Getting Up and Running Locally With Docker

The steps below will get you up and running with a local development environment. All of these commands assume you are in the root of your generated project.

Note

If you’re new to Docker, please be aware that some resources are cached system-wide and might reappear if you generate a project multiple times with the same name (e.g. this issue with Postgres).

Prerequisites

Build the Stack

This can take a while, especially the first time you run this particular command on your development system:

$ docker-compose -f local.yml build

Generally, if you want to emulate production environment use production.yml instead. And this is true for any other actions you might need to perform: whenever a switch is required, just do it!

Before doing any git commit, pre-commit should be installed globally on your local machine, and then:

$ git init
$ pre-commit install

Failing to do so will result with a bunch of CI and Linter errors that can be avoided with pre-commit.

Run the Stack

This brings up both Django and PostgreSQL. The first time it is run it might take a while to get started, but subsequent runs will occur quickly.

Open a terminal at the project root and run the following for local development:

$ docker-compose -f local.yml up

You can also set the environment variable COMPOSE_FILE pointing to local.yml like this:

$ export COMPOSE_FILE=local.yml

And then run:

$ docker-compose up

To run in a detached (background) mode, just:

$ docker-compose up -d

Execute Management Commands

As with any shell command that we wish to run in our container, this is done using the docker-compose -f local.yml run --rm command:

$ docker-compose -f local.yml run --rm django python manage.py migrate
$ docker-compose -f local.yml run --rm django python manage.py createsuperuser

Here, django is the target service we are executing the commands against.

(Optionally) Designate your Docker Development Server IP

When DEBUG is set to True, the host is validated against ['localhost', '127.0.0.1', '[::1]']. This is adequate when running a virtualenv. For Docker, in the config.settings.local, add your host development server IP to INTERNAL_IPS or ALLOWED_HOSTS if the variable exists.

Configuring the Environment

This is the excerpt from your project’s local.yml:

# ...

postgres:
  build:
    context: .
    dockerfile: ./compose/production/postgres/Dockerfile
  volumes:
    - local_postgres_data:/var/lib/postgresql/data
    - local_postgres_data_backups:/backups
  env_file:
    - ./.envs/.local/.postgres

# ...

The most important thing for us here now is env_file section enlisting ./.envs/.local/.postgres. Generally, the stack’s behavior is governed by a number of environment variables (env(s), for short) residing in envs/, for instance, this is what we generate for you:

.envs
├── .local
│   ├── .django
│   └── .postgres
└── .production
    ├── .django
    └── .postgres

By convention, for any service sI in environment e (you know someenv is an environment when there is a someenv.yml file in the project root), given sI requires configuration, a .envs/.e/.sI service configuration file exists.

Consider the aforementioned .envs/.local/.postgres:

# PostgreSQL
# ------------------------------------------------------------------------------
POSTGRES_HOST=postgres
POSTGRES_DB=<your project slug>
POSTGRES_USER=XgOWtQtJecsAbaIyslwGvFvPawftNaqO
POSTGRES_PASSWORD=jSljDz4whHuwO3aJIgVBrqEml5Ycbghorep4uVJ4xjDYQu0LfuTZdctj7y0YcCLu

The three envs we are presented with here are POSTGRES_DB, POSTGRES_USER, and POSTGRES_PASSWORD (by the way, their values have also been generated for you). You might have figured out already where these definitions will end up; it’s all the same with django service container envs.

One final touch: should you ever need to merge .envs/.production/* in a single .env run the merge_production_dotenvs_in_dotenv.py:

$ python merge_production_dotenvs_in_dotenv.py

The .env file will then be created, with all your production envs residing beside each other.

Tips & Tricks

Activate a Docker Machine

This tells our computer that all future commands are specifically for the dev1 machine. Using the eval command we can switch machines as needed.:

$ eval "$(docker-machine env dev1)"

Debugging

ipdb

If you are using the following within your code to debug:

import ipdb; ipdb.set_trace()

Then you may need to run the following for it to work as desired:

$ docker-compose -f local.yml run --rm --service-ports django

django-debug-toolbar

In order for django-debug-toolbar to work designate your Docker Machine IP with INTERNAL_IPS in local.py.

docker

The container_name from the yml file can be used to check on containers with docker commands, for example:

$ docker logs worker
$ docker top worker

Mailhog

When developing locally you can go with MailHog for email testing provided use_mailhog was set to y on setup. To proceed,

  1. make sure mailhog container is up and running;
  2. open up http://127.0.0.1:8025.

Celery tasks in local development

When not using docker Celery tasks are set to run in Eager mode, so that a full stack is not needed. When using docker the task scheduler will be used by default.

If you need tasks to be executed on the main thread during development set CELERY_TASK_ALWAYS_EAGER = True in config/settings/local.py.

Possible uses could be for testing, or ease of profiling with DJDT.

Celery Flower

Flower is a “real-time monitor and web admin for Celery distributed task queue”.

Prerequisites:

  • use_docker was set to y on project initialization;
  • use_celery was set to y on project initialization.

By default, it’s enabled both in local and production environments (local.yml and production.yml Docker Compose configs, respectively) through a flower service. For added security, flower requires its clients to provide authentication credentials specified as the corresponding environments’ .envs/.local/.django and .envs/.production/.django CELERY_FLOWER_USER and CELERY_FLOWER_PASSWORD environment variables. Check out localhost:5555 and see for yourself.

Developing locally with HTTPS

Increasingly it is becoming necessary to develop software in a secure environment in order that there are very few changes when deploying to production. Recently Facebook changed their policies for apps/sites that use Facebook login which requires the use of an HTTPS URL for the OAuth redirect URL. So if you want to use the users application with a OAuth provider such as Facebook, securing your communication to the local development environment will be necessary.

In order to create a secure environment, we need to have a trusted SSL certficate installed in our Docker application.

  1. Let’s Encrypt

    The official line from Let’s Encrypt is:

    [For local development section] … The best option: Generate your own certificate, either self-signed or signed by a local root, and trust it in your operating system’s trust store. Then use that certificate in your local web server. See below for details.

    See letsencrypt.org - certificates-for-localhost

  2. mkcert: Valid Https Certificates For Localhost

    mkcert is a simple by design tool that hides all the arcane knowledge required to generate valid TLS certificates. It works for any hostname or IP, including localhost. It supports macOS, Linux, and Windows, and Firefox, Chrome and Java. It even works on mobile devices with a couple manual steps.

    See https://blog.filippo.io/mkcert-valid-https-certificates-for-localhost/

After installing a trusted TLS certificate, configure your docker installation. We are going to configure an nginx reverse-proxy server. This makes sure that it does not interfere with our traefik configuration that is reserved for production environments.

These are the places that you should configure to secure your local environment.

certs

Take the certificates that you generated and place them in a folder called certs in the project’s root folder. Assuming that you registered your local hostname as my-dev-env.local, the certificates you will put in the folder should have the names my-dev-env.local.crt and my-dev-env.local.key.

local.yml

  1. Add the nginx-proxy service.

    ...
    
    nginx-proxy:
      image: jwilder/nginx-proxy:alpine
      container_name: nginx-proxy
      ports:
        - "80:80"
        - "443:443"
      volumes:
        - /var/run/docker.sock:/tmp/docker.sock:ro
        - ./certs:/etc/nginx/certs
      restart: always
      depends_on:
        - django
    
    ...
    
  2. Link the nginx-proxy to django through environment variables.

    django already has an .env file connected to it. Add the following variables. You should do this especially if you are working with a team and you want to keep your local environment details to yourself.

    # HTTPS
    # ------------------------------------------------------------------------------
    VIRTUAL_HOST=my-dev-env.local
    VIRTUAL_PORT=8000
    

    The services run behind the reverse proxy.

config/settings/local.py

You should allow the new hostname.

ALLOWED_HOSTS = ["localhost", "0.0.0.0", "127.0.0.1", "my-dev-env.local"]

Rebuild your docker application.

$ docker-compose -f local.yml up -d --build

Go to your browser and type in your URL bar https://my-dev-env.local

See https with nginx for more information on this configuration.

.gitignore

Add certs/* to the .gitignore file. This allows the folder to be included in the repo but its contents to be ignored.

This configuration is for local development environments only. Do not use this for production since you might expose your local rootCA-key.pem.