Flask Knowledge Pack

Applies to: Projects detected with requirements.txt, pyproject.toml, or Pipfile containing flask

Quick Reference

Property	Value
Signal files	requirements.txt/pyproject.toml/Pipfile containing flask
Default port	8000 prod (5000 dev — never in prod)
Health path	/health + /ready
Base template	templates/dockerfiles/python.Dockerfile (+ references/base-images.md)

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Health Endpoints

Flask does not include health check endpoints — they must be defined explicitly in application code:

Minimal health route

from flask import Flask, jsonify

app = Flask(__name__)

@app.route("/health")
def health():
    return jsonify(status="ok"), 200

Readiness route with database check

from flask import jsonify
from sqlalchemy import text

@app.route("/ready")
def ready():
    try:
        db.session.execute(text("SELECT 1"))
        return jsonify(status="ready"), 200
    except Exception:
        return jsonify(status="not ready"), 503

Probe configuration in Deployment manifest

livenessProbe:
  httpGet:
    path: /health
    port: 8000
  initialDelaySeconds: 5
  periodSeconds: 15
  timeoutSeconds: 3
  failureThreshold: 3
readinessProbe:
  httpGet:
    path: /ready
    port: 8000
  initialDelaySeconds: 5
  periodSeconds: 10
  timeoutSeconds: 3
  failureThreshold: 3

Note: Flask apps behind gunicorn start quickly (typically <3s), so initialDelaySeconds: 5 is sufficient — much lower than JVM-based frameworks.

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Database Profiles

Flask does not have a built-in profile system. Database configuration is typically driven by environment variables:

ORM / Driver	Package(s)	Connection String Env Var
Flask-SQLAlchemy	flask-sqlalchemy, psycopg2-binary	SQLALCHEMY_DATABASE_URI
SQLAlchemy direct	sqlalchemy, psycopg2-binary	DATABASE_URL
psycopg2 direct	psycopg2-binary	DATABASE_URL

Important: Flask-SQLAlchemy reads the connection string from app.config["SQLALCHEMY_DATABASE_URI"], which is typically set via os.environ.get("SQLALCHEMY_DATABASE_URI") or os.environ.get("DATABASE_URL"). Ensure the env var name matches what the app expects.

Environment variables for PostgreSQL on AKS

env:
  - name: SQLALCHEMY_DATABASE_URI
    value: "postgresql://{{IDENTITY_NAME}}@{{PG_SERVER_NAME}}.postgres.database.azure.com:5432/{{DB_NAME}}?sslmode=require"
  - name: SECRET_KEY
    valueFrom:
      secretKeyRef:
        name: {{APP_NAME}}-secrets
        key: secret-key

Secret for SECRET_KEY

Flask requires SECRET_KEY for session signing, CSRF tokens, and any use of flask.session. Never hardcode it — store it in a Kubernetes Secret:

apiVersion: v1
kind: Secret
metadata:
  name: {{APP_NAME}}-secrets
type: Opaque
stringData: