FasterLogHistorizationOutbox.PeekBatchAsync held the state lock across the
FasterLog scan. Once a backlog's head ages out of FasterLog's in-memory
window (any multi-minute historian outage), GetNext reads pages from disk
synchronously, and the recorder's appends (which index under the same lock)
blocked on an Akka dispatcher thread once per drain pass, exactly during
outage recovery.
The peek now snapshots the head under the lock, scans unlocked, and re-takes
the lock only when it met undecodable records, to reconcile them with the
index in O(records scanned) and drop one still at the head (re-checked,
since an ack or drop-oldest may have moved it). A test seam pauses the scan
and proves an append completes meanwhile; wrapping the scan in the lock
again fails it.
Rebased from the unpushed remed/lane-H2 branch (originally authored 2026-10-22
in session_01Ub9hGmYLQvn9XETzw7CMsT) onto current master.
Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV
Joseph Doherty
f4907d098c