A failed SDK start (port in use, PKI unwritable, bad OpcUa:* override) was one Error line: the
node stayed /health/ready 200, joined its mesh, could be elected driver Primary and acked deploys
through the Null sink while every client got connection-refused.
- IOpcUaEndpointState / OpcUaEndpointState: the start outcome is a fact the hosted service
maintains (NotStarted / Started / Failed / Stopped + reason).
- OpcUaEndpointHealthCheck ("opcua-endpoint", Ready + Active) is Unhealthy unless Started;
registered by AddOtOpcUaHealth(hasAdmin, hasDriver) on driver-role nodes.
- A driver-only node rethrows the start failure (Program.cs's fatal handler exits non-zero so
the supervisor restarts it); a fused node keeps its AdminUI up but is visibly not ready.
- StopAsync detaches the sinks and then STOPS the SDK (the port closes, clients get
connection-refused rather than a stale, inert endpoint); DisposeAsync is idempotent with it.
- The ServiceLevel calculator / redundancy election live in Cluster + Runtime (not this lane);
the fact is exposed for the Wave 3 follow-up to consume.
Tests: port-in-use ⇒ state Failed, probe Unhealthy, real /health/ready and /health/active 503
(positive control: 200 once Started); driver-only rethrows; StopAsync closes the port and
DisposeAsync twice is a no-op; the probe registration is on both tiers for driver nodes only.
Refs #733
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
Joseph Doherty
f5579e6ef2