Ways to store per-request context data

[matteocontrini]

Hello,

I was wondering if Python Powertools provide a way to store context data that is accessible from anywhere during the request lifecycle.

My use case would be passing along a variable that contains the language of the client, which could be parsed from headers/cookie/etc.

The field could then be used for example in exception handlers, to determine which language should be used when returning an HTML error page to the user. Adding a language field in my custom Python errors doesn't feel right since I raise those errors from various parts of the code, while app.current_event is read-only I think so I can't set fields in there.

How would you solve a problem like this one? Am I missing something?

Thanks!

[michaelbrewer]

I could be an interesting RFC in general.

But for now app.current_event.current_event can have values assigned to it for now

Here is an example where client_language key is set with your context variable

def test_custom_field():
    app = ApiGatewayResolver()

    @app.exception_handler(ValueError)
    def handle_value_error(ex: ValueError):
        return Response(
            status_code=418,
            content_type=content_types.TEXT_HTML,
            body=app.current_event["client_language"],
        )

    @app.get("/my/path")
    def get_lambda():
        # Setting a custom value via the `raw_event` dict
        app.current_event.raw_event["client_language"] = "FR"
        raise ValueError("Foo!")

    result = app(LOAD_GW_EVENT, {})

    assert result["statusCode"] == 418
    assert result["headers"]["Content-Type"] == content_types.TEXT_HTML
    assert result["body"] == "FR"