Wiring & Lifetime

from dynamic_config_web import Wiring

wiring = Wiring(config, debounce=0.25)

wiring.start()      # or `await wiring.start_async()`
...
wiring.stop()

Wiring is load-watch-stop for one configuration or a whole ConfigGroup. Every adapter builds one; setup(app, config) builds it for you and hands it back, and setup(app, wiring) takes one you already have — which is what two applications sharing a lifecycle, and a test that wants to inspect it, both need.

Idempotent at both ends

Starting a wiring that is running does nothing. Stopping one that is not is not an error. That is what makes it safe to call from a hook that fires more than once — Django's AppConfig.ready() under the autoreloader, a Flask app whose first two requests race — and it is why stop() belongs in a finally.

watch=False still loads

For a serverless function, where nothing lives long enough to watch, and for a test that reloads by hand. The configuration is loaded and the health surface answers; nothing observes the filesystem.

The lease

The engine refuses a second watcher per configuration, so counting per application would not be enough: two apps over one configuration is an ordinary thing (a service and its admin panel; a test client opened inside another's block). So the count lives with the configuration. The first holder starts the watcher, the last one to leave stops it, and dynamic_config_web._lease.holders(config) is what a lifetime test asserts.

Forking

A watcher is a thread. fork() does not copy threads — but it does copy memory, and the engine's "this configuration is already watched" registration is memory. A child would therefore be refused a fresh watcher while nothing at all was watching, and would serve the snapshot it was forked with, silently, for ever.

Every lease re-arms itself in the child through os.register_at_fork: it drops the inherited handle, which frees the registration, and starts a watcher on this process's own thread. Nothing to configure, and it is why gunicorn --preload works.

fork() exists on POSIX and not on Windows, so neither does the hazard.

Where each framework starts it

The deployment page has the gunicorn and uWSGI hooks for the cases where you would rather be explicit than lazy.