Joseph Doherty
1ea1da8236
Since #516 a DriverConfig change is stop + respawn, so DriverSpawnPlan.ToApplyDelta was always empty and the in-place path had no producer. #663 and #664 were both latent bugs in it. This deletes it: - host: ApplyChildDelta, _pendingDelta, HandleApplyResult and HandleDeltaApplied - plan: DriverSpawnPlan.ToApplyDelta - actor: the ApplyDelta, ApplyResult and DeltaApplied messages, the Connected reinit handler and the mid-connect AdoptConfigDuringInit - tests: the actor tests that drove the seam IDriver.ReinitializeAsync and each driver's implementation and unit tests stay. Comments and docs that cited AdoptConfigDuringInit as the reason a driver must release prior state at init now cite the IDriver contract and overlapping retries, which still apply. Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe
72 lines
5.1 KiB
Markdown
72 lines
5.1 KiB
Markdown
# Incremental Sync
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How a change reaches the running server's address space in v3. There is exactly one path that
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changes the served address space — the **deploy artifact** — and one advisory signal
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(`IRediscoverable`) that never changes it.
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## The deploy-artifact path
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1. **Compose.** `ConfigComposer` (`src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/AdminOperations/ConfigComposer.cs`)
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snapshots the whole Config DB into one gzip-compressed JSON blob (`Deployment.ArtifactBlob`) whose
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`RevisionHash` is the SHA-256 of those exact bytes. A deployment is fleet-wide; each node
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self-scopes the artifact (`DeploymentArtifact.ResolveClusterScope`).
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2. **Dispatch.** `ConfigPublishCoordinator` (`.../ControlPlane/Coordinators/`) sends each enabled
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`ClusterNode` a payload-free dispatch and waits for acks until the apply deadline. A node obtains the
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bytes either straight from central SQL (`ConfigSource:Mode=Direct`) or over gRPC with a SHA-256
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check (`FetchAndCache`) — see `docs/Configuration.md` §`ConfigSource`.
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3. **Apply.** `DriverHostActor` (`src/Server/ZB.MOM.WW.OtOpcUa.Runtime/Drivers/`) opens the artifact and
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reconciles in two halves:
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- **Drivers** — `DriverSpawnPlanner.Compute` yields `ToStop` / `ToSpawn`. A changed
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driver config (DriverConfig, DriverType or ResilienceConfig) is a stop + respawn (#516) — there is no
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in-place path (#665 deleted the unreachable `ApplyDelta` seam); a removed driver is stopped. An unreadable or empty blob is "no answer": the apply fails and the
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running children are left alone (never an empty configuration).
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- **Address space** — `AddressSpaceComposer` builds an `AddressSpaceComposition` from the artifact;
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`AddressSpacePlan` diffs it against the last applied composition; `AddressSpaceChangeClassifier`
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picks the delta class; `AddressSpaceApplier`
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(`src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/`) mutates `OtOpcUaNodeManager` through the sink.
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4. **Classes** (`AddressSpaceChangeKind`): `Empty`, `AttributeOnly`, `PureAdd`, `PureRemove`,
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`AddRemoveMix` — all applied surgically, so unrelated MonitoredItems survive — and `Rebuild`, the
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default-closed fallback for anything the classifier does not whitelist. Any surgical `false`/throw
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also ratchets to a safe rebuild, and a degraded non-rebuild apply does not advance the last-applied
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composition (the next deploy re-diffs and re-ensures). The whitelist, the UNS-mirror repair rule and
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the add/remove announcements are described in the "surgical deploys" paragraph of `CLAUDE.md`
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and `docs/plans/2026-08-15-surgical-deploys.md`.
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Virtual tags and scripted alarms ride the same artifact and the same plan; a script edit is just another
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changed record in the composition (see `docs/VirtualTags.md`, `docs/ScriptedAlarms.md`).
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## Driver-backend rediscovery is advisory
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Drivers whose backend signals a tag-set change implement `IRediscoverable`
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(`src/Core/ZB.MOM.WW.OtOpcUa.Core.Abstractions/IRediscoverable.cs`; `OnRediscoveryNeeded` carries a
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`Reason` and an optional `ScopeHint`). Raisers today: **Galaxy** (`DeployWatcher`, new
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`time_of_last_deploy`), **TwinCAT** (ADS symbol-version-changed), **MQTT/Sparkplug** and **MTConnect**.
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AbCip, AbLegacy, FOCAS, Modbus, S7 and the rest raise nothing.
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`DriverInstanceActor` is the only production consumer: it subscribes in `PreStart`, detaches in
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`PostStop`, and folds the raise into the driver-health snapshot
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(`DriverHealthChanged.RediscoveryNeededUtc` / `.RediscoveryReason`), which the AdminUI `/hosts` page shows
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as a **re-browse** chip. **It never rebuilds or edits the served address space** — v3 raw tags are authored
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explicitly in `/raw`, so an operator re-browses the device and commits, and the result reaches the
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server as an ordinary deployment. `ScopeHint` is not read by the actor. (The older runtime
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injection path was removed, #507 closed as superseded.)
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## Not part of the v3 path
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- `sp_PublishGeneration` / `sp_ComputeGenerationDiff` are stubs that `RAISERROR` in the v3 baseline
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migration; there is no generation-publish flow and no `DraftRevisionToken`.
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- `GenericDriverNodeManager` (`Core/OpcUa/`) is retained scaffolding with no production caller; the
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diff / teardown / subscription-replay "rebuild flow" described by earlier versions of this page does not
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exist in `src/`.
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## Key source files
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- `src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/AdminOperations/ConfigComposer.cs` — artifact composition + hash
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- `src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/Coordinators/ConfigPublishCoordinator.cs` — dispatch + ack set
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- `src/Server/ZB.MOM.WW.OtOpcUa.Runtime/Drivers/DriverHostActor.cs` — apply + driver reconcile
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- `src/Server/ZB.MOM.WW.OtOpcUa.Runtime/Drivers/DeploymentArtifact.cs` — node-side artifact parsing
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- `src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/AddressSpaceComposer.cs`, `AddressSpacePlan.cs`,
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`AddressSpaceChangeClassifier.cs`, `AddressSpaceApplier.cs` — compose, diff, classify, apply
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- `src/Server/ZB.MOM.WW.OtOpcUa.Runtime/Drivers/DriverInstanceActor.cs` — `IRediscoverable` consumer
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- `src/Core/ZB.MOM.WW.OtOpcUa.Commons/OpcUa/ISurgicalAddressSpaceSink.cs` — in-place update seam
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