Reading secrets from Kubernetes within Python based app

I’m packaging a Python app for use within a Kubernetes cluster. In the code base this method exists :

   def get_pymongo_client(self):
        username = test;
        password = 'test';
        url = ‘test
        conn_str = "mongodb+srv://" + username + ":" + password + “/”+ url

        return pymongo.MongoClient(conn_str)

I’m attempting to secure the username, password & URL fields so that they are not viewable within the src code. For this, I plan to use secrets.

The URL https://kubernetes.io/docs/tasks/configmap-secret/managing-secret-using-kubectl/ details how to create a secret. But I’m not sure how to read the secret from the Python app.

.Dockerfile for my app:

#https://docs.docker.com/language/python/build-images/

FROM python:3.8-slim-buster

WORKDIR /app

COPY requirements.txt requirements.txt

RUN pip3 install -r requirements.txt

COPY . .

CMD [ "python3", "-m" , "flask", "run", "--host=0.0.0.0"]

Reading Python flask application access to docker secrets in a swarm details the use of secrets in a docker-compose file, is this also required for Kubernetes? What steps are involved in order to read secret parameters from the Python src code file?

The traditional way is via environment variable

spec:
  containers:
  - name: your-app
    # ...
    env:
    - name: PYMONGO_USERNAME
      valueFrom:
        secretKeyRef:
           name: your-secret-name-here
           key: PYMONGO_USERNAME

Or you can make that yaml less chatty by using a well-formed Secret and the "envFrom:" field

kind: Secret
metadata:
  name: pymongo
stringData:
  PYMONGO_USERNAME: test
  PYMONGO_PASSWORD: sekrit
---
spec:
  containers:
  - name: your-app
    envFrom:
    - secretRef:
        name: pymongo
    # and now the pod has all environment variables matching the keys in the Secret

and then your code would just read it from its environment as normal

   def get_pymongo_client(self):
        username = os.getenv('PYMONGO_USERNAME')
        password = os.getenv('PYMONGO_PASSWORD')
        # etc

An alternative, but similar idea, is to mount the Secret onto the filesystem, and then read in the values as if they were files

spec:
  containers:
  - name: your-app
    env:
    # this part is 100% optional, but allows for easier local development
    - name: SECRETS_PATH
      value: /secrets
    volumeMounts:
    - name: pymongo
      mountPath: /secrets 
  volumes:
  - name: pymongo
    secret:
      secretName: your-secret-name-here

then:

   def get_pymongo_client(self):
        sec_path = os.getenv('SECRETS_PATH', './secrets')
        with open(os.path.join(sec_path, 'PYMONGO_USERNAME')) as fh:
            username = fh.read()