MqttDriver implemented no IWritable, so every MQTT node materialized read-only
regardless of what the operator authored. It now publishes.
Plain -> the tag's writeTopic; UTF-8 text (Raw/Scalar) or a bare JSON
literal (Json)
Sparkplug -> DCMD for a device metric, NCMD for an edge-node metric, carrying
the metric BY NAME with an explicit Datatype and no seq
Both at QoS 0, retain:false. Retain is deliberately not configurable — a retained
command is replayed by the broker on every future subscribe, including the
device's own reconnect, so one stale write would be re-applied forever.
writeTopic is a new, separate TagConfig key, and its ABSENCE is meaningful: the
write is refused BadNotWritable and the node is discovered ViewOnly. The issue's
"do not skip" warning drove the design — the one outcome worse than read-only
nodes is a node that looks writable, returns Good and publishes nothing. Reusing
the read topic would be worse still: it would echo back and read as a confirmed
device value. Browse-time writability is computed by the SAME encoder the write
path uses, so a node cannot advertise writability it would then refuse.
Good means published, not applied — MQTT has no application-level write ack, so
this is Galaxy's optimistic-Good posture and inherits its property: a failed
DEVICE write can never be surfaced. A failed PUBLISH is reported Bad; the
optimism covers what the device did with the command, never whether it was sent.
WriteIdempotent stays default-off.
The encoder is pure and lives in .Contracts, so both wire shapes are testable
without a broker. Unrepresentable values and types with no Sparkplug encoding are
refused rather than coerced — a Reference must not silently become a String on
the wire, and "not-a-number" must not become 0 on a live plant.
LIVE GATE PASSED against the real Mosquitto fixture on 10.100.0.35: 21/21
integration tests, including 6 new ones that observe the published message with
an INDEPENDENT broker subscriber — a fake asserting "publish was called" could
not tell the feature working from the feature publishing to the wrong topic.
The gate earned its keep: the NCMD test initially failed because NCMD is a SHARED
channel — the driver publishes its own rebirth request (Node Control/Rebirth) on
the very topic an edge-node metric write uses, and it arrived first. Correct
driver behaviour, wrong test; the watcher now matches on metric name. Documented,
because anything consuming that topic needs to know. DCMD has no contention.
Offline: 24 encoder + 9 driver tests. The four new status constants are NAMED so
StatusCodeParityTests can see them (#497/#519) — it went 258 -> 262 and validated
each against the pinned SDK.
Also corrects the Mqtt.md "Known gaps" table: prunes the six rows closed in this
round, and fixes the #507 row, which still described rediscovery as inert after
that issue was closed as superseded and its injection path deleted.
Claude-Session: https://claude.ai/code/session_015p7wGqy3YpZNCpDzTpGMKo
Adds a project-owned, controllable Sparkplug B edge node (SparkplugEdgeNode) that
encodes with the SAME generated Tahu schema the driver decodes with — so the live
gate checks encode/decode symmetry rather than the driver against itself — and
drives the §3.6 matrix end-to-end over the real TLS+auth Mosquitto fixture.
The simulator frames its topics independently of SparkplugTopic.Format: a
simulator borrowing the parser's formatter could not detect a bug in it, because
both sides of the comparison would be wrong together. It registers a real NDEATH
Last Will at CONNECT, restarts seq at 0 on NBIRTH, publishes DATA metrics as
alias-only, carries bdSeq per session, and encodes signed ints as two's
complement in the unsigned proto field.
SparkplugLiveTests (Category=LiveIntegration, env-gated, skip-clean) covers:
birth -> alias-only data -> OnDataChange under the RawPath; late-join rebirth
NCMD honoured by an independent decoder; alias reuse across a rebirth routing by
metric NAME; a stale-bdSeq NDEATH ignored while the current one stales; the real
broker-published Will staling and the next birth restoring; seq wrap 255->0
requesting no rebirth while a deliberate gap does; and the browser's passive
window asserted ON THE WIRE (a third client watching spBv1.0/{group}/NCMD/#),
plus RequestRebirthAsync node-vs-group enumeration.
Two things make the suite falsifiable rather than decorative: the seq-wrap test
builds its ingestor with rebirthDebounce: TimeSpan.Zero (at the shipped 10s
default a wrap-triggered NCMD would be swallowed and the test would pass for the
wrong reason) and pairs the silence with a deliberate gap that must produce one;
and the passivity assertion observes the broker rather than the session's own
publish counter, which can only see the seam it guards.
Docker/docker-compose.yml gains a profile-gated `sparkplug-sim` service running
the same engine standalone against the same broker (TLS, CA-pinned) — a manual
driving aid for the AdminUI picker, deliberately NOT a test dependency, since the
matrix needs an edge node it can command mid-test. Its app directory is publish
output (publish-simulator.sh), gitignored like secrets/.
Offline: 15 skipped, 0 failed with no env set. Live: 15/15 passed against
10.100.0.35:8883. Falsifiability spot-check: mutating AliasTable.RebuildFromBirth
to merge instead of replace, and neutering SparkplugCodec.ReinterpretSigned for
Int32, turned exactly the two corresponding tests red and nothing else; both
mutations reverted.
Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW
MQTTnet 5 does not throw on an unsuccessful CONNACK — it returns the reason in
MqttClientConnectResult.ResultCode and v5 removed v4's ThrowOnNonSuccessfulConnectResponse,
so ConnectCoreAsync's unconditional SetState(Connected) sealed a wrong-password deployment
green: DriverState.Healthy / HostState.Running on a session that never authenticated.
Caught by the Task-13 Mosquitto fixture; 240 offline tests missed it.
ConnectCoreAsync now inspects the CONNACK and raises MqttConnectRejectedException.
Credentials/identity/protocol/Last-Will refusals are unrecoverable and set Faulted, which
stops the reconnect supervisor; transient refusals (ServerUnavailable, ServerBusy,
QuotaExceeded, UseAnotherServer, ConnectionRateExceeded, and anything unrecognised) stay
Reconnecting under backoff. MqttDriverProbe now shares the rejection wording, so the
AdminUI Test-connect button and the running driver can no longer disagree.
Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW
Adds the MQTT driver integration-test project: an eclipse-mosquitto fixture running
auth AND TLS (allow_anonymous false on both listeners), a mosquitto_pub-based JSON
publisher emitting retained messages, a cert/password generator script whose output is
gitignored, and a live suite gated on MQTT_FIXTURE_ENDPOINT that skips clean offline.
The fixture is never anonymous by design: an anonymous broker would let the driver's
TLS/CA-pin and auth paths go untested, and those fail silently. The CA-pin leg carries
its own falsifiability control (a foreign CA generated in-process must be rejected).
Live gate on 10.100.0.35: 7/7 passed. It found a driver defect, reported not fixed
here (src/ is out of this task's scope): MqttConnection.ConnectAsync RETURNS NORMALLY
when Mosquitto rejects a CONNECT as not-authorized -- MQTTnet 5 does not throw on an
unsuccessful CONNACK, so a wrong broker password yields DriverState.Healthy from
InitializeAsync. The auth-negative test therefore asserts the invariant that holds
either way (no session is ever established) and documents the finding.
Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW
Joseph Doherty