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Deploying FastAPI to GCP using CNC

We are going to deploy a FastAPI app to Google Cloud using the run-lite flavor which is the lowest cost container deployment architecture available at the low end of cloud right now. It will be free to get started (depending on usage and free tier eligibility).

Before starting, follow the steps at Getting Started. In particular: - cnc installed with pip install cocnc. - gcloud installed (docs) and have run gcloud auth application-default login (unless you have an alternative auth setup for gcloud).

database choice (if applicable)

You can use a Cloud SQL instance by creating a database service type in cnc, see the Django setup example for what that looks like. In this case, cnc will automatically manage a secret and inject DATABASE_URL automatically, which will correspond to the database instance created for each environment.

With the run-lite flavor using more free-compatible services, it would be common to pair this deployment with a managed database offering such as firebase, supabase, neon, or similar. in this case, you'd set an environment variable for DATABASE_URL yourself (possibly using a secret_id instead of providing the value directly) and do the setup for that database instance outside of cnc. In this example, we'll use this option.

repo setup

You've followed the steps at FastAPI to get started. Here's an example.

add requirements file

You can either write your own Dockerfile and supply it under the build as dockerfile in the cnc.yml (docs) or you can use the built in support for nixpacks. As per nixpacks docs we are going to add a requirements.txt to configure as a python build. Add the following to requirements.txt:



You add this to cnc.yml

     # activating the venv is due to using nixpacks, if you write your own dockerfile you don't need this part of the command
    command: ". /opt/venv/bin/activate && uvicorn main:app --host --port $PORT"
      type: backend
      context: .


You add this to environments.yml

name: my-fastapi-app
provider: gcp
flavor: run-lite
version: 1

- name: dev
  region: us-east1
  account_id: "my-gcp-project"
  - name: staging
    - name: DATABASE_URL
      value: "value://from_db_provider"

See more about available options including environment variables in configuration.

Provision your infra

  • run cnc provision apply. confirm with yes when requested by terraform, and then wait for the infra to provision, should take just a few minutes

Deploy your app

  • run cnc update perform staging --service-tag app=v1. you can set v1 to whatever you want to use for the release tag, usually the git SHA is a good choice here, can get that with git rev-parse --short HEAD.
  • the first deploy will take the longest, once this runs once locally building the images will be faster due to docker cache in subsequent runs.
    • you can also run this step from CI/CD e.g. github actions once it works for you and you want to automate it

visit the URL

  • In the GCP console, check out your Cloud Run service and access it with the URL provided. You can add a custom domain to each service, as well, using the GCP UI.

Next steps

  • add another environment
  • customize your terraform
  • add additional services
  • explore the toolbox