AWS WebSocket support

[jordaneremieff]

I've removed the existing WebSocket support as part of #127 with the intention of developing it outside of this package, then later migrating it back in (if it makes sense to do so). My main concern is that I want to avoid impacting the stability of the HTTP implementation which is the primary use-case, and the maintenance burden was too much for the amount of capacity I have to spare currently. I also want to re-design it with broadcast support as an initial requirement rather than a feature added on later.

I think a new project might use Mangum as a dependency, or could end up looking something like this:

from mangum import Mangum
from mangum_ws import MangumWebSocket

def handler(event, context):
    if 'eventType' in event['requestContext']:
        asgi_handler = MangumWebSocket(app)
    else:
        asgi_handler = Mangum(app)

    return asgi_handler(event, context)

Not really sure. I haven't been motivated to take this up for awhile, but if anyone wants to give it a shot I can help where possible.

[jordaneremieff]

The next large item I'm interested in working on is #86, so I won't likely revisit this for awhile. Still happy to assist anyone that wants to take this on, but I'll be focusing on supporting multiple FaaS platforms before doing anything further myself.

[satyajitghana]

any update/progress on this ? i've been wanting to use websockets with lambda using mangum

[jordaneremieff]

@satyajitghana I've note had a chance to come back around to this and likely won't for awhile, but I was thinking about how to accommodate a plugin system to more easily integrate potential solutions for this kind of thing. Once I have made any progress here I'll update the ticket.

[ptrhck]

I am also interested and would like playing around with an older version. But where can I find the documentation for older versions that include the websockets info?

[satyajitghana]

@ptrhck 0.9.0 had websocket support, https://github.com/jordaneremieff/mangum/tree/8de9e84bfa22f1fa45ae601b781d9f0374b01dd9 you can find the docs there

[ptrhck]

Thanks! I have also found the commit before websocket was removed.

Very unfortunate that it has been removed but hopefully there will be a new project soon :-)

[villekr]

I would be interested to look at this in relation with mobilityhouse/ocpp#168. However AWS API Gateway WebSockets API is not primary focus due to it's incompatibility with ocpp-j endpoint format requirements. So instead custom websockets gateway will be used but the idea would be similar as with AWS API Gateway. Websocket broadcast support however is not in my interest.

I briefly checked the removed websockets related code and it looks good. Was there some major problems or missing things in the implementation that I should be aware of?

Basically I like idea having Mangum and MangumWebSocket being distinct classes and even so that one should explicitly define which one to use instead of dynamically instantiating either one based on incoming event's attributes.

Also implementation behind post_to_connection should be changeable to facilitate different websocket callback apis.

[jordaneremieff]

@villekr

I briefly checked the removed websockets related code and it looks good. Was there some major problems or missing things in the implementation that I should be aware of?

No, there weren't any specific issues in the implementation. My primary reason for removing it was that I did not have the capacity to properly support the pattern I ended up using, however, I think it is the correct solution for this problem generally. I agree a separate class would be better than trying to determine this based on the incoming event, though I haven't spent time to think about the specifics of how to implement this yet.

[jordaneremieff]

Given the changes in #170 I think we could potentially re-add WebSockets to this project using the new pattern for implementing handlers.

Probably something like

        if (
            "requestContext" in trigger_event
            and "routeKey" in trigger_event["requestContext"]
        ):
            from . import AwsWsGateway

            return AwsWsGateway(trigger_event, trigger_context, **kwargs)

as the entrypoint for the event handling, then what's in https://github.com/jordaneremieff/mangum/tree/broadcast can be refactored into the new event workflow.