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

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.

lalyos / timber