CRITICAL. The ack deadline was one absolute DateTime computed once for the whole
endpoint walk. Against the characteristic WAN failure — a central that HANGS
(SYN black-hole, frozen host) rather than refusing — endpoint 1 burned the whole
AckTimeoutSeconds and endpoint 2 was then dialled with a deadline already in the
past: instant DeadlineExceeded, no packet leaving the node, the surviving central
never really tried. Failover looked like it ran and did not. It also contradicted
MeshTransportOptions' own documented "applied per endpoint, not per ack". The
deadline is now computed fresh inside the loop; headers stay hoisted (read-only,
sequential walk).
Two test gaps that let that survive are closed: nothing pinned the ackRouter gate
(narrowing it back to ClusterClient-only compiled and passed every test while
dead-ending every Grpc ack to DPS), and the deadline fact's lower bound accepted
any positive timeout at all. Both new pins are mutation-verified.
Docs corrected where they overstated the case: duplicate acks CANNOT mis-seal a
deployment — ConfigPublishCoordinator.HandleAck keys _acks by NodeId behind an
expected-set guard, so a duplicate overwrites its own entry. The single-endpoint
rule is defence in depth and a bound on wasted work, not a correctness
dependency; and the walk is at-least-once on the deadline path, not at-most-once.
Joseph Doherty
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