FastAPI-Factory

Some simple utilities for building FastAPI application.

Installation

Install via pip

pip install git+https://github.com/Pandede/fastapi-factory

Usage

Exports the metrics to Prometheus

from fastapi import FastAPI
from fastapi_factory import set_prometheus_exporter


app = FastAPI()
set_prometheus_exporter(app)

Add a shared instance across the application

The instance can be accessed in endpoints or middlewares with attribute request.

For example, assume redis.Redis is going to be shared across the application, in main.py:

from fastapi import FastAPI
from fastapi_factory import set_shared_object
from redis import Redis

from routers import user_router
app = FastAPI()

# Share `redis.Redis`
redis_client = Redis()
set_shared_object(app, redis_client, 'redis')

Then, access the shared instance in the endpoint, in routers.py:

from fastapi import APIRouter, Request
from fastapi_factory import get_shared_object

user_router = APIRouter()

@user_router.get('/user')
def get_info(request: Request, user: str) -> str:
    redis_client = get_shared_object(request, 'redis')
    return redis_client.get(user)

@user_router.post('/user')
def set_info(request: Request, user: str, info: str):
    redis_client = get_shared_object(request, 'redis')
    return redis_client.set(user, info)

Catch the exception with specific status code

from fastapi import FastAPI, status
from fastapi.testclient import TestClient

from fastapi_factory import set_exception_status

app = FastAPI()
set_exception_status(app, ZeroDivisionError, status.HTTP_400_BAD_REQUEST)
set_exception_status(app, ValueError, status.HTTP_406_NOT_ACCEPTABLE)


@app.get('/inv')
def get_inv(n):
    if n == 'nan':
        raise TypeError('nan')
    return 1 / float(n)


test_client = TestClient(app, raise_server_exceptions=False)

# Normal request
res = test_client.get('/inv', params={'n': 4})
assert res.status_code == status.HTTP_200_OK
assert res.json() == 0.25

# Zero, must raise ZeroDivisionError
res_with_zero_div = test_client.get('/inv', params={'n': 0})
assert res_with_zero_div.status_code == status.HTTP_400_BAD_REQUEST

# String, must raise ValueError
res_with_val_err = test_client.get('/inv', params={'n': 'foo'})
assert res_with_val_err.status_code == status.HTTP_406_NOT_ACCEPTABLE
assert res_with_val_err.json() == {'detail': 'could not convert string to float: \'foo\''}

# nan, must raise TypeError
# Returns 500 as it's unexpected error
res_with_type_err = test_client.get('/inv', params={'n': 'nan'})
assert res_with_type_err.status_code == status.HTTP_500_INTERNAL_SERVER_ERROR

Create a simple homepage

from fastapi import FastAPI, status
from fastapi.testclient import TestClient

from fastapi_factory import set_home

app = FastAPI(title='fastapi_factory', version='0.1.0')
set_home(app)

test_client = TestClient(app)
res = test_client.get('/')
assert res.status_code == status.HTTP_200_OK
assert res.json() == {'message': 'Hello from fastapi_factory 0.1.0!'}

Test

Install the following packages before testing:

pip install pytest pytest-cov pytest-mock

Executing the tests:

python3 -m pytest tests --cov