WebSockets support only available within WebSockets methods (ValueError: WebsocketAPI.configure must be called before using the WebsocketAPI)

[convexset]

It seems that WebSockets support only available within WebSockets methods. From other application code, one gets:

ValueError: WebsocketAPI.configure must be called before using the WebsocketAPI

This may seem alright, but application code may need to communicate with clients connected over WebSockets.

I don't think it's too much to ask to have this enabled by default.

To work around this, what I've done is to have a script put my Chalice exports into chalicelib/chalice_exports.py which looks like:

exports = {
    "dev": {
        "rest_api": {
            "name": "rest_api",
            "resource_type": "rest_api",
            "rest_api_id": "abc123rd",
            "rest_api_url": "https://abc123rd.execute-api.ap-southeast-1.amazonaws.com/api-dev/"
        },
        "websocket_api": {
            "name": "websocket_api",
            "resource_type": "websocket_api",
            "websocket_api_url": "wss://abc123wd.execute-api.ap-southeast-1.amazonaws.com/api-dev/",
            "websocket_api_id": "abc123wd"
        }
    },
    "prod": {
        "rest_api": {
            "name": "rest_api",
            "resource_type": "rest_api",
            "rest_api_id": "abc123pr",
            "rest_api_url": "https://abc123pr.execute-api.ap-southeast-1.amazonaws.com/api/"
        },
        "websocket_api": {
            "name": "websocket_api",
            "resource_type": "websocket_api",
            "websocket_api_url": "wss://abc123pw.execute-api.ap-southeast-1.amazonaws.com/api/",
            "websocket_api_id": "abc123pw"
        }
    }
}

(I actually use Chalice with Amplify, so this had to be done to provide the same information to the front end.)

Then I have somewhere in my application code:

STAGE = os.environ.get('STAGE', 'dev')

# ...

websocket_api = None
def inject_websocket_api(_websocket_api):
    global websocket_api
    websocket_api = _websocket_api
    if websocket_api._endpoint is None:
        log.info('-' * 40)
        log.info(f'WebSockets Endpoint not set. Configuration needed.')
        current_chalice_exports = chalice_exports.exports.get(STAGE)
        if current_chalice_exports is not None:
            websocket_api_domain = current_chalice_exports['websocket_api']['websocket_api_url'].split('/')[2]
            websocket_api_stage = current_chalice_exports['websocket_api']['websocket_api_url'].split('/')[3]
            websocket_api.configure(websocket_api_domain, websocket_api_stage)
            log.info(f' - Configuring WebSockets: domain={websocket_api_domain}, stage={websocket_api_stage}')
        else: 
            log.info(f' - Information to configure WebSockets not available')
        log.info('-' * 40)
    else:
        log.info('-' * 40)
        log.info(f'WebSockets Configured: websocket_api._endpoint={websocket_api._endpoint}')
        log.info('-' * 40)

This is called from app.py as such:

chalicelib.websockets.inject_websocket_api(app.websocket_api)

(Sorry, a little lazy to edit this.)

[convexset]

I see how this might be troublesome since this seems to be configured within the WebsocketEventSourceHandler at...

https://github.com/aws/chalice/blob/master/chalice/app.py#L1768

... which is super easy and convenient. However, all other request contexts do not include this.

I would say that an automatically generated list of the last deployed resources on app would be a viable solution. That is, the content of .chalice/deployed/MYSTAGE.json. This means that a deploy would be needed, followed by another if there is a non-zero "diff".

This architectural change is troublesome, but does open up additional possibilities. How about CFN/CDK with exports available to the app?

[convexset]

Additionally, as it is, this fails with event sources. My workaround is "doing the regular thing" of setting up my own send method based on the aforementioned deployed data:

import boto3
from chalice import WebsocketDisconnectedError

# after each deployment, data from .chalice/deployed/ is written to...
from . import chalice_exports 

STAGE = os.environ.get('STAGE', 'dev')

current_chalice_exports = chalice_exports.exports.get(STAGE)

apigw_management_client = None
if current_chalice_exports is not None:
    websocket_api_domain = current_chalice_exports['websocket_api']['websocket_api_url'].split('/')[2]
    websocket_api_stage = current_chalice_exports['websocket_api']['websocket_api_url'].split('/')[3]
    log.info(f'Configuring WebSockets: domain={websocket_api_domain}, stage={websocket_api_stage}')
    apigw_management_client = boto3.client(
        'apigatewaymanagementapi',
        endpoint_url=f'https://{websocket_api_domain}/{websocket_api_stage}'
    )
else:
    log.error(f'Information to configure WebSockets not available')

def _send(connection_id, serialized_data):
    # https://github.com/aws/chalice/blob/master/chalice/app.py#L687
    if apigw_management_client is None:
        raise Exception('websocket_api not yet deployed')
    try:
        result = apigw_management_client.post_to_connection(
            ConnectionId=connection_id,
            Data=serialized_data,
        )
    except apigw_management_client.exceptions.GoneException:
        raise WebsocketDisconnectedError(connection_id)
    return result