A caller addressing a standby central node directly (or hitting Traefik inside its
/health/active probe window after a failover) used to get 503 STANDBY_NODE. The
standby now relays the request verbatim to the active peer over HTTP
(IStandbyRequestForwarder / HttpStandbyRequestForwarder) and replays the response;
method scripts and Route.To() still execute only on the active node.
- ScadaBridge:InboundApi:StandbyForwardPeerEndpoints (static list of the OTHER
central node's HTTP base URL; empty = old 503 behaviour) + StandbyForwardTimeout
(60s), both startup-validated.
- Peers tried in order: peer 503 stamped X-ScadaBridge-Standby, connection failure
or timeout → next peer; all fail → 503 ACTIVE_NODE_UNREACHABLE. A 503 without
the marker is the active node's own answer and is replayed.
- One-hop loop guard via X-ScadaBridge-Forwarded; 413 body cap now runs BEFORE
the active-node check so a standby never buffers/relays an oversized body.
- AuditWriteMiddleware skips its own ApiInbound row for a relayed request so a
call is audited once, on the node that executed it.
- Rig + env2 central nodes configured; spec (Component-InboundAPI.md → Standby
forwarding), Component-Host.md options row, CLAUDE.md updated.
- 20 new tests (filter decision + relay mechanics + validator).
Claude-Session: https://claude.ai/code/session_019ZxXT5sxZs5XrtdwYzJDPV
The row read 'central nodes expose no Prometheus endpoint'. That is not quite
what was wrong, and the difference matters. Central already maps /metrics
(Program.cs central branch) and telemetry is registered for both roles through
the shared BindSharedOptions, so the endpoint rides endpoint routing and has
always been served on central's web port (:5000 on the rig, anonymous — there
is no FallbackPolicy). What central lacked was the site branch's dedicated
MetricsPort, which is the port the established live-scrape recipe probes:
docker exec <node> bash -c 'exec 3<>/dev/tcp/localhost/8084 ...'
So a probe of central on 8084 failed and central-only series (KPI/outbox
counters, the bundle-import session gauge + its new rejection counter,
alarm-cache gauges) read as unscrapeable while they were in fact being
exported on a different port.
Central now binds a dedicated HTTP/1.1 listener on ScadaBridge:Node:MetricsPort,
so one probe recipe covers all eight rig nodes. HTTP/1.1-capable because a
standard Prometheus scraper cannot negotiate h2c, which is why this cannot
share the gRPC port.
Read as a PRESENCE check, not GetValue's defaulted read. NodeOptions defaults
MetricsPort to 8084, so a defaulted read would make every existing central node
start binding a new port on upgrade — and a port already in use is a hard boot
failure, not a degraded one. Central gains the listener only where an operator
asked for it; site nodes are unchanged and still bind theirs unconditionally.
The bind is also skipped when the port would collide with the gRPC port or an
ASPNETCORE_URLS port, since Kestrel throws on a duplicate ListenAnyIP and
/metrics is reachable on those ports anyway.
Config only — no host port mapping added, because the probe runs inside the
container. Applied to both docker/ centrals and both docker-env2/ centrals.
FILE EDITS ONLY: no docker command was run, and deploy.sh was not invoked.
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.
Populates ScadaBridge:Communication:CentralFetchBaseUrl in every central
appsettings for the notify-and-fetch deploy flow. An empty value now
causes a fail-fast on deploy; this config prevents that regression.
- docker/: http://scadabridge-traefik (in-network Traefik LB, port 80)
- docker-env2/: http://scadabridge-env2-traefik (env2 Traefik LB, port 80)
- src/Host base: http://localhost:5000 (ASP.NET Core default for single-host dev)
- deploy/wonder-app-vd03: http://localhost:8085 (gitignored; edited in main repo)
RUNBOOK Upgrading section updated with note on this setting.
Wire the M6 KPI History recorder into the central composition path:
- Program.cs: call services.AddKpiHistory(configuration) on the central-only
branch alongside AddNotificationOutbox/AddAuditLog/AddSiteCallAudit.
- AkkaHostedService.cs: register KpiHistoryRecorderActor as a central,
non-role-scoped ClusterSingletonManager + ClusterSingletonProxy + a
PhaseClusterLeave CoordinatedShutdown graceful-stop drain (singleton name
'kpi-history-recorder'), copied/adapted from the audit-log-purge block.
- appsettings.Central.json (Host + docker + docker-env2 central nodes): add a
ScadaBridge:KpiHistory section (SampleInterval 00:01:00, RetentionDays 90,
PurgeInterval 1.00:00:00, DefaultMaxSeriesPoints 200).
KPI history is observability/best-effort and MUST NOT gate readiness: the
recorder is deliberately NOT added to RequiredSingletonsHealthCheck or any
other readiness gate.
Both :9000 (docker) and :9100 (docker-env2) central nodes now bind the shared dev
GLAuth (scadaproj/infra/glauth/, dc=zb,dc=local) via the cn=serviceaccount search
account instead of the bundled scadabridge-ldap container (now commented out in
infra/docker-compose.yml, kept for rollback). Verified: multi-role -> all 4 roles
on both clusters with scadabridge-ldap stopped.
The auth cookie name was hardcoded to ZB.MOM.WW.ScadaBridge.Auth. Because
browser cookies are scoped by host+path but NOT by port, two ScadaBridge
clusters on the same host (the local docker stack on localhost:9000 and
docker-env2 on localhost:9100) shared one cookie jar: signing into one
overwrote the other's cookie, and since the clusters use different JWT
signing keys + separate Data Protection key rings, the overwritten side
could no longer validate its cookie and the session died.
Add SecurityOptions.CookieName (default = canonical ZB.MOM.WW.ScadaBridge.Auth,
blank falls back to the default) applied via the SecurityOptions-bound cookie
PostConfigure. Override it to ...Auth.env2 in both docker-env2 Central nodes so
the two local clusters no longer collide; the primary cluster keeps the default
so its live sessions and production are unaffected. Adds 3 Security.Tests cases.
Replace dc=scadabridge,dc=local with dc=zb,dc=local in all dev/test LDAP
references — app config, docker test-cluster node configs (docker/ and
docker-env2/), GLAuth fixture, dev tooling, Host.Tests fixtures,
IntegrationTests factory, and operational test_infra docs. OU structure
(ou=SCADA-Admins,ou=users,etc.) preserved throughout. Email domains
(@scadabridge.local), hostnames, and container names are untouched.
Historical plan docs (2026-05-24-second-environment.md,
2026-05-31-folder-repo-rename-scadabridge-design.md) excluded as
point-in-time records. No synthetic dc=example,dc=com placeholders touched.
Joseph Doherty