# Set Up Crons | Sentry for ASP.NET Core

Once implemented, it'll allow you to get alerts and metrics to help you solve errors, detect timeouts, and prevent disruptions to your service.

If you are using [Hangfire](https://www.hangfire.io/), please see [how to setup monitoring for Hangfire jobs](https://docs.sentry.io/platforms/dotnet/guides/aspnetcore/crons/hangfire.md).

## [Requirements](https://docs.sentry.io/platforms/dotnet/guides/aspnetcore/crons.md#requirements)

* Use our [getting started](https://docs.sentry.io/platforms/dotnet/guides/aspnetcore.md) guide to install and configure the Sentry .NET SDK (min 4.2.0) for your recurring job.
* [Create and configure](https://sentry.io/crons/create/) your first Monitor.

## [Check-Ins (Recommended)](https://docs.sentry.io/platforms/dotnet/guides/aspnetcore/crons.md#check-ins-recommended)

Check-in monitoring allows you to track a job's progress by completing two check-ins: one at the start of your job and another at the end of your job. This two-step process allows Sentry to notify you if your job didn't start when expected (missed) or if it exceeded its maximum runtime (failed).

```csharp
// 🟡 Notify Sentry your job is running:
var checkInId = SentrySdk.CaptureCheckIn("<monitor-slug>", CheckInStatus.InProgress);

// Execute your scheduled task here...

// 🟢 Notify Sentry your job has completed successfully:
SentrySdk.CaptureCheckIn("<monitor-slug>", CheckInStatus.Ok, checkInId);
```

If your job execution fails, you can notify Sentry about the failure:

```csharp
// 🔴 Notify Sentry your job has failed:
SentrySdk.CaptureCheckIn("<monitor-slug>", CheckInStatus.Error, checkInId);
```

## [Alerts](https://docs.sentry.io/platforms/dotnet/guides/aspnetcore/crons.md#alerts)

When your recurring job fails to check in (missed), runs beyond its configured maximum runtime (failed), or manually reports a failure, Sentry will create an error event with a tag to your monitor.

To receive alerts about these events:

1. Navigate to **Alerts** in the sidebar.
2. Create a new alert and select "Issues" under "Errors" as the alert type.
3. Configure your alert and define a filter match to use: `The event's tags match {key} {match} {value}`.

Example: `The event's tags match monitor.slug equals my-monitor-slug-here`

[![Cron completed alert filter](https://docs.sentry.io/_next/image/?url=%2Fmdx-images%2Fcrons-alerts-example-CJJAWX24.png%231956x1084\&w=3840\&q=75)](https://docs.sentry.io/mdx-images/crons-alerts-example-CJJAWX24.png)

Learn more in [Issue Alert Configuration](https://docs.sentry.io/product/alerts/create-alerts/issue-alert-config.md).

## [Rate Limits](https://docs.sentry.io/platforms/dotnet/guides/aspnetcore/crons.md#rate-limits)

Crons imposes a rate limit on check-ins to prevent abuse and resource overuse. Specifically, you can only send a maximum of **6 check-ins per minute per existing monitor environment**. This limit is enforced on a per-project basis, meaning that the rate limit applies collectively to all monitor environments within a given project. You can check if any of your check-ins are being dropped in the [Usage Stats](https://docs.sentry.io/product/stats.md#usage-stats) page.

To avoid dropped check-ins, it is crucial to manage and distribute your check-ins efficiently within the rate limits. This will help maintain accurate monitoring and ensure that all critical check-ins are captured and processed.
