Azure Triggered Webjobs Scope for Dependency Injection

Question

I've read and asked some questions on how to use DI using WebJob and especially Triggered Webjobs.

I still try to figure out how to integrate gracefully DI in triggered webjobs and @Steven asked me a good question :

Isn't there a way to wrap the execution of your service in some scope? For instance, MVC and Web API have an IDependencyScope abstraction for this. This notifies the starting and ending of a request. To be able to do scoping, you either need to have such interception point or you need to be able to wrap the call to JobActivator.

I know that I can start a scope inside my triggered function but I would like to know if there are any point of extensibility in the sdk that allow us to do scoping ?

Thanks.

Doesn't this answer on the post you linked already answer your question? — TylerOhlsen
@TylerOhlsen, in fact not... I am able to create instance of my service each time my function is triggered but I am not able to find the proper scope so that I will be able to dispose resources... I will update my older answer. Thanks. — Thomas
When I create Azure WebJobs, I create them as standard console applications; I don't use the SDK at all. In a standard console application, the Main method is the Composition Root. Problem solved. — Mark Seemann
@MarkSeemann, I would like to take advantage of the webjob sdk ^^ — Thomas
I need this to be answered as well... I was using InRequestScope() because I copied it from my MVC app, but then it definitely doesn't work when you start running a static function multiple times. I would need to have something like .InWebJobScope() — jsgoupil

Thomas Thomas · Accepted Answer · 2016-04-06T23:21:07

I've opened an request Add IDependencyScope to handle scoping to the Azure Webjob team.

I've create a small library to gather classes around Azure Webjobs and SimpleInjector :

For QueueTrigger and ServiceBustrigger, I've come accross these solutions :

ServiceBusTrigger (from this answer: https://stackoverflow.com/a/33759649/4167200):

public sealed 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 ScopedMessageProcessor(_config.MessageOptions, _container);
    }

    private class ScopedMessageProcessor : MessageProcessor
    {
        private readonly Container _container;

        public ScopedMessageProcessor(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)
        {
            _container.GetCurrentExecutionContextScope()?.Dispose();
            return base.CompleteProcessingMessageAsync(message, result, cancellationToken);
        }
    }
}

You can use your custom MessagingProvider in your JobHostConfiguration like

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

QueueTrigger:

public sealed class ScopedQueueProcessorFactory : IQueueProcessorFactory
{
    private readonly Container _container;

    public ScopedQueueProcessorFactory(Container container)
    {
        _container = container;
    }

    public QueueProcessor Create(QueueProcessorFactoryContext context)
    {
        return new ScopedQueueProcessor(context, _container);
    }

    private class ScopedQueueProcessor : QueueProcessor
    {
        private readonly Container _container;

        public ScopedQueueProcessor(QueueProcessorFactoryContext context, Container container)
            : base(context)
        {
            _container = container;
        }

        public override Task<bool> BeginProcessingMessageAsync(CloudQueueMessage message, CancellationToken cancellationToken)
        {
            _container.BeginExecutionContextScope();
            return base.BeginProcessingMessageAsync(message, cancellationToken);
        }

        public override Task CompleteProcessingMessageAsync(CloudQueueMessage message, FunctionResult result,
            CancellationToken cancellationToken)
        {
            _container.GetCurrentExecutionContextScope()?.Dispose();
            return base.CompleteProcessingMessageAsync(message, result, cancellationToken);
        }
    }
}

You can use your custom IQueueProcessorFactory in your JobHostConfiguration like this:

 var config = new JobHostConfiguration();
 config.Queues.QueueProcessorFactory = new ScopedQueueProcessorFactory(container);

Azure Triggered Webjobs Scope for Dependency Injection

1 Answers