Site nodes served no health surface at all — gRPC on the HTTP/2-only listener and
/metrics on the HTTP/1.1 one — so nothing outside the cluster could ask a site
node whether it was ready or which half of the pair was active. The family
overview dashboard probes every instance the same way, and this is the one gap.
Three checks, registered in SiteServiceRegistration.Configure (not Program.cs, so
the composition-root tests that build this graph actually cover them) and mapped
by app.MapZbHealth() on the site's HTTP/1.1 listener (default :8084) alongside
/metrics:
akka-cluster [Ready] the shared AkkaClusterHealthCheck. Also carries the
cluster-view data (leader/memberCount/...) the dashboard
reads, free with ZB.MOM.WW.Health 0.2.0.
localdb [Ready] NEW SiteLocalDbHealthCheck — SELECT 1 through the
registered ILocalDb. Site has no EF context; central's
DatabaseHealthCheck<ScadaBridgeDbContext> is central-only.
Replication state rides along as data ENRICHMENT only:
replication is default-OFF, so failing on it would mark
every correctly-configured node unready.
active-node [Active] NEW SitePairActiveNodeHealthCheck, delegating to
IClusterNodeProvider.SelfIsPrimary. Deliberately NOT
central's OldestNodeActiveHealthCheck: that one calls
SelfIsOldest(cluster) with no role argument and would
compute "oldest" across the wrong member set on a mesh
carrying more than one site.
Anonymous, as central's are: the site pipeline runs no authentication middleware
and has no FallbackPolicy, so nothing extra was needed.
Also bumps ZB.MOM.WW.Health* 0.1.0 -> 0.2.0 (central gains data.leader for free).
Tests: SiteHealthCheckTests builds the REAL site container and activates every
registration through its factory (exact-set names, one tier tag each, resolved
types, central-only checks absent behind a positive control) plus behaviour for
both new checks. SiteHealthEndpointTests boots the real site Program over
WebApplicationFactory and proves the endpoints are MAPPED — without it, deleting
MapZbHealth would leave every registration test green while site nodes 404'd.
Prereq for scadaproj docs/plans/2026-07-22-overview-dashboard-impl-plan.md Phase 1.
Central and each site are SEPARATE Akka clusters, so central cannot act on a
site's membership -- it asks. New TriggerSiteFailover/SiteFailoverAck contract
travels the existing ClusterClient command/control channel (mirroring the
RetryParkedOperation relay); the site's own SiteCommunicationActor performs the
graceful Leave and acks the outcome.
- ClusterFailoverCoordinator moved out of Host into Communication/ClusterState,
beside ActiveNodeEvaluator. Both paths now share ONE oldest-Up implementation;
SiteCommunicationActor cannot reference Host, and the two definitions must not
drift or the node asked to leave stops being the singleton host.
- Site scope is the SITE-SPECIFIC role (site-{SiteId}), not the base Site role --
site singletons are placed on the former, so the base role would move the wrong
node. Pinned by a unit test asserting the role string and by a real-cluster test.
- Site-side guards: refuses a command addressed to another site (a misroute must
never fail over a site the operator did not select), refuses when there is no
peer, and reports a fault as an ack rather than throwing into supervision --
a restart there would drop central's Ask into a bare timeout and lose the reason.
- Ack is sent before the Leave takes effect so it still reaches central.
- UI: the same control now serves both scopes via a SiteId parameter. The site
confirmation deliberately does NOT claim the admin's page will disconnect --
it won't, and crying wolf there devalues the central warning that is real. A
site refusal and an unreachable site surface distinctly.
- Rolling upgrade: a site on an older binary has no handler, so the message
dead-letters and the Ask times out, reported as "site did not respond". That
is the honest outcome; documented on the contract.
Fallout fixed: HealthPageTests now renders the page inside
CascadingAuthenticationState with the real policy set and IAuthorizationService,
because the cards embed an AuthorizeView. That mirrors production, where the
layout supplies the cascading value.
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).
Remove project bookkeeping citations from shipped code comments across the
solution: hyphenated task IDs (WP-14, StoreAndForward-025), milestone/task/
issue refs (M3, Task 4, Audit Log #23, #21), Bundle X task-bundle labels,
and C/D/K/S/T phase labels.
Comment text only — no code logic, string/log literals, or XML-doc structure
changed. Genuine descriptions are preserved (only the citation is stripped),
and technical lookalikes are retained (UTF-8, SHA-256, T00:00:00, M365,
UTC-5, pre-C4/pre-C5 schema versions). Flagged by the new CommentChecker
TaskReferenceInComment / TrackingReferenceInComment checks plus targeted
grep passes; full solution builds clean, append-only guard tests pass.
- Remove redundant linked CancellationTokenSource in ProbeAsync; pass the
framework cancellationToken and ProbeTimeout directly to Ask (the two-CTS
pattern was redundant — Ask already honours both the timeout and the token).
- Add EchoActor XML <remarks> explaining why no Receive<Identify> handler is
needed (ActorBase answers Identify automatically).
- Add PreCancelledToken_ReportsUnhealthy_DoesNotThrow test: verifies the
never-throws guarantee on the shutdown-race path (token already cancelled
before CheckHealthAsync is invoked).
REQ-HOST-4a lists "required cluster singletons running (if applicable)" as a
readiness criterion, but /health/ready only checked database + akka-cluster.
Add a third Ready-tagged check, RequiredSingletonsHealthCheck, registered in the
Central-role AddHealthChecks() chain (so it is naturally role-scoped — site nodes
never run it).
Probe: for each required central singleton, Ask its local ClusterSingletonProxy
an Identify with a short bounded per-singleton timeout (~2s, probes run
concurrently via Task.WhenAll). A non-null ActorIdentity.Subject within the
timeout means the singleton is running and reachable through the proxy; a null
subject or a timeout means unreachable → Unhealthy, naming the unreachable
singleton(s). The check never throws (catch-all → Unhealthy) and resolves
ActorSystem lazily from DI per probe (Unhealthy if Akka not yet up).
Required-always set = the five singleton proxies created unconditionally in
AkkaHostedService.RegisterCentralActors: notification-outbox, audit-log-ingest,
site-call-audit, audit-log-purge, site-audit-reconciliation. There are no
feature/config-gated central singletons today; any future gated singleton is the
"if applicable" case and must NOT be added to the required set.
Leadership-agnostic: the proxy reaches the singleton from either central node, so
a ready standby still reports ready (readiness must not require cluster
leadership — that is the Active tier's job). During a brief singleton handover the
probe may time out and the node flaps to not-ready, which is correct (a node
mid-handover is legitimately not fully ready); no retries, to keep the probe fast.
Tests (TDD): RequiredSingletonsHealthCheckTests exercises the probe against a
TestKit ActorSystem — all proxies present+reachable → Healthy; one missing →
Unhealthy naming it; ActorSystem absent → Unhealthy, no throw. HealthCheckTests
regression-guards the Ready tag + absence of the Active tag on the new check.
Resolve all 622 issues flagged by the enhanced CommentChecker: add missing
<returns> tags (incl. the standard phrasing on non-generic Task methods),
add missing <summary> tags, and replace misused/redundant <inheritdoc/> on
members that override or implement nothing with real documentation.
Documentation-only — no behavior change; solution builds clean.
Joseph Doherty