Admin-triggered failover of the central pair. IManualFailoverService is declared in
CentralUI (plain strings, so that project stays Akka-free); AkkaManualFailoverService
implements it in the Host and is registered only in the Central branch.
- Leave, never Down: singletons hand over instead of being killed.
- Target = oldest Up member with the Central role, mirroring ActiveNodeEvaluator, so
the node acted on is exactly the one hosting the singletons (never the leader,
whose address-ordered definition diverges from singleton placement after a restart).
- Peer guard: returns null when fewer than 2 Up Central members — failing over a lone
node is an outage, not a failover.
- Audited BEFORE the Leave is issued via ICentralAuditWriter: the acting node can be
the one that goes away, and an audit written after could be lost to the shutdown it
describes. Best-effort — audit failure never blocks the failover.
New audit taxonomy: AuditChannel.Cluster + AuditKind.ManualFailover (operator-initiated
topology actions are not script trust-boundary crossings, but are exactly what an audit
log exists to attribute). Lock-in tests updated 5->6 channels, 16->17 kinds.
alog.md §4 updated per the lock-in tests' contract. Both tables were already stale --
the Channel row omitted SecuredWrite and the Kind table claimed 10 while the code had
16 -- so they are completed here, not merely appended to.
ManualFailoverTests: 3 real-cluster tests (oldest leaves + survivor takes over, peer
guard refuses with a positive still-running assert, dry-run probe does not perturb).
Every node now lists ITSELF as seed-nodes[0] and its partner second. Akka runs
FirstSeedNodeProcess -- the only bootstrap path that can form a NEW cluster when
no peer answers InitJoin -- exclusively for seed-nodes[0]; every other node runs
JoinSeedNodeProcess and retries InitJoin forever. That is why a lone cold-starting
central-b never came Up (the "registered outage gap"), and self-first ordering
closes it using Akka's own protocol.
- 6 node appsettings swapped (the *-node-b configs; the -a nodes were already
self-first). All 14 shipped node configs now satisfy the invariant.
- StartupValidator enforces it at boot, comparing host AND port -- the invariant
fails silently when broken, so it is enforced loudly. NOTE: the gitignored
deploy/wonder-app-vd03/ overlay must be reordered before its next deploy or
that node will refuse to boot.
- SelfFirstSeedBootstrapTests: real in-process clusters at production
failure-detection timings, incl. a falsifiability control proving the OLD
peer-first ordering never forms.
Rejected alternative (implemented, measured, discarded): an external self-form
timer calling Cluster.Join(SelfAddress) after a window. It sits outside Akka's
join handshake and so cannot tell "no seed answered" from "a seed answered and
the join is in flight". On a routine standby restart the peer is alive but the
join stalls behind removal of the node's own stale incarnation; a Join(self)
during TryingToJoin abandons the in-flight join and forms a second cluster at
the same address -- still split after 90s. Docs that claimed self-first ordering
was unsafe for simultaneous cold start are corrected: while mutually reachable
the InitJoin handshake converges them to one cluster (measured).
Two-node keep-oldest could NEVER survive a crash of the oldest/active node:
Akka.NET 1.5.62 KeepOldest.OldestDecision only lets down-if-alone rescue a
side with >= 2 members, so the 1-vs-1 survivor takes DownReachable and downs
ITSELF — proven live on the rig ('SBR took decision ... including myself')
before this change. static-quorum(1) is worse (IsTooManyMembers -> DownAll);
keep-majority just re-keys the fatal crash to the lowest address.
SplitBrainResolverStrategy gains 'auto-down' (new default): BuildHocon emits
Akka's AutoDowning provider with auto-down-unreachable-after = StableAfter.
The leader among the REACHABLE members downs the unreachable peer, so the
survivor takes over singletons and /health/active in ~25s regardless of which
node died. Accepted trade (explicit owner decision): a real network partition
runs dual-active until an operator restarts one side. keep-oldest remains
supported; DownIfAlone validation is now scoped to it.
Live drill on the rebuilt rig: active-crash TAKEOVER in 28s (victim still
down; all 7 singletons Younger->Oldest), standby-crash removal 27s with 0
routing blips; victims rejoin as standby in 2s. New real-cluster tests pin
both directions (SbrFailoverTests.AutoDown_*); TwoNodeClusterFixture gains a
strategy knob. All 16 appsettings flipped (src, docker, docker-env2, and the
gitignored wonder-app-vd03 overlay on disk — owner must sync to the host).
Docs: decision record docs/plans/2026-07-21-auto-down-availability-decision.md,
Component-ClusterInfrastructure downing section rewritten, drill + README
reworked (active mode now asserts takeover), deferred-work SBR row resolved.
Tasks 14, 15 and 16, landed as ONE commit.
PLAN DEFECT: these three tasks cannot compile separately. SiteReplicationActor
takes a ReplicationService and calls ReplaceAllAsync (Task 14 deletes both);
DeploymentManagerActor Tells message types declared in ReplicationMessages.cs
(Task 15 deletes it); AkkaHostedService constructs the actor (Task 16). Any
ordering leaves a broken intermediate. Combining them also strengthens the
invariant Task 14 already stated for itself — the two mechanisms never both
run, and never neither.
Registered 8 tables in SiteLocalDbSetup.OnReady: sf_messages plus the 7 site
config tables. notification_lists and smtp_configurations are deliberately NOT
registered — permanently empty by design, so registering them would open a
standing replication channel whose only historical payload was plaintext SMTP
passwords. Migrate stays the LAST call in OnReady, after all registrations, so
migrated rows enter the oplog through live capture triggers.
Deleted: SiteReplicationActor, ReplicationMessages.cs, ReplicationService,
StoreAndForwardStorage.ReplaceAllAsync, and 6 test files. ReplaceAllAsync is
not merely unused but unsafe to keep: a mass DELETE on a now-replicated table
would be captured and shipped to the peer.
Kept ActiveNodeEvaluator (delivery gate + heartbeat still need it) with its doc
corrected, and activeNodeCheck in AkkaHostedService (SiteCommunicationActor).
The positional-argument hazard the plan flagged was real: removing
DeploymentManagerActor's optional IActorRef? replicationActor shifted 6
trailing optionals, and 4 test call sites bound the wrong arguments with no
compile error at some positions. Converted them to named arguments where
possible — Props.Create builds an expression tree, which rejects out-of-position
named args, so the rest are padded positionally with a comment saying why.
The Task 7 'not yet registered' test was INVERTED rather than deleted, and is
exact in both directions: too few means a table silently stops replicating, too
many means the SMTP tables leak. Added a separate security-named test for those
two, and a composite-PK test (LWW keys on the full PK, so a truncated key set
would collapse distinct rows). The convergence suites now get their
registrations from the real OnReady — their temporary harness registration is
deleted, so they prove the cutover rather than agreeing with themselves.
Verified: build 0 warnings; SiteRuntime 512, StoreAndForward 130, Host 330,
AuditLog 355, ExternalSystemGateway 142, HealthMonitoring 97, LocalDb
integration 16 — all pass, 0 failures.
Claude-Session: https://claude.ai/code/session_01BL2Vu1ESDQ9SCN4gVKkdts
Tasks 5 and 6 of the Phase 2 plan, committed together because their test
fallout is entangled — several fixtures construct both stores.
StoreAndForwardStorage and SiteStorageService now take ILocalDb. Connections
come from ILocalDb.CreateConnection(), which hands out an already-open,
pragma-configured connection carrying the zb_hlc_next() UDF the capture triggers
call; a raw connection would lack the UDF and every write to a replicated table
would fail closed. Deleted with the connection strings: S&F's
EnsureDatabaseDirectoryExists and its per-open busy_timeout pragma, and the site
service's BusyTimeoutFloorSeconds normalization — LocalDb owns all of it now.
DI: AddSiteRuntime's string overload is gone (nothing left to supply), so the
Host calls the no-arg form. ScadaBridge:Database:SiteDbPath and
StoreAndForwardOptions.SqliteDbPath survive only as the migrator's source
locations in Tasks 8/9.
Two things the plan did not anticipate, both worth reading:
1. FOUND A REAL LATENT DEFECT, from Phase 1, now fixed. The plan assumed
directory creation simply moved to LocalDb along with file ownership. It did
not: the LocalDb library never creates the parent directory, and
SqliteLocalDb opens the file eagerly in its constructor — so a missing
directory is a hard boot failure ("SQLite Error 14: unable to open database
file"), not a degraded start. The default site config points at the RELATIVE
path ./data/site-localdb.db, so any site node without a pre-existing data/
directory fails to boot. The docker rig escapes only because its volume mount
happens to create /app/data — a coincidence that would have hidden this until
a bare-metal or fresh deployment. This has been latent since Phase 1 made
LocalDb:Path required; deleting S&F's EnsureDatabaseDirectoryExists here
would have widened it. Re-established the guarantee at the layer that now
owns the path (SiteLocalDbDirectory.Ensure, called before AddZbLocalDb) and
pinned it with SiteLocalDbDirectoryTests. Non-vacuity is not assumed: two
tests written against the wrong assumption failed with exactly this
SQLite Error 14 before the fix existed.
2. Test fallout was ~7x the plan's estimate. The plan named "fixtures" in one
project; the constructor change actually reaches 40 files across 7 test
projects, and most used Mode=Memory;Cache=Shared — which LocalDb has no
equivalent for, so every one had to move to a real temp file. Rather than
copy the Phase 1 TestLocalDb fixture into 7 projects, added a shared
tests/ZB.MOM.WW.ScadaBridge.TestSupport library (not a test project) so the
WAL-sidecar cleanup and the "real, not stubbed" rationale live in one place.
Retargeted rather than deleted, in both directions: the S&F WAL test now asserts
against the LocalDb-backed store (WAL genuinely is LocalDb's job), while the
directory-creation test moved to Host.Tests (that guarantee is NOT LocalDb's).
SiteStorageServiceTests.Initialize_EnablesWalJournalMode got the same treatment.
DeploymentManagerMediumFindingsTests induced a persistence failure via an
unopenable path, which no longer reaches the assertion since the fixture now
throws first; it induces the same failure shape via an uninitialized store.
Verified: full solution build 0 warnings; SiteRuntime 532, Host 318,
AuditLog 355, ExternalSystemGateway 142, HealthMonitoring 97,
StoreAndForward 153 — 1597 passed, 0 failed.
Claude-Session: https://claude.ai/code/session_01BL2Vu1ESDQ9SCN4gVKkdts
Rewritten from the plan's oldest-crash scenario: empirically, 2-node keep-oldest downs
the non-oldest partition, so a hard crash of the OLDEST makes the younger survivor down
itself (total cluster loss) — the survivable case is a crash of the younger node. The
member-removal assertion has teeth (impossible under the pre-fix NoDowning default).
See the test's XML doc for the active/oldest-node-crash gap.
Joseph Doherty