Prevent overlap between multiple tasks #350

DuelingCats · 2023-10-09T21:04:30Z

DuelingCats
Oct 9, 2023

From reading the docs on PreventOverlapping, it sounds like the functionality is more targeted towards preventing a specific task from running concurrently. In my situation, I want to prevent two tasks from running concurrently in regards to itself and the other tasks, if that makes sense. So at any one time there should be only 1 task running 1 instance of said task.

Given the scenario, if I share the same key for PreventOverlapping, would this work or is the scheduler not designed to work in this way?

For example:

host.Services.UseScheduler(scheduler => 
{
    scheduler.Schedule<FirstInvocableTask>().EverySeconds(3).PreventOverlapping("SharedOverlapKey");
    scheduler.Schedule<SecondInvocableTask>().EverySeconds(30).PreventOverlapping("SharedOverlapKey");
});

jamesmh · 2023-10-10T23:03:31Z

jamesmh
Oct 10, 2023
Maintainer

Yes, the intent is to prevent overlapping on 1 invocable.

What would end up happening depends on when and how long each task runs. In the scenario you laid out the following would occur:

FirstInvocableTask will run at seconds 30 (within each minute).
It will lock and prevent SecondInvocableTask from running at this point.
This will occur every 30 seconds because both tasks/invocables are due at seconds 30.
SecondInvocableTask will therefore never run.

You'd have to come up with your own way to lock both tasks - either a semaphore, lock, or a distributed lock of some kind.

2 replies

DuelingCats Oct 11, 2023
Author

I did some testing earlier today, and it appears to be working without a semaphore or lock. With the below example code, I don't see where the LongRunningTask2 gets prevented from running with a shared key.

Task 1 complete at 10/10/2023 11:47:02 PM
Task 1 complete at 10/10/2023 11:47:04 PM
Task 1 complete at 10/10/2023 11:47:06 PM
Task 1 complete at 10/10/2023 11:47:08 PM
Task 2 complete at 10/10/2023 11:47:10 PM
Task 1 complete at 10/10/2023 11:47:10 PM
Task 1 complete at 10/10/2023 11:47:12 PM
Task 1 complete at 10/10/2023 11:47:14 PM
Task 1 complete at 10/10/2023 11:47:16 PM
Task 1 complete at 10/10/2023 11:47:18 PM
Task 2 complete at 10/10/2023 11:47:20 PM
Task 1 complete at 10/10/2023 11:47:20 PM
Task 1 complete at 10/10/2023 11:47:22 PM
Task 1 complete at 10/10/2023 11:47:24 PM
Task 1 complete at 10/10/2023 11:47:26 PM
Task 1 complete at 10/10/2023 11:47:28 PM
Task 2 complete at 10/10/2023 11:47:30 PM
Task 1 complete at 10/10/2023 11:47:30 PM
Task 1 complete at 10/10/2023 11:47:32 PM
Task 1 complete at 10/10/2023 11:47:34 PM
Task 1 complete at 10/10/2023 11:47:36 PM
Task 1 complete at 10/10/2023 11:47:38 PM
Task 2 complete at 10/10/2023 11:47:40 PM
Task 1 complete at 10/10/2023 11:47:40 PM
Task 1 complete at 10/10/2023 11:47:42 PM
Task 1 complete at 10/10/2023 11:47:44 PM

using Coravel;
using Coravel.Invocable;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.DependencyInjection;

var builder = Host.CreateApplicationBuilder(args);
builder.Services.AddScheduler();
builder.Services.AddTransient<LongRunningTask1>();
builder.Services.AddTransient<LongRunningTask2>();

var host = builder.Build();

host.Services.UseScheduler(scheduler =>
{
    scheduler.Schedule<LongRunningTask1>().EverySeconds(2).PreventOverlapping("SharedOverlapKey");
    scheduler.Schedule<LongRunningTask2>().EverySeconds(10).PreventOverlapping("SharedOverlapKey");
});
    
    
await host.RunAsync();

public class LongRunningTask1 : IInvocable
{
    public async Task Invoke()
    {

        await Task.Delay(50);
        Console.WriteLine($"Task 1 complete at {DateTime.Now}");
    }
}

public class LongRunningTask2 : IInvocable
{
    public async Task Invoke()
    {
        await Task.Delay(50);
        Console.WriteLine($"Task 2 complete at {DateTime.Now}");
    }
}

jamesmh Oct 11, 2023
Maintainer

Looks like it's allowing the two tasks to go through. I'd have to check the code to see what's going on. But ya, this isn't the intended way to use PreventOverlapping.

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Prevent overlap between multiple tasks #350

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jamesmh Oct 10, 2023 Maintainer

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DuelingCats Oct 11, 2023 Author

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jamesmh
Oct 10, 2023
Maintainer

DuelingCats Oct 11, 2023
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jamesmh Oct 11, 2023
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