# Automatic Retries


This sample shows the different ways that NServiceBus [recoverability features](/nservicebus/recoverability/index.md) retry messages that have failed.

## Running the sample

Run the sample **without debugging**.

The message handler in both endpoints (`WithoutDelayedRetries` and `WithDelayedRetries`) is set to throw an exception, causing the handled message to end up in the error queue. The portable Particular Service Platform will list the messages arriving in the error queue.

<!-- snippet: handler -->

```cs
public class MyMessageHandler : IHandleMessages<MyMessage>
{
    public Task Handle(MyMessage message, IMessageHandlerContext context)
    {
        Console.WriteLine($"Handling {nameof(MyMessage)} with MessageId:{context.MessageId}");
        throw new Exception("An exception occurred in the handler.");
    }
}
```

<!-- endsnippet -->

The `WithDelayedRetries` endpoint uses the standard Delayed Retries settings.

The `WithoutDelayedRetries` endpoint disables Delayed Retries with the following:

<!-- snippet: Disable -->

```cs
var endpointConfiguration = new EndpointConfiguration("Samples.ErrorHandling.WithoutDelayedRetries");
var recoverability = endpointConfiguration.Recoverability();
recoverability.Delayed(
    customizations: delayed =>
    {
        delayed.NumberOfRetries(0);
    });
```

<!-- endsnippet -->

## The output

> [!WARNING]
> This sample uses `Console.WriteLine` instead of standard logging only for brevity and should not be used in production code.

### Without Delayed Retries

In this endpoint, the message is retried successively without any delay and then, after the final failure, it is forwarded to the configured error queue.

```bash
Handling MyMessage with MessageId:b5d0ea24-63c7-4729-8fd3-a6dc0161a7f8
Handling MyMessage with MessageId:b5d0ea24-63c7-4729-8fd3-a6dc0161a7f8
Handling MyMessage with MessageId:b5d0ea24-63c7-4729-8fd3-a6dc0161a7f8
Handling MyMessage with MessageId:b5d0ea24-63c7-4729-8fd3-a6dc0161a7f8
Handling MyMessage with MessageId:b5d0ea24-63c7-4729-8fd3-a6dc0161a7f8
Handling MyMessage with MessageId:b5d0ea24-63c7-4729-8fd3-a6dc0161a7f8
2016-12-14 13:27:41.232 ERROR NServiceBus.RecoverabilityExecutor Moving message 'b5d0ea24-63c7-4729-8fd3-a6dc0161a7f8' to the error queue 'error' because processing failed due to an exception:
System.Exception: An exception occurred in the handler.
```

### With Delayed Retries

In this endpoint, the message is first [retried immediately](/nservicebus/recoverability/index.md#immediate-retries), then retried again after a [configured delay](/nservicebus/recoverability/configure-delayed-retries.md). After the final configured retry, the message is moved to the error queue. The sample displays the retry number for clarity.

```bash
This is retry number 1
Handling MyMessage with MessageId:05b97154-04b9-405a-92d7-a6dc0163273f
Handling MyMessage with MessageId:05b97154-04b9-405a-92d7-a6dc0163273f
Handling MyMessage with MessageId:05b97154-04b9-405a-92d7-a6dc0163273f
Handling MyMessage with MessageId:05b97154-04b9-405a-92d7-a6dc0163273f
Handling MyMessage with MessageId:05b97154-04b9-405a-92d7-a6dc0163273f
2016-12-14 13:33:18.790 WARN  NServiceBus.RecoverabilityExecutor Delayed Retry will reschedule message '05b97154-04b9-405a-92d7-a6dc0163273f' after a delay of 00:00:20 because of an exception:
System.Exception: An exception occurred in the handler.
. . .
Handling MyMessage with MessageId:05b97154-04b9-405a-92d7-a6dc0163273f
This is retry number 2
Handling MyMessage with MessageId:05b97154-04b9-405a-92d7-a6dc0163273f
Handling MyMessage with MessageId:05b97154-04b9-405a-92d7-a6dc0163273f
Handling MyMessage with MessageId:05b97154-04b9-405a-92d7-a6dc0163273f
Handling MyMessage with MessageId:05b97154-04b9-405a-92d7-a6dc0163273f
Handling MyMessage with MessageId:05b97154-04b9-405a-92d7-a6dc0163273f
2016-12-14 13:33:40.886 WARN  NServiceBus.RecoverabilityExecutor Delayed Retry will reschedule message '05b97154-04b9-405a-92d7-a6dc0163273f' after a delay of 00:00:30 because of an exception:
System.Exception: An exception occurred in the handler.
. . .
Handling MyMessage with MessageId:05b97154-04b9-405a-92d7-a6dc0163273f
This is retry number 3
Handling MyMessage with MessageId:05b97154-04b9-405a-92d7-a6dc0163273f
Handling MyMessage with MessageId:05b97154-04b9-405a-92d7-a6dc0163273f
Handling MyMessage with MessageId:05b97154-04b9-405a-92d7-a6dc0163273f
Handling MyMessage with MessageId:05b97154-04b9-405a-92d7-a6dc0163273f
Handling MyMessage with MessageId:05b97154-04b9-405a-92d7-a6dc0163273f
2016-12-14 13:34:15.750 ERROR NServiceBus.RecoverabilityExecutor Moving message '05b97154-04b9-405a-92d7-a6dc0163273f' to the error queue 'error' because processing failed due to an exception:
System.Exception: An exception occurred in the handler.
. . .
```