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obs-streamer-tools-plugin/core
shadowdaoandClaude Opus 5 b23644fa3e
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fix(http): enforce a hard deadline on WinHTTP by cancelling the request
Setting WINHTTP_OPTION_RECEIVE_RESPONSE_TIMEOUT (previous commit) fixed the
original failure -- the request is now always cancelled instead of waiting out
a stall and returning 200 -- but the instrumented CI probe shows it is not
cancelled on TIME. Five attempts with a 700ms budget against a server that
accepts and then stalls 5s returned after 1490, 1529, 2485, 3493 and 4506ms,
every one of them ERROR_WINHTTP_TIMEOUT (12002). One exceeded the test's 4s
bound, which is why Windows CI was still red.

That is the documented behaviour, not a mystery: both receive timeouts are
"checked only when data is received from the socket", so an expired timeout is
not surfaced until the peer sends something. Neither option is a deadline.

It matters because `fetchSlots` is called synchronously on the OBS UI thread,
behind the properties dialog's "Refresh camera list" button
(obs-adapter/src/plugin-main.cpp:486, kPropertiesTimeoutMs = 5000). At the
overshoot ratio measured above, a stalling server freezes that dialog for
something like half a minute -- the exact failure the shortened timeout there
was chosen to avoid.

So: a watchdog thread that closes the request handle once the deadline passes,
which is the documented way to cancel a WinHTTP operation. `RequestDeadline`
owns the handle and both threads close it through an
`atomic::exchange(nullptr)`, so exactly one close ever happens. Failures are
reported as a timeout rather than as a raw GetLastError when the deadline is
what fired.

The ceiling is twice the caller's budget, not the budget itself: resolve,
connect, send and receive each get `timeout` from WinHttpSetTimeouts, so a
slow-but-progressing exchange can legitimately exceed one budget and must not
be cancelled. There is one accepted race, documented at the class: the caller
can load the handle just before the watchdog closes it, turning the call into
ERROR_INVALID_HANDLE instead. Both mean the deadline expired.

Cross-compiled with mingw-w64 (`-fsyntax-only`) rather than waiting on CI to
find syntax errors; also confirmed by preprocessor probe that
WINHTTP_OPTION_RECEIVE_RESPONSE_TIMEOUT is defined in those headers, so the
#ifdef guard is not silently skipping the option. Linux: all 6 suites pass.
Real verification is the Windows job's probe output.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AzGnvQ6wfD7bw7PZN35ft9
2026-09-09 18:37:58 -07:00
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