Handle Failures¶

Subscriber failures can happen during deserialization, handler execution or acknowledgement.

ServiceBus.Core exposes hooks that allow applications to observe and react to failures.

Processing Handler¶

subscriber.Received.Add(
    async (sender, args) =>
    {
        try
        {
            var message = args.Message.Data;

            Console.WriteLine(
                $"processing order: {message.OrderId}");

            args.Acknowledged = true;
            args.Requeue = false;
        }
        catch
        {
            args.Acknowledged = false;
            args.Requeue = true;

            throw;
        }

        await Task.CompletedTask;
    });

Exception Event¶

subscriber.OnException.Add(
    async (sender, args) =>
    {
        Console.WriteLine(
            $"subscriber exception: {args.Exception.Message}");

        await Task.CompletedTask;
    });

Max Retry Event¶

subscriber.OnMaxRetryFailed.Add(
    async (sender, args) =>
    {
        Console.WriteLine(
            $"max retry failed: {args.Exception.Message}");

        await Task.CompletedTask;
    });

Failure Flow¶

graph TD
    Message --> Handler
    Handler --> Success
    Handler --> Failure
    Failure --> Retry
    Retry --> Handler
    Failure --> ErrorHandling

Acknowledgement Strategy¶

Scenario	Acknowledged	Requeue
Message processed successfully	`true`	`false`
Temporary failure	`false`	`true`
Invalid message	`false`	`false`

Guidance¶

Keep failure handlers focused on observability and recovery.

Avoid placing complex business logic inside failure events.