }
  ]
}

POST — create a new context:

$ curl -i -H "Content-Type: application/json" -X POST -d '{"title":"Ubuntu 20.04 LTS", "description":"focal"}' http://pytbak.ing.h4x0r3d.lan/api/post/context
HTTP/1.1 201 CREATED
Content-Type: application/json

{
  "task": {
    "description": "focal",
    "done": false,
    "title": "Ubuntu 20.04 LTS",
    "uri": "http://pytbak.ing.h4x0r3d.lan/api/get/context/5"
  }
}

PUT — update an existing context:

$ curl -i -H "Content-Type: application/json" -X PUT -d '{"description":"Focal Fossa"}' http://pytbak.ing.h4x0r3d.lan/api/put/context/5
HTTP/1.1 200 OK
Content-Type: application/json

{
  "task": {
    "description": "Focal Fossa",
    "done": false,
    "title": "Ubuntu 20.04 LTS",
    "uri": "http://pytbak.ing.h4x0r3d.lan/api/get/context/5"
  }
}

DELETE — remove a context:

$ curl -i -H "Content-Type: application/json" -X DELETE http://pytbak.ing.h4x0r3d.lan/api/delete/context/5
HTTP/1.1 200 OK
Content-Type: application/json

{
  "result": true
}

Verify it’s gone:

$ curl -i http://pytbak.ing.h4x0r3d.lan/api/get/context/5
HTTP/1.1 404 NOT FOUND
Content-Type: application/json

{
  "error": "Not found"
}

This application shows up throughout the blog — it’s the backend behind the API gateway post, the rate limiting tests, and various HPA experiments. Having a purpose-built test backend that you fully control makes platform testing much cleaner than hacking against real applications.