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FastAPI Project - Development

Development in `localhost` with a custom domain

You might want to use something different than localhost as the domain. For example, if you are having problems with cookies that need a subdomain, and Chrome is not allowing you to use localhost.

In that case, you have two options: you could use the instructions to modify your system hosts file with the instructions below in Development with a custom IP or you can just use localhost.tiangolo.com, it is set up to point to localhost (to the IP 127.0.0.1) and all its subdomains too. And as it is an actual domain, the browsers will store the cookies you set during development, etc.

If you used the default CORS enabled domains while generating the project, localhost.tiangolo.com was configured to be allowed. If you didn't, you will need to add it to the list in the variable BACKEND_CORS_ORIGINS in the .env file.

To configure it in your stack, follow the section Change the development "domain" below, using the domain localhost.tiangolo.com.

After performing those steps you should be able to open: http://localhost.tiangolo.com and it will be served by your stack in localhost.

Check all the corresponding available URLs in the section at the end.

Development with a custom IP

If you are running Docker in an IP address different than 127.0.0.1 (localhost), you will need to perform some additional steps. That will be the case if you are running a custom Virtual Machine or your Docker is located in a different machine in your network.

In that case, you will need to use a fake local domain (dev.example.com) and make your computer think that the domain is served by the custom IP (e.g. 192.168.99.150).

If you have a custom domain like that, you need to add it to the list in the variable BACKEND_CORS_ORIGINS in the .env file.

Open your hosts file with administrative privileges using a text editor:
- Note for Windows: If you are in Windows, open the main Windows menu, search for "notepad", right click on it, and select the option "open as Administrator" or similar. Then click the "File" menu, "Open file", go to the directory c:\Windows\System32\Drivers\etc\, select the option to show "All files" instead of only "Text (.txt) files", and open the hosts file.
- Note for Mac and Linux: Your hosts file is probably located at /etc/hosts, you can edit it in a terminal running sudo nano /etc/hosts.
Additional to the contents it might have, add a new line with the custom IP (e.g. 192.168.99.150) a space character, and your fake local domain: dev.example.com.

The new line might look like:

192.168.99.150    dev.example.com

Save the file.
- Note for Windows: Make sure you save the file as "All files", without an extension of .txt. By default, Windows tries to add the extension. Make sure the file is saved as is, without extension.

...that will make your computer think that the fake local domain is served by that custom IP, and when you open that URL in your browser, it will talk directly to your locally running server when it is asked to go to dev.example.com and think that it is a remote server while it is actually running in your computer.

To configure it in your stack, follow the section Change the development "domain" below, using the domain dev.example.com.

After performing those steps you should be able to open: http://dev.example.com and it will be server by your stack in 192.168.99.150.

Check all the corresponding available URLs in the section at the end.

Change the development "domain"

If you need to use your local stack with a different domain than localhost, you need to make sure the domain you use points to the IP where your stack is set up.

To simplify your Docker Compose setup, for example, so that the API docs (Swagger UI) knows where is your API, you should let it know you are using that domain for development.

Open the file located at ./.env. It would have a line like:

DOMAIN=localhost

Change it to the domain you are going to use, e.g.:

DOMAIN=localhost.tiangolo.com

That variable will be used by the Docker Compose files.

After that, you can restart your stack with:

docker compose up -d

and check all the corresponding available URLs in the section at the end.

Docker Compose files and env vars

There is a main docker-compose.yml file with all the configurations that apply to the whole stack, it is used automatically by docker compose.

And there's also a docker-compose.override.yml with overrides for development, for example to mount the source code as a volume. It is used automatically by docker compose to apply overrides on top of docker-compose.yml.

These Docker Compose files use the .env file containing configurations to be injected as environment variables in the containers.

They also use some additional configurations taken from environment variables set in the scripts before calling the docker compose command.

The .env file

The .env file is the one that contains all your configurations, generated keys and passwords, etc.

Depending on your workflow, you could want to exclude it from Git, for example if your project is public. In that case, you would have to make sure to set up a way for your CI tools to obtain it while building or deploying your project.

One way to do it could be to add each environment variable to your CI/CD system, and updating the docker-compose.yml file to read that specific env var instead of reading the .env file.

Pre-commits and code linting

we are using a tool called pre-commit for code linting and formatting.

When you install it, it runs right before making a commit in git. This way it ensures that the code is consistent and formatted even before it is committed.

You can find a file .pre-commit-config.yaml with configurations at the root of the project.

Install pre-commit to run automatically

pre-commit is already part of the dependencies of the project, but you could also install it globally if you prefer to, following the official pre-commit docs.

After having the pre-commit tool installed and available, you need to "install" it in the local repository, so that it runs automatically before each commit.

Using Poetry, you could do it with:

❯ poetry run pre-commit install
pre-commit installed at .git/hooks/pre-commit

Now whenever you try to commit, e.g. with:

git commit

...pre-commit will run and check and format the code you are about to commit, and will ask you to add that code (stage it) with git again before committing.

Then you can git add the modified/fixed files again and now you can commit.

Running pre-commit hooks manually

you can also run pre-commit manually on all the files, you can do it using Poetry with:

❯ poetry run pre-commit run --all-files
check for added large files..............................................Passed
check toml...............................................................Passed
check yaml...............................................................Passed
ruff.....................................................................Passed
ruff-format..............................................................Passed
eslint...................................................................Passed
prettier.................................................................Passed