Timber

Hey there! This is Timber.

Timber is an app that you'll use in the challenge we've set you following your recent training.

It replicates a "traditional web app" setup, where there is a frontend, a backend and a database (you'll use Redis).

Functionality in the app is enabled & disabled mostly through environment variables.

Timber is written in Python 3, but if you're not a Python expert, fear not! It is, we hope, well-documented and fairly easy to understand.

Backend

The backend is an API exposing data through HTTP endpoints. They are all GET endpoints for simplicity. Some endpoints have a description value to pass a human readable sentence to the frontend. Some endpoints require Timber to be running in a Kubernetes cluster, and so their descriptions are omitted for this challenge.

The entrypoint of the Backend API is app.py.

/api/v1/fortune

Returns a fortune cookie read from a file on a volume. This file is generated by a separate service.

/api/v1/configuration

This API endpoint returns the configuration of Timber, which is set through environment variables.

Environment Variable	What it does	Default
TIMBER_LIVENESS_PROBE_ENABLED	Set to any value to enable /probe/liveness	Disabled
TIMBER_READINESS_PROBE_ENABLED	Set to any value to enable /probe/readiness	Disabled
TIMBER_VERSION	Currently running application version	v1.0
TIMBER_REDIS_HOST	Redis server used if state is set to redis	redis
TIMBER_STATE	State storage: inmemory, redis	inmemory
TIMBER_LISTEN_PORT	Set the port Timber listens on	8080

{
    description: <...>,
    liveness_probe_enabled: <true/false>,
    readiness_probe_enabled: <true/false>,
    redis_host: <...>,
    state: <...>,
    version: <...>
}

/api/v1/colors

This API endpoint returns deterministic hex colors.

Colors are generated based on the values of TIMBER_VERSION, TIMBER_HOSTNAME, TIMBER_STATE.

{
    hostname: <...>,
    state: <...>,
    version: <...>
}

/api/v1/state

This API returns information about the state kept by the backend.

{
    type: <inmemory|redis>,
    image_link: <...>  # The picture we are keeping in state
    state_hits: <int>  # Number of times the state has been checked
}

Frontend

The frontend shows all the data that the backend provides, and some more.

Data from all the backend APIs is used, as well as showing the frontend hostname.

/

This is the frontend index. It uses index.html as a template, and gets the data from the backend API.

configuration.py

The frontend is configured using environment variables.

Environment Variable	What it does	Default
TIMBER_BACKEND_API_URL	Sets the backend URL	http://backend:8080
TIMBER_LISTEN_PORT	Sets the port Timber listens on	8080

Fortune

The fortune service is a basic bash script. It's a simple loop that writes a fortune cookie to the directory /var/htdocs every 10 seconds.