Fix round 1 (review task-9-review.md), all rulings:
1. (Important 1) ApplyReplicatedAsync is no longer trusted blindly. Every apply is
confirmed by a store.GetAsync read-back before ledgering: a tombstoned local row
(routine remove-then-re-add) is safely re-stamped past the tombstone and re-applied
(confirmed neither UpdatedUtc nor Revision is AEAD-bound in AesGcmEnvelopeCipher, so
the bump cannot break decryption); a live local row with different ciphertext (a
strictly-newer out-of-band secret) is left untouched, never ledgered, never verified
against, and reported with a distinct Failed message so a later central tombstone can
never delete it via this mirror.
2. (Important 2) Per-row try/catch (rethrow only on ct.IsCancellationRequested) so one
poisoned row (e.g. an unrecognised ContentType from a newer central) no longer blocks
every row after it.
3. (Important 3) Optional ISecretCacheInvalidator, invalidated after every successful
apply/delete and before verify, so a rotated/removed secret's plaintext cannot be
served stale for the remainder of the resolver's TTL.
4. (Minor 4) Loop and VerifyAsync OperationCanceledException handling now filters on
ct/stoppingToken.IsCancellationRequested specifically, rather than swallowing every OCE.
5. (Minor 5) Class remarks note the mirror assumes a node-local ISecretStore; Task 11
will reject SqlServer secrets replication on the Site role.
6. (Minor 6/7) Added cancellation + concurrent-callers tests, dropped the redundant
FailFor (tests now use ThrowFor/ReturnNullFor to exercise distinct decrypt-failure
paths), and Dispose() now disposes the gate SemaphoreSlim.
Verify: dotnet test tests/ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests --filter FullyQualifiedName~DeployedSecretsMirrorTests (24/24); full SiteRuntime.Tests suite 876/876.
Joseph Doherty