TLS/SSL asyncio/uvloop leaks memory

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#565 opened on Sep 18, 2023 3 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty: 4/5
Estimated time: 3-5 days
Newbie friendliness: 25/100

Issue type: Bug
Clarity: Needs clarification
Activity status: Stale
Tech stack: python
Domain: networking

Research direction

Start with the minimal asyncio.Protocol reproducer using uvloop.new_event_loop, loop.create_server, and the TLS context, then run the provided ab -n15000 -c15000 -r command on Linux across the reported Python versions. Compare memory behavior with and without TLS and uvloop; done means the leak is isolated and memory no longer grows excessively under the reproduced load.

Written by the indexing model from the issue text.

Description

python3.9 or uvloop seems to leak smaller, but python3.11 (and others?) leaks A LOT OF memory under load
test command: ab -n15000 -c15000 -r https://127.0.0.1/
(apt install apache2-utils)

import asyncio, ssl, uvloop

class HTTP(asyncio.Protocol):
    
    def __init__(self):
        self.transport = None
        
    def connection_made(self, transport) -> None:
        self.transport = transport

    def data_received(self, data) -> None:
        self.transport.write(
            b'HTTP/1.1 200 OK\r\nContent-Length: 0\r\nConnection: keep-alive\r\n\r\n'
        )
        self.transport.close()

    def connection_lost(self, _=0) -> bool | None:
        self.transport.close()

def make_tls_context():
    ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
    ctx.load_cert_chain('cert.crt', 'cert.key')
    return ctx

tls_context = make_tls_context()
loop = uvloop.new_event_loop()
loop.set_debug(True)

async def start_server(loop):
    return await loop.create_server(
        HTTP, '127.0.0.1', 443, backlog=65535,
        ssl=tls_context)

loop.run_until_complete(start_server(loop))
loop.run_forever()
loop.close()

CPython versions tested on:
3.9, 3.11

Operating systems tested on:
Linux

Dominant language: Cython
Stars: 11.9k
Forks: 615
PR merge metrics: No merged PRs in 30d

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