Using UvicornWorkers in Gunicorn cause OOM on K8s

Checklist

• The bug is reproducible against the latest release and/or master.
• There are no similar issues or pull requests to fix it yet.

Describe the bug

I’m developing a FastApi application deployed on a Kubernetes cluster using gunicorn as process manager.

I’m also using UvicornWorkers for sure, because of the async nature of fastapi.

After the application deployment I can see the memory growing up at rest, until OOM.

This happen just when I use UvicornWorker.

Tests made by me:

• Comment all my code to ensure is not a my application mem leak (leak present);
• Start the application using uvicorn instead of gunicorn (no leak present);
• Start application using gunicorn sync workers (no leak present);
• Start application using gunicorn + UvicornWorker (leak present);
• Start application using gunicorn + UvicornWorker + max_requests (leak present);

Plus, this happens just on the Kubernetes cluster, when I run my application locally (MacBook pro 16) (is the same docker image used on k8s) the leak is not present.

Anyone else had a similar problem?

[evalkaz]

EDIT: it seems that I cannot reproduce the numbers.

Hey, I encounter the same issue. My code snippet to reproduce the issue:

async def app(scope, receive, send):
    assert scope['type'] == 'http'

    data = [0] * 10_000_000

    await send({
        'type': 'http.response.start',
        'status': 200,
        'headers': [
            [b'content-type', b'text/plain'],
        ],
    })
    await send({
        'type': 'http.response.body',
        'body': b'Hello, world!',
    })

Launched using uvicorn main:app --host 0.0.0.0 --port 8000. After sending ~10k requests to the API, memory usage goes from ~18MB to 39MB. The same thing happens with startlette and apidaora (launching them with uvicorn) and the memory usage patterns looks quite similar. I also tested flask with gunicorn, sanic and their memory usage stayed ± the same. I also checked PR#1244, but the issue persists.

Library	ASGI	memory (start)	memory (end)	requests
uvicorn	uvicorn	18 MB	38 MB	11k
starlette	uvicorn	19 MB	39 MB	10k
apidoara	uvicorn	18 MB	39 MB	12k
uvicorn PR#1244	uvicorn	18 MB	39 MB	10k
quart	hypercorn	26 MB	63 MB	10k
apidoara	hypercorn	16 MB	42 MB	10k
starlette	daphne	34 MB	46 MB	10k
apidoara	daphne	32 MB	45 MB	10k
flask	gunicorn	35 MB	35 MB	10k
sanic	sanic	17 MB	22 MB	10k

[Kludex]

For the record: Issue was solved by uvicorn 0.17.1.