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gh-christianlouis-docuelevate/app/utils/settings_sync.py
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2026-02-23 11:42:37 +00:00

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Python

"""
Worker settings synchronisation helper.
When an admin saves a configuration change through the UI, any running Celery
workers still hold the *old* values in their in-process ``settings`` singleton.
This module provides two complementary mechanisms to propagate the change:
1. **Publish** (API side): :func:`notify_settings_updated` writes a monotonically
increasing timestamp to a Redis key. This is called immediately after every
successful ``save_setting_to_db`` / ``delete_setting_from_db`` operation.
2. **Subscribe** (worker side): :func:`register_settings_reload_signal` installs
a Celery ``task_prerun`` signal handler. Before each task begins the handler
reads the Redis version key; if it has changed since the last reload it calls
:func:`~app.utils.config_loader.reload_settings_from_db` so the worker picks
up the new values *before* executing the task body.
The Redis key used is ``docuelevate:settings_version``. Workers cache the last
seen version in a module-level variable to avoid redundant DB round-trips when
nothing has changed.
"""
import logging
import time
from typing import Any
import redis
from celery.signals import task_prerun
logger = logging.getLogger(__name__)
#: Redis key that stores the current settings "version" (epoch timestamp string).
SETTINGS_VERSION_KEY = "docuelevate:settings_version"
#: Module-level cache: the settings version seen by *this* process on its last reload.
_last_seen_version: str = ""
def notify_settings_updated() -> None:
"""
Publish a settings-updated signal by updating the Redis version key, and
immediately reload the in-process ``settings`` singleton so the API
process serves fresh values without a restart.
Call this after every successful settings write so that all worker
processes know they need to reload their in-memory configuration.
Errors are caught and logged rather than raised so that a Redis
connectivity issue does not prevent the primary save from succeeding.
"""
try:
from app.config import settings
r = redis.from_url(settings.redis_url, socket_connect_timeout=2)
version = str(time.time())
r.set(SETTINGS_VERSION_KEY, version)
logger.debug(f"Settings version bumped to {version}")
except Exception as exc:
logger.warning(f"Could not publish settings update to Redis: {exc}")
# Reload the in-process settings singleton immediately so the API node
# returns updated values (e.g. oauth_provider_name on the login page)
# without needing a restart. Workers use the task_prerun signal handler
# instead, so this only affects the API/web process.
try:
from app.config import settings
from app.utils.config_loader import reload_settings_from_db
reload_settings_from_db(settings)
logger.debug("In-process settings reloaded after settings update")
except Exception as exc:
logger.warning(f"Could not reload in-process settings: {exc}")
def register_settings_reload_signal() -> None:
"""
Install a Celery ``task_prerun`` signal handler for worker processes.
This should be called once during Celery worker initialisation (e.g. from
``celery_worker.py``). After registration, every task will check the
settings version key in Redis before it starts and reload configuration
from the database if a newer version is detected.
"""
@task_prerun.connect(weak=False)
def _reload_if_stale(sender: Any, **kwargs: Any) -> None:
"""Reload settings from DB if the Redis version key has changed."""
global _last_seen_version
try:
from app.config import settings
from app.utils.config_loader import reload_settings_from_db
r = redis.from_url(settings.redis_url, socket_connect_timeout=2)
current_version = (r.get(SETTINGS_VERSION_KEY) or b"").decode()
if current_version and current_version != _last_seen_version:
reload_settings_from_db(settings)
_last_seen_version = current_version
logger.info(f"Worker settings reloaded (version={current_version})")
except Exception as exc:
logger.debug(f"Settings version check skipped: {exc}")
logger.info("Settings reload signal handler registered on task_prerun")