Add option to create reusable sockets

[bablokb]

According to the release-notes for CP 9.0.0:

• Incompatible change: Require explicit socket port reuse. Use socket.setsockopt(pool.SOL_SOCKET, pool.SO_REUSEADDR, 1), as in CPython.

you have to explicitly mark sockets for reuse. Currently, user code has to create a session, call get and then manipulate the socket from the Response-object.

I think it would be much simpler to have this rather low-level manipulation of sockets as part of ConnectionManager. Or even better, as part of socketpool as the factory of sockets. But the latter would need changes to CP itself.

[justmobilize]

@tannewt do you think this would be a good idea? Where we set the timeout, we could also check the CP version and if it's greater than 9, set this option

[anecdata]

I've been wrestling with trying to understand the socket reuse issue, there's a lot of history in the core issues and PRs, and a lot of unclear info out on the ethers.

My understanding is that SO_REUSEADDR used to be always set for listen-ing sockets implicitly, but now it needs to be done explicitly (better Python compatibility). But is setting SO_REUSEADDR something that only applies to servers / listen, or would there be benefit (or at least no side effects) of setting it for all sockets?

[dhalbert]

Yes, SO_REUSEADDR would be set for server-side sockets. You'd set it before bind(), which is before listen(). I don't know of a purpose for using it on the client set, in adafruit_requests.

Server examples that set SO_REUSEADDR:
https://www.codementor.io/@joaojonesventura/building-a-basic-http-server-from-scratch-in-python-1cedkg0842#sending-http-responses-using-sockets
https://medium.com/@stephen.biston/write-an-http-server-from-the-ground-up-in-9-minutes-with-python-1fdb9800a26a
etc.

[justmobilize]

Ahh, so we wouldn't add that here, unless we added support for getting server-side sockets in connection manager

[anecdata]

I was actually wondering about that this morning... was going to see if CM meshed with adafruit_http_server.

[dhalbert]

Ahh, so we wouldn't add that here, unless we added support for getting server-side sockets in connection manager

That does not seem necessary to me. adafruit_httpserver takes a socket pool as an argument and takes care of getting a socket and setting it for reuse: https://github.com/adafruit/Adafruit_CircuitPython_HTTPServer/blob/dc9f83cd1a212520f4728dc3025dc881ffad3035/adafruit_httpserver/server.py#L207. That is typically the server's job.

I would suggest closing this issue unless, @bablokb, you have a particular use case in mind. The point of connection manager to me is to wrap and hide the multiple sources of socket pools and ssl contexts.

[bablokb]

Thanks for the clarification, it was not clear for me that this is not an issue for the client side.