docs(mesh-phase4): ServiceLevel semantics on DB-less nodes + driver ConfigDb cut
Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW
This commit is contained in:
Joseph Doherty
+16
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@@ -162,9 +162,24 @@ On the docker-dev rig every node carries these keys already; flip the whole rig
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On the docker-dev rig the central pair carries `ConfigServe` (port `4055`, dev key) and stays `Direct`; the four site nodes carry `ConfigSource` (endpoints + matching key) defaulting to `Direct`. Flip only the site nodes with `OTOPCUA_CONFIG_MODE=FetchAndCache` at `docker compose up` — central keeps SQL and models the target topology.
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**`FetchAndCache` is mandatory on a driver-only node — per-cluster mesh Phase 4.** `Program.cs` now
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registers `AddOtOpcUaConfigDb` only when the node carries the `admin` role, so a **driver-only**
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node (`Cluster:Roles` has `driver`, not `admin`) holds **no `ConfigDb` connection string at all** —
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there is nothing for `Direct` to read. `ConfigSourceOptionsValidator` enforces this at
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`ValidateOnStart`: a driver-only node whose `ConfigSource:Mode` is `Direct` **fails host start**
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with an error naming the fix (`ConfigSource:Mode=FetchAndCache`). A **fused** `admin,driver` node
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still owns its ConfigDb via the admin role and may stay `Direct` — the validator only fires on
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`driver` without `admin`. On a driver-only node the deployed configuration, the scripted-alarm Part
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9 condition state (`LocalDbAlarmConditionStateStore`, replacing the ConfigDb-backed
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`EfAlarmConditionStateStore`), and the alarm store-and-forward buffer all live in the node's
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LocalDb; central remains the system of record for deploy acks (`ConfigPublishCoordinator.
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PersistNodeAck`) and LDAP group→role DB grants (a driver-only node maps LDAP groups to roles from
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the `Security:Ldap:GroupToRole` appsettings baseline only — see `docs/Redundancy.md` and
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`CLAUDE.md` §"Phase 4" for the full picture, including the client-visible ServiceLevel change).
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### `ConnectionStrings` → `ConfigDb`
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- **Purpose:** the central Config DB connection string. **Required for every role** — `Program.cs` calls `AddOtOpcUaConfigDb` unconditionally.
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- **Purpose:** the central Config DB connection string. **Required on admin-role nodes only** — `Program.cs` calls `AddOtOpcUaConfigDb` when `hasAdmin` (per-cluster mesh Phase 4). A driver-only node holds no `ConfigDb` connection string; it fetches its configuration via `ConfigSource:Mode=FetchAndCache` instead (see above). A fused `admin,driver` node still requires it.
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- **Bound by:** `AddOtOpcUaConfigDb(config)` (`src/Core/ZB.MOM.WW.OtOpcUa.Configuration/ServiceCollectionExtensions.cs`). The connection-string name constant is `ConnectionStringName = "ConfigDb"`, read via `configuration.GetConnectionString("ConfigDb")`. If absent, startup throws with a message pointing to either `appsettings.json` or the `OTOPCUA_CONFIG_CONNECTION` env var.
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- **Shape:** standard `ConnectionStrings:ConfigDb` SQL Server connection string. There is no checked-in default in the thin `appsettings*.json` — supply it per environment.
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+28
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@@ -16,7 +16,7 @@ The runtime pieces live in:
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| `OpcUaPublishActor` | `OtOpcUa.Runtime.OpcUa` | Per-driver-node; subscribes to the `redundancy-state` topic, computes a health-aware ServiceLevel byte via `ServiceLevelCalculator` (see below), and forwards it to `IServiceLevelPublisher`. |
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| `IServiceLevelPublisher` / `SdkServiceLevelPublisher` | `OtOpcUa.Commons.OpcUa` / `OtOpcUa.OpcUaServer` | Writes the byte into the SDK's `Server.ServiceLevel` Variable. Production binds `DeferredServiceLevelPublisher`, which swaps in the real `SdkServiceLevelPublisher` once the SDK is up (it needs `IServerInternal`, available only after `StandardServer.Start`); until then writes route through `NullServiceLevelPublisher`. |
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| `ServiceLevelCalculator` | `OtOpcUa.Cluster.Redundancy` (`Core.Cluster`) | Pure function `(NodeHealthInputs) → byte` — the DB/probe-aware tiering (see truth table below). Covered by `ServiceLevelCalculatorTests`. **Now the live publish path** — `OpcUaPublishActor` calls it on every `HealthTick` and `RedundancyStateChanged` event. Moved to `Core.Cluster` so Runtime can reach it without a Runtime→ControlPlane reference. |
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| `DbHealthProbeActor` | `OtOpcUa.Runtime.Health` | Per-node; runs `SELECT 1` against ConfigDb every 5s. Read by the health endpoint AND by `OpcUaPublishActor` (the `DbReachable` ServiceLevel input). |
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| `DbHealthProbeActor` | `OtOpcUa.Runtime.Health` | Runs `SELECT 1` against ConfigDb every 5s. Read by the health endpoint AND by `OpcUaPublishActor` (the `DbReachable` ServiceLevel input). **Spawned only when a ConfigDb is present** (admin-role or fused admin+driver nodes) — a driver-only node has no `IDbContextFactory<OtOpcUaConfigDbContext>` to probe, so this actor is not spawned there at all; see "DB-less nodes" below. |
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| `PeerProbeSupervisor` | `OtOpcUa.Runtime.Health` | Per-node; subscribes to the `redundancy-state` topic and maintains one `PeerOpcUaProbeActor` child per OTHER driver-role peer (spawn on join, stop on departure), so every node is continuously probed by its peers. |
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| `PeerOpcUaProbeActor` | `OtOpcUa.Runtime.Health` | Spawned by `PeerProbeSupervisor`; pings a peer `opc.tcp://peer:4840` with a TCP connect (2s timeout) and publishes `OpcUaProbeResult` on the `redundancy-state` topic. A full secure-channel Hello handshake is a possible future upgrade; the TCP connect is the current real probe. |
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| `ClusterRoleInfo` | `OtOpcUa.Cluster` | Live view of cluster membership + role-leader; exposes `IClusterRoleInfo` to the rest of the host. (Akka's role-leader is *not* what elects the redundancy Primary — see below.) |
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@@ -56,6 +56,33 @@ The resulting truth table (all tiers are now reachable at runtime):
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> by the +10 bonus. Clients with the standard "pick highest ServiceLevel"
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> heuristic continue to prefer the primary.
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#### DB-less (driver-only) nodes — per-cluster mesh Phase 4
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**Client-visible change.** Per-cluster mesh Phase 4 cut the ConfigDb connection off driver-only
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nodes (Akka role `driver`, not `admin`) — `Program.cs` registers `AddOtOpcUaConfigDb` only when
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`hasAdmin`. With no ConfigDb to probe, `DbHealthProbeActor` is **not spawned** on such a node
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(`ServiceCollectionExtensions.WithOtOpcUaRuntimeActors` skips it whenever the resolved
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`IDbContextFactory<OtOpcUaConfigDbContext>` is null), and `OpcUaPublishActor` runs in a `dbLess`
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mode instead of the health-aware path above:
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- `DbReachable` is fed **constant `true`** — LocalDb is the config store and is in-process, so it
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can never be "unreachable" the way a remote SQL Server can.
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- `Stale` is derived from the `redundancy-state` snapshot age alone (`(now − snapshotEntry.AsOfUtc)
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> 30 s`) — there is no DB-health term to fold in.
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- `OpcUaProbeOk` and `IsDriverPrimary` are unchanged (peer OPC UA probe, oldest-Up-member election).
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**Consequence:** a healthy driver-only node publishes **240** as a follower or **250** as the
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driver Primary **even when central SQL is unreachable** — the survive-alone posture the fetch-and-
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cache design (Phase 3) exists to support. Contrast this with a `Direct`/DB-backed node (fused
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admin+driver, or any node still reading ConfigDb directly): an unreachable ConfigDb there still
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drives `DbReachable=false`, which forces `Stale=true` in the derivation above and the node drops to
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**100** (or **0** once the sample itself goes stale) via the health-aware tiering, not 240/250.
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Same byte, opposite meaning depending on which kind of node is publishing it — a client or operator
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reading ServiceLevel in isolation cannot tell "central is down and I don't care" (driver-only, 240)
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from "central is down and I'm degraded" (DB-backed, 100/0) without also knowing the node's role
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shape. `ServiceLevelCalculator.Compute` itself is unchanged; only the inputs a DB-less node feeds
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it changed — see `OpcUaPublishActor.RecomputeServiceLevel`'s `_dbLess` branch.
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#### Backward-compatible fallback (legacy seam)
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A node with no `DbHealthStatus` wired (e.g. early bootstrap window before the
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@@ -141,7 +141,7 @@ admin-change refresh), clusters know central from appsettings (static, restart t
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flow over ClusterClient (DPS paths deleted or dark-switched), including an Ask timing out cleanly
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against a stopped node.
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### Phase 3 — Config fetch-and-cache from central — **CODE-COMPLETE 2026-07-23 (Tasks 0–8; live gate Task 10 pending)**
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### Phase 3 — Config fetch-and-cache from central — **DONE 2026-07-23 (merged `d01b0695`, live gate PASSED, pushed to origin)**
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**Decisions taken:** the deploy artifact is served **by central over a gRPC fetch RPC**
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(`DeploymentArtifactService.Fetch`, streamed chunks — chosen over token-gated HTTP), authenticated by
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a **shared node bearer key** (`ConfigServe:ApiKey == ConfigSource:ApiKey`, `FixedTimeEquals`,
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@@ -160,13 +160,14 @@ config SQL read); #485 coverage; and a **real two-Host gRPC boundary test** (rig
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wrong-key control returns null, failover). Chunking, SHA-256 verify, newest-2 retention, pair
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replication carry over unchanged. **Phase boundary held:** config **reads** only — the
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`NodeDeploymentState` ack-row write, `DbHealthProbe`, `EfAlarmConditionStateStore` stay for Phase 4.
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**Remaining (Tasks 9–10):** rig config + docs (done) and the live gate — deploy on a site pair flipped
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to `FetchAndCache` with central SQL stopped mid-fetch → retry lands; #485 last-known-good re-proven on
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the new path.
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**Exit gate:** live gate green on the rig; a driver node with an empty LocalDb and reachable central
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boots into the current config; with central down it boots last-known-good.
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**Live gate PASSED:** deployed on a site pair flipped to `FetchAndCache` with central SQL stopped
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mid-fetch — retry landed; #485 last-known-good re-proven on the new path. Merged to master
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`d01b0695` and pushed to origin; the scadaproj umbrella index was updated + pushed (`b5e7bc8`) in the
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same pass.
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**Exit gate — MET:** live gate green on the rig; a driver node with an empty LocalDb and reachable
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central boots into the current config; with central down it boots last-known-good.
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### Phase 4 — Cut the driver-side ConfigDb connection
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### Phase 4 — Cut the driver-side ConfigDb connection — **CODE-COMPLETE 2026-07-23 (Tasks 0–7 + 1b; Task 9 table-drop deferred; Task 10 rig + Task 11 live gate remain)**
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**Scope (design §6.1 audit table):** re-home `EfAlarmConditionStateStore` to LocalDb (pair-local
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state, same journey as the Phase-2 alarm S&F buffer); **resolve the `DbHealthProbeActor`
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question** — driver nodes have no DB to probe, and DB health currently feeds ServiceLevel tiering,
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@@ -176,6 +177,27 @@ transports) — this is a client-visible ServiceLevel semantics change and must
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design) and re-source it; registration cleanup in `ServiceCollectionExtensions`; driver-role
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`Program.cs` branch registers no EF ConfigDb context at all (mirror ScadaBridge's central-only
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`AddConfigurationDatabase`).
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**Shipped (branch `feat/mesh-phase4`, Tasks 0–7 + 1b):** `Program.cs` gates `AddOtOpcUaConfigDb` +
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the ConfigDb health check on `hasAdmin`, so a driver-only node registers no ConfigDb connection
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string at all; `ConfigSourceOptionsValidator` fails host start if a driver-only node's
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`ConfigSource:Mode` is left `Direct` (fused `admin,driver` may stay `Direct`); the DB-health
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question resolved as **retire, don't replace** — `DbHealthProbeActor` is simply not spawned when no
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ConfigDb is present, and `OpcUaPublishActor` runs a `dbLess` mode feeding `DbReachable=true`
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constant with staleness from the redundancy-snapshot age alone (documented as the client-visible
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change in `docs/Redundancy.md`); `LocalDbAlarmConditionStateStore` (replicated
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`alarm_condition_state` table) replaces `EfAlarmConditionStateStore` on every driver-role node;
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`DriverHostActor` no longer writes `NodeDeploymentState` on a driver-only node (central's
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`ConfigPublishCoordinator.PersistNodeAck` was already the ack system of record); driver-only nodes
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register `NullLdapGroupRoleMappingService` so LDAP group→role falls back to the
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`Security:Ldap:GroupToRole` appsettings baseline (DB grants were never delivered to driver nodes via
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config anyway). Docs updated: `docs/Redundancy.md`, `docs/Configuration.md`, `CLAUDE.md`.
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**Deferred:** Task 9 — dropping the now-unused `ScriptedAlarmState` ConfigDb table (a follow-up, not
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a blocker; the table is simply unread).
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**Remaining (Tasks 10–11):** rig config for a driver-only node with no `ConfigDb` connection string,
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and the live gate itself — a driver pair runs a full deploy + alarm + historian cycle with no
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ConfigDb configured at all, confirming ServiceLevel 240/250 while central SQL is down and
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grep-level proof no driver-branch service can resolve the ConfigDb context. **Not yet run — treat
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Phase 4 as code-complete, not verified, until this lands.**
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**Exit gate:** its own live gate — a driver pair runs a full deploy + alarm + historian cycle with
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**no ConfigDb connection string configured at all**; grep-level proof no driver-branch service can
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resolve the ConfigDb context.
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@@ -243,8 +265,8 @@ resource sizing on the site VMs should be checked once both products run the ful
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| Prereq: selfform-fallback + manual-failover plan | **DONE 2026-07-22**, merged `a78425ea`. Shipped *not* as the planned `SelfFormAfter` watchdog — the live gate caught that islanding a manually-failed-over node — but as self-first seed ordering + `AkkaClusterOptionsValidator`. Phase 6's seed-ordering scope is therefore already discharged. |
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| 1 ClusterNode columns + DB ack set | **DONE 2026-07-22**, merged `7654f24d`. Deploy-seal semantics changed as flagged, but the escape hatch is **`ClusterNode.MaintenanceMode`**, not `Enabled=0` — the live gate found `Enabled=0` is rejected by `DraftValidator.ValidateClusterTopology` on any 2-node pair. Gate record: `2026-07-22-mesh-phase1-live-gate.md`. |
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| 2 ClusterClient transport | **DONE 2026-07-22** (live gate PASSED, shipped dark) — shipped dark (`MeshTransport:Mode=Dps` default), both comm actors registered in both modes. Corrections: `SendToAll` not `Send`, one fleet-wide client not one per cluster, `/user/node-communication` not `/user/cluster-communication`. The gate's "Ask timing out" item does not exist to test — no cross-boundary Ask in this phase; see the phase section. |
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| 3 fetch-and-cache | **CODE-COMPLETE 2026-07-23** (Tasks 0–8 merged to the phase branch, all green + sabotage-checked; live gate Task 10 pending). gRPC fetch RPC + shared node key; dark switch `ConfigSource:Mode` (Direct default). Rig flip: `OTOPCUA_CONFIG_MODE=FetchAndCache` on the site nodes. See `2026-07-22-mesh-phase3-config-fetch-and-cache.md`. |
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| 4 cut driver ConfigDb | not started |
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| 3 fetch-and-cache | **DONE 2026-07-23**, merged `d01b0695`, live gate PASSED, pushed to origin (scadaproj umbrella index updated + pushed `b5e7bc8`). gRPC fetch RPC + shared node key; dark switch `ConfigSource:Mode` (Direct default). Rig flip: `OTOPCUA_CONFIG_MODE=FetchAndCache` on the site nodes. See `2026-07-22-mesh-phase3-config-fetch-and-cache.md`. |
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| 4 cut driver ConfigDb | **CODE-COMPLETE 2026-07-23** on `feat/mesh-phase4` (Tasks 0–7 + 1b done; Task 9 table-drop deferred; Task 10 rig + Task 11 live gate remain — not yet run). ConfigDb admin-only; `DbHealthProbeActor` not spawned driver-only (client-visible ServiceLevel 240/250 with central down); alarm condition state in LocalDb; central persists acks; driver-only LDAP maps from appsettings only. See `2026-07-23-mesh-phase4-cut-driver-configdb.md`. |
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| 5 gRPC telemetry | not started |
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| 6 mesh partition + co-location | not started |
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| 7 drill + live gates | not started |
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@@ -76,14 +76,16 @@
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{
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"id": 7,
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"subject": "Task 7: Registration cleanup + full-graph driver-only DI sweep",
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"status": "pending",
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"status": "completed",
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"blockedBy": [
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"1b",
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2,
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3,
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4,
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6
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]
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],
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"commit": "6f21213f",
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"result": "12/12; sweep verified clean; ordering+lazy-resolve pins APPROVED (red-check confirmed load-bearing)"
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},
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{
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"id": 8,
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@@ -96,10 +98,11 @@
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{
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"id": 9,
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"subject": "Task 9: Drop dead ConfigDb ScriptedAlarmState table + retire EfAlarmConditionStateStore",
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"status": "pending",
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"status": "deferred",
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"blockedBy": [
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6
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]
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],
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"result": "DEFERRED to follow-up (plan-sanctioned): EF store is inert on all real nodes (test-harness fallback only); table-drop migration is irreversible. Not needed for the ConfigDb-cut goal. Tracked in program doc."
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},
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{
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"id": 10,
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