Impossible to use dependency injection in an Hangfire job - asp.net-core

Question

Context
I use Hangfire (version 1.7.11) as a scheduler. But I can't use proper DI in my jobs.
What works so far
I have no problem scheduling something like this, given the fact SomeConcreteService have a parameterless constructor:
RecurringJob.AddOrUpdate<SomeConcreteService>(jobId, mc => Console.WriteLine(
$"Message from job: {mc.GetValue()}"), "1/2 * * * *");
What does not work
But I get an exception when I try to inject a service into a Hangfire job using what is recommended here: https://docs.hangfire.io/en/latest/background-methods/using-ioc-containers.html
When I try to add a new scheduled job using DI, I get the following exception:
Exception thrown: 'System.InvalidOperationException' in System.Linq.Expressions.dll: 'variable 'mc' of type 'TestHangfire.IMyContract' referenced from scope '', but it is not defined'
The exception occurs a this line:
RecurringJob.AddOrUpdate<IMyContract>(jobId, mc => Console.WriteLine(
$"Message from job {jobId} => {mc.GetValue()}"), "1/2 * * * *");
The problem is so trivial that I am sure I am missing something obvious.
Thanks for helping.
The (nearly) full code
Service:
public interface IMyContract
{
string GetValue();
}
public class MyContractImplementation : IMyContract
{
public string _label;
public MyContractImplementation(string label)
{
_label = label;
}
public string GetValue() => $"{_label}:{Guid.NewGuid()}";
}
2 kinds of activators:
public class ContainerJobActivator : JobActivator
{
private IServiceProvider _container;
public ContainerJobActivator(IServiceProvider serviceProvider) =>
_container = serviceProvider;
public override object ActivateJob(Type type) => _container.GetService(type);
}
public class ScopedContainerJobActivator : JobActivator
{
readonly IServiceScopeFactory _serviceScopeFactory;
public ScopedContainerJobActivator(IServiceProvider serviceProvider)
{
_serviceScopeFactory = serviceProvider.GetService<IServiceScopeFactory>();
}
public override JobActivatorScope BeginScope(JobActivatorContext context) =>
new ServiceJobActivatorScope(_serviceScopeFactory.CreateScope());
private class ServiceJobActivatorScope : JobActivatorScope
{
readonly IServiceScope _serviceScope;
public ServiceJobActivatorScope(IServiceScope serviceScope) =>
_serviceScope = serviceScope;
public override object Resolve(Type type) =>
_serviceScope.ServiceProvider.GetService(type);
}
}
Startup:
public class Startup
{
public void ConfigureServices(IServiceCollection services)
{
services.AddHangfire(configuration => configuration
.SetDataCompatibilityLevel(CompatibilityLevel.Version_170)
.UseSimpleAssemblyNameTypeSerializer()
.UseRecommendedSerializerSettings()
.UseSqlServerStorage("connection string", new SqlServerStorageOptions
{
CommandBatchMaxTimeout = TimeSpan.FromMinutes(5),
SlidingInvisibilityTimeout = TimeSpan.FromMinutes(5),
QueuePollInterval = TimeSpan.Zero,
UseRecommendedIsolationLevel = true,
UsePageLocksOnDequeue = true,
DisableGlobalLocks = true
}));
services.AddHangfireServer();
services.BuildServiceProvider();
services.AddScoped<IMyContract>(i => new MyContractImplementation("blabla"));
// doesn't work either
// services.AddSingleton<IMyContract>(i => new MyContractImplementation("blabla"));
// doesn't work either
// services.AddTransient<IMyContract>(i => new MyContractImplementation("blabla"));
}
public void Configure(
IApplicationBuilder app,
IWebHostEnvironment env,
IServiceProvider serviceProvider)
{
// Just to ensure the service is correctly injected...
Console.WriteLine(serviceProvider.GetService<IMyContract>().GetValue());
// I face the problem for both activators: ScopedContainerJobActivator or ContainerJobActivator
GlobalConfiguration.Configuration.UseActivator(new ContainerJobActivator(serviceProvider));
// GlobalConfiguration.Configuration.UseActivator(new ScopedContainerJobActivator(serviceProvider));
app.UseRouting();
app.UseHangfireDashboard();
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
app.UseEndpoints(endpoints =>
{
endpoints.MapGet("/", async context =>
{
await context.Response.WriteAsync(
JsonSerializer.Serialize(
Hangfire.JobStorage.Current.GetConnection().GetRecurringJobs()
.Select(i => new { i.Id, i.CreatedAt, i.Cron }).ToList()));
});
endpoints.MapGet("/add", async context =>
{
var manager = new RecurringJobManager();
var jobId = $"{Guid.NewGuid()}";
// I GET AN EXCEPTION HERE:
// Exception thrown: 'System.InvalidOperationException' in System.Linq.Expressions.dll: 'variable 'mc' of type 'TestHangfire.IMyContract' referenced from scope '', but it is not defined'
manager.AddOrUpdate<IMyContract>(jobId, mc => Console.WriteLine(
$"Message from job {jobId} => {mc.GetValue()}"), "1/2 * * * *");
// doesn't work either: it's normal, it is just a wrapper of what is above
// RecurringJob.AddOrUpdate<IMyContract>(jobId, mc => Console.WriteLine($"Message from job {jobId} => {mc.GetValue()}"), "1/2 * * * *");
await context.Response.WriteAsync($"Schedule added: {jobId}");
});
});
}
}

Answer 1

I found the issue.
As it was actually the expression that seemed to cause an issue, and given the fact that the other way to add a recurring job is to transmit a type, and a method info, it seemed to me that the problem was caused by an expression that was too evolved. So I changed the approach to have a method of my service that make the whole job by being given a parameter.
Here is the new code that works:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Hangfire;
using Hangfire.SqlServer;
using Hangfire.Storage;
using System.Text.Json;
namespace TestHangfire
{
#region Service
public interface IMyContract
{
void MakeAction(string someText);
}
public class MyContractImplementation : IMyContract
{
public string _label;
public MyContractImplementation(string label)
{
_label = label;
}
public void MakeAction(string someText) => Console.WriteLine($"{_label}:{someText}");
}
#endregion
#region 2 kinds of activators
public class ContainerJobActivator : JobActivator
{
private IServiceProvider _container;
public ContainerJobActivator(IServiceProvider serviceProvider)
{
_container = serviceProvider;
}
public override object ActivateJob(Type type)
{
return _container.GetService(type);
}
}
#endregion
public class Startup
{
public void ConfigureServices(IServiceCollection services)
{
services.AddHangfire(configuration => configuration
.SetDataCompatibilityLevel(CompatibilityLevel.Version_170)
.UseSimpleAssemblyNameTypeSerializer()
.UseRecommendedSerializerSettings()
.UseSqlServerStorage("Server=localhost,1433;Database=HangfireTest;user=sa;password=xxxxxx;MultipleActiveResultSets=True", new SqlServerStorageOptions
{
CommandBatchMaxTimeout = TimeSpan.FromMinutes(5),
SlidingInvisibilityTimeout = TimeSpan.FromMinutes(5),
QueuePollInterval = TimeSpan.Zero,
UseRecommendedIsolationLevel = true,
UsePageLocksOnDequeue = true,
DisableGlobalLocks = true
}));
services.AddHangfireServer();
services.BuildServiceProvider();
services.AddTransient<IMyContract>(i => new MyContractImplementation("blabla"));
}
public void Configure(IApplicationBuilder app, IWebHostEnvironment env, IServiceProvider serviceProvider)
{
GlobalConfiguration.Configuration.UseActivator(new ContainerJobActivator(serviceProvider));
app.UseRouting();
app.UseHangfireDashboard();
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
app.UseEndpoints(endpoints =>
{
endpoints.MapGet("/", async context =>
{
await context.Response.WriteAsync(JsonSerializer.Serialize(Hangfire.JobStorage.Current.GetConnection().GetRecurringJobs()
.Select(i => new { i.Id, i.CreatedAt, i.Cron }).ToList()));
});
endpoints.MapGet("/add", async context =>
{
var manager = new RecurringJobManager();
var jobId = $"{Guid.NewGuid()}";
manager.AddOrUpdate<IMyContract>(jobId, (IMyContract mc) => mc.MakeAction(jobId), "1/2 * * * *");
await context.Response.WriteAsync($"Schedule added: {jobId}");
});
});
}
}
}