Timber - the Training companion app

Hey there! This is Timber.

Timber is a companion app for the ContainerSolutions trainings.

Its aim is to provide with engineers attending the trainings with a sample application they can build upon and play with during the trainings.

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

Functionality is enabled & disabled mostly through environment variables.

Timber is written in Python 3. Fear not! It is, we hope, well-documented and fairly easy to understand.

• Timber - the Training companion app
  • 💻 Running it locally
  • 🚀 Running it on Kubernetes
  • 🐉 Backend
    • /api/v1/fortune
    • /api/v1/metadata
    • /api/v1/configuration
    • /api/v1/colors
    • /api/v1/redis_detection
    • /api/v1/state
  • 💎 Frontend
    • /
    • configuration.py
    • backend.py

💻 Running it locally

Pretty straightforward! - $ docker-compose up

Editing any .py files will make the application reload with your changes.

🚀 Running it on Kubernetes

Some manifests are provided for you in the manifests/ folder.

There are different ways to set this up, namely, you could at least:

• Run the backend alone
• Run the backend and the frontend in the same pod
• Run the backend and the frontend in different pods, accessing each other with services
• Run the frontend, backend and redis in different pods, accessing each other with services
• Run the frontend, backend and redis in the same pod

And many more!

🐉 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.

The entrypoint of the 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 container. See manifests/backend/solutions/deploy-volume.yml

/api/v1/metadata

The metadata is gathered mostly through the Kubernetes downward API.

These environment variables are read, defaulting to unknown if empty:

• MY_POD_NAME
• MY_POD_IP
• MY_POD_NAMESPACE
• MY_NODE_NAME

This API returns this data in JSON:

{
    description: <...>,
    hostname: <...>,  # container hostname
    ip: <...>,  # IP from the downward API
    namespace: <...>,  # namespace from the downward API
    node: <...>,  # node from the downward API
    pod: <...>  # pod from the downward API
}

/api/v1/configuration

This API endpoint returns the configuration of Timber.

This 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/redis_detection

This API endpoint tells you whether Redis is detected in the same pod.

It works by trying to connect to Redis on localhost, and since pods share networking, this would work if Redis is running alongside the backend.

{
    description: <...>,
    is_detected: <true/false>
}

/api/v1/state

This API returns informations 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

Frontend configuration, through environment variables

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

backend.py

This file contains a get_api() helper function to get data as dictionary from the backend API endpoints.