* filer: bound metadata log flush retries during shutdown
On SIGTERM the filer could hang forever in Shutdown: the final
LocalMetaLogBuffer flush retries appendToFile indefinitely, and with
the master already down each AssignVolume attempt just kept failing.
WaitForShutdown never returned, the interrupt hook never reached
os.Exit, and the half-dead filer kept its ports bound.
Thread a context through appendToFile/assignAndUpload and switch to
a 15s-bounded context once the filer is stopping: the flush abandons
with a log line instead of retrying forever. Normal operation keeps
the unbounded retry so no metadata is dropped while running.
Generated with [Devin](https://devin.ai)
Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
* filer: share one shutdown deadline across all pending meta log flushes
Review feedback on the per-flush timeout: a deadline armed at flush start
could already be expired when shutdown arrived, the first append of a flush
still ran unbounded, each queued window got a fresh budget (16 windows *
15s), and an abandoned window still advanced the flushed watermark as if it
had landed.
Rework to a single shared flush context on the Filer, cancelled once by
Shutdown via AfterFunc. Every append - the in-flight one and every queued
window - observes the same deadline, so the whole drain is bounded at 15s.
A flush that gives up reports its dropped bytes through the new
LogBuffer.NoteFlushDropped, and loopFlush then skips the offset/timestamp
advance and subscriber notifications for that window.
Generated with [Devin](https://devin.ai)
Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
* filer: bound append attempts and commit uploaded pieces detached
Store operations check then drop request cancellation, so a stalled
backend could still hold flushFn past the shutdown deadline; run each
append attempt on its own goroutine and give up on it at the deadline.
Once a piece is uploaded, commit its entry on a detached context so the
expired deadline cannot strand the chunk.
Generated with [Devin](https://devin.ai)
Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
* filer: keep shutdown flushes synchronous
Detaching the append attempt let flushFn return while the goroutine
still held the pooled flush buffer and could commit after the metadata
store closed; abandonment is only safe for the cancelable assign/upload
phase, which the shared flush context already bounds.
Generated with [Devin](https://devin.ai)
Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
---------
Co-authored-by: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
