M1 IsPoison classified every SQL Server transient as poison:
Microsoft.Data.SqlClient never sets DbException.IsTransient, so a deadlock
(1205), timeout (-2 / Win32 258), dropped connection or AG failover was
counted from memory and the node's row left Applying. Poison is now an
ALLOWLIST: a DbUpdateException (not concurrency) carrying a SqlException
whose number is 8152, 2628, 547, 515, 2627 or 2601. Everything else
retries, bounded by the deadline deferral cap. IsPoison is public for tests.
Acks counted only from memory (poison branch and the deferral cap) are kept
in _memoryOnlyAcks and re-sent by PreRestart alongside _unpersisted, so a
restart before the terminal write does not lose them.
M2 Revisions adopted without an outcome-reporting apply are unconfirmed, so a
same-revision dispatch re-applies instead of short-circuiting a clean
Applied over an empty address space: TryRecoverFromStale (restores only the
revision marker) and RestoreApplied when the artifact read fails (null
blob, LoadArtifactBlob swallows the error) or the restore throws.
L1 The re-drive comment documents the CreatedAtUtc recompute after a second
restart / failover.
L2 _currentRevisionDegraded renamed _currentRevisionUnconfirmed; the stale
TryBootFromCache remark corrected.
L3 docs/Redundancy.md: a Direct node running from cache that still cannot
reach the ConfigDb acks a same-revision re-dispatch Failed
(PartiallyFailed, not Sealed); Stale recovery and failed restores are
unconfirmed too.
Test harness: SqlExceptionFactory builds real SqlExceptions (reflection on
SqlError / SqlErrorCollection / SqlException.CreateException);
ConstraintEnforcingDbFactory now throws DbUpdateException over SQL 2628
(over-length), 547 (poison) and 1205 (transient), plus FailNextContexts.
Tests (all fail on the previous code): poison allowlist theory (1205, 40613,
10054, 4060 not poison) + timeout/concurrency/providerless not poison; a
deadlocked ack write is retried and recorded; a memory-counted ack survives a
coordinator restart; Stale-recovered and failed-restore revisions re-apply on
re-dispatch.
Claude-Session: https://claude.ai/code/session_01GT67AD99zQQqpLCVm3p7xk
Joseph Doherty