Hangfire recurring job to call method is Startup using existing services

Question

I'm trying to setup Hangfire to run a recurring job within Startup.cs with a standalone method. For this to work, I need to grab some ApplicationServices I have injected already. But the job execution fails with this error:

Recurring job 'Job: Dispatch Email from Queue' can't be scheduled due to an error and will be retried in 00:00:15.
System.InvalidOperationException: Recurring job can't be scheduled, see inner exception for details.
 ---> Hangfire.Common.JobLoadException: Could not load the job. See inner exception for the details.
 ---> Newtonsoft.Json.JsonSerializationException: Could not create an instance of type DA.BrrMs.Application.Interfaces.ServiceInterfaces.IBudgetReleaseRequestService. Type is an interface or abstract class and cannot be instantiated.

Here is what I have:

public class Startup
{
    private IConfiguration Configuration { get; }

     private RecurringJobManager _jobManager;

    public Startup(IConfiguration configuration) => Configuration = configuration;

    public void ConfigureServices(IServiceCollection services)
    {
        ...

        if (Configuration["SystemSettings:UseHangfire"] == "1")
        {
            services.AddHangfire(c => c.UseMemoryStorage());
            JobStorage.Current = new MemoryStorage();
            services.AddHangfireServer();
            GlobalConfiguration.Configuration.UseMemoryStorage();
        }

        RegisterServices(services);
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        ...

        var requestService = app.ApplicationServices.GetService<IBudgetReleaseRequestService>();
        var mailService    = app.ApplicationServices.GetService<IMailer>();

        _jobManager = new RecurringJobManager();
        _jobManager.AddOrUpdate("Job: Dispatch Email from Queue", () => StartupMailJob(requestService, mailService), Cron.Minutely);
    }

    private static void RegisterServices(IServiceCollection services) => DependencyContainer.RegisterServices(services);

    public static async Task StartupMailJob(IBudgetReleaseRequestService requestService, IMailer mailService)
    {
        try
        {
            var emailsToSend = await requestService.DispatchEmails();

            // Send emails
            foreach (var emailToSend in emailsToSend)
            {

            }

            // Update status of sent                
        }
        catch (Exception e)
        {
            Console.WriteLine(e);
        }
    }

}

// In a project, far far away...

public static void RegisterServices(IServiceCollection services)
{
    ...
    services.AddScoped<IBudgetReleaseRequestService, BudgetReleaseRequestService>();
    ...
}

How do I satisfy Hangfire's requirment of a class instance instead of an interface?

Answer 1

Here is the implementation that I found best worked for me:

1 Register the service I wanted to schedule in Startup.cs

 services.AddScoped<IMyJob, MYJob>();

2 Created an activator class that is used to define the scope for the execution of the job.

public class HangFireActivatorMyJob : IHangFireActivatorMyJob
{
    private readonly IServiceProvider _serviceProvider;

    public HangFireActivatorMyJob (IServiceProvider serviceProvider)
    {
        this._serviceProvider = serviceProvider ?? throw new ArgumentNullException(nameof(serviceProvider));
    }

    public async Task Run(IJobCancellationToken token)
    {
        token.ThrowIfCancellationRequested();
        await RunAtTimeOf(DateTime.Now);
    }

    public async Task RunAtTimeOf(DateTime now)
    {
        using IServiceScope scope = this._serviceProvider.CreateScope();
        var myJobService= scope.ServiceProvider.GetRequiredService<IMyJob>();
        await myJobService.RunSomeTaskOnJob();
    }
}

3 Register the activator

services.AddTransient<IHangFireActivatorMyJob, HangFireActivatorMyJob >();

4 Add the IRecurringJobManager interface to the configure method within Startup.cs

 public void Configure(
      IApplicationBuilder app,
      IWebHostEnvironment env,
      IRecurringJobManager recurringJobManager)

5 Add the job to the provided IRecurringJobManager

recurringJobManager.AddOrUpdate<HangFireActivatorMyJob >(nameof(HangFireActivatorMyJob ),
                job => serviceProvider.GetRequiredService<IHangFireActivatorMyJob>()
                    .Run(JobCancellationToken.Null)
                , Cron.Hourly(3), TimeZoneInfo.Utc);