How to pass extra data to fastapi APIRouter? - python-3.x

Question

This is my 1st fastapi exercise. I've my old model serving code implemented with Flask as following:
class HealthCheck(Resource):
def __init__(self, **kwargs):
super(HealthCheck, self).__init__()
self._model = kwargs['model']
self._logger = kwargs['logger']
def get(self):
if self._model:
return {"status" : "healthy"}, HTTPStatus.OK
return {"status": "unavailable"}, HTTPStatus.BAD_REQUEST
def put(self):
raise MethodNotAllowed('PUT request not supported')
# similarly other methods are disabled
# In a different module, say in App class
class App():
def __init__(self, name, logger, config):
self._logger = logger
self._model = load_model(config['model_path'])
self._flask_app = Flask(name)
api = Api(self._flask_app)
# logger and model is passed to HealthCheck resource
api.add_resource(HealthCheck, "/api/healthcheck",
resource_class_kwargs={'model': self._model, 'logger': self._logger})
How do I achieve same with fastapi APIRouter?
My example fastapi implementation is following:
class HealthResult(BaseModel):
healthy: bool
health_router = fastapi.APIRouter()
#health_router.get("/healthcheck", response_model=HealthResult, name="heathcheck")
async def heartbeat() -> HealthResult:
hb = HealthResult(healthy=True)
return hb
# in the App module
class App():
def __init__(self, name, logger, config):
self._logger = logger
self._model = load_model(config['model_path'])
self._api = fastapi.FastAPI(title=name)
self._api.include_router(health_router, prefix="/api")
# how do I pass model and logger to health_router to use that in heartbeat method?
I want to avoid using any global storage for model and logger and access in health_router from there.
Also, since my fastapi object is inside App class, how can I invoke multiple worker with uvicorn in this case?

Answer 1

Though I don't like it, I modified my App class as following to get around the problem - still looking for cleaner solution.
class App(metaclass=Singleton):
_MODEL: Union[None, Model] = None
_LOGGER: Union[None, CustomLogger] = None
#classmethod
def setLogger(cls, logger: CustomLogger) -> None:
cls._LOGGER = logger
#classmethod
def getLogger(cls) -> CustomLogger:
return cls._LOGGER
#classmethod
def setModel(cls, model: Model) -> None:
assert model
cls._MODEL = model
#classmethod
def getModel(cls) -> Model:
return cls._MODEL
def __init__(self, name: str, logger: CustomLogger, config: YAML) -> None:
App.setLogger(logger)
model: Model = load_model(config['model_path'])
App.setModel(model)
self._api = fastapi.FastAPI(title=name)
self._api.include_router(health_router, prefix="/api")
....
class HealthResult(BaseModel):
healthy: bool
health_router = fastapi.APIRouter()
#health_router.get("/healthcheck", response_model=HealthResult, name="heathcheck")
async def heartbeat() -> HealthResult:
model: Model = App.getModel()
hb: HealthResult = HealthResult(healthy=True) if model else HealthResult(healthy=False)
return hb

Answer 2

from fastapi import Request
app = FastAPI()
app.share_text = 'aaa'
# in Apirouter
#router.get("/share}", request: Request)
async def read( request: Request):
#retrieve from app context
share_text = request.app.share_text
return {}
You could retrive the app context from Request
Ref: https://fastapi.tiangolo.com/advanced/using-request-directly/#use-the-request-object-directly
Ref: https://www.starlette.io/requests/
Application The originating Starlette application can be accessed via
request.app.
Other state If you want to store additional information on the request
you can do so using request.state.
For example:
request.state.time_started = time.time()