The Request Scope

from dynamic_config_web import current, get, latest

db = current(config)     # the model this request began with
db = get("db")           # the same, by section key
db = latest(config)      # what is installed *now* — unscoped

A contextvars.ContextVar holds one reading of each configuration for the length of one request. The adapter opens it; a handler reads out of it.

Reading through the scope

Because it answers a different question every time it is called. Two reads either side of a reload are two configurations, and a response built from both is a response nobody can reproduce. current(config) answers the same object for the whole request, and that is the only difference.

The cost is a dictionary lookup — the engine's own read is an attribute lookup on a cached model, and this is that model, taken once.

What happens outside a request

It raises. OutsideRequestScopeError, with a message naming the configuration and pointing at latest().

Answering would mean silently doing the thing the scope exists to prevent. Code that is genuinely not serving a request — a startup task, a management command, a consumer — uses latest(config), which says so at the call site.

Threads, tasks and Django's sync path

contextvars is propagated by all three, which is why it is the mechanism:

• an asyncio task started inside a request inherits the snapshot;
• a def FastAPI endpoint, which runs on a worker thread, sees it because anyio copies the context into the thread;
• a Django sync view sees it because Django's own request handling does the same.

A task started before the request does not see it, which is the correct answer: it is not serving that request.

A configuration the scope does not carry

A scope covers the configurations its wiring was set up with. Reading one that is not among them raises rather than falling back — a handler reading a configuration nobody wired is a bug in the wiring, and a fallback would hide it until it mattered.

In a test

from dynamic_config_web import as_request

with as_request(config):
    assert view() == "db.internal"

as_request opens the same scope by hand, for a unit test that calls a handler directly and has no adapter in the way — and for a background job that wants one configuration for the length of a unit of work.