Here’s an example implementation of the Inbox-Outbox pattern in C# using ASP.NET Core and Entity Framework Core.
Inbox Pattern Example
- Inbox Entity: Define an entity to represent the inbox table in the database.
public class Inbox
{
public long Id { get; set; }
public string Message { get; set; }
public bool Processed { get; set; }
public DateTime ReceivedAt { get; set; }
}
- Inbox Repository: Create a repository to interact with the inbox table.
public interface IInboxRepository
{
Task<List<Inbox>> GetUnprocessedMessagesAsync();
Task SaveAsync(Inbox inbox);
}
public class InboxRepository : IInboxRepository
{
private readonly ApplicationDbContext _context;
public InboxRepository(ApplicationDbContext context)
{
_context = context;
}
public async Task<List<Inbox>> GetUnprocessedMessagesAsync()
{
return await _context.Inboxes.Where(i => !i.Processed).ToListAsync();
}
public async Task SaveAsync(Inbox inbox)
{
_context.Inboxes.Update(inbox);
await _context.SaveChangesAsync();
}
}
- Inbox Service: Implement a service to process the inbox messages.
public class InboxService
{
private readonly IInboxRepository _inboxRepository;
public InboxService(IInboxRepository inboxRepository)
{
_inboxRepository = inboxRepository;
}
public async Task ProcessInboxMessagesAsync()
{
var inboxMessages = await _inboxRepository.GetUnprocessedMessagesAsync();
foreach (var inbox in inboxMessages)
{
// Process the message
inbox.Processed = true;
await _inboxRepository.SaveAsync(inbox);
}
}
}
Outbox Pattern Example
- Outbox Entity: Define an entity to represent the outbox table in the database.
public class Outbox
{
public long Id { get; set; }
public string Message { get; set; }
public bool Sent { get; set; }
public DateTime CreatedAt { get; set; }
}
- Outbox Repository: Create a repository to interact with the outbox table.
public interface IOutboxRepository
{
Task<List<Outbox>> GetUnsentMessagesAsync();
Task SaveAsync(Outbox outbox);
}
public class OutboxRepository : IOutboxRepository
{
private readonly ApplicationDbContext _context;
public OutboxRepository(ApplicationDbContext context)
{
_context = context;
}
public async Task<List<Outbox>> GetUnsentMessagesAsync()
{
return await _context.Outboxes.Where(o => !o.Sent).ToListAsync();
}
public async Task SaveAsync(Outbox outbox)
{
_context.Outboxes.Update(outbox);
await _context.SaveChangesAsync();
}
}
- Outbox Service: Implement a service to send the outbox messages.
public class OutboxService
{
private readonly IOutboxRepository _outboxRepository;
public OutboxService(IOutboxRepository outboxRepository)
{
_outboxRepository = outboxRepository;
}
public async Task ProcessOutboxMessagesAsync()
{
var outboxMessages = await _outboxRepository.GetUnsentMessagesAsync();
foreach (var outbox in outboxMessages)
{
// Send the message
outbox.Sent = true;
await _outboxRepository.SaveAsync(outbox);
}
}
}
Integration
You can use a hosted service to periodically call the inbox and outbox service methods to process the messages.
public class MessageProcessingService : IHostedService, IDisposable
{
private Timer _timer;
private readonly InboxService _inboxService;
private readonly OutboxService _outboxService;
public MessageProcessingService(InboxService inboxService, OutboxService outboxService)
{
_inboxService = inboxService;
_outboxService = outboxService;
}
public Task StartAsync(CancellationToken cancellationToken)
{
_timer = new Timer(ProcessMessages, null, TimeSpan.Zero, TimeSpan.FromSeconds(5));
return Task.CompletedTask;
}
private async void ProcessMessages(object state)
{
await _inboxService.ProcessInboxMessagesAsync();
await _outboxService.ProcessOutboxMessagesAsync();
}
public Task StopAsync(CancellationToken cancellationToken)
{
_timer?.Change(Timeout.Infinite, 0);
return Task.CompletedTask;
}
public void Dispose()
{
_timer?.Dispose();
}
}
This implementation ensures that messages are reliably received and sent, providing data consistency across your microservices.