Cache doesn't work with GZIPMiddleware about cashews

[AndreyKuchko]

I have the same problem with following(simplified) middlewares setup in fastapi application:

app.add_middleware(gzip.GZipMiddleware, minimum_size=100)
app.add_middleware(CacheRequestControlMiddleware)

cache.setup(settings_url="mem://?check_interval=10&size=10000")

$ python --version
Python 3.9.18
$ pip freeze
...
cashews==7.0.2
fastapi==0.110.0
starlette==0.36.3
uvicorn==0.28.0
...

After quick debug I see that CacheRequestControlMiddleware stores decompressed response body with headers from compressed response(it contains Content-Encoding: gzip) as a cached page to the memory. On the next request GZipMiddleware ignores compressing the response body, because according to Content-Encoding it assumes that it is already done.
If I use redis backed for the cache instead of mem, the same code works without any problems. As I see in this case it stores correct(without Content-Encoding: gzip) response headers together with decompressed response body as a cache page.

I hope this information will help with investigation.

[Krukov]

Thanks for explanation. And sure that we need to store a copy of object - I thought that it so ) , I gonna fix it

[Krukov]

Sorry for a delay

I spend some time trying to reproduce it but can't
Can you help me with a code?
I have a next snippet but it works as expected

from fastapi import FastAPI, Response
from starlette.middleware import gzip

from cashews import cache
from cashews.contrib.fastapi import (
    CacheDeleteMiddleware,
    CacheEtagMiddleware,
    CacheRequestControlMiddleware,
)

app = FastAPI()

app.add_middleware(gzip.GZipMiddleware, minimum_size=100)
app.add_middleware(CacheDeleteMiddleware)
app.add_middleware(CacheEtagMiddleware)
app.add_middleware(CacheRequestControlMiddleware)

cache.setup("mem://")


@app.get("/")
@cache(ttl="5m")
async def root():
    return Response(status_code=200)


if __name__ == "__main__":
    import uvicorn
    uvicorn.run(app, host="0.0.0.0", port=8000)

[sergey-burkov-trailstone]

Hey, the underlying issue happens only when caching RAW FastAPI response objects. As they are getting modified later in the chain by GZipMiddleware - additional headers are added. And as the cache is only maintaining references of the objects, they would get modified by it. One approach would be to make a copy of object placed into the cache.

[Krukov]

Fixed with 7.1.0 version. Please reopen the issue if it still exist