application performance with response_model

Issue

I found that when use response_model, application performance dropped dramatically.

no response_model is about 4 times than having response_model in efficiency

How should I solve this problem?

Is my way of using it incorrect?

relative information

py-version: python 3.7

FastAPI-version: lastest

screenshot：

no response_model

with response_model

model code

class ResponseSchema(BaseModel):
    code: int
    message: str

# config skip_defaults: True
# NovelSchema field count about 10
# ChapterSchema field count about 7
class BookCatalogData(BaseSchema):
    novel: NovelSchema = SchemaValue(None)
    chapters: List[ChapterSchema] = SchemaValue(None)

class BookCatalogRsm(ResponseSchema):
    data: BookCatalogData

controller code

novel field contain 6 field

chapters field contain about 700 items

@app.get(
    '/v1/api/book/catalog',
    response_model=BookCatalogRsm,
    tags=[TAG]
)
async def book_catalog(novelId: int = -1):
    chapters = await services.chapter.get_catalog(novelId)
    novel = await services.novel.get_by_id(
        novelId,
        columns=[services.novel.table.c.id, services.novel.table.c.name]
    )
    return return_ok({
        'novel': novel,
        'chapters': chapters
    })

helping

Thank you for your help.

[dmontagu]

Yeah, using a response model currently adds a lot of overhead in order to make sure extra fields don’t get serialized. The fix will be to more carefully walk the structure so that fields don’t have to be reparsed.

Fixing this is my top fastapi priority I just haven’t been able to find time to focus on it, but I’m hoping to soon.

[euri10]

out of curiosity what was the reason ? for timing purposes you can use timing-asgi like this

from timing_asgi import TimingMiddleware, TimingClient
from timing_asgi.integrations import StarletteScopeToName

class PrintTimings(TimingClient):
    def timing(self, metric_name, timing, tags):
        logger.debug(f"{metric_name}, {timing}, {tags}")

app.add_middleware(
    TimingMiddleware,
    client=PrintTimings(),
    metric_namer=StarletteScopeToName(prefix="app", starlette_app=app)
)