Hangfire.Autofac

Autofac integration for Hangfire. Provides an implementation of the JobActivator class and registration extensions, allowing you to use Autofac container to resolve job type instances as well as control the lifetime of the all related dependencies.

Hangfire.Autofac resolves service instances using a child, tagged lifetime scope. A child scope is created and disposed each time when background job processing takes place, so you have precise control of your service's lifetime, including shared instances and deterministic disposal.

Installation

Hangfire.Autofac is available as a NuGet Package. Type the following command into NuGet Package Manager Console window to install it:

> dotnet add package Hangfire.Autofac

Usage

The package provides an extension methods for the IGlobalConfiguration interface, so you can enable Autofac integration using the GlobalConfiguration class:

var builder = new ContainerBuilder();
// builder.Register...

GlobalConfiguration.Configuration.UseAutofacActivator(builder.Build());

After invoking the UseAutofacActivator method, Autofac-based implementation of the JobActivator class will be used to resolve job type instances during the background job processing.

Shared Components

Sometimes it is required to share the same service instance for different components, such as database connection, unit of work, etc. Hangfire.Autofac allows you to share them in a scope, limited to the current background job processing, just call the InstancePerBackgroundJob method in your component registration logic:

builder.RegisterType<Database>().InstancePerBackgroundJob();

Non-tagged scopes

Whenever the scopes in AutofacActivator are created, by default they are created using tag BackgroundJobScope. There might be a scenario when it is needed not to use tagged scopes though. This might be a case if it is required to have a new instance of every service for each lifetime scope (in Hangfire it would be for every job). To disable tagged scopes you can use a flag useTaggedLifetimeScope during initialization of AutofacActivator for Hangfire.

var builder = new ContainerBuilder();
// builder.Register...

GlobalConfiguration.Configuration.UseAutofacActivator(builder.Build(), false);

Then you can register services by using InstancePerLifetimeScope and expect them to work like intended.

builder.RegisterType<Database>().InstancePerLifetimeScope();

Deterministic Disposal

The child lifetime scope is disposed as soon as current background job is performed, successfully or with an exception. Since Autofac automatically disposes all the components that implement the IDisposable interface (if this feature not disabled), all of the resolved components will be disposed if appropriate.

For example, the following components will be disposed automatically:

builder.RegisterType<SmsService>();
builder.RegisterType<EmailService>().InstancePerDependency();
builder.RegisterType<Database>().InstancePerBackgroundJob();

And the following components will not be disposed:

builder.RegisterType<BackgroundJobClient>().SingleInstance();
builder.RegisterType<MyService>().ExternallyOwned();

Please refer to the Autofac documentation to learn more about Automatic Disposal feature.

Registering With Multiple Lifetime Scopes

Services registered with tagged lifetime scopes (eg InstancePerBackgroundJob, Autofac's InstancePerRequest or a scope your specific application requires) will not resolve outside of these named scopes, a common situation is when using Hangfire in an ASP.NET web application. In these situations you must register all your lifetimescopes together if you want the services to be resolved from any of the scopes. Hangfire.Autofac exposes it's lifetime tag and an overload of InstancePerBackgroundJob to help you do this.

To register a service with both Autofac's PerRequest and Hangfire's PerBackgroundJob you could do any of the following:

Passing Hangfire's scope tag to Autofac's InstancePerHttpRequest:

builder.RegisterType<SharedService>().InstancePerHttpRequest(AutofacJobActivator.LifetimeScopeTag);

From Autofac 3.4.0 Autofac exposed their lifetime tag, MatchingScopeLifetimeTags.RequestLifetimeScopeTag, which can be used with InstancePerBackgroundJob:

builder.RegisterType<SharedService>().InstancePerBackgroundJob(MatchingScopeLifetimeTags.RequestLifetimeScopeTag);

Both scope tags can also be used directly with Autofac's InstancePerMatchingLifetimeScope

var requestTag = MatchingScopeLifetimeTags.RequestLifetimeScopeTag;
var jobTag = AutofacJobActivator.LifetimeScopeTag;
builder.RegisterType<SharedService>().InstancePerMatchingLifetimeScope(requestTag, jobTag);

Mixed Lifetime Scopes

Beaware that if you are using multiple lifetime scopes to share services that all dependencies of those services need to be similarly registered. For example:

public class WebOnlyService(){ ... }
public class SharedService(WebOnlyService){ ... }

builder.RegisterType<SharedService>().InstancePerRequest();
builder.RegisterType<SharedService>().InstancePerMatchingLifetimeScope(requestTag, jobTag);

Attempting to resolve SharedService from a background job will throw an exception as Autofac will need to resolve WebOnlyService outside of a RequestLifetimeScope.

Also be aware that many web related properties that you may be using such as HttpContext.Current will be unavailable.