# Service Hosting

## Overview

A production OtOpcUa deployment runs **two or three processes**, each
with a distinct runtime and install surface:

| Process | Project | Runtime | Platform | Responsibility |
|---|---|---|---|---|
| **OtOpcUa Server** | `src/ZB.MOM.WW.OtOpcUa.Server` | .NET 10 | x64 | Hosts the OPC UA endpoint; loads every driver in-process (Modbus, S7, AbCip, AbLegacy, TwinCAT, FOCAS, OPC UA Client, Galaxy via mxaccessgw); exposes `/healthz`. |
| **OtOpcUa Admin** | `src/ZB.MOM.WW.OtOpcUa.Admin` | .NET 10 (ASP.NET Core / Blazor Server) | x64 | Operator UI for Config DB editing + fleet status, SignalR hubs (`FleetStatusHub`, `AlertHub`), Prometheus `/metrics`. |
| **OtOpcUa Wonderware Historian** *(optional)* | `src/ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware` | .NET Framework 4.8 | x86 (32-bit) | Out-of-process sidecar exposing the Wonderware Historian SDK over a named pipe. Required only when `Historian:Wonderware:Enabled=true` in `appsettings.json`. |

Galaxy access uses a separately-installed **mxaccessgw** running out
of a sibling repo (`c:\Users\dohertj2\Desktop\mxaccessgw\`) — see
`docs/v2/Galaxy.ParityRig.md` for setup. The mxaccessgw owns the
MXAccess COM bitness constraint (its worker is x86 net48); nothing
in the OtOpcUa repo carries that constraint anymore. PR 7.2 retired
the legacy in-process `Galaxy.Host` / `Galaxy.Proxy` / `Galaxy.Shared`
projects + the `OtOpcUaGalaxyHost` Windows service.

## OtOpcUa Server

Hosted via `Microsoft.Extensions.Hosting` with `AddWindowsService`
(decision #30 — replaced TopShelf in v2). The host's `Build()`
returns immediately when launched interactively (e.g. `dotnet run`)
but blocks for SCM signals when running as a Windows service.

In-process drivers are registered at startup in `Program.cs`'s
`DriverFactoryRegistry` block; the `DriverInstance` rows in the
central Config DB select which driver factories materialise into
live `IDriver` instances. See `docs/v2/driver-specs.md` for the
per-driver `DriverConfig` JSON shapes.

## OtOpcUa Admin

Same hosting model; runs the Blazor Server UI + SignalR hubs.
Reads from the same Config DB the Server writes to.

## OtOpcUa Wonderware Historian (optional)

When `Historian:Wonderware:Enabled=true`, the Server speaks to a
sidecar that wraps the Wonderware Historian SDK (which is .NET
Framework only). The pipe IPC contract is in
`src/ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware.Client/Contracts/`
and the sidecar's pipe handler lives at
`src/ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware/Pipe/`.

Install via the `-InstallWonderwareHistorian` switch on
`scripts/install/Install-Services.ps1`.

## Install / Uninstall

- `scripts/install/Install-Services.ps1` — installs `OtOpcUa` and
  optionally `OtOpcUaWonderwareHistorian`.
- `scripts/install/Uninstall-Services.ps1` — stops + removes both,
  plus `OtOpcUaGalaxyHost` if a pre-7.2 rig still carries it.

## Logging

Serilog with rolling-daily file sinks. Each service writes to
`%ProgramData%\OtOpcUa\<service>-*.log` plus stdout (NSSM-friendly).
