[Python] AttributeError: 'Depends' object has no attribute 'add'

I am trying to use database session in the middleware (to write metrics to the database)

I am using fastapi.params.Depends in @app.middleware("http")

I read this question FastAPI - dependency inside Middleware? and was using solution from this question

My code:

database.py

from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker


SQLALCHEMY_DATABASE_URL = "postgresql://username@localhost/feast_db" # Checked that psql postgresql://username@localhost/feast_db is working

engine = create_engine(
SQLALCHEMY_DATABASE_URL
)
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)

Base = declarative_base()


Main app:

from fastapi import FastAPI, HTTPException, Request, Response, status
from fastapi.params import Depends

from myapp.metrics_service import models, schemas
from myapp.metrics_service.database import SessionLocal, engine


models.Base.metadata.create_all(bind=engine) # create database table


def get_db():
db = SessionLocal()
try:
yield db
finally:
db.close()

def get_app(store: "feast.FeatureStore"):
proto_json.patch()

app = FastAPI(dependencies=[Depends(get_db)])
request_id_contextvar = contextvars.ContextVar("request_id", default=None)
...
@app.middleware("http")
async def log_requests(request: Request, call_next, db: Session = Depends(get_db)):
response = await call_next(request)
...
curr_metric = models.Metric(rqid=request_id, name="request_duration", duration_ms=total_time_ms)
print("XXX_ curr_metric")
db.session.add(curr_metric)
db.session.commit()
return response





I have an error

db.add(curr_metric)
AttributeError: 'Depends' object has no attribute 'add'


How to fix the error?

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