This is a very simple hello-world-walkthrough with FastAPI and Cloud Run.

To play through this tutorial, I recommend creating a new project. You can do this in the console or with the Cloud SDK (recommended). You can find your billing account id here

Create your new project.

export PROJECT_ID=<YOUR_UNIQUE_LOWER_CASE_PROJECT_ID>
export BILLING_ACCOUNT_ID=<YOUR_BILLING_ACCOUNT_ID>
export APP=myapp 
export PORT=1234
export REGION="europe-west3"
export TAG="gcr.io/$PROJECT_ID/$APP"

gcloud projects create $PROJECT_ID --name="My FastAPI App"

# Set Default Project (all later commands will use it) 
gcloud config set project $PROJECT_ID

# Add Billing Account (no free lunch^^)
gcloud beta billing projects link $PROJECT_ID --billing-account=$BILLING_ACCOUNT_ID

Enable the services you need.

gcloud services enable cloudbuild.googleapis.com \
    containerregistry.googleapis.com \
    run.googleapis.com

Let's keep it bloody simple and focus on the general process. This is a our hello world app src/main.py.

from fastapi import FastAPI

app = FastAPI()


@app.get("/")
async def root():
    return {"message": "Hello World"}

If you want to test it locally, run:

pip install -r src/requirements.txt
cd src 
uvicorn main:app --reload

You can check the output in your browser by opening http://127.0.0.1:1234 or "curling" the app in another terminal tab via:

curl http://127.0.0.1:$PORT

As a response you'll see {"message":"Hello World"}.

You need to put your app into an image before deploying it. Here you see an example docker file. Note that you should use a PORT as environment variable. If you don't you'll get an error like Cloud Run error: The user-provided container failed to start and listen on the port defined provided by the PORT=8080 environment variable.

FROM python:3.9-slim@sha256:980b778550c0d938574f1b556362b27601ea5c620130a572feb63ac1df03eda5 

ENV PYTHONUNBUFFERED True

ENV APP_HOME /app
WORKDIR $APP_HOME
COPY . ./

ENV PORT 1234

RUN pip install --no-cache-dir -r requirements.txt

# As an example here we're running the web service with one worker on uvicorn.
CMD exec uvicorn main:app --host 0.0.0.0 --port ${PORT} --workers 1

To try your app locally with docker simply run inside src:

docker build -t $TAG .
docker run -dp $PORT:$PORT -e PORT=$PORT $TAG

Again you can check it in your browser our curl it:

 curl http://127.0.0.1:$PORT

If everything worked out so far, we're ready to deploy our app. First we create a Google Cloud Build. Maybe it's similar to pushing a docker image to a docker registry.

gcloud builds submit --tag $TAG

After this is done, well it's finally time to deploy your cloud run app :).

gcloud run deploy $APP --image $TAG --platform managed --region $REGION --allow-unauthenticated

Note, this may take some minutes. The URL of your app will show up in the terminal. But you can also check your app via:

# See all info about the app
gcloud run services describe $APP --region $REGION

Note, even though we've chosen a random port like 1234, the deployed service will use 8080 by default. This is why we need --port ${PORT} in the last line of our Dockerfile.

Let's send a request to our app.

# get url
URL=$(gcloud run services describe $APP --region $REGION --format 'value(status.url)')

curl $URL

Perfect! Again, we receive {"message":"Hello World"}.

If you don't need the app anymore remove it. (You may also delete the whole project instead.)

gcloud run services delete $APP --region $REGION

# Check if it disAPPeared (optional)
gcloud run services list