docs(requirements): add Site Call Audit component (#22)
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Joseph Doherty
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docs/requirements/Component-SiteCallAudit.md
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docs/requirements/Component-SiteCallAudit.md
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# Component: Site Call Audit
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## Purpose
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Provides central, queryable audit and operational visibility for cached calls
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made by site scripts — `ExternalSystem.CachedCall()` and `Database.CachedWrite()`.
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Each such call carries a `TrackedOperationId`; sites report lifecycle telemetry
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to this component, which maintains a central audit record, computes KPIs, and
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relays Retry/Discard actions back to the owning site.
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This is the second centrally-hosted observability component for site
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store-and-forward activity (the Notification Outbox is the first). Unlike the
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Notification Outbox, Site Call Audit is **not a dispatcher** — it never delivers
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anything. Cached calls are delivered by the site's Store-and-Forward Engine
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against site-local external systems and databases, which central cannot reach.
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## Location
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Central cluster only. A singleton actor (`SiteCallAuditActor`) on the active
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central node. Registered as component #22 in the Host role configuration.
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## Responsibilities
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- Ingest cached-call lifecycle telemetry from sites into the central `SiteCalls`
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table.
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- Run periodic per-site reconciliation pulls so missed telemetry self-heals.
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- Compute point-in-time KPIs (global and per-site) from the `SiteCalls` table.
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- Relay operator Retry/Discard actions for parked cached calls to the owning
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site over the command/control channel.
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- Purge terminal audit rows after a configurable retention window.
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## The `SiteCalls` Table
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Lives in the central MS SQL configuration database — a sibling of the
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`Notifications` table. One row per `TrackedOperationId`:
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- **TrackedOperationId** — GUID, primary key. Generated site-side at call time.
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- **SourceSite** — site that issued the call.
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- **Kind** — `ExternalCall` or `DatabaseWrite`.
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- **TargetSummary** — external system + method name, or database connection name.
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- **Status** — `Pending`, `Retrying`, `Delivered`, `Parked`, `Failed`, `Discarded`.
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- **RetryCount** — attempts so far.
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- **LastError** — most recent error detail, if any.
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- **Provenance** — source instance / script.
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- **CreatedAtUtc**, **UpdatedAtUtc**, **TerminalAtUtc** — key timestamps.
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## Status Lifecycle
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`Pending → Retrying → Delivered / Parked / Failed / Discarded`
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- **Delivered** — succeeded. A cached call that succeeds on its first immediate
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attempt is recorded directly as `Delivered`.
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- **Parked** — transient retries exhausted; awaiting manual action.
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- **Failed** — permanent failure (e.g. HTTP 4xx). The error was also returned
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synchronously to the calling script; the record captures it.
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- **Discarded** — an operator discarded a parked operation.
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The site is the source of truth. The `SiteCalls` row is an eventually-consistent
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mirror — never queried by scripts (`Tracking.Status()` is answered site-locally).
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## Ingest & Idempotency
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Telemetry ingestion is **insert-if-not-exists** keyed on `TrackedOperationId`,
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then **upsert-on-newer-status**. The lifecycle is monotonic, so status only
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advances and never regresses; at-least-once and out-of-order telemetry are
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therefore harmless.
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## Reconciliation
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Because telemetry is best-effort, `SiteCallAuditActor` periodically — and on site
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reconnect — pulls "all tracking rows changed since cursor X" from each site.
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Gaps left by lost telemetry self-heal. Central converges to the site; the site
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never depends on central.
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## Retry / Discard Relay
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Parked cached calls live in the owning site's S&F buffer. Operator Retry/Discard
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from the Central UI is relayed to that site as a `RetryParkedOperation` /
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`DiscardParkedOperation` command over the command/control channel. The site
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applies the change and emits telemetry reflecting the new state; central never
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mutates the `SiteCalls` row directly. If the site is offline the command fails
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fast and the UI surfaces a "site unreachable" message.
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## KPIs
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Point-in-time, computed from the `SiteCalls` table, global and per-source-site,
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mirroring the Notification Outbox KPI shape:
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- Buffered count (`Pending` + `Retrying`)
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- Parked count
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- Failed-last-interval
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- Delivered-last-interval
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- Oldest-pending age
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- Stuck count — `Pending`/`Retrying` older than a configurable threshold
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(default 10 minutes); display-only, no escalation.
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## Retention
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Daily purge of terminal rows (`Delivered`, `Failed`, `Discarded`) after a
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configurable window (default 365 days), matching the `Notifications` purge.
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## Dependencies
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- **Configuration Database**: hosts the `SiteCalls` table and its repository.
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- **Central–Site Communication**: receives cached-call telemetry and reconciliation
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responses; sends Retry/Discard commands.
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- **Store-and-Forward Engine**: the site-side origin of cached-call telemetry and
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the executor of relayed Retry/Discard commands.
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- **Commons**: `TrackedOperationId`, status enum, telemetry message contracts.
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## Interactions
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- **Central UI**: the Site Calls page queries this component and issues
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Retry/Discard actions.
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- **Health Monitoring**: surfaces Site Call Audit KPI tiles on the dashboard.
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- **Cluster Infrastructure**: hosts the `SiteCallAuditActor` singleton with
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active/standby failover.
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