flask-healthz 0.0.2

A simple module to allow you to easily add health endpoints to your Flask application

Flask-Healthz

Define endpoints in your Flask application that Kubernetes can use as liveness and readiness probes.

Setting it up

Register the blueprint on your Flask application:

from flask import Flask
from flask_healthz import healthz

app = Flask(__name__)
app.register_blueprint(healthz, url_prefix="/healthz")

Define the functions you want to use to check health. To signal an error, raise flask_healthz.HealthError.

from flask_healthz import HealthError

def liveness():
    pass

def readiness():
    try:
        connect_database()
    except Exception:
        raise HealthError("Can't connect to the database")

Now point to those functions in the Flask configuration:

HEALTHZ = {
    "live": "yourapp.checks.liveness",
    "ready": "yourapp.checks.readiness",
}

It is possible to directly set callables in the configuration, so you could write something like:

HEALTHZ = {
    "live": lambda: None,
}

Check that the endpoints actually work:

$ curl http://localhost/yourapp/healthz/live
OK
$ curl http://localhost/yourapp/healthz/ready
OK

Now your can configure Kubernetes or OpenShift to check for those endpoints. Here's an example of how you could do that in OpenShift's deploymentconfig:

kind: DeploymentConfig
spec:
  [...]
  template:
    [...]
    spec:
      containers:
      - name: yourapp
        [...]
        livenessProbe:
          httpGet:
            path: /healthz/live
            port: 8080
          initialDelaySeconds: 5
          timeoutSeconds: 1
        readinessProbe:
          httpGet:
            path: /healthz/ready
            port: 8080
          initialDelaySeconds: 5
          timeoutSeconds: 1

Examples

Here are some projects that have setup flask-healthz:

• Noggin: https://github.com/fedora-infra/noggin/pull/287
• FASJSON: https://github.com/fedora-infra/fasjson/pull/81

License

Copyright 2020 Red Hat

Flask-Healthz is licensed under the same license as Flask itself: BSD 3-clause.