Chuck 0c7d03a476 fix(web-ui): support multiple browser tabs via SSE broadcaster (#349) ...

* fix(web-ui): support multiple browser tabs via SSE broadcaster pattern

Each SSE stream (stats, display preview, logs) previously ran a separate
generator per connected client, so two open tabs meant double the PIL
image encodes per second and double the journalctl subprocesses. Under
load or on reconnect storms the tight "20 per minute" rate limit was
easily exhausted, silently breaking tabs without any user-facing
explanation.

- Replace per-client sse_response generators with _StreamBroadcaster:
  one background thread per stream type fans data to all subscribed
  client queues, keeping CPU/subprocess work constant regardless of
  how many tabs are open
- Add 30-second SSE heartbeat comments to keep idle connections alive
  through proxies
- Raise SSE rate limit from "20/min" to "200/min" to prevent reconnect
  storms from exhausting the limit
- Assign statsSource/displaySource to window.* so reconnectSSE() in
  app.js can actually reach them (was dead code due to const scoping)
- Add displaySource error handler so display preview failures are no
  longer completely silent
- Improve connection status badge: shows "Reconnecting…" on first few
  errors, "Disconnected" with tooltip hint after persistent failure
- Complete the empty displaySource.onmessage stub in reconnectSSE()

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix(web-ui): harden SSE broadcaster — drop-oldest on full queue, exit on no subscribers, reattach reconnect handlers

- _broadcast: on queue.Full drop the oldest item and retry the put
  instead of removing the client from _clients — a slow tab now stays
  subscribed and receives the latest data rather than being silently
  ejected
- _broadcast: break instead of continue when _clients is empty so the
  background generator thread exits rather than spinning indefinitely;
  subscribe() already restarts it on the next connection
- base.html: expose _statsOpenHandler, _statsErrorHandler, and
  _displayErrorHandler as window properties so reconnectSSE() can
  reattach them after replacing the EventSource instances
- app.js: reconnectSSE() now reattaches those handlers after creating
  each new EventSource so the status badge and display-stream console
  logging survive a manual reconnect

Heartbeat path (~line 646) is a queue read (q.get), not a write; no
queue.Full can occur there so no change needed.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix(lint): declare updateDisplayPreview in ESLint global comment

Codacy flagged 'updateDisplayPreview is not defined' at app.js:73.
The function is defined in base.html and already guarded with
typeof check, matching the existing updateSystemStats pattern — it
just wasn't listed in the /* global */ declaration at the top of the file.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Chuck <chuck@example.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

2026-05-25 14:37:03 -04:00

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