The 0.2.3b4 #1003 "fix" POSTed JPEG bytes as multipart form data,
but Obico's /p/ endpoint is declared methods=['GET'] upstream and
reads ?img=URL from the query string. Every POST was 405'd by
Flask's router before any handler ran, which is why the Obico
container logs were silent while Bambuddy kept reporting
"ML API call failed for printer N:" with a blank suffix —
raise_for_status() on the 405 produced an exception whose str()
rendered empty.
Restored the pre-#1003 nonce-URL approach (commit 3e434458):
capture locally with a 20s timeout we control, stash the JPEG
under a single-use 32-byte nonce, hand Obico a
GET /api/v1/obico/cached-frame/{nonce} URL that resolves in
<50ms so its hardcoded 5s read timeout never races RTSP.
Also guards against future silent exceptions: the error format
now falls back to type(exc).__name__ when str(exc) is empty.
Detection also early-returns with an explicit error if
external_url is unset instead of handing Obico a URL it can't
resolve.
The #1003 reverse-proxy scenario (Authelia/Authentik/CF Access
in front of Bambuddy) is addressed by documenting that the
/api/v1/obico/cached-frame/ path must be whitelisted from
external auth at the proxy layer — it is already public on
Bambuddy's side.
Backend: services/obico_detection.py, api/routes/obico.py,
main.py (PUBLIC_API_PATTERNS).
Frontend: FailureDetectionSettings banner + client.ts type +
all 7 locales restored.
Tests: 15 unit + 5 integration tests pass.
The ML API previously called back into Bambuddy to fetch snapshots,
which failed behind reverse proxies with external auth (Authelia, etc.).
Now the detection loop captures the JPEG locally and POSTs it directly
as multipart form data — no callback URL, no nonce cache, no
external_url dependency.
Obico's ML API has a hardcoded 5s read timeout on the URL it fetches, which
our /camera/snapshot regularly exceeds on cold calls (TLS proxy + ffmpeg +
RTSP keyframe wait). The detection loop now captures the JPEG locally with
a 20s timeout we control, stashes the bytes under a single-use 32-byte
nonce, and hands Obico a new /api/v1/obico/cached-frame/{nonce} URL that
returns the cached bytes instantly. The 5s ceiling is no longer a factor.
The nonce is the credential (URL-safe, 256 bits of entropy, single-use,
30s TTL) so the endpoint can be unauthenticated without widening the
camera access surface. Replaces the previous camera-stream-token snapshot
URL approach, which remained vulnerable to the upstream 5s timeout even
when auth was disabled.
Thanks to @fblix for the detailed reproducer with timeout numbers.
maziggy