* Centralize filesystem paths in a single module
Add paths.py, which resolves the repo root once and derives the cache,
accounts DB, logs, templates, frontend and bundled-city-data locations
from it. Replace the 13 per-module `dirname(__file__)/..` anchors with
references to it, so a module's location no longer determines where the
app reads its data. Env overrides (accounts DB, VAPID, IndexNow) are
unchanged; every resolved path is byte-identical to before.
Groundwork for moving modules into packages without re-pointing paths.
Claude-Session: https://claude.ai/code/session_01XXxmNFy9cZ6Gh8Y9thZn62
* Split the backend into domain packages
Group the flat backend modules into packages that mirror their concerns:
data/ climate, grading, scoring, grid, places, cities,
city_events, store
web/ app, views, homepage, content, schemas
notifications/ notify, digest, push, mailer, discord,
discord_interactions, discord_link
accounts/ models, users, api_accounts, db
core/ metrics, singleton, audit
Intra-project imports are rewritten to the package-qualified form. The
entry scripts (indexnow, warm_cities, migrate, gen_cities, gen_flavor)
and paths.py stay at the backend/ root, and backend/app.py becomes a
shim re-exporting web.app:app so the launch target stays `app:app` —
run.sh, the systemd units, and CI need no change.
Verified: full suite (318) passes, `uvicorn app:app` boots and serves
the home/SEO/static/API surfaces, and every root script imports clean.
Claude-Session: https://claude.ai/code/session_01XXxmNFy9cZ6Gh8Y9thZn62
Prod runs 3 uvicorn workers, but the in-process subscription notifier was
started in every worker's lifespan (it was written assuming a single-worker
deploy). Its sweep fetches recent-forecast/archive data from Open-Meteo on a
15-min timer independent of any request, so running it 3× tripled the
background upstream load against a shared quota — the source of the overnight
429/503 rate-limit errors in logs/errors, and 3× redundant subscription scans.
Elect one worker to own the notifier via a non-blocking exclusive flock on a
lockfile (THERMOGRAPH_SINGLETON_LOCK): the first worker wins and holds the fd
for its lifetime; others stand down; the OS releases the lock if the leader
dies, so a restart re-elects cleanly. Unset (single worker / dev / tests)
always wins, so behavior there is unchanged. Mirrors the shared-metrics store's
env-selected cross-worker coordination.
The neighbor warmer stays per-worker on purpose: each worker drains its own
request-fed queue, so gating it would leave non-leader queues undrained.
- backend/singleton.py: flock-based leader election (claim()).
- backend/app.py: gate notify.start() on singleton.claim().
- deploy/thermograph.service: default THERMOGRAPH_SINGLETON_LOCK to
data/notifier.lock (needs the unit reinstalled on prod to take effect).
- deploy/thermograph.env.example: document it alongside WORKERS.
- Tests: leader election — single-worker default, first-wins, idempotent
re-claim, second-holder stands down, re-election after release. 183 passed.
Co-authored-by: root <root@vmi3417050.contaboserver.net>
