# Hangfire Usage

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This sample illustrates the use of [Hangfire](https://www.hangfire.io/) to send messages from within an NServiceBus endpoint.

> Hangfire - An easy way to perform background processing in .NET and .NET Core applications. Hangfire is an open-source framework that helps you to create, process and manage your background jobs.



## Running the project

 1. Start both the Scheduler and Receiver projects.
 1. At startup, Scheduler will schedule sending a message to Receiver every minute.
 1. Receiver will handle the message.


## Code Walk-through

### Endpoint Helper

This is a helper class used to make the NServiceBus `IMessageSession` available inside Hangfire jobs. In this sample it is implemented as a static property.

<!-- snippet: EndpointInstance -->

```cs
public static class EndpointHelper
{
    public static IEndpointInstance Instance { get; set; }
}
```

<!-- endsnippet -->

Hangfire also supports Dependency Injection (DI) via the [JobActivator API](https://docs.hangfire.io/en/latest/background-methods/using-ioc-containers.html) for more advanced scenarios.


### Configure and start the scheduler

The endpoint is started, and the `IMessageSession` is stored in the static endpoint helper.

This sample uses in-memory storage for the jobs. Production scenarios should use more robust alternatives: e.g. SQL Server or Redis.

Hangfire calls their scheduler a [BackgroundJobServer](https://docs.hangfire.io/en/latest/background-processing/processing-background-jobs.html). It is started automatically when an instance of the `BackgroundJobServer` class is instantiated.

<!-- snippet: Configuration -->

```cs
var endpointInstance = await Endpoint.Start(endpointConfiguration);

// store the endpointInstance in a static helper class
EndpointHelper.Instance = endpointInstance;

// use in memory storage. Production should use more robust alternatives:
// SqlServer, Redis etc
GlobalConfiguration.Configuration.UseMemoryStorage();

GlobalConfiguration.Configuration.UseColouredConsoleLogProvider();

// create and start scheduler instance
var scheduler = new BackgroundJobServer();
```

<!-- endsnippet -->


### Job definition

This sample passes in an expression pointing to the static `Run` method in `SendMessageJob`.

<!-- snippet: SendMessageJob -->

```cs
public static class SendMessageJob
{
    public static Task Run()
    {
        var endpoint = EndpointHelper.Instance;
        return endpoint.Send("Samples.HangfireScheduler.Receiver", new MyMessage());
    }
}
```

<!-- endsnippet -->

Note that the `EndpointHelper` is used by the job to get access to the `IMessageSession` .


### Schedule a job

Hangfire accepts any lambda expression as a job definition.

The expression is serialized, stored, and scheduled for execution by the `BackgroundJobServer` in Hangfire.

The schedule is set using [Cron](https://en.wikipedia.org/wiki/Cron) syntax through the `Cron` class. In this sample the job gets scheduled to run every minute.

<!-- snippet: scheduleJob -->

```cs
// Tell Hangfire to schedule the job and trigger every minute
RecurringJob.AddOrUpdate("myJob", () => SendMessageJob.Run(), Cron.Minutely);
```

<!-- endsnippet -->


### Cleanup

The Hangfire server should be disposed when the endpoint is shut down.

<!-- snippet: shutdown -->

```cs
scheduler.Dispose();
await endpointInstance.Stop();
```

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The Hangfire scheduler implements the `IDisposable` interface. For cleanup purposes, keep a reference to the scheduler instance and call `Dispose()` at shutdown. Alternatively, use [dependency injection](/nservicebus/dependency-injection/index.md), and let cleanup be automatically be managed.


## Scale Out

Note that in this sample, an instance of the Hangfire scheduler is configured to run in every endpoint instance. If an endpoint is [scaled out](/nservicebus/scaling.md), then the configured jobs will be executed by each of the running instances. A persistent [job storage](https://docs.hangfire.io/en/latest/configuration/index.html) can help to manage the Hangfire scheduler shared state, including jobs, triggers, calendars, etc.


## Further information on Hangfire

 * [Hangfire Quick Start Guide](https://docs.hangfire.io/en/latest/quick-start.html)
 * [Hangfire Tutorials](https://docs.hangfire.io/en/latest/tutorials/index.html)
 * [Dealing with exceptions](https://docs.hangfire.io/en/latest/background-processing/dealing-with-exceptions.html)