DriverHostActor.StopChild released the tracker (Invalidate) and evicted the hub synchronously, but
Context.Stop is asynchronous: the stopping child's in-flight SubscribeBulk completed through its
capability invoker AFTER the release, and its RecordCallStart/RecordSuccess/RecordCallComplete
re-created the tracker entry, which DriverResilienceStatusPublisherService then re-emitted every tick
forever. Confirmed with a temporary stack capture in the tracker (removed): every post-Release write
came from DriverInstanceActor.HandleSubscribeAsync -> CapabilityInvoker.ExecuteAsync; the test failed
whenever it landed before the second publisher tick.
- DriverResilienceStatusTracker.Retire (Release) drops the id's snapshots and ignores every later
Record* for it; one guarded write path re-checks after the upsert so a write racing Retire cannot
survive it. Reinstate (called by DriverCapabilityInvokerFactory.Create) lifts it, so the same id
re-added in a later deployment records again.
- TelemetryLocalHub.Evict now also holds the id (late Health/Resilience dropped, neither cached nor
fanned out); ITelemetryLocalHub.Readmit (default no-op), called at the top of SpawnChild, lifts it.
- The removal test is now deterministic: an invoker decorator holds the child's subscribe inside the
real invoker's bracket across the removal and signals when its late writes are done (positive
control) — red 5/5 without the fix, green 20/20 with it. New unit tests for the tracker guard
(incl. a Retire race), the factory Release/Create pair, the hub hold/readmit, and a re-add-same-id
host test.
Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe
Review R1 M1: StopChild evicted the hub cache, but DriverResilienceStatusPublisherService re-emits the
tracker every tick. IDriverCapabilityInvokerFactory.Release (default no-op) now invalidates the pipeline
builder + status tracker; the host calls it before Evict. Test runs a publisher tick after removal, with a
neighbour instance as positive control.
Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe
Five drivers ignored the config handed to them on reinitialize, serving the
options their constructor captured — and the deployment sealed green anyway.
Fixed on both halves, as chosen.
Seam (load-bearing): DriverSpawnPlanner routes a changed DriverConfig to
ToStop + ToSpawn instead of an in-place delta, making the factory the single
parse authority. This REVERSES the deliberate decision documented at
DriverSpawnPlan.cs:49-50 ("a pure DriverConfig change stays an in-place delta
— no reconnect"). That reasoning was correct about the resilience pipeline and
wrong about the driver. The accepted price is a reconnect per config edit.
Per-driver, and this split was not anticipated:
- Re-parse in place — Modbus, AbLegacy, OpcUaClient. ParseOptions extracted
from each factory, called from InitializeAsync behind a HasConfigBody guard
so "{}" still keeps the constructor options.
- Respawn-only, deliberately NOT re-parsed — Sql and FOCAS. Each builds more
than options from config (Sql's dialect + resolved connection string,
FOCAS's client-factory backend, both injected at construction), so adopting
new options alone would run a NEW tag set against an OLD connection. Half a
re-parse is worse than none. SqlDriver's doc-comment asserted the opposite
premise — "config parsing belongs to the factory, which builds a fresh
instance" — which was false when written and is true only now.
Two green seals removed from ApplyChildDelta: it overwrote the cached Spec
synchronously BEFORE the child dequeued the message, so the host believed the
new config was live and the next reconcile computed no delta, sealing the
drift permanently; and it Tell'd with no Receive<ApplyResult> registered, so a
failed reinit — including Galaxy's deliberate NotSupportedException —
dead-lettered.
Exposed (not created) by the change: a factory throw is a CONFIG error, and
SpawnChild catches it and silently substitutes a stub. Only a brand-new driver
could reach that before; an ordinary config edit can now. Raised Warning ->
Error with an actionable message. It still does not fail the deployment —
doing so would let one malformed driver block a fleet deploy, so that is a
follow-up rather than a drive-by.
Tests: every pre-existing reinit test in these suites passes "{}", the exact
input a guarded re-parser treats as "keep constructor options" — blind to this
defect by construction. New tests pass CHANGED json; the Modbus one was
verified falsifiable by deleting the re-parse (goes red). Two tests asserted
the old behaviour and were rewritten, including the positive control in
DriverHostActorUnreadableArtifactTests, whose observable moved from
UnsubscribeAsync to ShutdownAsync now that teardown happens by stopping the
child rather than emptying its desired set.
Remaining full-suite failures are pre-existing and environmental, verified
identical on the pre-change tree: Host.IntegrationTests (3) and
Driver.AbLegacy.IntegrationTests (4, docker fixture-gated).
ApplyAndAck advanced _currentRevision and recorded NodeDeploymentState=Applied
immediately after ReconcileDrivers, which returns null when the artifact could
not be read. So a node that applied NOTHING reported success, claimed a
revision whose configuration it never applied, and — because
HandleDispatchFromSteady short-circuits on a revision match — could never be
healed by re-dispatching that revision. Only a later, different revision
recovered it.
Now a null blob fails the apply: the revision is left where it was,
NodeDeploymentState records Failed with the reason, and the coordinator gets a
Failed ACK. Leaving the revision alone is what makes the retry actually land
instead of being waved through.
This is about telling the truth, not about tearing anything down — the node
keeps serving its last-known-good address space, drivers and subscriptions
throughout (#485).
Tests, RED-first (both verified failing with "should be Failed but was
Applied"): the ACK/revision assertion, plus the one that matters — after a
failed apply, re-dispatching the SAME revision now genuinely applies. Its
recovered artifact adds a second driver precisely so a short-circuited ACK
(which has no side effects) cannot satisfy it.
Four existing tests changed, and both changes are deliberate:
- DriverHostActorTests.SeedDeployment never set ArtifactBlob at all. Its three
consumers are about the apply/ACK/state machine, not the artifact, and now
need a genuine apply — so the helper seeds a well-formed artifact declaring
no drivers. That is what the composer emits for an empty configuration, and
is precisely what "bytes we could not read" is NOT.
- EmptyArtifact_IsNotCached asserted "the apply still succeeds — an empty
artifact is a legitimate no-op deployment". That premise is the bug. Flipped
to Failed; the test's actual subject (nothing is cached) is untouched and now
holds for two independent reasons.
Closes#486
Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW
The driver-side half of the same mistake the address-space fix corrected.
ReconcileDrivers and PushDesiredSubscriptionsFromArtifact both read the
artifact as `...FirstOrDefault() ?? Array.Empty<byte>()`. Their THROW paths
already returned early, but empty bytes flowed onwards as a real answer: zero
driver specs, so DriverSpawnPlanner planned every running child for StopChild,
and then an empty desired set dropped each surviving driver's live
subscription handle. A node lost its entire field I/O and still ACKed Applied.
Same rule as the address space: no bytes is no answer, not "a configuration
with no drivers". Nothing legitimate produces a zero-length blob — deleting
the last driver still deploys a JSON document with empty arrays. Both sites
now skip and keep what is running. The two guards are independent because
PushDesiredSubscriptions does its OWN ConfigDb read, so the row can go missing
between them.
Also corrects the ReconcileDrivers doc comment, which claimed an empty blob
made it "effectively a no-op" — with children running it was the opposite.
Tests: DriverHostActorUnreadableArtifactTests, RED-first (verified failing —
after the empty dispatch the driver list was empty). A zero-length ArtifactBlob
reproduces byte-for-byte what the missing-row case delivers, so the race does
not have to be constructed.
Two controls, both load-bearing:
- a READABLE driverless artifact still stops the driver, so the guard keys on
"the read gave us nothing", not on "fewer drivers than before";
- dropping a driver's LAST TAG still clears its subscription. This one was
added after the absence assertion was caught passing on a race: the
unsubscribe is an async self-tell, so with the second guard deleted the test
still went green. The control observes that same unsubscribe arriving well
inside the settle window, which is what makes the absence meaningful — with
the guard deleted the suite now correctly goes RED.
SubscribableStubDriver gains an UnsubscribeCount for that observation.
Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW
Joseph Doherty