[FEATURE] Encina.Dapr - Dapr PubSub integration

[dlrivada]

Summary

Add Dapr (Distributed Application Runtime) PubSub as a transport abstraction layer.

Motivation

• Dapr abstracts multiple message brokers behind a single API
• Deep integration with .NET Aspire (March 2025)
• Broker-agnostic: switch between Redis, RabbitMQ, Kafka, Azure Service Bus without code changes
• Built-in features: retries, dead-letter, CloudEvents format
• Service invocation for request/reply patterns
• Sidecar architecture simplifies local development

Proposed Solution

New Package

• Encina.Dapr

Interfaces

• IDaprMessagePublisher
• IDaprMessageSubscriber
• IDaprServiceInvoker (for request/reply)

Features

• Pub/Sub messaging via Dapr sidecar
• CloudEvents format (native to Dapr)
• Service invocation for synchronous calls
• Bulk publish support
• Topic subscriptions with routing
• Dead-letter topic handling
• Integration with Dapr Workflows

Configuration

services.AddEncinaDapr(options =>
{
    options.PubSubName = "pubsub";
    options.AppId = "my-app";
    options.DaprHttpPort = 3500;
    options.DaprGrpcPort = 50001;
});

Alternatives Considered

1. Direct broker integration: Implementing each broker directly without Dapr abstraction. This provides more control but requires more code per broker.

2. Custom abstraction layer: Building our own broker abstraction. This is flexible but duplicates what Dapr already provides.

3. Dapr-only architecture: Using Dapr for everything instead of native integrations. This simplifies but may not optimize for specific broker features.

Affected Packages

• Encina (core)
• Encina.AspNetCore
• Encina.EntityFrameworkCore
• Encina.Dapper.*
• Encina.ADO.*
• Encina.MongoDB
• Encina.Messaging
• Encina.Caching.*
• Other: Encina.Dapr

Additional Context

Implementation Tasks

• Create Encina.Dapr package
• Implement publisher via Dapr SDK
• Implement subscriber with topic routing
• Implement service invocation support
• CloudEvents format handling
• Health check integration
• OpenTelemetry traces/metrics (via Dapr built-in)
• Unit tests
• Integration tests with Dapr sidecar

References

• Dapr Pub/Sub Documentation
• .NET Aspire + Dapr
• Dapr .NET SDK

Acceptance Criteria

• Publisher implementation via Dapr SDK
• Subscriber implementation with topic routing
• Service invocation support
• CloudEvents format handling
• Health check integration
• OpenTelemetry traces/metrics (via Dapr built-in)
• Unit tests
• Integration tests with Dapr sidecar

Related Issues

• [FEATURE] CloudEvents format support #260 - CloudEvents Format
• [FEATURE] Encina.Pulsar - Apache Pulsar transport #239 - Apache Pulsar Transport