Fastapi: Why Http headers is being vanished when using ORJSONResponse() in fastAPI?

[ahadrt]

Http headers can be modified in fastAPI; however when I tried to use faster serializer (in this instance ORJSONResponse) in order to have faster response, all added or modified headers confusingly is being vanished. I don't have any idea that why it happens and how can I fix it?
also we got the same result for UJSONResponse too.

thanks for sharing your experiences.

A. This code can't modify headers

from fastapi import APIRouter, Response
from fastapi.responses import ORJSONResponse
router = APIRouter()

@router.get("/test")
async def plan_list(response:Response):
    response.headers["test-header"]="test-value"
    return ORJSONResponse(list(range(10000)))

Output header list of code A:

date: Thu, 22 Oct 2020 18:42:19 GMT
server: uvicorn
content-length: 48891
content-type: application/json

B. This code modifies headers normally

from fastapi import APIRouter, Response
from fastapi.responses import ORJSONResponse
router = APIRouter()

@router.get("/test")
async def plan_list(response:Response):
    response.headers["test-header"]="test-value"
    return list(range(10000))

Output header list of code B:

date: Thu, 22 Oct 2020 18:42:19 GMT
server: uvicorn
content-length: 48891
content-type: application/json
test-header: test-value

test platform:

• OS: macOS 10.15.7
• client: insomnia 2020.14.1
• python: 3.8.5

[includeamin]

try this

from fastapi import APIRouter, Response
from fastapi.responses import ORJSONResponse

router = APIRouter()


@router.get("/test", response_class=ORJSONResponse)
async def plan_list(response: Response):
    response.headers["test-header"] = "test-value"
    return list(range(10000))

[ahadrt]

@includeamin Actually, as I tested before, using response_class=ORJSONResponse is more than 10 times slower than calling the ORJSONResponse()directly. Specifically when data is very large object >10 MB I have to use it as function call.

[includeamin]

I'm not sure that it's good to do that or not.
if you want to directly use that:

from fastapi import APIRouter, Response, FastAPI
from fastapi.responses import ORJSONResponse

app = FastAPI()
router = APIRouter()


@router.get("/test")
async def plan_list():
    response = ORJSONResponse(list(range(10000)))
    response.headers.update({"test-header": "test-value"})
    return response


app.include_router(router)

[ahadrt]

@includeamin Yes thanks, it seems good idea. With inspiration of your answer I found another way. what about this one?

from fastapi import APIRouter, Response, FastAPI
from fastapi.responses import ORJSONResponse

app = FastAPI()
router = APIRouter()


@router.get("/test")
async def plan_list(response:Response):
       response.headers["test"]="test-value"
       return ORJSONResponse(list(range(10000)),headers=response.headers)



app.include_router(router)

[includeamin]

@includeamin Yes thanks, it seems good idea. With inspiration of your answer I found another way. what about this one?

from fastapi import APIRouter, Response, FastAPI
from fastapi.responses import ORJSONResponse

app = FastAPI()
router = APIRouter()


@router.get("/test")
async def plan_list(response:Response):
       response.headers["test"]="test-value"
       return ORJSONResponse(list(range(10000)),headers=response.headers)



app.include_router(router)

sounds good!

[ahadrt]

@includeamin thanks once more . I close this issue