Azure WebJobs - multiple background task in single WebJob and Ef error An attempt was made to use the context while it is being configured

Question

I have multiple background Batch jobs to Run and I have been asked to have single webJob to run all task, which I need to schedule to run at different time.

I have used Timer feature from webJob.Extensions.

i.e in the Program.cs

var config = new JobHostConfiguration
            {
                JobActivator = new AutofacActivator(ContainerConfig<Functions>.GetContainer())
            };

            if (config.IsDevelopment)
            {
                config.UseDevelopmentSettings();
            }
            config.UseTimers();

            var host = new JobHost(config);
            host.RunAndBlock();

And the function will have multiple method and are triggered in interval of 30 min.

public void ProcessMethod1([TimerTrigger("0 0/30 * * * *")] TimerInfo timer)
{
   //Logic
}

public void ProcessMethod2([TimerTrigger("0 0/30  * * * *")] TimerInfo timer)
{
   //Logic
}

Issue: Since I am using Autofac DI. I am creating the instance for dbContext at the start of the Job

JobActivator = new AutofacActivator(ContainerConfig<Functions>.GetContainer())

While executing the webJob I am getting errors while executing DB select like "An attempt was made to use the context while it is being configured".

Since I gave scope as InstancePerLifetimeScope(). I want to know if the Two operation will get same instance?

Also for Logging I have similar issue, since it looks like only one instance is created for these two different Operation.

All I want is to have separate instance for both DBCOntext and Logger based on operation. Pls advise me how I can set DI for this scenario.

Update:

public class AutofacActivator: IJobActivator
    {
        private readonly Autofac.IContainer _container;

        public AutofacActivator(Autofac.IContainer container)
        {
            _container = container;
        }

        public T CreateInstance<T>()
        {
            return _container.Resolve<T>();
        }
    }

 internal class WebJobIocModule<T> : Autofac.Module
    {
        protected override void Load(ContainerBuilder builder)
        {
            if (builder == null)
                throw new ArgumentNullException("WebJobBuilder");


            //Cascade  
            builder.RegisterModule(new BusinessObjectIocModule());

            // Register the functions class - WebJobs will discover our triggers this way
            builder.RegisterType<T>();
        }
    }



  public class BusinessObjectIocModule :Autofac.Module
    {
        protected override void Load(ContainerBuilder builder)
        {
            if(builder == null) throw new ArgumentNullException("BusinessObjectBuilder");


            //Cascade
            builder.RegisterModule(new DataAccessRepoIocModule());

            builder.RegisterType<BusinessObjBpc>().AsImplementedInterfaces();

        }
    }

In DataAccessIOC:

 string connectionString = ConfigurationManager.ConnectionStrings["DBConnectionAppKeyName"].ConnectionString;
            optionsStagingBuilder.UseSqlServer(connectionString);

            builder.RegisterType<DataAccessDbContext>()
                .AsSelf()
                .WithParameter("options", optionsStagingBuilder.Options)
                .InstancePerLifetimeScope();

Answer 1

If you use a LifetimeScope for the DbContext you should make sure that you make a new scope in each execution of the processing methods, by using code like this:

public void ProcessMethod1([TimerTrigger("0 0/30 * * * *")] TimerInfo timer)
{
    using (var scope = container.BeginLifetimeScope())
    {
        //Logic
    }
}

It would work, but I think it may have side effects. Also, for other components it is more efficient not to instantiate them in each execution of the processing methods. Perhaps you would like to use a different scope.

Update - How to inject the container in the function constructor:

In your constructor you can use a parameter Func<IContainer> instead of a IContainer. It will work as a container factory.

When you build your container (at the beginning of the job, at the point where you build your container) you register the instance of your container factory:

Func<IContainer> containerFactory = () => yourContainer;
...
builder.RegisterInstance(containerFactory);

Then in your constructor you let Autofac inject the factory and you store the container in a property:

public SomeConstructor(Func<IContainer> containerFactory, ...<other injected params>)
{
    ...
    this.container = containerFactory();
}