scadalink-design/Component-CentralUI.md

Component: Central UI

Purpose

The Central UI is a web-based management interface hosted on the central cluster. It provides all configuration, deployment, monitoring, and troubleshooting workflows for the SCADA system. There is no live machine data visualization — the UI is focused on system management, with the exception of on-demand debug views.

Location

Central cluster only. Sites have no user interface.

Technology

• Framework: Blazor Server (ASP.NET Core). UI logic executes on the server, updates pushed to the browser via SignalR.
• Keeps the entire stack in C#/.NET, consistent with the rest of the system (Akka.NET, EF Core).
• SignalR provides built-in support for real-time UI updates.

Failover Behavior

• A load balancer sits in front of the central cluster and routes to the active node.
• On central failover, the Blazor Server SignalR circuit is interrupted. The browser automatically attempts to reconnect via SignalR's built-in reconnection logic.
• Since sessions use authentication cookies carrying an embedded JWT (not server-side state), the user's authentication survives failover — the new active node validates the same cookie-embedded JWT. No re-login required if the token is still valid.
• Active debug view polling and in-progress deployment status subscriptions are lost on failover and must be re-opened by the user.
• Both central nodes share the same ASP.NET Data Protection keys (stored in the configuration database or shared configuration) so that tokens and anti-forgery tokens remain valid across failover.

Real-Time Updates

• Debug view: Near-real-time display of attribute values and alarm states, updated via a 2-second polling timer. This avoids the complexity of cross-cluster streaming while providing responsive feedback — 2s latency is imperceptible for debugging purposes.
• Health dashboard: Site status, connection health, error rates, and buffer depths update via a 10-second auto-refresh timer. Since health reports arrive from sites every 30 seconds, a 10s poll interval catches updates within one reporting cycle without unnecessary overhead.
• Deployment status: Pending/in-progress/success/failed transitions push to the UI immediately via SignalR (built into Blazor Server). No polling required for deployment tracking.

Responsibilities

• Provide authenticated access to all management workflows.
• Enforce role-based access control in the UI (Admin, Design, Deployment with site scoping).
• Present data from the configuration database, and from site clusters via remote queries.

Workflows / Pages

Template Authoring (Design Role)

• Create, edit, and delete templates.
• Template deletion is blocked if any instances or child templates reference the template. The UI displays the references preventing deletion.
• Manage template hierarchy (inheritance) — visual tree of parent/child relationships.
• Manage composition — add/remove feature module instances within templates. Naming collision detection provides immediate feedback if composed modules introduce duplicate attribute, alarm, or script names.
• Define and edit attributes, alarms, and scripts on templates.
• Set lock flags on attributes, alarms, and scripts.
• Visual indicator showing inherited vs. locally defined vs. overridden members.
• On-demand validation: A "Validate" action allows Design users to run comprehensive pre-deployment validation (flattening, naming collisions, script compilation, trigger references) without triggering a deployment. Provides early feedback during authoring.
• Last-write-wins editing — no pessimistic locks or conflict detection on templates.

Shared Script Management (Design Role)

• Create, edit, and delete shared (global) scripts.
• Shared scripts are not associated with any template.
• On-demand validation (compilation check) available.

External System Management (Design Role)

• Define external system contracts: connection details, API method definitions (parameters, return types).
• Define retry settings per external system (max retry count, fixed time between retries).

Database Connection Management (Design Role)

• Define named database connections: server, database, credentials.
• Define retry settings per connection (max retry count, fixed time between retries).

Notification List Management (Design Role)

• Create, edit, and delete notification lists.
• Manage recipients (name + email) within each list.
• Configure SMTP settings.

Site & Data Connection Management (Admin Role)

• Create, edit, and delete site definitions.
• Define data connections and assign them to sites (name, protocol type, connection details).

Area Management (Admin Role)

• Define hierarchical area structures per site.
• Parent-child area relationships.
• Assign areas when managing instances.

Instance Management (Deployment Role)

• Create instances from templates at a specific site.
• Assign instances to areas.
• Bind data connections — per-attribute binding where each attribute with a data source reference individually selects its data connection from the site's available connections. Bulk assignment supported: select multiple attributes and assign a data connection to all of them at once.
• Set instance-level attribute overrides (non-locked attributes only).
• Filter/search instances by site, area, template, or status.
• Disable instances — stops data collection, script triggers, and alarm evaluation at the site while retaining the deployed configuration.
• Enable instances — re-activates a disabled instance.
• Delete instances — removes the running configuration from the site. Blocked if the site is unreachable. Store-and-forward messages are not cleared.

Deployment (Deployment Role)

• View list of instances with staleness indicators (deployed config differs from template-derived config).
• Filter by site, area, template.
• View diff between deployed and current template-derived configuration.
• Deploy updated configuration to individual instances. Pre-deployment validation runs automatically before any deployment is sent — validation errors are displayed and block deployment.
• Track deployment status (pending, in-progress, success, failed).

System-Wide Artifact Deployment (Deployment Role)

• Explicitly deploy shared scripts, external system definitions, database connection definitions, data connection definitions, notification lists, and SMTP configuration to all sites or to an individual site.
• Per-site deployment: A "Deploy Artifacts" button on the Sites admin page allows deploying all artifacts to an individual site.
• Deploy all: A bulk action deploys artifacts to all sites at once.
• This is a separate action from instance deployment — system-wide artifacts are not automatically pushed when definitions change.
• Track per-site deployment status.

Debug View (Deployment Role)

• Select a deployed instance and open a live debug view.
• Near-real-time polling (2s interval) of all attribute values (with quality and timestamp) and alarm states for that instance.
• Initial snapshot of current state followed by periodic polling for updates.
• Stream includes attribute values formatted as [InstanceUniqueName].[AttributePath].[AttributeName] and alarm states formatted as [InstanceUniqueName].[AlarmName].
• Subscribe-on-demand — stream starts when opened, stops when closed.

Parked Message Management (Deployment Role)

• Query sites for parked messages (external system calls, notifications, cached DB writes).
• View message details (target, payload, retry count, timestamps).
• Retry or discard individual parked messages.

Health Monitoring Dashboard (All Roles)

• Overview of all sites with online/offline status.
• Per-site detail: active/standby node status, data connection health, script error rates, alarm evaluation error rates, store-and-forward buffer depths.

Site Event Log Viewer (Deployment Role)

• Query site event logs remotely.
• Filter by event type, time range, instance.
• View script executions, alarm events (activations, clears, evaluation errors), deployment events (including script compilation results), connection status changes, store-and-forward activity, instance lifecycle events (enable, disable, delete).

Audit Log Viewer (Admin Role)

• Query the central audit log.
• Filter by user, entity type, action type, time range.
• View before/after state for each change.

LDAP Group Mapping (Admin Role)

• Map LDAP groups to system roles (Admin, Design, Deployment).
• Configure site-scoping for Deployment role groups.

Dependencies

• Template Engine: Provides template and instance data models, flattening, diff calculation, and validation.
• Deployment Manager: Triggers deployments, system-wide artifact deployments, and instance lifecycle commands. Provides deployment status.
• Communication Layer: Routes debug view subscriptions, remote queries to sites.
• Security & Auth: Authenticates users and enforces role-based access.
• Configuration Database: All central data, including audit log data for the audit log viewer. Accessed via ICentralUiRepository.
• Health Monitoring: Provides site health data for the dashboard.