`ActAsPrimaryHost` was accepted by config and by the AdminUI form and did nothing but
log a warning. It now delivers the whole three-part contract or none of it: a retained
`ONLINE` on `spBv1.0/STATE/{hostId}`, a matching retained `OFFLINE` armed as the MQTT
Last Will, and an explicit `OFFLINE` on a clean stand-down.
**The claim is a dedicated connection, not a message.** A Will can only be registered in
the CONNECT packet — it cannot be added to a live session, changed, or withdrawn. So a
claim that is acquired and released at runtime cannot ride the long-lived ingest session.
`SparkplugPrimaryHost` opens its own connection (client id `{clientId}-spbhost`, forced
clean-session) when the node gains Primary and closes it when the node loses Primary; the
connection's lifetime *is* the claim, so every leg follows from its lifecycle. Ingest is
untouched by a role change — no dropped subscriptions, no lost birth cache, no data gap at
the Secondary->Primary transition.
**Primary-gated** (owner decision, recorded on the issue). Both pair nodes subscribe
independently, so an ungated claim means both claim the same host id — and the sharp
failure is not the two fighting over the retained STATE, it is that the SECONDARY's death
fires its Will and publishes OFFLINE while the Primary is healthy, stopping every edge node
in the group. Registering the Will only on whichever node is Primary at connect time fails
the other way: a node that later gains Primary would publish ONLINE with no Will behind it.
New seam: `IDriverPrimaryRoleSource` (`Core.Abstractions`) carrying the *data-plane* verdict
(`PrimaryGatePolicy.ShouldServiceAsPrimary`), not the alarm-drain verdict — an unknown role
with a driver peer present must deny. Registered unconditionally by `AddOtOpcUaRuntime`,
deliberately NOT alongside `IRedundancyRoleView`, which `AddAlarmHistorian` registers only
when that section is enabled: piggybacking would leave a pair with no alarm historian
falling back to "claim unconditionally". Polled on a 1s timer rather than evented — a
process singleton raising events at per-instance drivers outlives every driver it holds.
Accepted trade: a brief edge-visible OFFLINE window during failover. That is a genuine
state transition, not a glitch to hide.
Live-gated 5/5 against the Mosquitto fixture, including the Will leg — `AbandonForTests`
drops the socket with no DISCONNECT, because a clean disconnect makes the broker discard
the Will by protocol rule, so a test driven through `StopAsync` would observe the
stand-down OFFLINE and pass against an implementation that never armed a Will. Falsified:
removing the Will turns that leg and only that leg red.
Also corrects two stale claims found en route: the AdminUI form still said MQTT tags are
read-only (#508 shipped), and the driver doc still said nothing consumes `IRediscoverable`.
Claude-Session: https://claude.ai/code/session_015p7wGqy3YpZNCpDzTpGMKo
Task 9. Adds MqttDriverFactoryExtensions (DriverTypeName = DriverTypeNames.Mqtt,
direct deserialization of MqttDriverOptions — no intermediate DTO, mirroring
OpcUaClientDriverFactoryExtensions), the DriverTypeNames.Mqtt constant, and both
host wiring sites: the factory in DriverFactoryBootstrap.Register and the probe in
AddOtOpcUaDriverProbes (the admin-node path Program.cs calls in its hasAdmin
block — a probe wired only on driver nodes makes Test-connect silently dead).
Carried-forward items:
- Converges every MQTT config-parsing seam onto ONE JsonSerializerOptions —
MqttJson.Options, in .Contracts alongside MqttDriverOptions. It replaces the
probe's internal JsonOpts and the browser's separate private copy; the factory,
the probe, MqttDriver.ParseOptions and MqttDriverBrowser now all parse through
it. .Contracts is the only assembly all four consumers reference, and the
browser's reference to the runtime .Driver project is a documented layering
exception scheduled for removal — anchoring the options there would resurrect
the duplicate the day it goes away.
- Replaces the "Mqtt" literals in MqttDriverProbe, MqttDriverBrowser and
MqttDriver with the constant (string value unchanged).
- Tightens MqttDriverProbeTests.ProbeAsync_EnumAsName: it asserted only
Ok == false + non-empty message, which is also exactly what a JSON-parse
failure produces — so it stayed green under the very regression it names.
It now asserts the probe got past the parse and reached the network.
Falsifiability: deleting JsonStringEnumConverter from MqttJson.Options reddens 9
tests across 4 suites, including the tightened probe test (message becomes
"Config JSON is invalid: The JSON value could not be converted to
MqttProtocolVersion") — which the pre-fix assertions would have passed.
Also references the MQTT driver from Core.Abstractions.Tests so
DriverTypeNamesGuardTests' reflective bin scan discovers the new factory and the
constant/factory parity check stays honest.
Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW
Joseph Doherty