262de38cee3087cd5b9a8b35514d0cd0b08d69ab
3 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
 Joseph Doherty
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c57e74e660 |
fix(siteruntime): arbitrate DCL connection config — definitions store wins (rows 89 + 90)
Closes deferred-work-register rows 89 and 90, and corrects their premise twice.
THE RULE
The `data_connection_definitions` store wins wherever it has an opinion; an
instance's flattened `Connections` entry is a deploy-time snapshot and is
authoritative only for names the store has never owned (the deploy-only site,
where that table is legitimately empty).
PREMISE CORRECTION 1 — the peer's DCL is EMPTY, not stale
`DeploymentManagerActor` is a `site-{SiteId}`-scoped singleton and the only
sender of Create/RemoveConnectionCommand, to its OWN node's `dcl-manager`
(which exists on every node but is populated only where the singleton runs).
So the standby serves nothing. The real defect is that `_createdConnections`
is in-memory per singleton incarnation: a restart or failover rebuilds every
connection from the flattened snapshots and silently discards a newer
connection-only artifact deploy. Row 89 is therefore create-time, not
message-delivery, and NOT replication-specific — the same loss happens on an
unreplicated single-node restart.
PREMISE CORRECTION 2 — a changed config never reached a LIVE connection either
`DataConnectionManagerActor.HandleCreateConnection` is create-only (warns and
returns on a name it holds), so `EnsureDclConnection`'s documented "re-issues
the create so the DCL adopts the new configuration" has never been true on any
node. Now surfaced with a Warning saying exactly that, once per changed config.
Not fixed here: stop-and-recreate drops every tag subscription and InstanceActor
cancels its subscribe-retry timer on first success, so nothing re-subscribes.
MECHANISM
`data_connection_definitions` gains its first production reader. It is read on
the SAME off-thread task as the deployed configs (`ReadStoreSnapshotAsync`), by
the boot load and every sweep tick, into an actor-thread-confined arbitration
overlay applied BEFORE the boot batch and BEFORE the sweep's repair loop. A
CDC-delivered definition change converges within one tick on whichever node runs
the singleton — no new cross-node message. A failed definitions read yields null
and leaves the overlay untouched (distinct from an empty list, which is a real
answer); clearing it would reintroduce the ping-pong through the error path.
THE PING-PONG, KILLED BY CONSTRUCTION
§7.4 of the sweep memo rejected a store-level pass because two sources would
flip the single per-name hash slot, recreating the actor every tick. That is a
property of WHERE the hash is computed: every ensure path now resolves the
winner BEFORE hashing, so only one configuration can ever occupy the slot. The
artifact-deploy path writes its rows into the overlay in the same pass, closing
the same flip arriving through the other door.
REMOVAL (row 90)
Both removal paths share `RemoveConnectionCentrally` and record an in-memory
tombstone, so a centrally removed connection is not resurrected by the next
instance start — a pre-existing bug. Tombstones are deliberately not persisted;
a definition row reappearing clears one.
TESTS
tests/.../Actors/DclConnectionArbitrationTests.cs — 8 tests. Fail-before
(behavioral revert: overlay inert + tombstone check disabled): 5 fail, 3 pass;
the 3 passers are the two deploy-only regression guards and the ping-pong guard.
DOCS
New decision memo docs/plans/2026-08-17-dcl-connection-arbitration-decision.md
(topology, rule, ping-pong mechanism, tombstones, residuals); Component-SiteRuntime,
Component-DataConnectionLayer + their docs/components mirrors; the §7.4 residual in
the sweep memo marked closed with its premise corrected.
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|
Joseph Doherty
|
8f2c2813ea |
fix(siteruntime): self-healed and newly-enabled instances now get their DCL connections (register row 85)
An Instance Actor started by a self-heal came up with NO DCL connection actors, so every tag it subscribed was answered "Unknown connection: <name>" by the DCL manager indefinitely. Proven live 2026-08-16 by the row-78 close-out probe: the sweep correctly started the replication-seeded instances, then every subscribe failed for 6+ min until a second pair restart. Root cause is narrower than the register assumed. A DCL connection actor is never created from data_connection_definitions -- that table has no production reader at all (GetAllDataConnectionDefinitionsAsync is called only by a test). It exists only as a side effect of starting an instance, from the Connections map inside that instance's own flattened config, via EnsureDclConnections. That ensure was the CALLER's job and only two of the four callers made it: CreateInstanceActorBatch (boot) ensured OK ApplyDeployment (deploy) ensured OK StartStoredInstance MISSING <- row-67 ensure-started + row-78 sweep HandleEnableResult MISSING <- enabling a disabled instance The two misses are the two paths added after the original pair -- the signature of a convention living at call sites instead of in the funnel. It was never replication-specific: the boot load reads only ENABLED configs, so a node booting with an instance disabled never creates its connections either, and enabling it afterwards hit the identical dead end on an ordinary unreplicated site. Fix: EnsureDclConnections moves into CreateInstanceActor, already documented as the single Instance Actor creation funnel (it is where the running revision is stamped for the same reason), and the two caller-side calls are removed. Placed before the already-exists guard so the two paths that already called it keep their exact previous semantics. No new message, option or DCL change -- it reuses EnsureDclConnection's existing per-name hash guard, so steady state is silent. Structural rather than another guard: a fifth start path cannot forget. Deliberately NOT done, with rationale in the memo: a sweep pass over data_connection_definitions. It would not have fixed row 85 (that table is empty on a site that has only ever received instance deploys), and re-hashing from it would fight the deploy path over the same per-name hash slot, recreating connection actors and dropping live subscriptions on a loop. Two residual sibling gaps (connection-only artifact deploy replicating to a peer that never adopts it, and the mirror-image removal case) are recorded in the memo and the component docs as open, not silently skipped. Tests: SelfHealCreatesDclConnectionTests, 7 tests asserting on the CreateConnectionCommand messages sent to a recording DCL stand-in. Verified fail-before against a behavioral revert (call removed from the funnel, restored at the two original sites): 4 fail / 3 pass, the 3 being steady-state silence plus two refactor guards that must pass on both sides. Docs: sweep design memo gains section 7; Component-SiteRuntime, Component-DataConnectionLayer, docs/components/SiteRuntime and docs/components/DataConnectionLayer updated (the deploy-flow step ordering in docs/components/SiteRuntime was stale as written). |
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|
Joseph Doherty
|
e606b24a55 |
fix(siteruntime): instance reconcile sweep closes config/runtime divergence (register rows 78, 72)
The site's deployed_configurations rows are the durable truth about what should be
running; the set of live Instance Actors is what IS running. Nothing kept the two in
agreement after boot, and nothing surfaced a disagreement.
Row 78 (availability, proven live 2026-08-15) -- deployed_configurations is one of
LocalDb's ten replicated tables, so on a replicated pair a config can appear in a
node's file with no local actor involved at all: the CDC sync applier writes the row
directly. Live sequence: site-a-b's reconcile fetched 4 configs at its solo boot; the
pair was then restarted with a fresh site-a-a file and snapshot replication seeded
site-a-a's table within ~5s -- AFTER its boot-time load had read an empty table, and
invisibly to its own reconcile (central rightly reported "0 fetched", because central's
view of the site was correct). Enabled instances sat dead with their configs present
until yet another restart. Row 67's EnsureInstanceStartedCommand only covers configs
the reconcile itself FETCHES; this is the same gap through a side door.
Row 72 (silent divergence) -- for a STALE ReconcileGapItem the pass writes the newer
config via StoreDeployedConfigIfNewerAsync, a pure file write, while the running
Instance Actor keeps executing the previously compiled config until the next restart
or redeploy. Nothing said "stored revision != running revision".
Both are closed by one periodic sweep owned by the Deployment Manager singleton
(ScadaBridge:SiteRuntime:InstanceSweepIntervalSeconds, default 60, validated >= 0;
0 disables). Each tick re-reads the durable rows off-thread and, on the actor thread,
for every ENABLED stored config either starts a missing Instance Actor (row 78) or --
when the running one's revision no longer matches the stored one -- re-applies the
stored config through the ordinary redeploy path (row 72).
A sweep was chosen over a LocalDb change hook deliberately: a hook covers only the
replication arrival path, and only on the half of the fleet running with replication
enabled, whereas the sweep is arrival-path-agnostic (replication seeding, post-boot
snapshot resync, a hand-restored file, any future path). It is also not available --
ILocalDb 0.3.0 exposes no change-notification or applied-rows callback, so a hook would
mean a new upstream capability in scadaproj plus an in-process bus into this singleton,
a cross-repo change to close a site-local gap.
Row 72's decision is to CONVERGE, not merely warn. The stored row is what central
successfully deployed; an actor serving the config central believes was replaced is the
actual fault, and a surface-only warning leaves the operator to issue by hand exactly
the redeploy the sweep would have performed. Reusing HandleDeploy means the compile
gate, warm-then-gate ordering, redeploy-supersede, the static-override / native-alarm
reset and all-or-nothing-per-instance are the production ones, not a second
implementation -- and a stop still does NOT cancel an in-flight script run, exactly as
for a central redeploy.
Guards, shared with row 67 via the extracted InstanceIsOwnedByADeployPipeline predicate
and the shared StartStoredInstance helper:
- a DISABLED instance is never started (config row, no actor is its correct state);
- the sweep defers to any deploy pipeline owning the instance (compile warm in flight,
predecessor still terminating, deployment awaiting its persistence/init join), so it
can never interleave with a real redeploy -- that window has the config stored and no
actor, which an unguarded sweep would answer by creating a child whose actor name is
still registered;
- inert until boot-time Instance Actor creation has finished, so a tick between
staggered batches does not "heal" instances the boot load is about to create;
- ONE repair attempt per (instance, revision) pair -- this is what stops a periodic
self-heal becoming a restart loop for an actor that dies during init, or for a stored
config the compile gate rejects (a rejection leaves the running instance untouched:
the gate returns before anything is stopped);
- reads never overlap, so a slow read cannot stack ticks into duplicate repairs.
A sweep that finds nothing is completely silent -- no log above Trace, no site event.
A repair emits the same Warning `deployment` site-event pattern as row 67 with the
trigger named ("deployment-manager sweep self-heal") so it is distinguishable from a
startup-reconcile heal; a stale-revision restart names BOTH revisions and a rejected
one adds an Error event. The synthetic redeploy replies to the singleton itself rather
than NoSender, because dead letters are a monitored site health metric.
CreateInstanceActor gains a revisionHash parameter and is the single creation funnel
that records it, so the stale check covers every path that can start an Instance Actor;
a missing entry reads as "unknown", never "stale", so a future path bypassing the funnel
degrades to no-op rather than to spurious restarts.
Fail-before by behavioral revert (sweep timer left unarmed): 5 of 10 new tests fail,
including both live symptoms -- the row-78 repro ("A replication-seeded config for an
enabled instance left no running Instance Actor") and the row-72 repro, whose snapshot
still shows the rev-1 value 111 while the store holds rev-2's 222. The 5 negative
guards (disabled / in-flight redeploy / matching revisions / silent-when-healthy /
interval-zero) are green in both states, as they must be.
SiteRuntime 626/626, Host 505/505, AuditLog 383/383.
Design note: docs/plans/2026-08-15-instance-sweep-self-heal-design.md
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