Dependency injection using Azure WebJobs SDK?

Question

The problem is that the Azure WebJobs SDK supports only public static methods as job entry-points which means there is no way of implementing constructor/property injection.

I am unable to find anything about this topic in official WebJobs SDK documentation/resources. The only solution that I came across is based on service locator (anti) pattern described on this post here.

Is there a good way to use "proper" dependency injection for projects based on Azure WebJobs SDK?

Answer 1

Azure WebJobs SDK now supports instance methods. Combining this with a custom IJobActivator allows you to use DI.

First, create the custom IJobActivator that can resolve a job type using your favourite DI container:

public class MyActivator : IJobActivator {     private readonly IUnityContainer _container;      public MyActivator(IUnityContainer container)     {         _container = container;     }      public T CreateInstance<T>()     {         return _container.Resolve<T>();     } } 

You need to register this class using a custom JobHostConfiguration:

var config = new JobHostConfiguration {     JobActivator = new MyActivator(myContainer) }; var host = new JobHost(config); 

Then, you can use a simple class with instance methods for your jobs (here I'm using Unity's constructor injection feature):

public class MyFunctions {     private readonly ISomeDependency _dependency;      public MyFunctions(ISomeDependency dependency)     {         _dependency = dependency;     }      public Task DoStuffAsync([QueueTrigger("queue")] string message)     {         Console.WriteLine("Injected dependency: {0}", _dependency);          return Task.FromResult(true);     } } 

Answer 2

This is how I handled scoping using the new SDK. Using the IJobactivator as described by Alexander Molenkamp.

public class ScopedMessagingProvider : MessagingProvider {     private readonly ServiceBusConfiguration _config;     private readonly Container _container;      public ScopedMessagingProvider(ServiceBusConfiguration config, Container container)         : base(config)     {         _config = config;         _container = container;     }      public override MessageProcessor CreateMessageProcessor(string entityPath)     {         return new CustomMessageProcessor(_config.MessageOptions, _container);     }      private class CustomMessageProcessor : MessageProcessor     {         private readonly Container _container;          public CustomMessageProcessor(OnMessageOptions messageOptions, Container container)             : base(messageOptions)         {             _container = container;         }          public override Task<bool> BeginProcessingMessageAsync(BrokeredMessage message, CancellationToken cancellationToken)         {             _container.BeginExecutionContextScope();             return base.BeginProcessingMessageAsync(message, cancellationToken);          }          public override Task CompleteProcessingMessageAsync(BrokeredMessage message, FunctionResult result, CancellationToken cancellationToken)         {             var scope = _container.GetCurrentExecutionContextScope();             if (scope != null)             {                 scope.Dispose();             }              return base.CompleteProcessingMessageAsync(message, result, cancellationToken);         }     } } 

You can the use your custom MessagingProvider in your JobHostConfiguration like

var serviceBusConfig = new ServiceBusConfiguration {      ConnectionString = config.ServiceBusConnectionString }; serviceBusConfig.MessagingProvider = new ScopedMessagingProvider(serviceBusConfig, container); jobHostConfig.UseServiceBus(serviceBusConfig);