FastAPI object from middleware to actual endpoint

Question

I try to build a middleware for my app.

I need a way to create some object in my middleware function and i want to have access to that object in a next endpoint method . Please see my code example .

from fastapi import FastAPI, Request

app = FastAPI()

@app.middleware("http")
async def add_process_time_header(request: Request, call_next):
    myObject = MyClass(request)
    response = await call_next(request)
    
    return response

@app.get("/")
def read_root(arg:str):
    data = myObject.build_data(arg)
    return {"Hello": "World", "data": data}

Is it possible to do? How to do this correctly?

Also, if it is not possible to create new object and pass it to an endpoint code. Maybe i can create kinda "global variable" for object? But how will it work in terms of multithreading?

app = FastAPI()
myObject = MyClass()

@app.middleware("http")
async def add_process_time_header(request: Request, call_next):
    myObject.use_request(request)
    response = await call_next(request)
    
    return response

@app.get("/")
def read_root(arg:str):
    data = myObject.build_data(arg)
    return {"Hello": "World", "data": data}

Will this work fine or there will be some specifics of multithreading etc?

Answer 1

The answer posted by MatsLindh in a comment works fine. Also i have got the full answer here https://github.com/fastapi/fastapi/discussions/12250

import time

from fastapi import FastAPI, Request

app = FastAPI()

@app.middleware("http")
async def add_process_time_header(request: Request, call_next):
    myObject = MyClass(request)
    response = await call_next(request)
    
    return response

@app.get("/")
def read_root(arg:str):
    data = myObject.build_data(arg)
    return {"Hello": "World", "data": data}