Application and request storage keys

Safir apps use the key storage on the aiohttp.web.Application instance to globally store data. Middleware also stores data in the aiohttp.web.Request instances. This page describes the conventions and keys that Safir-based apps use.


Use the root app for storage

Safir apps typically have two Application instances: a root application and a sub-application. The sub-application serves externally-accessible routes under the application’s name (/<app-name>/), while the root application serves internally-accessible routes relative to the root path (/).

Safir attaches data to the root application whenever possible.

In a request context, you can access application data, regardless of whether it is an internal or external route using the aiohttp.web.Request.config_dict lookup method:

async def get_index(request: web.Request) -> web.Response:
    """GET /<path>/ (the app's external root).
    metadata = request.config_dict["safir/metadata"]
    data = {"_metadata": metadata}
    return web.json_response(data)

safir/ key prefix

Safir uses the safir/ prefix for keys to prevent collisions with your code. If your application adds custom data (outside the Safir framework) to the application, consider using a custom prefix to namespace that data.

Safir’s application keys

These keys are available from the root application in general, or from the config_dict attribute of Request objects in handlers:


The conventional key for storing your application’s configuration instance.


The aiohttp.ClientSession created by safir.http.init_http_session generator. See Using the aiohttp client.


The application’s metadata dictionary.

Safir’s request keys

These keys are available directly from Request objects in handlers (without using config_dict):


This is a structlog logger added to the request by the logging middleware. See Logging in Safir applications.