ASP NET Core 6 Launch without Debugging doesn't block Background Service but Debug Does Hi, I'm trying to have a ASP.NET Core BackgroundService run really in background, i mean really don't interrupt with request/response part and I've been trying many stuff cs private Thread? _workerThread; protected override async Task ExecuteAsync(CancellationToken stoppingToken) { Logger.LogInformation("Monitoring Event Triggering Start"); _workerThread = new Thread(() => { while (!stoppingToken.IsCancellationRequested) { if (EventQueue.Count == 0) continue; var monitoringEvent = EventQueue.Dequeue(); using (var scope = ServiceProvider.CreateScope()) { var db = scope.ServiceProvider.GetRequiredService<AppDbContext>(); db.MonitoringEvents.Add(monitoringEvent); db.SaveChanges(); } // TODO Trigger events, notifications Logger.LogInformation($"{monitoringEvent.DateTime} Rule {monitoringEvent.Message} triggered"); } }); _workerThread.IsBackground = true; _workerThread.Start(); } That is the code i currently have, and one weird thing is if I debug the code, the service blocks the program execution, while if I use run, it doesn't block and continue as expected. Is there any mistakes there? Also, is there other ways to do this? I tried Task.Run(), Task.Factory.StartNew() and they all block. I'm on Jetbrains Rider on Ubuntu 20.04 if that matters for the threading part. Thanks in advance!

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Root Question Message

kunio_kun10/24/2022

ASP NET Core 6 Launch without Debugging doesn't block Background Service but Debug Does

Hi,

I'm trying to have a ASP.NET Core BackgroundService run really in background, i mean really don't interrupt with request/response part and I've been trying many stuff

    private Thread? _workerThread;

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        Logger.LogInformation("Monitoring Event Triggering Start");
        _workerThread = new Thread(() =>
        {
            while (!stoppingToken.IsCancellationRequested)
            {
                if (EventQueue.Count == 0) continue;
                var monitoringEvent = EventQueue.Dequeue();
                using (var scope = ServiceProvider.CreateScope())
                {
                    var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();
                    db.MonitoringEvents.Add(monitoringEvent);
                    db.SaveChanges();
                }

                // TODO Trigger events, notifications
                Logger.LogInformation($"{monitoringEvent.DateTime} Rule {monitoringEvent.Message} triggered");
            }
        });
        _workerThread.IsBackground = true;
        _workerThread.Start();
    }

That is the code i currently have, and one weird thing is if I debug the code, the service blocks the program execution, while if I use run, it doesn't block and continue as expected.

Is there any mistakes there?
Also, is there other ways to do this? I tried Task.Run(), Task.Factory.StartNew() and they all block.

I'm on Jetbrains Rider on Ubuntu 20.04 if that matters for the threading part.

Thanks in advance!

Kouhai10/24/2022

There's no way to achieve that, all threads are halted when reaching a breakpoint

kunio_kun10/24/2022

ah it's not that i put any breakpoints there

kunio_kun10/24/2022

i meant this buttons

kunio_kun10/24/2022

If i started it with Debug, it never made it to the next service

kunio_kun10/24/2022

but it works correctly with Run

kunio_kun10/24/2022

I have been investigating for a few hours and with Jetbrains' IDE i found that it doesn't get to the TryExecuteBackgroundServiceAsync() and the foreach loop stucks

Kouhai10/24/2022

That's weird, do you have specific code that runs for development vs production builds?
Does the foreach loop even execute or is _hostedServices empty?

kunio_kun10/24/2022

it is not empty

kunio_kun10/24/2022

I have 2 background services and with the debugger breakpoint it didn't evaluate to true for the first background service (this one)

kunio_kun10/24/2022

also i dont have any specific code that runs on different configuration

Kouhai10/24/2022

does hostedService.StartAsync await infinitely? (or it's not even reached)

kunio_kun10/24/2022

at least not in my own code (non library), and not in this service

kunio_kun10/24/2022

does it refer to this backgroundservice?

kunio_kun10/24/2022

it is reached

kunio_kun10/24/2022

it does have infinite loop

kunio_kun10/24/2022

I have updated the code to this

kunio_kun10/24/2022

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        if (LongRunningTask is not null) throw new InvalidOperationException("Already running");

        Logger.LogInformation("Monitoring Event Triggering Start");
        LongRunningTask = Task.Run(async () =>
            {
                while (!stoppingToken.IsCancellationRequested)
                {
                    if (EventQueue.Count == 0) continue;
                    var monitoringEvent = EventQueue.Dequeue();
                    using (var scope = ServiceProvider.CreateScope())
                    {
                        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();
                        await db.MonitoringEvents.AddAsync(monitoringEvent, stoppingToken);
                        await db.SaveChangesAsync(stoppingToken);
                    }

                    // TODO Trigger events, notifications
                    Logger.LogInformation($"{monitoringEvent.DateTime} Rule {monitoringEvent.Message} triggered");
                }
            },
            stoppingToken
        );
        Logger.LogInformation("Task is running");
    }

kunio_kun10/24/2022

ooh

kunio_kun10/24/2022

now wonder if it blocks somewhere else

kunio_kun10/24/2022

but according to the debugger it doesnt even get to the second backgroundservice i have

Kouhai10/24/2022

Based on these logs, I assume both services seem to be started

kunio_kun10/24/2022

i will try putting breakpoint again

kunio_kun10/24/2022

these are the hostedServices

kunio_kun10/24/2022

the next step after the last picture is nowhere

kunio_kun10/24/2022

and the log is also stuck here

kunio_kun10/24/2022

that was Host.cs, class Host in Microsoft.Extensions.Hosting.Internal

kunio_kun10/24/2022

but i mean even having breakpoints vs no breakpoints on debug has different result?

Kouhai10/24/2022

Hmm so it's stuck after calling StartAsync on the MonitoringEventTriggeringService, I'm not sure if Host.cs has any conditions for production vs development but I doubt that

kunio_kun10/24/2022

it does get to

if (hostedService is BackgroundService backgroundService)

kunio_kun10/24/2022

and then next step is nowhere

Kouhai10/24/2022

kunio_kun10/24/2022

okay just tried it again

kunio_kun10/24/2022

this time the next step was the closing curly brackets of the foreach loop, as if the hostedService is not BackgroundService

kunio_kun10/24/2022

got to the next enumeration (is it?) in the in _hostedService and then next step is nowhere

Kouhai10/24/2022

The condition hostedService is BackgroundService backgroundServic fails?
Hmm even if it fails it should continue looping

kunio_kun10/24/2022

just tried again

kunio_kun10/24/2022

it didnt continue after the hostedService is BackgroundService part

kunio_kun10/24/2022

i mean even if it fails, it may be throwing something right?

Kouhai10/24/2022

But what would throw?
is T just checks if the instance is of that type, if so it would run the code inside the braces

kunio_kun10/24/2022

while it does inherit from BackgroundService

Kouhai10/24/2022

idk if it would help, but what version of ASP.NET Core are you using

kunio_kun10/24/2022

ASP.NET Core MVC 6

kunio_kun10/24/2022

dotnet --version
6.0.402

kunio_kun10/24/2022

Linux 5.15.0-52-generic #58~20.04.1-Ubuntu SMP Thu Oct 13 13:09:46 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

kunio_kun10/24/2022

maybe i should also try it on Windows and see if it happens

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