HTTP session override may not work correctly

[irtimir]

I use my custom HTTP session with overridden TCPConnector.

conn = aiohttp.TCPConnector(ssl=ssl_context)

socketio.AsyncClient(
    ...,
    http=aiohttp.ClientSession(connector=conn),
)

And after the reconnect is called, the default session can override the session I passed:

python-engineio/src/engineio/async_client.py

Lines 308 to 310 in 7a41390

	if self.http is None or self.http.closed: # pragma: no cover
	self.http = aiohttp.ClientSession()

My suggestion is to create a separate method in the base class that contains the logic for creating a session.

Then you can do it like this:

# engineio.async_client.AsyncClient
class EIOCustomSession(engineio.AsyncClient):
    def create_session(self):
        return aiohttp.ClientSession()

    async def _connect_websocket(self, url, headers, engineio_path):
        ...
        if self.http is None or self.http.closed:  # pragma: no cover
            self.http = self.create_session()
        ...

# mymodule
class EIOCustomSession(engineio.AsyncClient):
    def __init__(self, *args, **kwargs, conn=None)
        self.conn = conn

    def create_session(self):
        return aiohttp.ClientSession(connector=self.conn)


class SIOCustomSession(socketio.AsyncClient):
    def _engineio_client_class(self):
        return EIOCustomSession

[miguelgrinberg]

I don't understand how your HTTP session can be closed. The intention was that when an HTTP session is provided by the caller it is not closed, even if the client needs to reconnect.

Does this happen every time there is a reconnect? Or are there any special conditions that cause your session to be closed and replaced?

[irtimir]

Sorry, I didn't fully understand how it really works. _reset method closes the session only if the external_http parameter is True:

python-engineio/src/engineio/async_client.py

Line 214 in 7a41390

if not self.external_http: # pragma: no cover

This does not cause me a problem right now. But this can be a problem if external code has closed the session.

I would like to discuss the concept that was laid down here. I understand that if I pass the client in the constructor, engineio code will not close the session, and this is delegated to the external code.

But in my case, I would like to completely delegate session management to engineio code, while customizing the session creation logic. In my case, I want to force it to use my SSL context. That is, I create a session and would not like to worry about when it needs to be closed.

I can be wrong, but I think I'm not the only one who creates a session just to pass it to the library. Also, my proposal extends the API and does not seem to break anything.

P.S.: I like the reconnection feature inside the library, but when using an external client, I cannot use the ability to recreate the client (in my case, I need to recreate the socket). I got out of the situation by limiting the number of reconnections, and if there are no more attempts, then I recreate all the classes again.

[miguelgrinberg]

What makes the most sense is to accept a callable in the http parameter. If you pass a function, then the framework can call the function every time it needs to make a session. This is consistent with other arguments of the client which can also be given as direct values or functions.

While some people do subclass the Engine.IO and Socket.IO clients to introduce custom behavior this is actually rare, most people do not like to do this. Passing functions is easier and requires less code on the caller's side.