Notifications — Multi-Channel Email, SMS & Push Engine

Granit.Notifications is a multi-channel notification engine built on a fan-out pattern. A single INotificationPublisher.PublishAsync() call fans out to every registered channel (InApp, Email, SMS, WhatsApp, Mobile Push, SignalR, SSE, Web Push, Zulip) after filtering through user preferences. Delivery attempts are recorded in an immutable audit trail (ISO 27001). By default, notifications dispatch via an in-process Channel<T> — add Granit.Notifications.Wolverine for durable outbox-backed dispatch with exponential backoff retry.

Package structure

Channel packages (Email, Sms, MobilePush, WhatsApp, …) define the capability contracts; provider packages sit at the top level and implement one or more capabilities as Keyed Services. Multi-capability providers (AwsSns, AzureCommunicationServices, Brevo, Twilio) register each capability only when its configuration section exists — an SMS-only host never wires the push sender.

• DirectoryGranit.Notifications/ Core: fan-out engine, InApp channel, definitions, entity tracking

  • Granit.Notifications.EntityFrameworkCore EF Core persistence (all stores)
  • Granit.Notifications.Endpoints Minimal API REST endpoints
  • Granit.Notifications.Wolverine Durable outbox dispatch via IMessageBus
  • Granit.Notifications.Privacy GDPR export/deletion satellite (notifications data)
  • Granit.Notifications.Email Email channel abstraction (Keyed Services)
  • Granit.Notifications.Sms SMS channel abstraction (Keyed Services)
  • Granit.Notifications.WhatsApp WhatsApp Business API channel
  • DirectoryGranit.Notifications.MobilePush/ Mobile push abstraction + token store

    • Granit.Notifications.MobilePush.Privacy GDPR export/deletion satellite (push tokens)
  • Granit.Notifications.SignalR Real-time SignalR channel + Redis backplane
  • DirectoryGranit.Notifications.WebPush/ W3C Web Push (VAPID, RFC 8030)

    • Granit.Notifications.WebPush.Privacy GDPR export/deletion satellite (subscriptions)
  • DirectoryGranit.Notifications.Sse/ Server-Sent Events channel (.NET 10)

    • Granit.Notifications.Sse.StackExchangeRedis Redis pub/sub backplane for multi-replica SSE
  • Granit.Notifications.Smtp MailKit SMTP provider (Email)
  • Granit.Notifications.AwsSes AWS SES provider (Email)
  • Granit.Notifications.Scaleway Scaleway TEM provider (Email)
  • Granit.Notifications.SendGrid SendGrid provider (Email)
  • Granit.Notifications.AzureCommunicationServices Azure Communication Services (Email + SMS)
  • Granit.Notifications.AwsSns AWS SNS (SMS + Mobile Push)
  • Granit.Notifications.Brevo Unified Brevo provider (Email + SMS + WhatsApp)
  • Granit.Notifications.Twilio Twilio provider (SMS + WhatsApp)
  • Granit.Notifications.GoogleFcm Firebase Cloud Messaging provider (Mobile Push)
  • Granit.Notifications.AzureNotificationHubs Azure Notification Hubs provider (Mobile Push)
  • Granit.Notifications.Zulip Zulip chat integration

Package	Role	Depends on
Granit.Notifications	Fan-out engine, InApp channel, definitions, entity tracking	Granit.Guids, Granit.Timing, Granit.QueryEngine
Granit.Notifications.EntityFrameworkCore	EF Core stores (all entities + mobile push tokens)	Granit.Notifications, Granit.Notifications.MobilePush, Granit.Persistence
Granit.Notifications.Endpoints	Minimal API endpoints (inbox, preferences, subscriptions, followers)	Granit.Notifications, Granit.Notifications.MobilePush, Granit.Validation, Granit.Http.ApiDocumentation
Granit.Notifications.Wolverine	Durable outbox-backed dispatch via IMessageBus	Granit.Notifications, Granit.Wolverine
Granit.Notifications.Privacy	GDPR export/deletion satellite for notifications data	Granit.Notifications, Granit.Privacy.BlobStorage
Granit.Notifications.Email	Email channel abstraction, Keyed Services resolution	Granit.Notifications
Granit.Notifications.Sms	SMS channel abstraction, Keyed Services resolution	Granit.Notifications
Granit.Notifications.WhatsApp	WhatsApp Business API channel	Granit.Notifications
Granit.Notifications.MobilePush	Mobile push abstraction + device token store	Granit.Notifications
Granit.Notifications.MobilePush.Privacy	GDPR export/deletion satellite for push device tokens (masked)	Granit.Notifications.MobilePush, Granit.Privacy.BlobStorage
Granit.Notifications.Smtp	MailKit SMTP provider (Keyed Service "Smtp")	Granit.Notifications.Email
Granit.Notifications.AwsSes	AWS SES email provider (Keyed Service "AwsSes")	Granit.Notifications.Email
Granit.Notifications.Scaleway	Scaleway TEM email provider (Keyed Service "Scaleway")	Granit.Notifications.Email
Granit.Notifications.SendGrid	SendGrid email provider (Keyed Service "SendGrid")	Granit.Notifications.Email
Granit.Notifications.AzureCommunicationServices	Azure Communication Services provider — Email + SMS, each capability activated by its config section (Keyed Service "AzureCommunicationServices")	Granit.Notifications.Email, Granit.Notifications.Sms
Granit.Notifications.AwsSns	AWS SNS provider — SMS + Platform Application push, each capability activated by its config section (Keyed Service "AwsSns")	Granit.Notifications.Sms, Granit.Notifications.MobilePush
Granit.Notifications.Brevo	Unified Brevo provider (Email + SMS + WhatsApp)	Granit.Notifications.Email, Granit.Notifications.Sms, Granit.Notifications.WhatsApp
Granit.Notifications.Twilio	Twilio SMS + WhatsApp provider (Keyed Service "Twilio")	Granit.Notifications.Sms, Granit.Notifications.WhatsApp
Granit.Notifications.GoogleFcm	Firebase Cloud Messaging (FCM HTTP v1 API, OAuth2 bearer via service account)	Granit.Notifications.MobilePush
Granit.Notifications.AzureNotificationHubs	Azure Notification Hubs push provider (Keyed Service "AzureNotificationHubs")	Granit.Notifications.MobilePush
Granit.Notifications.SignalR	Real-time SignalR channel + Redis backplane	Granit.Notifications
Granit.Notifications.WebPush	W3C Web Push (VAPID, RFC 8030/8291/8292)	Granit.Notifications
Granit.Notifications.WebPush.Privacy	GDPR export/deletion satellite for Web Push subscriptions (masked)	Granit.Notifications.WebPush, Granit.Privacy.BlobStorage
Granit.Notifications.Sse	Server-Sent Events channel (.NET 10 native SSE)	Granit.Notifications
Granit.Notifications.Sse.StackExchangeRedis	Redis pub/sub backplane for multi-replica SSE delivery (shared IConnectionMultiplexer)	Granit.Notifications.Sse
Granit.Notifications.Zulip	Zulip Bot API chat integration	Granit.Notifications

Dependency graph

graph TD
    N[Granit.Notifications] --> G[Granit.Guids]
    N --> T[Granit.Timing]
    N --> Q[Granit.QueryEngine]

    NEF[Granit.Notifications.EntityFrameworkCore] --> N
    NEF --> MP[Granit.Notifications.MobilePush]
    NEF --> P[Granit.Persistence]

    NE[Granit.Notifications.Endpoints] --> N
    NE --> MP
    NE --> V[Granit.Validation]
    NE --> AD[Granit.Http.ApiDocumentation]

    NW[Granit.Notifications.Wolverine] --> N
    NW --> W[Granit.Wolverine]

    EM[Granit.Notifications.Email] --> N
    SMTP[Granit.Notifications.Smtp] --> EM
    SES[Granit.Notifications.AwsSes] --> EM
    SCW[Granit.Notifications.Scaleway] --> EM
    SG[Granit.Notifications.SendGrid] --> EM
    ACS[Granit.Notifications.AzureCommunicationServices] --> EM
    ACS --> SMS[Granit.Notifications.Sms]
    BR[Granit.Notifications.Brevo] --> EM
    BR --> SMS
    BR --> WA[Granit.Notifications.WhatsApp]

    SMS --> N
    SNS[Granit.Notifications.AwsSns] --> SMS
    SNS --> MP
    TW[Granit.Notifications.Twilio] --> SMS
    TW --> WA
    WA --> N
    MP --> N
    FCM[Granit.Notifications.GoogleFcm] --> MP
    ANH[Granit.Notifications.AzureNotificationHubs] --> MP
    SR[Granit.Notifications.SignalR] --> N
    WP[Granit.Notifications.WebPush] --> N
    SSE[Granit.Notifications.Sse] --> N
    SSER[Granit.Notifications.Sse.StackExchangeRedis] --> SSE
    ZU[Granit.Notifications.Zulip] --> N

    PRV[Granit.Notifications.Privacy] --> N
    MPPRV[Granit.Notifications.MobilePush.Privacy] --> MP
    WPPRV[Granit.Notifications.WebPush.Privacy] --> WP

Setup

Production (Wolverine + EF Core)

[DependsOn(typeof(GranitNotificationsWolverineModule))]
[DependsOn(typeof(GranitNotificationsEntityFrameworkCoreModule))]
[DependsOn(typeof(GranitNotificationsEndpointsModule))]
public class AppModule : GranitModule
{
    public override void ConfigureServices(ServiceConfigurationContext context)
    {
        // EF Core persistence (replaces in-memory defaults)
        context.Builder.AddGranitNotificationsEntityFrameworkCore(
            opts => opts.UseNpgsql(context.Configuration
                .GetConnectionString("Notifications")));

        // Email channel via SMTP
        context.Services.AddGranitNotificationsEmail(opts => opts.Provider = "Smtp");
        context.Services.AddGranitNotificationsSmtp();

        // SignalR real-time channel with Redis backplane
        context.Services.AddGranitNotificationsSignalR(
            context.Configuration.GetConnectionString("Redis")!);
    }

    public override void OnApplicationInitialization(ApplicationInitializationContext context)
    {
        context.App.MapGranitNotifications();
        context.App.MapHub<NotificationHub>("/hubs/notifications");
    }
}

Development (in-memory)

[DependsOn(typeof(GranitNotificationsModule))]
public class AppModule : GranitModule { }

In-memory stores, in-process Channel<T> dispatch. No database, no outbox. Notifications are lost on crash — suitable for development only.

With Brevo (Email + SMS + WhatsApp)

// One provider for three channels
context.Services.AddGranitNotificationsBrevo();
context.Services.AddGranitNotificationsEmail(opts => opts.Provider = "Brevo");
context.Services.AddGranitNotificationsSms(opts => opts.Provider = "Brevo");
context.Services.AddGranitNotificationsWhatsApp(opts => opts.Provider = "Brevo");

{
  "Notifications": {
    "Brevo": {
      "ApiKey": "vault:secret/data/brevo#api-key",
      "DefaultSenderEmail": "noreply@clinic.example.com",
      "DefaultSenderName": "Clinic Portal",
      "DefaultSmsSenderId": "CLINIC"
    }
  }
}

Building your own *.Notifications package

Modules that emit user-facing events (export ready, payment succeeded, quota exceeded…) ship a sibling Granit.{Module}.Notifications package wiring the event to the fan-out engine and providing the email templates. The notifications package conventions page documents the canonical file layout, the Wolverine handler shape, the <title>-tag subject extraction, the JSON-array *Display companion gotcha, the manifest pinning test, and the embedded-vs-DB template override mechanics.

What’s next

• Fan-Out Engine — multi-channel dispatch, preference filtering, audit trail
• Channels Overview — capability matrix across InApp, Email, SMS, Push, Realtime
• Email Channel — SMTP, SendGrid, Azure, Scaleway, Brevo providers
• SMS, Push & Real-Time — WhatsApp, FCM, SignalR, SSE, Web Push
• Wolverine Integration — durable outbox dispatch with retry
• Data Model — entities, CQRS stores, user preferences
• Endpoints — inbox, preferences, subscriptions, follower REST API
• Configuration — options, health checks, provider selection
• Package Conventions — file layout, Wolverine handler shape, manifest pinning
• Recipes — workflow integration, authorization, encryption patterns

See also

• Templating module — the engine that renders notification subjects and bodies
• Wolverine messaging — outbox pattern and tenant context propagation
• Multi-tenancy — tenant-scoped delivery and preferences
• Set up notifications guide — step-by-step provider wiring
• Blog: Multi-channel notifications in .NET — architectural walkthrough of the channels and fan-out engine