Phase 2 Task 5. DriverHostActor and ScriptedAlarmHostActor now subscribe to the
node-local EventStream alongside their existing DPS topic subscriptions, so the
transport flag lives ENTIRELY on the publishing side -- exactly one of the two
ever publishes, and the switch can be flipped or reverted without touching a
single subscriber.
Note the alarm case is not symmetric: the DPS subscribe there still carries the
node-LOCAL publisher (OtOpcUaServerHostedService's OPC UA Part 9 method calls),
which never crosses the boundary and stays on DPS in both modes. Only the
central AdminUI leg moves.
Renamed DriverHostActor._coordinatorOverride to _ackRouter. Under ClusterClient
mode that ref is the NodeCommunicationActor, emphatically not a coordinator,
and the old name would send the next reader looking for one.
Adds two wiring tests, because the unit tests either side of this seam BOTH pass
with the subscription deleted -- the comm actor's test asserts a probe receives
the message, and the host tests drive the actor by direct Tell. Neither notices
a missing PreStart subscribe. Sabotage-verified: deleting either subscription
reddens exactly its own wiring test and nothing else.
Three things went wrong while writing those tests, all worth keeping:
- The first version raced. ActorOf returns before PreStart runs, and an
EventStream.Publish with no subscriber is dropped silently -- no buffering, no
dead letter. Fixed with a warm-up whose ack proves PreStart completed; the
comment says why it is not ceremony.
- The alarm version was VACUOUS: it told the host directly INSIDE the assertion
window alongside the relay, so the direct Tell alone produced the log the
assertion waited for. Split into warm-up (outside) and relay (inside).
- The alarm test needs its own ActorSystem: the shared harness pins
loglevel = WARNING and the only signal an unowned alarm gives is a Debug line.
Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW
CacheAppliedArtifact ran only on a fresh apply (ApplyAndAck), never on the
bootstrap RestoreApplied path. So a node whose cache was lost — fresh/wiped
volume, disk failure — recovered its served state from central yet stayed
cache-less, unable to boot-from-cache on the NEXT central outage until some
future new deploy happened to land. Replication does not heal this: a peer's
already-acked cache rows are pruned from its oplog, so a fully-wiped, converged
node is never back-filled. RestoreApplied now writes the served artifact back to
the cache (invariant: the cache holds what the node serves). Found on the
docker-dev live gate wiping a node's LocalDb volume.
Boot-from-cache told OpcUaPublishActor to RebuildAddressSpace(deploymentId), which
re-loads the artifact from the ConfigDb by id — the very database that is
unreachable during the outage this path exists to survive. The rebuild no-op'd, so
a cache-booted node ran its drivers but served OPC UA clients an EMPTY address
space. RebuildAddressSpace now carries an optional in-hand Artifact blob;
ApplyCachedArtifact passes the cached bytes so materialisation happens from them
directly. Found on the docker-dev live gate: healthy peer served 16 nodes, the
cache-booted node served 1.
Hooks the Bootstrap catch that previously went straight to Stale. On a cache hit the
node serves its last-known-good configuration through the outage instead of coming
up with an empty address space; on a miss, behaviour is byte-for-byte what it was.
The read is unkeyed because ClusterId is only derivable from an artifact you already
hold or from the unreachable central DB (recon D-1). Newest pointer wins, which is
correct in every real topology - a node belongs to one cluster and its peer
replicates that same row.
Splits PushDesiredSubscriptionsFromArtifact out of PushDesiredSubscriptions: the
cache path runs precisely when the ConfigDb read cannot succeed, so re-reading the
artifact there would fail by definition.
RunningFromCache is surfaced on NodeDiagnosticsSnapshot (optional param, existing
call sites unaffected). A node running from cache looks entirely healthy from
outside - full address space, live values - but its config is frozen and no deploy
can reach it. It clears only on a real apply from central.
Joseph Doherty