The single-connection barrier from the last round was correct and was being
bypassed. shutdown_broadcaster() popped the broadcaster out of the registry
and only then awaited its teardown, so while the socket was still closing the
slot sat empty: a /camera/stream request landing in that window minted a
broadcaster with no predecessor and dialled port 6000 immediately. A page
reload fires /camera/stop and the new stream request concurrently, so a P1S
ended up holding two connections, kept feeding the orphan, and starved the
live viewer until its TCP keepalive reaped the dead one ~20 min later. The
stopped broadcaster now stays in the registry so the successor chains behind
its socket close.
The camera page also rendered the <img> src before the stream token arrived
whenever auth was disabled, then swapped it once the token landed — aborting
the in-flight request and issuing a second one. With auth off both reached the
backend, so every load attached two viewers to a one-socket printer. The src
now waits for the token query to settle.
Subscribers only checked for client disconnect after yielding a frame or on a
30s idle timeout, so a viewer that left during a black stream stayed counted —
and /camera/stop trusts that count to decide whether to tear the upstream down.
Chamber-image printers came up black on load and only recovered ~20 min
later. Two causes: (1) late fan-out subscribers got an empty queue and
waited for the next frame, so the browser never fired onLoad and the
stall-detector reconnect-looped, churning short-lived viewers; (2) the
churn reopened the port-6000 socket before the old one closed, so the
printer fed an orphaned socket until its TCP keepalive reaped it.
Prime late subscribers with the last pumped frame; make a replacement
broadcaster's pump wait for the predecessor's socket to close before
dialing (bounded 10s); require two consecutive stalled reads before the
frontend reconnects.
streams when one viewer closes
1) Offline tiles now show OFF (not LIVE)
CameraWall.modeByPrinter assigned 'live' to any visible printer
without considering status.connected, so a disconnected X1C wasted
a live-budget slot AND rendered the red LIVE chip on top of the
WifiOff placeholder. Disconnected printers now map to 'paused' and
don't decrement liveBudget — the existing WifiOff + Off chip
rendering takes over.
2) /camera/stop no longer kills other viewers' streams
The cam-wall tile, EmbeddedCameraViewer, and the /camera/:id popup
all subscribe to the same fan-out broadcaster for a printer.
/camera/stop used to unconditionally shutdown_broadcaster() + kill
every ffmpeg process for the printer, so closing the embedded viewer
while the cam-wall tile of the same printer was live force-killed
the source the tile was pulling from — the tile's <img> errored.
New get_subscriber_count(key) accessor in camera_fanout.py exposes
the broadcaster's subscriber list length. /camera/stop now reads
that first; when >= 1 subscriber is still attached, return
{stopped: 0, skipped: true} and leave the broadcaster + ffmpeg
processes alone. The leaving viewer's HTTP teardown still runs the
natural iter_subscriber.finally -> unsubscribe path, so its slot is
released; the broadcaster keeps serving the other viewers. Single-
viewer close still hits the immediate force-teardown (count is 0).
Most Bambu Lab printers only allow one concurrent camera connection, but
GET /printers/{id}/camera/stream opened a fresh upstream per viewer.
Two browser tabs → second viewer fails or kicks the first off.
New MjpegBroadcaster (services/camera_fanout.py) owns one upstream per
printer and fans MJPEG chunks out to N subscribers. 5 s grace window
absorbs tab refreshes without reconnecting. Bounded subscriber queues
drop frames for slow viewers rather than blocking the broadcaster.
Audit-pass fixes:
- _stream_start_times set with setdefault() so stream_uptime reflects
the shared upstream's age, not the most-recent viewer's
- subscribe() retried once on RuntimeError to close a tiny grace race
- unsubscribe() returns post-removal count atomically so the detach log
no longer races with concurrent leavers
Permission gates unchanged; broadcaster has no FastAPI surface.
Tests: 13 broadcaster unit tests + 2 integration tests on /camera/stop.
External-camera path untouched.
maziggy