# Using Docker in Development

Pegasus optionally includes support for [Docker](https://www.docker.com/) during development.
The Docker development setup can also be used as a foundation for deploying to containerized platforms.
See [our deployment page](/deployment/) for more details.

## Prerequisites

You need to install [Docker](https://www.docker.com/get-started) prior to setting up your environment.

Mac users have reported better performance on Docker using [OrbStack](https://orbstack.dev/),
which is a Docker Desktop alternative optimized for performance.

Windows users may also need to install a 3rd-party package to run `make` commands.
The easiest way to do that is via [these instructions](https://stackoverflow.com/a/57042516/8207).

## Getting Started

First set up your Pegasus project with Docker enabled and using Postgres as a database
following the [getting started guide](/getting-started/).

### Enter the project directory

```
cd {{ project_name }}
```

### Run the initialization script

```python
make init
```

This will spin up a database, web worker, celery worker, and Redis broker and create and
run your database migrations.

Note: users of older versions of Windows may [need to install "make" separately to use it](https://stackoverflow.com/questions/32127524/how-to-install-and-use-make-in-windows).
Alternatively, you can just inspect the `Makefile` in the repository and run the commands manually
(e.g. `docker compose up -d`).

### Load server

Visit [http://localhost:8000/](http://localhost:8000/) in a browser and you
should be up and running!

## Using the Makefile

Pegasus ships with a self-documenting `Makefile` that will run common commands for you,
including starting your containers, performing database operations, and building your front end.

You can run `make` to list helper functions, and you can view the source
of the `Makefile` file in case you need to add to it or run any once-off commands.

For example, you can run management commands in containers using the same method 
used in the `Makefile`. E.g.

```
docker compose exec web python manage.py createsuperuser
```

## Architecture and how it works

### Containers 

The Docker configuration is primarily in `docker-compose.yml`.

There are four containers that start: a Postgres database, a Redis instance (for caching and use as a Celery broker),
a web container running your Django process, and a Celery container for background jobs.

### Settings

The docker environment sets environment variables using the included `.env` file.

The `.env` file is automatically ignored by git, so you can put any additional secrets there.
It generally should not be checked into source control.
You can instead add variables to `.env.example` to show what should be included.

### Python environments

The Python environment is run in the containers, which means you do not need to have your
own local environment if you are always using Docker for development.
Python requirements are automatically installed when the container builds.

However, keep in mind that if you go this route, you will need to run all commands inside the containers
as per the instructions below. 

## Running once-off management commands

Running commands on the server can be done using `docker compose`, by following
the pattern used in the `Makefile`.

For example, to bootstrap Stripe subscriptions, run:

```
docker compose exec web python manage.py bootstrap_subscriptions
```

Or to promote a user to superuser, run: 
```
docker compose exec web python manage.py promote_user_to_superuser me@example.com
```

Commonly used commands can be added to the `Makefile` for convenience.

## Updating Python packages

If you add or modify anything in your `requirements.in` (and `requirements.txt`) files, you will have to rebuild
your containers.

The easiest way to add new packages is to add them to `requirements.in` and then run:

```
make requirements
``` 

Which will rebuild your `requirements.txt` file, rebuild your Docker containers,
and then restart your app with the latest dependencies.

## Debugging

You can use debug tools like `pdb` or `ipdb` by enabling service ports.

This can be done by running your web container with the following:

```
docker compose run --service-ports web
```

If you want to set up debugging with PyCharm, it's recommended to follow [this guide on the topic](https://testdriven.io/blog/django-debugging-pycharm/).

## Other Resources

- [Dockerizing Django with Postgres, Gunicorn, and Nginx](https://testdriven.io/blog/dockerizing-django-with-postgres-gunicorn-and-nginx/)
  provides an overview of the setup, and has additional information about using Docker in production
- [Environment variables in Compose](https://docs.docker.com/compose/environment-variables/) is a good resource
  on the different ways to work with environment variables in Docker