Files
ScadaBridge/src/ScadaLink.SiteCallAudit/SiteCallAuditActor.cs
T

676 lines
27 KiB
C#

using Akka.Actor;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using ScadaLink.Commons.Entities.Audit;
using ScadaLink.Commons.Interfaces.Repositories;
using ScadaLink.Commons.Messages.Audit;
using ScadaLink.Commons.Messages.RemoteQuery;
using ScadaLink.Commons.Types;
using ScadaLink.Commons.Types.Audit;
using ScadaLink.Communication;
namespace ScadaLink.SiteCallAudit;
/// <summary>
/// Central singleton for Site Call Audit (#22). Receives
/// <see cref="UpsertSiteCallCommand"/> messages and persists each
/// <see cref="ScadaLink.Commons.Entities.Audit.SiteCall"/> row via
/// <see cref="ISiteCallAuditRepository.UpsertAsync"/> — idempotent monotonic
/// upsert. Out-of-order or duplicate updates are silent no-ops at the
/// repository layer; the actor always replies <see cref="UpsertSiteCallReply"/>
/// with <c>Accepted=true</c> in that case because storage state is consistent
/// and the site is free to consider its packet acked.
/// </summary>
/// <remarks>
/// <para>
/// Query, detail and KPIs (Task 4) and the central→site Retry/Discard relay
/// (Task 5 — the relay handlers live in this actor) are implemented; only
/// reconciliation remains deferred (per CLAUDE.md scope discipline — it lands
/// in a later follow-up).
/// </para>
/// <para>
/// Per CLAUDE.md "audit-write failure NEVER aborts the user-facing action" —
/// the actor catches every exception from the repository call and replies
/// <c>Accepted=false</c> without rethrowing, so the central singleton stays
/// alive. The <see cref="SupervisorStrategy"/> uses <c>Resume</c> so an
/// unexpected throw before the catch (defence in depth) does not restart the
/// actor and reset in-flight state.
/// </para>
/// <para>
/// Two constructors exist for the same reason as
/// <c>AuditLogIngestActor</c>: production wiring (Bundle F) resolves the
/// scoped EF repository from a fresh DI scope per message because the actor
/// is a long-lived cluster singleton, while tests inject a concrete
/// <see cref="ISiteCallAuditRepository"/> against a per-test MSSQL fixture
/// so the actor exercises the real monotonic upsert SQL end to end.
/// </para>
/// </remarks>
public class SiteCallAuditActor : ReceiveActor
{
/// <summary>Maximum page size honoured by a <see cref="SiteCallQueryRequest"/>.</summary>
private const int MaxPageSize = 200;
private readonly IServiceProvider? _serviceProvider;
private readonly ISiteCallAuditRepository? _injectedRepository;
private readonly SiteCallAuditOptions _options;
private readonly ILogger<SiteCallAuditActor> _logger;
/// <summary>
/// Task 5 (#22): the central→site command transport — the
/// <c>CentralCommunicationActor</c>, which owns the per-site
/// <c>ClusterClient</c> map and routes a <see cref="SiteEnvelope"/> to the
/// owning site. Set via <see cref="RegisterCentralCommunication"/> by the
/// Host after both actors exist (this actor is a cluster singleton; the
/// transport actor is created separately). Null until registration
/// completes — a relay arriving before then is answered with a
/// <see cref="SiteCallRelayOutcome.SiteUnreachable"/> outcome, because there
/// is genuinely no route to any site yet.
/// </summary>
private IActorRef? _centralCommunication;
/// <summary>
/// Test-mode constructor — injects a concrete repository instance whose
/// lifetime exceeds the test, so the actor reuses the same instance
/// across every message. Used by Bundle C's MSSQL-backed TestKit fixture.
/// An optional <paramref name="options"/> lets a test pin the stuck/KPI
/// windows; when omitted the production defaults apply.
/// </summary>
public SiteCallAuditActor(
ISiteCallAuditRepository repository,
ILogger<SiteCallAuditActor> logger,
SiteCallAuditOptions? options = null)
{
ArgumentNullException.ThrowIfNull(repository);
ArgumentNullException.ThrowIfNull(logger);
_injectedRepository = repository;
_logger = logger;
_options = options ?? new SiteCallAuditOptions();
RegisterHandlers();
}
/// <summary>
/// Production constructor — resolves <see cref="ISiteCallAuditRepository"/>
/// from a fresh DI scope per message because the repository is a scoped EF
/// Core service registered by <c>AddConfigurationDatabase</c>. The actor
/// itself is a long-lived cluster singleton, so it cannot hold a scope
/// across messages.
/// </summary>
public SiteCallAuditActor(
IServiceProvider serviceProvider,
SiteCallAuditOptions options,
ILogger<SiteCallAuditActor> logger)
{
ArgumentNullException.ThrowIfNull(serviceProvider);
ArgumentNullException.ThrowIfNull(options);
ArgumentNullException.ThrowIfNull(logger);
_serviceProvider = serviceProvider;
_options = options;
_logger = logger;
RegisterHandlers();
}
/// <summary>
/// Wires up the message handlers shared by both constructors: the M3
/// ingest path plus the Task 4 read-side (query, detail, global + per-site
/// KPI). All read handlers reply to an Ask, so they capture <c>Sender</c>
/// before the first await and <c>PipeTo</c> the result back.
/// </summary>
private void RegisterHandlers()
{
ReceiveAsync<UpsertSiteCallCommand>(OnUpsertAsync);
Receive<SiteCallQueryRequest>(HandleQuery);
Receive<SiteCallDetailRequest>(HandleDetail);
Receive<SiteCallKpiRequest>(HandleKpi);
Receive<PerSiteSiteCallKpiRequest>(HandlePerSiteKpi);
// Task 5 (#22): central→site Retry/Discard relay for parked cached calls.
Receive<RegisterCentralCommunication>(msg =>
{
_centralCommunication = msg.CentralCommunication;
_logger.LogInformation("SiteCallAudit registered central→site communication transport");
});
Receive<RetrySiteCallRequest>(HandleRetrySiteCall);
Receive<DiscardSiteCallRequest>(HandleDiscardSiteCall);
}
/// <summary>
/// Audit-write failures are best-effort by design (CLAUDE.md §Audit): a
/// thrown exception in the upsert pipeline must not crash the actor.
/// Resume keeps the actor's state intact so the next packet is processed
/// against the same repository instance.
/// </summary>
protected override SupervisorStrategy SupervisorStrategy()
{
return new OneForOneStrategy(maxNrOfRetries: 0, withinTimeRange: TimeSpan.Zero, decider:
Akka.Actor.SupervisorStrategy.DefaultDecider);
}
private async Task OnUpsertAsync(UpsertSiteCallCommand cmd)
{
// Sender is captured before the first await — Akka resets Sender
// between message dispatches, so a post-await Tell would go to
// DeadLetters.
var replyTo = Sender;
var id = cmd.SiteCall.TrackedOperationId;
// Scope-per-message mirrors AuditLogIngestActor — production EF
// repository is scoped; the injected-repository mode (tests) skips
// the scope entirely.
IServiceScope? scope = null;
ISiteCallAuditRepository repository;
if (_injectedRepository is not null)
{
repository = _injectedRepository;
}
else
{
scope = _serviceProvider!.CreateScope();
repository = scope.ServiceProvider.GetRequiredService<ISiteCallAuditRepository>();
}
try
{
await repository.UpsertAsync(cmd.SiteCall).ConfigureAwait(false);
replyTo.Tell(new UpsertSiteCallReply(id, Accepted: true));
}
catch (Exception ex)
{
// Per CLAUDE.md: audit-write failure NEVER aborts the user-facing
// action — log and reply Accepted=false; do NOT rethrow (the
// central singleton MUST stay alive).
_logger.LogError(ex, "SiteCallAudit upsert failed for {TrackedOperationId}", id);
replyTo.Tell(new UpsertSiteCallReply(id, Accepted: false));
}
finally
{
scope?.Dispose();
}
}
// ── Task 4: read-side (query / detail / KPI) ──
/// <summary>
/// Handles a paginated, filtered query over the <c>SiteCalls</c> table.
/// Builds a <see cref="SiteCallQueryFilter"/> + <see cref="SiteCallPaging"/>
/// keyset cursor from the request, runs the query on a scoped repository,
/// and pipes the mapped response back to the captured sender. A repository
/// fault yields a failure response with an empty list.
/// </summary>
private void HandleQuery(SiteCallQueryRequest request)
{
var sender = Sender;
var now = DateTime.UtcNow;
QueryAsync(request, now).PipeTo(
sender,
success: response => response,
failure: ex => new SiteCallQueryResponse(
request.CorrelationId,
Success: false,
ErrorMessage: ex.GetBaseException().Message,
SiteCalls: Array.Empty<SiteCallSummary>(),
NextAfterCreatedAtUtc: null,
NextAfterId: null));
}
private async Task<SiteCallQueryResponse> QueryAsync(SiteCallQueryRequest request, DateTime now)
{
var stuckCutoff = now - _options.StuckAgeThreshold;
var filter = new SiteCallQueryFilter(
Channel: NullIfBlank(request.ChannelFilter),
SourceSite: NullIfBlank(request.SourceSiteFilter),
Status: NullIfBlank(request.StatusFilter),
Target: NullIfBlank(request.TargetKeyword),
FromUtc: request.FromUtc,
ToUtc: request.ToUtc,
// StuckOnly is pushed into the repository SQL via StuckCutoffUtc —
// TerminalAtUtc IS NULL AND CreatedAtUtc < cutoff composes with the
// keyset cursor, so the page is always honest (full pages, no empty
// pages with a non-null next cursor).
StuckCutoffUtc: request.StuckOnly ? stuckCutoff : null);
var pageSize = Math.Clamp(request.PageSize, 1, MaxPageSize);
var paging = new SiteCallPaging(
PageSize: pageSize,
AfterCreatedAtUtc: request.AfterCreatedAtUtc,
AfterId: request.AfterId is { } id ? new TrackedOperationId(id) : null);
var (scope, repository) = ResolveRepository();
try
{
var rows = await repository.QueryAsync(filter, paging).ConfigureAwait(false);
var summaries = rows
.Select(row => ToSummary(row, stuckCutoff))
.ToList();
// The next-page cursor is the last row of the materialised page.
var cursorRow = rows.Count > 0 ? rows[^1] : null;
return new SiteCallQueryResponse(
request.CorrelationId,
Success: true,
ErrorMessage: null,
SiteCalls: summaries,
NextAfterCreatedAtUtc: cursorRow?.CreatedAtUtc,
NextAfterId: cursorRow?.TrackedOperationId.Value);
}
finally
{
scope?.Dispose();
}
}
/// <summary>
/// Handles a full-detail query for a single cached call — backs the report
/// detail modal. A missing row yields <c>Success=false</c> with a "not
/// found" message; a repository fault yields <c>Success=false</c> with the
/// fault message.
/// </summary>
private void HandleDetail(SiteCallDetailRequest request)
{
var sender = Sender;
DetailAsync(request).PipeTo(
sender,
success: response => response,
failure: ex => new SiteCallDetailResponse(
request.CorrelationId,
Success: false,
ErrorMessage: ex.GetBaseException().Message,
Detail: null));
}
private async Task<SiteCallDetailResponse> DetailAsync(SiteCallDetailRequest request)
{
var (scope, repository) = ResolveRepository();
try
{
var row = await repository
.GetAsync(new TrackedOperationId(request.TrackedOperationId))
.ConfigureAwait(false);
if (row is null)
{
return new SiteCallDetailResponse(
request.CorrelationId,
Success: false,
ErrorMessage: "site call not found",
Detail: null);
}
return new SiteCallDetailResponse(
request.CorrelationId,
Success: true,
ErrorMessage: null,
Detail: ToDetail(row));
}
finally
{
scope?.Dispose();
}
}
/// <summary>
/// Handles a global KPI snapshot request, deriving the stuck cutoff from
/// <see cref="SiteCallAuditOptions.StuckAgeThreshold"/> and the
/// failed/delivered interval bound from <see cref="SiteCallAuditOptions.KpiInterval"/>.
/// </summary>
private void HandleKpi(SiteCallKpiRequest request)
{
var sender = Sender;
var now = DateTime.UtcNow;
var stuckCutoff = now - _options.StuckAgeThreshold;
var intervalSince = now - _options.KpiInterval;
KpiAsync(request.CorrelationId, stuckCutoff, intervalSince).PipeTo(
sender,
success: response => response,
failure: ex => new SiteCallKpiResponse(
request.CorrelationId,
Success: false,
ErrorMessage: ex.GetBaseException().Message,
BufferedCount: 0,
ParkedCount: 0,
FailedLastInterval: 0,
DeliveredLastInterval: 0,
OldestPendingAge: null,
StuckCount: 0));
}
private async Task<SiteCallKpiResponse> KpiAsync(
string correlationId, DateTime stuckCutoff, DateTime intervalSince)
{
var (scope, repository) = ResolveRepository();
try
{
var snapshot = await repository
.ComputeKpisAsync(stuckCutoff, intervalSince)
.ConfigureAwait(false);
return new SiteCallKpiResponse(
correlationId,
Success: true,
ErrorMessage: null,
snapshot.BufferedCount,
snapshot.ParkedCount,
snapshot.FailedLastInterval,
snapshot.DeliveredLastInterval,
snapshot.OldestPendingAge,
snapshot.StuckCount);
}
finally
{
scope?.Dispose();
}
}
/// <summary>
/// Handles a per-source-site KPI request, using the same stuck cutoff and
/// interval bound as <see cref="HandleKpi"/>.
/// </summary>
private void HandlePerSiteKpi(PerSiteSiteCallKpiRequest request)
{
var sender = Sender;
var now = DateTime.UtcNow;
var stuckCutoff = now - _options.StuckAgeThreshold;
var intervalSince = now - _options.KpiInterval;
PerSiteKpiAsync(request.CorrelationId, stuckCutoff, intervalSince).PipeTo(
sender,
success: response => response,
failure: ex => new PerSiteSiteCallKpiResponse(
request.CorrelationId,
Success: false,
ErrorMessage: ex.GetBaseException().Message,
Sites: Array.Empty<SiteCallSiteKpiSnapshot>()));
}
private async Task<PerSiteSiteCallKpiResponse> PerSiteKpiAsync(
string correlationId, DateTime stuckCutoff, DateTime intervalSince)
{
var (scope, repository) = ResolveRepository();
try
{
var sites = await repository
.ComputePerSiteKpisAsync(stuckCutoff, intervalSince)
.ConfigureAwait(false);
return new PerSiteSiteCallKpiResponse(
correlationId, Success: true, ErrorMessage: null, sites);
}
finally
{
scope?.Dispose();
}
}
// ── Task 5: central→site Retry/Discard relay ──
/// <summary>
/// Relays an operator Retry of a parked cached call to its owning site. The
/// site is the source of truth — this handler NEVER writes the central
/// <c>SiteCalls</c> mirror row. It wraps a <see cref="RetryParkedOperation"/>
/// in a <see cref="SiteEnvelope"/> addressed to <c>SourceSite</c>, Asks the
/// <c>CentralCommunicationActor</c> (which routes it over the per-site
/// <c>ClusterClient</c>), and maps the site's
/// <see cref="ParkedOperationActionAck"/> — or an Ask timeout — onto a
/// <see cref="RetrySiteCallResponse"/>. A timeout / no-route is reported as
/// the distinct <see cref="SiteCallRelayOutcome.SiteUnreachable"/> outcome,
/// not a generic failure, so the Central UI can tell "site offline" from
/// "operation failed".
/// </summary>
private void HandleRetrySiteCall(RetrySiteCallRequest request)
{
var sender = Sender;
if (_centralCommunication is null)
{
// No transport registered yet — there is genuinely no route to any
// site, so the only honest answer is unreachable.
_logger.LogWarning(
"RetrySiteCall {TrackedOperationId} for site {SourceSite} arrived before the "
+ "central→site transport was registered; reporting site unreachable",
request.TrackedOperationId, request.SourceSite);
sender.Tell(UnreachableRetry(request.CorrelationId));
return;
}
var relay = new RetryParkedOperation(
request.CorrelationId, new TrackedOperationId(request.TrackedOperationId));
var envelope = new SiteEnvelope(request.SourceSite, relay);
_centralCommunication.Ask<ParkedOperationActionAck>(envelope, _options.RelayTimeout)
.PipeTo(
sender,
success: ack => MapRetryResponse(request.CorrelationId, ack),
failure: ex => MapRetryFailure(request.CorrelationId, request.SourceSite, ex));
}
/// <summary>
/// Relays an operator Discard of a parked cached call to its owning site.
/// Mirrors <see cref="HandleRetrySiteCall"/> — see that method for the
/// source-of-truth and site-unreachable rationale.
/// </summary>
private void HandleDiscardSiteCall(DiscardSiteCallRequest request)
{
var sender = Sender;
if (_centralCommunication is null)
{
_logger.LogWarning(
"DiscardSiteCall {TrackedOperationId} for site {SourceSite} arrived before the "
+ "central→site transport was registered; reporting site unreachable",
request.TrackedOperationId, request.SourceSite);
sender.Tell(UnreachableDiscard(request.CorrelationId));
return;
}
var relay = new DiscardParkedOperation(
request.CorrelationId, new TrackedOperationId(request.TrackedOperationId));
var envelope = new SiteEnvelope(request.SourceSite, relay);
_centralCommunication.Ask<ParkedOperationActionAck>(envelope, _options.RelayTimeout)
.PipeTo(
sender,
success: ack => MapDiscardResponse(request.CorrelationId, ack),
failure: ex => MapDiscardFailure(request.CorrelationId, request.SourceSite, ex));
}
/// <summary>
/// Maps the site's <see cref="ParkedOperationActionAck"/> for a Retry onto a
/// <see cref="RetrySiteCallResponse"/>: an applied action is
/// <see cref="SiteCallRelayOutcome.Applied"/>; a clean no-op
/// (<c>Applied=false</c>, no error) is <see cref="SiteCallRelayOutcome.NotParked"/>;
/// an ack carrying an error is <see cref="SiteCallRelayOutcome.OperationFailed"/>
/// — in every case the site WAS reached.
/// </summary>
private static RetrySiteCallResponse MapRetryResponse(string correlationId, ParkedOperationActionAck ack)
{
var outcome = ClassifyAck(ack);
return new RetrySiteCallResponse(
correlationId,
outcome,
Success: outcome == SiteCallRelayOutcome.Applied,
SiteReachable: true,
ErrorMessage: AckErrorMessage(outcome, ack));
}
private static DiscardSiteCallResponse MapDiscardResponse(string correlationId, ParkedOperationActionAck ack)
{
var outcome = ClassifyAck(ack);
return new DiscardSiteCallResponse(
correlationId,
outcome,
Success: outcome == SiteCallRelayOutcome.Applied,
SiteReachable: true,
ErrorMessage: AckErrorMessage(outcome, ack));
}
private RetrySiteCallResponse MapRetryFailure(string correlationId, string sourceSite, Exception ex)
{
_logger.LogWarning(ex,
"Retry relay to site {SourceSite} did not complete; reporting site unreachable", sourceSite);
return UnreachableRetry(correlationId);
}
private DiscardSiteCallResponse MapDiscardFailure(string correlationId, string sourceSite, Exception ex)
{
_logger.LogWarning(ex,
"Discard relay to site {SourceSite} did not complete; reporting site unreachable", sourceSite);
return UnreachableDiscard(correlationId);
}
/// <summary>
/// Classifies a site ack: <c>Applied=true</c> → applied; <c>Applied=false</c>
/// with no error → the site definitively had nothing parked; <c>Applied=false</c>
/// with an error → the site could not apply the action.
/// </summary>
private static SiteCallRelayOutcome ClassifyAck(ParkedOperationActionAck ack)
{
if (ack.Applied)
{
return SiteCallRelayOutcome.Applied;
}
return ack.ErrorMessage is null
? SiteCallRelayOutcome.NotParked
: SiteCallRelayOutcome.OperationFailed;
}
private static string? AckErrorMessage(SiteCallRelayOutcome outcome, ParkedOperationActionAck ack)
{
return outcome switch
{
SiteCallRelayOutcome.Applied => null,
SiteCallRelayOutcome.NotParked =>
"The operation is no longer parked at the site (already delivered, discarded, or retrying).",
SiteCallRelayOutcome.OperationFailed => ack.ErrorMessage,
// SiteUnreachable is never produced from a ParkedOperationActionAck —
// unreachable responses are built by UnreachableRetry/UnreachableDiscard
// before any ack is classified, so this arm is unreachable by construction.
SiteCallRelayOutcome.SiteUnreachable => ack.ErrorMessage,
_ => throw new ArgumentOutOfRangeException(
nameof(outcome), outcome, "unknown SiteCallRelayOutcome"),
};
}
/// <summary>Shared "site unreachable" detail text for both relay directions.</summary>
private const string SiteUnreachableMessage =
"The owning site is unreachable; the action was not applied. Retry when the site is back online.";
private static RetrySiteCallResponse UnreachableRetry(string correlationId)
{
return new RetrySiteCallResponse(
correlationId,
SiteCallRelayOutcome.SiteUnreachable,
Success: false,
SiteReachable: false,
ErrorMessage: SiteUnreachableMessage);
}
private static DiscardSiteCallResponse UnreachableDiscard(string correlationId)
{
return new DiscardSiteCallResponse(
correlationId,
SiteCallRelayOutcome.SiteUnreachable,
Success: false,
SiteReachable: false,
ErrorMessage: SiteUnreachableMessage);
}
/// <summary>
/// Resolves an <see cref="ISiteCallAuditRepository"/> for one read message.
/// In test mode the injected instance is returned with a null scope; in
/// production a fresh DI scope is created and returned so the caller can
/// dispose it once the read completes — the same scope-per-message pattern
/// as <see cref="OnUpsertAsync"/>.
/// </summary>
private (IServiceScope? Scope, ISiteCallAuditRepository Repository) ResolveRepository()
{
if (_injectedRepository is not null)
{
return (null, _injectedRepository);
}
var scope = _serviceProvider!.CreateScope();
return (scope, scope.ServiceProvider.GetRequiredService<ISiteCallAuditRepository>());
}
/// <summary>
/// A cached call counts as stuck when it is still non-terminal and was
/// created before <paramref name="stuckCutoff"/>. Non-terminal is keyed off
/// <see cref="SiteCall.TerminalAtUtc"/> being <c>null</c> — the
/// <c>SiteCalls</c> operational mirror stores <c>AuditStatus</c>-derived
/// status strings (<c>Attempted</c>/<c>Delivered</c>/<c>Parked</c>/...), not
/// the tracking-lifecycle <c>Pending</c>/<c>Retrying</c> names the spec's
/// KPI section uses, so there is no status string that means "buffered".
/// <c>TerminalAtUtc</c> is the entity's own active/terminal discriminator
/// and is consistent with the repository KPI counts and
/// <c>PurgeTerminalAsync</c>.
/// </summary>
private static bool IsStuck(SiteCall row, DateTime stuckCutoff)
{
return row.TerminalAtUtc is null && row.CreatedAtUtc < stuckCutoff;
}
private static SiteCallSummary ToSummary(SiteCall row, DateTime stuckCutoff)
{
return new SiteCallSummary(
TrackedOperationId: row.TrackedOperationId.Value,
SourceSite: row.SourceSite,
Channel: row.Channel,
Target: row.Target,
Status: row.Status,
RetryCount: row.RetryCount,
LastError: row.LastError,
HttpStatus: row.HttpStatus,
CreatedAtUtc: row.CreatedAtUtc,
UpdatedAtUtc: row.UpdatedAtUtc,
TerminalAtUtc: row.TerminalAtUtc,
IsStuck: IsStuck(row, stuckCutoff));
}
private static SiteCallDetail ToDetail(SiteCall row)
{
return new SiteCallDetail(
TrackedOperationId: row.TrackedOperationId.Value,
SourceSite: row.SourceSite,
Channel: row.Channel,
Target: row.Target,
Status: row.Status,
RetryCount: row.RetryCount,
LastError: row.LastError,
HttpStatus: row.HttpStatus,
CreatedAtUtc: row.CreatedAtUtc,
UpdatedAtUtc: row.UpdatedAtUtc,
TerminalAtUtc: row.TerminalAtUtc,
IngestedAtUtc: row.IngestedAtUtc);
}
/// <summary>
/// Treats an empty/whitespace filter string as "no constraint" — the
/// repository's <see cref="SiteCallQueryFilter"/> interprets <c>null</c> as
/// a no-op predicate, so a blank UI filter must collapse to <c>null</c>.
/// </summary>
private static string? NullIfBlank(string? value)
{
return string.IsNullOrWhiteSpace(value) ? null : value;
}
}
/// <summary>
/// Registers the central→site command transport (the <c>CentralCommunicationActor</c>)
/// with the <see cref="SiteCallAuditActor"/> so it can relay Retry/Discard
/// actions on parked cached calls to their owning sites. Sent by the Host after
/// both actors exist. Lives here (not in Commons) because it carries an
/// <see cref="IActorRef"/> and <c>ScadaLink.Commons</c> has no Akka reference —
/// the same rationale as <c>RegisterAuditIngest</c>.
/// </summary>
public sealed record RegisterCentralCommunication(IActorRef CentralCommunication);