Replace the config push mechanism that broadcast the full config
blob on a 'state' class pub/sub queue with a lightweight notify
signal containing only the version number and affected config
types. Processors fetch the full config via request/response from
the config service when notified.
This eliminates the need for the pub/sub 'state' queue class and
stateful pub/sub services entirely. The config push queue moves
from 'state' to 'flow' class — a simple transient signal rather
than a retained message. This solves the RabbitMQ
late-subscriber problem where restarting processes never received
the current config because their fresh queue had no historical
messages.
Key changes:
- ConfigPush schema: config dict replaced with types list
- Subscribe-then-fetch startup with retry: processors subscribe
to notify queue, fetch config via request/response, then
process buffered notifies with version comparison to avoid race
conditions
- register_config_handler() accepts optional types parameter so
handlers only fire when their config types change
- Short-lived config request/response clients to avoid subscriber
contention on non-persistent response topics
- Config service passes affected types through put/delete/flow
operations
- Gateway ConfigReceiver rewritten with same notify pattern and
retry loop
Tests updated
New tests:
- register_config_handler: without types, with types, multiple
types, multiple handlers
- on_config_notify: old/same version skipped, irrelevant types
skipped (version still updated), relevant type triggers fetch,
handler without types always called, mixed handler filtering,
empty types invokes all, fetch failure handled gracefully
- fetch_config: returns config+version, raises on error response,
stops client even on exception
- fetch_and_apply_config: applies to all handlers on startup,
retries on failure
