peter
71d7646bf1
Round 6 turned `artifact_may_arrive` into a positive rule, but keyed it to the HLS vocabulary in
general rather than to what THIS session produces: the playlist regex accepted master/index/stream_*
for every session and the `seq == 0` branch accepted any variant token unconditionally. The two argv
branches are disjoint — a single-audio session is given `seg_%d.ts` + `index.m3u8` and no `%v` at
all, so `master.m3u8`, `stream_*.m3u8` and every `seg_<variant>_<n>.ts` are names it can never write,
and vice versa — so each of those was read as "an HLS name, so wait and see" and held a threadpool
worker, plus its pooled DB connection, for the full timeout. That is verbatim the round-5 outage the
route's own comment claims it prevents.
Measured through the real route against a live single-audio session, before: master.m3u8 404 after
30.0s, stream_q7z.m3u8 404 after 30.0s, seg_a0_0.ts / seg_zzzz_0.ts / seg_0_0.ts 404 after 20.1s
each. After, on the running localdev API: 404 in 44-316ms for all of them, while index.m3u8,
seg_0.ts and seg_1.ts still answer 200 — nothing is over-refused.
The session now carries the rendition names its ffmpeg was told to write, and `entry` is derived from
them instead of passed. And "one place" now means the argv BUILDS its patterns from the same
functions the parser reads back (`segment_name("%d", "%v")`, `variant_playlist_name("%v")`): the
layout was still spelled out independently in six places, with `_VIDEO_VARIANT` read by no consumer,
which is the drift that caused round 6's HIGH. A test asserts the argv's own patterns are what those
functions produce, and that every name they expand to is one the guard accepts.
The load-bearing MEASURED comment cited ffmpeg 8.1.1 — the Windows host's. The binary that writes
these files is the API container's 7.1.5; re-measured there, the conclusion holds.
Backend conventions
The rules below are already followed across backend/app — they lived only in a few module
docstrings (demo.py, userscope.py, routes/_common.py) until this file collected them (E3 S3,
B-core-20). When you add code, match these so the next reader doesn't have to guess "which pattern do
I copy".
Module layering
Three layers, by who runs the code — not by feature:
-
routes/…— request-only. A route module holds HTTP concerns: auth dependencies, request/ response models, status-code mapping, serialization. It owns logic that runs only on a request. Business logic that a request happens to trigger does not live here if anything else runs it too. -
plex/,downloads/,sync/— domain logic shared by more than one caller. Anything the scheduler or the worker runs (not just a request) lives in one of these domain packages, so the route, the worker, and the scheduler share one definition. Examples from this codebase:downloads/service.pyowns enqueue + the job state transitions (routes call it);plex/sync.pyis run by both the admin route and the scheduler;downloads/pipeline.pyis the worker's child pipeline. -
Flat
app/*.pycore modules — cross-cutting primitives.auth,sysconfig,quota,audit,notifications,userscope,realtime,ratelimit,progress, … are single-file primitives many layers import. They depend on nothing above them (a core module must never import aroutes/…module).
Extraction trigger: the SECOND consumer. Keep new logic inline in its first caller. The moment a second caller needs it (a worker as well as a route; a scheduler as well as a route), extract it down a layer — into the relevant domain package, or a flat core module if it's cross-cutting. Don't pre-abstract for a single caller; don't leave shared logic duplicated once there are two.
Transaction ownership
This follows CLAUDE.md's canonical rule verbatim — "the handler/job-wrapper commits; helpers flush
(only quota owns its session)" — so read it that way, not as an exception to it. The commit belongs
to the operation owner; anything called inside another transaction only stages its change
(db.add / flush) and lets the owner commit, so the whole operation is one transaction.
audit.record() is the reference: it adds the audit row and the caller commits it together with the
mutation it records, so an audit entry can never exist without its change (or vice-versa).
- The operation owner is usually the route handler. A
service.*operation the handler delegates a whole transition to (e.g.service.cancel) is that owner and commits its one transition — it isn't a mid-operation helper. A helper that owns its OWN short-lived session (the worker'sjobdbwrites, the same carve-out CLAUDE.md grantsquota) commits that session. Everything else flushes. SessionLocalisexpire_on_commit=False: after a rawUPDATE+ commit, an ORM object you already loaded is stale. Read the fresh value from the row (RETURNING, or a re-SELECT), not the ORM attribute — seeservice.decr_ref_count.
Shared counters and status: do it atomically at the DB
- Never read-modify-write a shared counter in Python (
x.count = x.count + 1). Concurrent sessions lose an update. Use a DB-atomic statement —col = col + 1, orgreatest(col - 1, 0)withRETURNINGso the caller branches on the post-value under the row lock (service.incr_ref_count/decr_ref_count). - Download job status is a
JobStatusStrEnum (downloads/status.py), not bare strings. TheHOLDINGset defines which states hold aMediaAsset(so release accounting stays correct);STOPPED_BY_ROUTEis the route-initiated stop set. A worker child's terminal write goes throughservice.finalize_if_running(an atomicUPDATE … WHERE status='running') so a finishing child can't resurrect a job a route just stopped.
Config: one home per kind
app.config.settings— boot/env config (DB URL, download root, worker concurrency): read once at startup, not user-tunable at runtime.sysconfig.SPECS— the runtime admin knobs (DB-override-or-default). A new admin-tunable value goes inSPECS; don't invent a fourth store. (state.py'smaintenance_batchpredates this and is slated to fold intosysconfig— do not add more like it.)
The gate
Everything below must be green before a change is done (run via siftlode check):
ruff (backend) · tsc ×3 + eslint + prettier + knip (frontend) · vitest · pytest. The
pytest lane runs in backend/docker-compose.test.yml — an ephemeral Postgres + the backend tree
bind-mounted — so the DB-backed integration tests (the db fixture) actually run; SIFTLODE_TEST_ REQUIRE_DB=1 there turns a would-be silent skip into a hard failure. See docs/development.md.