Close transport on asyncio client disconnect

[mgrachten]

The current disconnect method of asyncio.MPDClient does not close the writing transport. A warning for this is issued when running the python3 interpreter with -Wdefault. As a result, the MPD server keeps alive the connection to the client unnecessarily. If this happens repeatedly, the dangling connections may cause the MPD server to reach its maximal connection limit.

[mgrachten]

A minimal working example to show the issue is:

import asyncio
from mpd.asyncio import MPDClient

async def main():
    client = MPDClient()
    try:
        await client.connect('localhost', 6600)
    except Exception as e:
        print("Connection failed:", e)
        return

    # Uncommenting the following line avoids the warning
    # client._MPDClient__wfile.close()

    client.disconnect()

if __name__ == '__main__':
    loop = asyncio.get_event_loop()
    loop.run_until_complete(main())
    loop.close()

Running the above script using python3 -Wdefault will issue a resource warning:

/usr/lib/python3.5/asyncio/selector_events.py:574: ResourceWarning: unclosed transport <_SelectorSocketTransport fd=6> warnings.warn("unclosed transport %r" % self, ResourceWarning)

Uncommenting the line client._MPDClient__wfile.close() (as a proof of concept) avoids the warning.

When the transport is not closed, the connection to the MPD server is maintained until the script exits.

[Mic92]

The ancient python version that breaks on travis was removed in our CI.

[varac]

What's the current state ? This PR is pending for quite a while.

[mgrachten]

As far as I know this PR is still pending review by @supermihi, but it's really a tiny PR, so maybe somebody else can review.