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Worker Service dynamically changing execution interval

I have a worker service with the base class for all workers, which accepts the IOptionsMonitor constructor parameter. This monitor contains options object instance with the execution interval value. The question is how to dynamically change the interval, even when the await Task.Delay(Interval); was called? I mean if the Interval value is set to one day, and after the Task.Delay method being called it changes, for example, to one hour - I still need to wait one day and only on the next call the delay would be updated. How I can cancel the current delay and start a new one if the property Interval value was updated?
Thanks.
Please see the code attached below:
public abstract class WorkerBase<TWorker, TWorkerOptions> : BackgroundService
where TWorker : WorkerBase<TWorker, TWorkerOptions>
where TWorkerOptions : IHaveIntervalProperty
{
protected WorkerBase(IServiceProvider serviceProvider, ILogger<TWorker> logger, IOptionsMonitor<TWorkerOptions> options)
{
_logger = logger;
_serviceProvider = serviceProvider;
_workerName = typeof(TWorker).Name;
Interval = options.CurrentValue.Interval;
options.OnChange(UpdateOptions);
}
public TimeSpan Interval { get; private set; }
public virtual void UpdateOptions(TWorkerOptions options)
=> Interval = options.Interval;
public abstract Task DoWork(IServiceProvider provider);
protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
while (!stoppingToken.IsCancellationRequested)
{
_logger.LogInformation(Logs.InformationWorkerRunning, _workerName, DateTime.UtcNow);
try
{
using var scope = _serviceProvider.CreateScope();
await DoWork(scope.ServiceProvider);
}
catch (Exception e)
{
_logger.LogCritical(e, e.Message);
}
finally
{
await Task.Delay(Interval, stoppingToken);
}
}
}
}

Okay, so based on #Panagiotis Kanavos comment I came up with the following code:
public abstract class RepeatableWorker<TWorker, TOptions> : IHostedService, IDisposable
where TWorker : RepeatableWorker<TWorker, TOptions>
where TOptions : IHaveIntervalProperty
{
#region Fields
private readonly IServiceProvider _serviceProvider;
private protected readonly ILogger<TWorker> _logger;
private readonly string _workerName;
private Timer? _executionTimer;
private TimeSpan _interval;
#endregion
#region Constructors
protected RepeatableWorker(IServiceProvider serviceProvider,
ILogger<TWorker> logger,
IOptionsMonitor<TOptions> options)
{
_serviceProvider = serviceProvider;
_logger = logger;
_workerName = typeof(TWorker).Name;
_interval = options.CurrentValue.Interval;
options.OnChange(UpdateOptions);
}
#endregion
#region Properties
public TimeSpan Interval
{
get => _interval;
private set
{
if (value != _interval)
{
_executionTimer?.Change(TimeSpan.Zero, value);
_interval = value;
}
}
}
#endregion
#region Public methods
public virtual void UpdateOptions(TOptions options)
=> Interval = options.Interval;
public abstract void DoWork(IServiceProvider serviceProvider);
public Task StartAsync(CancellationToken cancellationToken)
{
_logger.LogInformation(Logs.InformationWorkerStarting, _workerName, DateTime.UtcNow);
_executionTimer = new(DoWorkInternal, null, TimeSpan.Zero, Interval);
return Task.CompletedTask;
}
public Task StopAsync(CancellationToken cancellationToken)
{
_logger.LogInformation(Logs.InformationWorkerStopping, _workerName, DateTime.UtcNow);
_executionTimer?.Change(Timeout.Infinite, 0);
return Task.CompletedTask;
}
public void Dispose()
{
GC.SuppressFinalize(this);
_executionTimer?.Dispose();
}
#endregion
#region Private methods
private void DoWorkInternal(object? state)
{
try
{
_logger.LogInformation("Worker {0} running at {1}.", _workerName, DateTime.UtcNow);
using var scope = _serviceProvider.CreateScope();
DoWork(scope.ServiceProvider);
}
catch (Exception e)
{
_logger.LogCritical(e, e.Message);
}
}
#endregion
}
And the IHaveIntervalProperty interface:
public interface IHaveIntervalProperty
{
TimeSpan Interval { get; set; }
}
Just in case someone will need such a solution.

How to write xUnit Test for a method which calls another method in its body?

This is the class contains EnqueueJobAsync method which I want to write test for it :
public class ConsumerBaseForTesting
{
protected IJobStore JobStore { get; private set; }
public ConsumerBaseForTesting(IJobStore jobStore)
{
JobStore = jobStore;
}
public async Task<IJob> EnqueueJobAsync(IJob job)
=> await JobStore.CreateAsync(job);
}
This is my test which Fails and its actual return is always NULL !
public class ConsumerBaseTest
{
private readonly Mock<IJobStore> _moqIJobStore;
private readonly ConsumerBaseForTesting _consumerBase;
public ConsumerBaseTest()
{
_moqIJobStore = new Mock<IJobStore>();
_consumerBase = new ConsumerBaseForTesting(_moqIJobStore.Object);
}
[Theory]
[ClassData(typeof(JobClassForTesting))]
public async Task EnqueueJobAsyncTest(IJob job)
{
var jobResult = await _consumerBase.EnqueueJobAsync(job);
Assert.Equal(job, jobResult);
}
}

The mock needs to be setup to do two things in order to replicate the expected behavior.
It needs to return the passed job in a completed task.
//...
public ConsumerBaseTest() {
_moqIJobStore = new Mock<IJobStore>();
_consumerBase = new ConsumerBaseForTesting(_moqIJobStore.Object);
//setup the mock to capture and return the job when CreateAsync(IJob job) is invoked
_moqIJobStore
.Setup(_ => _.CreateAsync(It.IsAny<IJob>()))
.Returns((IJob x) => Task.FromResult(x)); }
//...
.Returns((IJob x) => Task.FromResult(x)) captures the argument and returns completed Task<IJob>

.net core - Passing an unknown number of IProgress<T> to class library

I have a console app which uses a class library to execute some long running tasks. This is a .net core console app and uses the .net core Generic Host. I also use the ShellProgressBar library to display some progress bars.
My Hosted service looks like this
internal class MyHostedService : IHostedService, IDisposable
{
private readonly ILogger _logger;
private readonly IMyService _myService;
private readonly IProgress<MyCustomProgress> _progress;
private readonly IApplicationLifetime _appLifetime;
private readonly ProgressBar _progressBar;
private readonly IProgressBarFactory _progressBarFactory;
public MyHostedService(
ILogger<MyHostedService> logger,
IMyService myService,
IProgressBarFactory progressBarFactory,
IApplicationLifetime appLifetime)
{
_logger = logger;
_myService = myService;
_appLifetime = appLifetime;
_progressBarFactory = progressBarFactory;
_progressBar = _progressBarFactory.GetProgressBar(); // this just returns an instance of ShellProgressBar
_progress = new Progress<MyCustomProgress>(progress =>
{
_progressBar.Tick(progress.Current);
});
}
public void Dispose()
{
_progressBar.Dispose();
}
public Task StartAsync(CancellationToken cancellationToken)
{
_myService.RunJobs(_progress);
_appLifetime.StopApplication();
return Task.CompletedTask;
}
public Task StopAsync(CancellationToken cancellationToken)
{
return Task.CompletedTask;
}
}
Where MyCustomProgress looks like this
public class MyCustomProgress
{
public int Current {get; set;}
public int Total {get; set;}
}
and MyService looks something like so (Job1, Job2, Job3 implement IJob)
public class MyService : IMyService
{
private void List<IJob> _jobsToRun;
public MyService()
{
_jobsToRun.Add(new Job1());
_jobsToRun.Add(new Job2());
_jobsToRun.Add(new Job3());
}
public void RunJobs(IProgress<MyCustomProgress> progress)
{
_jobsToRun.ForEach(job =>
{
job.Execute();
progress.Report(new MyCustomProgress { Current = _jobsToRun.IndexOf(job) + 1, Total = _jobsToRun.Count() });
});
}
}
And IJob is
public interface IJob
{
void Execute();
}
This setup works well and I'm able to display the progress bar from my HostedService by creating a ShellProgressBar instance and using the one IProgress instance I have to update it.
However, I have another implementation of IMyService that I also need to run that looks something like this
public class MyService2 : IMyService
{
private void List<IJob> _sequentialJobsToRun;
private void List<IJob> _parallelJobsToRun;
public MyService()
{
_sequentialJobsToRun.Add(new Job1());
_sequentialJobsToRun.Add(new Job2());
_sequentialJobsToRun.Add(new Job3());
_parallelJobsToRun.Add(new Job4());
_parallelJobsToRun.Add(new Job5());
_parallelJobsToRun.Add(new Job6());
}
public void RunJobs(IProgress<MyCustomProgress> progress)
{
_sequentialJobsToRun.ForEach(job =>
{
job.Execute();
progress.Report(new MyCustomProgress { Current = _jobsToRun.IndexOf(job) + 1, Total = _jobsToRun.Count() });
});
Parallel.ForEach(_parallelJobsToRun, job =>
{
job.Execute();
// Report progress here
});
}
}
This is the one I'm struggling with. when _parallelJobsToRun is executed, I need to be able to create a new child ShellProgressBar (ShellProgressBar.Spawn) and display them as child progress bars of let's say 'Parallel Jobs'.
This is where I'm looking for some help as to how I can achieve this.
Note: I don't want to take a dependency on ShellProgressBar in my class library containing MyService
Any help much appreciated.

I am a little confused by your description, but let's see if I understand what you are up to. So if you wrap all of this in a class, then taskList1 and taskList2 could be class variables. (By the way taskList1/2 should be named better: say parallelTaskList and whatever . . . anyway.) Then you could write a new method on the class CheckTaskStatus() and just iterate over the two class variables. Does that help or have I completely missed your question?

Can you modify it like this?
public Task<ICollection<IProgress<int>>> StartAsync(CancellationToken cancellationToken)
{
var progressList = _myServiceFromLibrary.RunTasks();
return Task.FromResult(progressList);
}
public ICollection<IProgress<int>> RunTasks()
{
var taskList1 = new List<ITask> { Task1, Task2 };
var plist1 = taskList1.Select(t => t.Progress).ToList();
var taskList2 = new List<ITask> { Task3, Task4, Task5 }:
var plist2 = taskList2.Select(t => t.Progress).ToList();
taskList1.foreach( task => task.Run() );
Parallel.Foreach(taskList2, task => { task.Run() });
return plist1.Concat(plist2).ToList();
}
Task.Progress there is probably a progress getter. realistically IProgress should probably be injected via Tasks constructors. But the point is your public interface doesn't accept list of tasks, thus it should just return collection of progress reports.
How to inject progress reporters into your tasks is a different story that depends on tasks implementations and it may or may not be supported. out of the box.
However what you probably should do is to supply progress callback or progress factory so that progress reporters of your choice are created:
public Task StartAsync(CancellationToken cancellationToken, Action<Task,int> onprogress)
{
_myServiceFromLibrary.RunTasks(onprogress);
return Task.CompletedTask;
}
public class SimpleProgress : IProgress<int>
{
private readonly Task task;
private readonly Action<Task,int> action;
public SimpleProgress(Task task, Action<Task,int> action)
{
this.task = task;
this.action = action;
}
public void Report(int progress)
{
action(task, progress);
}
}
public ICollection<IProgress<int>> RunTasks(Action<Task,int> onprogress)
{
var taskList1 = new List<ITask> { Task1, Task2 };
taskList1.foreach(t => t.Progress = new SimpleProgress(t, onprogress));
var taskList2 = new List<ITask> { Task3, Task4, Task5 }:
taskList2.foreach(t => t.Progress = new SimpleProgress(t, onprogress));
taskList1.foreach( task => task.Run() );
Parallel.Foreach(taskList2, task => { task.Run() });
}
you may see here, that it really is mostly question about how your tasks are going to call IProgress<T>.Report(T value) method.

Honestly I would just use an event in your task prototype.
It's not really clear exactly what you want because the code you posted doesn't match the names you then reference in your question text... It would be helpful to have all the code (the RunTasks function for example, your IProgress prototype, etc).
Nevertheless, an event exists specifically to signal calling code. Let's go back to the basics. Let's say you have library called MyLib, with a method DoThings().
Create a new class that inherits from EventArgs, and that will carry your task's progress reports...
public class ProgressEventArgs : EventArgs
{
private int _taskId;
private int _percent;
private string _message;
public int TaskId => _taskId;
public int Percent => _percent;
public string Message => _message;
public ProgressEventArgs(int taskId, int percent, string message)
{
_taskId = taskId;
_percent = percent;
_message = message;
}
}
Then on your library's class definition, add an event like so:
public event EventHandler<ProgressEventArgs> Progress;
And in your console application, create a handler for progress events:
void ProgressHandler(object sender, ProgressEventArgs e)
{
// Do whatever you want with your progress report here, all your
// info is in the e variable
}
And subscribe to your class library's event:
var lib = new MyLib();
lib.Progress += ProgressHandler;
lib.DoThings();
When you are done, unsubscribe from the event:
lib.Progress -= ProgressHandler;
In your class library, now you can send back progress reports by raising the event in your code. First create a stub method to invoke the event:
protected virtual void OnProgress(ProgressEventArgs e)
{
var handler = Progress;
if (handler != null)
{
handler(this, e);
}
}
And then add this to your task's code where you want it:
OnProgress(new ProgressEventArgs(2452343, 10, "Reindexing google..."));
The only thing to be careful about is to report progress sparingly, because each time your event fires it interrupts your console application, and you can really bog it down hard if you send 10 million events all at once. Be logical about it.

Alternate way; If you own the code IProgress<T> and Progress
IProgress<T>
{
IProgress<T> CreateNew();
Report(T progress);
}
Progress<T> : IProgress<T>
{
Progress(ShellProgressClass)
{
// initialize progressBar or span new
}
....
IProgress<T> CreateNew()
{
return new Progress();
}
}
you can later improvise to have one big progressBar (collection of Sequential or Parallel) and what not

Your MyService could have a dependency similar to:
public interface IJobContainer
{
void Add(IJob job);
void RunJobs(IProgress<MyProgress> progress, Action<IJob>? callback = null); // Using an action for extra work you may want to do
}
This way you don't have to worry about reporting progress in MyService (which doesn't feel like it should be MyService's job anyway. The implementation could look something like this for the parallel job container:
public class MyParallelJobContainer
{
private readonly IList<IJob> parallelJobs = new List<IJob>();
public MyParallelJobContainer()
{
this.progress = progress;
}
public void Add(IJob job) { ... }
void RunJobs(IProgress<MyProgress> progress, Action<IJob>? callback = null)
{
using (var progressBar = new ProgressBar(options...))
{
Parallel.ForEach(parallelJobs, job =>
{
callback?.Invoke(job);
job.Execute();
progressBar.Tick();
})
}
}
}
MyService would then look like this:
public class MyService : IMyService
{
private readonly IJobContainer sequentialJobs;
private readonly IJobContainer parallelJobs;
public MyService(
IJobContainer sequentialJobs,
IJobContainer parallelJobs)
{
this.sequentialJobs = sequentialJobs;
this.parallelJobs = parallelJobs;
this.sequentialJobs.Add(new DoSequentialJob1());
this.sequentialJobs.Add(new DoSequentialJob2());
this.sequentialJobs.Add(new DoSequentialJob3));
this.parallelJobs.Add(new DoParallelJobA());
this.parallelJobs.Add(new DoParallelJobB());
this.parallelJobs.Add(new DoParallelJobC());
}
public void RunJobs(IProgress<MyCustomProgress> progress)
{
sequentialJobs.RunJobs(progress, job =>
{
// do something with the job if necessary
});
parallelJobs.RunJobs(progress, job =>
{
// do something with the job if necessary
});
}
The advantage of this way is that MyService only has one job and doesn't have to worry about what you do once the job is completed.

From my understanding of your issue the question is how do you display progress across both completion of the synchronous jobs and parallelized jobs.
In theory the parallel jobs could start and finish at the same time, so you could treat the parallel jobs as a single job. Instead of using the count of sequential jobs as your total, increase that number by one. This might be satisfactory for a small number of parallel jobs.
If you want to add progress between the parallel jobs, you will need to handle multi-threading in your code because the parallel jobs will be running concurrently.
object pJobLock = new object();
int numProcessed = 0;
foreach(var parallelJob in parallelJobs)
{
parallelJob.DoWork();
lock (pJobLock)
{
numProcessed++;
progress.Report(new MyCustomProgress { Current = numProcessed, Total = parallelJobs.Count() });
}
}

Background task of writing to the database by timer

How to write to the database on a timer in the background. For example, check mail and add new letters to the database. In the example, I simplified the code just before writing to the database.
The class names from the example in Microsoft.
The recording class itself:
namespace EmailNews.Services
{
internal interface IScopedProcessingService
{
void DoWork();
}
internal class ScopedProcessingService : IScopedProcessingService
{
private readonly ApplicationDbContext _context;
public ScopedProcessingService(ApplicationDbContext context)
{
_context = context;
}
public void DoWork()
{
Mail mail = new Mail();
mail.Date = DateTime.Now;
mail.Note = "lala";
mail.Tema = "lala";
mail.Email = "lala";
_context.Add(mail);
_context.SaveChangesAsync();
}
}
}
Timer class:
namespace EmailNews.Services
{
#region snippet1
internal class TimedHostedService : IHostedService, IDisposable
{
private readonly ILogger _logger;
private Timer _timer;
public TimedHostedService(IServiceProvider services, ILogger<TimedHostedService> logger)
{
Services = services;
_logger = logger;
}
public IServiceProvider Services { get; }
public Task StartAsync(CancellationToken cancellationToken)
{
_logger.LogInformation("Timed Background Service is starting.");
_timer = new Timer(DoWork, null, TimeSpan.Zero,
TimeSpan.FromMinutes(1));
return Task.CompletedTask;
}
private void DoWork(object state)
{
using (var scope = Services.CreateScope())
{
var scopedProcessingService =
scope.ServiceProvider
.GetRequiredService<IScopedProcessingService>();
scopedProcessingService.DoWork();
}
}
public Task StopAsync(CancellationToken cancellationToken)
{
_logger.LogInformation("Timed Background Service is stopping.");
_timer?.Change(Timeout.Infinite, 0);
return Task.CompletedTask;
}
public void Dispose()
{
_timer?.Dispose();
}
}
#endregion
}
Startup:
services.AddHostedService<TimedHostedService>();
services.AddScoped<IScopedProcessingService, ScopedProcessingService>();
It seems everything is done as in the example, but nothing is added to the database, which is not so?

This is a rather interesting question, that boils down to "How do you correctly handle an async timer callback?"
The immediate problem is that SaveChangesAsync isn't getting awaited. The DbContext almost certainly gets disposed before SaveChangesAsync has a chance to run. To await it, DoWork must become an async Task method (never async void) :
internal interface IScheduledTask
{
Task DoWorkAsync();
}
internal class MailTask : IScheduledTask
{
private readonly ApplicationDbContext _context;
public MailTask(ApplicationDbContext context)
{
_context = context;
}
public async Task DoWorkAsync()
{
var mail = new Mail
{ Date = DateTime.Now,
Note = "lala",
Tema = "lala",
Email = "lala" };
_context.Add(mail);
await _context.SaveChangesAsync();
}
}
The problem now is how to call DoWorkAsync from the timer callback. If we just call it without awaiting, we'll get the same problem we had in the first place. A timer callback can't handle methods that return Task. We can't make it async void either, because this would result in the same problem - the method will return before any async operation has a chance to finish.
David Fowler explains how to properly handle asynchronous timer callbacks in the Timer Callbacks section of his Async Guidance
article :
private readonly Timer _timer;
private readonly HttpClient _client;
public Pinger(HttpClient client)
{
_client = new HttpClient();
_timer = new Timer(Heartbeat, null, 1000, 1000);
}
public void Heartbeat(object state)
{
// Discard the result
_ = DoAsyncPing();
}
private async Task DoAsyncPing()
{
await _client.GetAsync("http://mybackend/api/ping");
}
The actual method should be async Task but the returned task only has to be assigned, not awaited, in order for it to work properly.
Applying this to the question leads to something like this :
public Task StartAsync(CancellationToken cancellationToken)
{
...
_timer = new Timer(HeartBeat, null, TimeSpan.Zero,
TimeSpan.FromMinutes(1));
return Task.CompletedTask;
}
private void Heartbeat(object state)
{
_ = DoWorkAsync();
}
private async Task DoWorkAsync()
{
using (var scope = Services.CreateScope())
{
var schedTask = scope.ServiceProvider
.GetRequiredService<IScheduledTask>();
await schedTask.DoWorkAsync();
}
}
David Fowler explains why async void is ALWAY BAD in ASP.NET Core - it's not only that async actions won't be awaited, exceptions will crash the application.
He also explains why we can't use Timer(async state=>DoWorkAsync(state)) - that's an async void delegate.

Mocking events (event based async pattern) using Moq - how to react to event in UT?

I have a service that exposes async operation via event driven async pattern.
public interface IService
{
void DoAsync(int param);
event DoCompleted;
}
There is another class that depends on IService service object
public class Foo
{
private IService _service;
public EventHandler CalculationComplete;
public void Foo(IService service) {_service = service};
public int Calculated;
public void CalculateAsync(int param)
{
//Invoke _service.DoAsync(param)
//(...)
}
}
Basically after calling foo.CalculateAsyc CalculationComplete should notify consumer of calc completion.
The question is how to mock IService when unit testing Foo ? I am using Moq. More specifically how to make unittest wait for CalculationComplete event and react accordingly?

Hard to know what you are trying to test here, so I can't give you a 100% accurate sample. Your sample code seems to be missing quite a few details... I filled some of the missing bits in, but there are more questions.
In any case, a method I use for waiting on events is a semaphore. I like to use AutoResetEvent for this in simple occasions like this.
public class Foo
{
private IService _service;
public EventHandler CalculationComplete;
public Foo(IService service)
{
_service = service;
_service.DoCompleted += (o,e) =>
{
Calculated = e.Result;
if(CalculationComplete != null) { CalculationComplete(this, new EventArgs()); }
};
}
public int Calculated;
public void CalculateAsync(int param)
{
_service.DoAsync(param);
}
}
public interface IService
{
void DoAsync(int param);
event EventHandler<DoResultEventArgs> DoCompleted;
}
public class DoResultEventArgs : EventArgs
{
public int Result { get; set; }
}
[TestMethod]
public void CalculateAsync_CallsService_CalculatedIsPopulated()
{
//Arrange
Mock<IService> sMock = new Mock<IService>();
sMock.Setup(s => s.DoAsync(It.IsAny<int>()))
.Raises(s => s.DoCompleted += null, new DoResultEventArgs() { Result = 324 });
Foo foo = new Foo(sMock.Object);
AutoResetEvent waitHandle = new AutoResetEvent(false);
foo.CalculationComplete += (o,e) => waitHandle.Set();
//Act
foo.CalculateAsync(12);
waitHandle.WaitOne();
//Assert
Assert.IsEqual(foo.Calculated, 324);
}
Without more information, this is the best I can do. I hope it was what you were looking for.