aiohttp ClientSession requests memory leak?

[grantsloman]

I believe I have unearthed a memory leak in my long-lived application when using aiohttp ClientSession requests. If each coroutine which makes a request is awaited sequentially, then all seems fine. However there seems to be a leak of request context manager objects when run concurrently.

Please consider the following example code:

async def do_request():

    try:
        async with session.request("GET", "http://127.0.0.1") as response:
            text = await response.text()
            print(text)
    except:
        logger.exception("Request failed")


async def main():

    timeout = aiohttp.ClientTimeout(total=1)
    global session
    session = aiohttp.ClientSession(timeout=timeout)

    while True:

        tasks = [ do_request(), do_request() ]
        await asyncio.gather(*tasks)
        await asyncio.sleep(2)


if __name__ == '__main__':

    loop = asyncio.get_event_loop()
    loop.run_until_complete(main())

Some tracemalloc code is then used to periodically log memory allocations. This shows the count for allocations in aiohttp/client.py where request() returns a _RequestContextManager increasing over time, initially quickly but then slows until reaching a peak and then seems to be fairly stable.
However, It has then been observed that if there is a network problem and requests start to fail then the count ramps back up again - and doesn't come back down after the problem has been resolved.

Is this a leak? If so, is there a way to work around it? Thanks.