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Dead-Letter EF Core Integration

The Hermodr.Publisher.DeadLetter.EntityFramework package provides a ready-made EF implementation.

What's Included​

TypePurpose
DbDeadLetterMessageConcrete dead-letter entity implementing IDeadLetterMessage
DbDeadLetterAttributeStores CloudEvents extension attributes
DeadLetterDbContextMinimal EF DbContext for dead-letter storage
EntityDeadLetterMessageStore<TMessage>EF-backed IDeadLetterMessageStore implementation
DefaultDeadLetterMessageFactory<TMessage>Converts DeadLetterContext into DbDeadLetterMessage
using Hermodr;
using Microsoft.EntityFrameworkCore;

services.AddEventPublisher(options =>
    {
        options.Source = new Uri("https://orders.example.com");
        options.ThrowOnErrors = false;
    })
    .AddRabbitMq(options =>
    {
        options.ConnectionString = "amqp://guest:guest@localhost:5672";
        options.ExchangeName = "orders";
    })
    .AddDeadLetter()
    .WithEntityFramework(options =>
        options.UseSqlite("Data Source=deadletters.db"))
    .WithReplayWorker(options =>
    {
        options.Interval = TimeSpan.FromSeconds(30);
        options.MaxRetryCount = 3;
        options.RetryInterval = TimeSpan.FromMinutes(1);
    });

What DbDeadLetterMessage Stores​

DbDeadLetterMessage maps the most important CloudEvents data as columns:

  • Id, EventType, Source, Subject, EventTime
  • DataContentType, DataSchema
  • Event payload in DataText or DataBytes
  • Replay metadata: Status, ReplayCount, NextReplayAt, CreatedAt, LastStatusAt
  • Channel and publisher metadata: PublisherName, ChannelName, ChannelType

CloudEvents extension attributes are stored in child rows through DbDeadLetterAttribute.

Creating the Database​

The package provides model configuration through DeadLetterDbContext. Create the database the same way you would for any other EF Core context:

await using var scope = host.Services.CreateAsyncScope();
var db = scope.ServiceProvider.GetRequiredService<DeadLetterDbContext>();
await db.Database.EnsureCreatedAsync();

Or use migrations if you want the dead-letter tables to be managed as part of your normal schema lifecycle.