acg-crossing-app REST API

The REST API for the ACG Crossing Guard App (RHoK #11).

1. This app will recieve REST API requests we generate from a react web app (and hopefully we can get this working in a way where folks can just call in with their phone).
2. That will trigger validation and updates to the crossing guard shifts in the database.
3. Finally it will Publish the update to redis, where the live map can subscribe and consume this data to show who is able to make it or not.

Dev Dependencies (Docker)

Dev Dependencies (Mac)

• Docker for Mac

Dev Dependencies (Windows)

• Docker Desktop for Windows

Dev Dependencies (Linux)

• Docker Engine
• Docker Compose

Dev Workflow (Docker)

Getting Started

This will build the images and set everything up for you. Assuming you are in the project root directory:

# Builds the environment image with all dependencies installed and also builds the dev runtime image for you
pushd docker && update_pipfile && popd

This is the only command you will need for setting up the images for dev work.

Gotchas

(Linux)

I discovered running on ubuntu 19.04: Docker will throw some permission denied errors if you dont have the right permissions for the docker user. To rectify this and test it run the following:

sudo groupadd docker
sudo usermod -aG docker $USER
docker run hello-world 

This should give you a hello world message from docker as follows:

Hello from Docker!
This message shows that your installation appears to be working correctly.

To generate this message, Docker took the following steps:
 1. The Docker client contacted the Docker daemon.
 2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
    (amd64)
 3. The Docker daemon created a new container from that image which runs the
    executable that produces the output you are currently reading.
 4. The Docker daemon streamed that output to the Docker client, which sent it
    to your terminal.

To try something more ambitious, you can run an Ubuntu container with:
 $ docker run -it ubuntu bash

Share images, automate workflows, and more with a free Docker ID:
 https://hub.docker.com/

For more examples and ideas, visit:
 https://docs.docker.com/get-started/

---

(Windows)

Similar thing for windows, permissions can be configured with these steps, courtesy of @abraaoz from docker/for-win#3385.

1. Stop your container.
2. Open cmd with admin rights and enter the following commands:

> net user /add DockerDiskSharing DockerDiskSharing
> net localgroup Administrators DockerDiskSharing /add
> net localgroup docker-users DockerDiskSharing /add
> icacls "%UserProfile%" /q /c /t /grant docker-users:F

1. At Docker -> Settings -> Shared Drives screen:

• click Reset credentials
• tick drive C
• click Apply
• type DockerDiskSharing in user name and DockerDiskSharing in password and click OK

---

Adding a new dependency for the django app

Since we don't want to muck about with managing a python installation on our local machines, we will do everything in a standardized container that will work the same for everyone.

We will manage the environment and the app as separate images so we don't have to rebuild something massive each time and can update the Pipfile quickly when developing.

1. Add the dependency to the Pipfile
2. Run docker/update_pipfile

This will:

1. Build the image with your updated Pipfile in it and tag it
2. Install the environment from the updated Pipfile
3. Create a lockfile
4. Update the lockfile in your local git repo using docker volumes

Running the app

Set up Postgres

Now that you've built the images as described above, we will need a postgres instance for local development.

Installing postgres in a hackathon setting also managed to waste away the better part of a day, so let's bring that down to a few simple steps independent of platform.

1. Navigate to the docker directory
2. Run docker-compose up -d

This will spin up a local postgres and persist data to /var/lib/postgresql/data. So while the process is ephemeral, your dev data will be persisted.

You can quickly validate it with docker ps

Also, feel free to connect to it with your favourite dbadmin tool like DbVisualizer or something.

To kill postgres when you're done developing, just run docker-compose kill in the docker directory.

---

Set up Redis for PUB/SUB

Redis will be turned on with the above docker-compose command that you use for setting up postgres.

To use the redis-cli:

docker run -it --rm redis redis-cli -h host.docker.internal

This spins up a docker container that connects to the redis instance we spun up with docker-compose and cleans itself up when youre done.

We will be publishing to a channel for consumption by the live map. To debug the channel and see messages flowing in, we can just subscribe using the cli.

Once you are in using the above command, you can simply invoke (replacing [channel] with the channel name):

SUBSCRIBE [channel]

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Setting up the superuser

When you run the app for the first time, you'll need to set up the superuser for the browsable API.

Run the following:

bash manage createsuperuser

Sample output:

Username: admin
Email address:
Password:
Password (again):
The password is too similar to the username.
This password is too short. It must contain at least 8 characters.
This password is too common.
Bypass password validation and create user anyway? [y/N]: y
Superuser created successfully.

Then you can start the server back up with

bash manage runserver 0.0.0.0:8000

---

Running the app

Once postgres is up, you can run

bash manage runserver 0.0.0.0:8000

to start the app. (It will bind to localhost by default, which would make it impossible to reach outside of the container.)

This will be the code from your git repo mounted in the container, so it will be able to live-reload.

To exit, just ue Ctrl+C and the container will shut itself down.

Note: Any command you pass to manage.py can be passed to the manage script and it will pass it to the container an execute it.

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Running Unit Tests

I've mostly been doing TDD for this app since it lends itself really nicely to it.

You can run unit tests for a module in a docker container using the manage script.

# sh manage test [module], e.g.
bash manage test schedule
bash manage test livedata

You can get more specific as well as we build out more tests.

# Run both test suites for Locations and Shifts defined in the test_models.py file
bash manage test schedule.tests.test_models

# Only run the test_shifts test in the ShiftTest suite in the test_models.py
bash manage test schedule.tests.test_models.ShiftTest.test_shifts