Add 2 parameters to Start-ThreadJob: timeout seconds, priority

[kasini3000]

Summary of the new feature / enhancement

Add 2 parameters to Start-ThreadJob: timeout seconds, priority

Proposed technical implementation details (optional)

priority:

A single asynchronous task has no timeout and no priority， It is very original.

The priority range is 1-9, and the default is 5,priority 1 will be executed first.

---

timeoutseconds:

For that things, I think thread-timeout is a good medicine:

• can not stop Invoke-WebRequest / Invoke-RestMethod by ctrl + c .see:
  Invoke-WebRequest not responding to «Ctrc+c» PowerShell#16145
• “Shit-mountain-code”
• HANG
  The regularity of unpredictable execution time
• Regular expression for a long time and unpredictable time.
• Code executed remotely.
• memory leaks
• cpu 100%

like：
golang : “context.WithTimeout”
python : timeout* in threading lib

It is better to add a Boolean type of parameter : -AutoRemoveJob
whether to automatically remove threadjob after timeout,
parameter likes “receive-job -AutoRemoveJob”
In this way, users can only consider new thread and put ps1 script code.

both "ForEach-Object -Parallel" and "Start-ThreadJob" without timeout, This has seriously affected my development of "kasini3000" at present.

Powershell community do a "engine"，i do a "car". the car is kasini3000 and k4t .
I love powershell. I want to give my opinion to the engine.
I hope the engine factory can transform a better engine.
I think timeoutseconds can make the ps1 script in the thread more robust.
I hope powershell will become stronger and stronger.

[rhubarb-geek-nz]

• “Shit-mountain-code”

How does a timeout solve this? All you end up with is a section the task run and an indeterminate end state.

• HANG

If the thread is hung and unresponsive, you won't be able to cancel it with a cooperative cancellation mechanism (eg cancellation is an unwind performed in the thread). Preemptive termination leaves the process in an indeterminate state.

• The regularity of unpredictable execution time.

PowerShell is not a RTOS

• Code executed remotely.

Is the expectation that cancelling a local thread will also propagate to cancel remote threads, processes or any child local processes? What mechanism should be used to terminate a remote process?

• memory leaks

How does a timeouts solve memory leaks? If a thread is leaking memory and you stop it, it has still leaked memory, the memory won't be recovered. If the memory is recovered by the thread termination then it is not actually a leak, it is just memory usage.

• cpu 100%

100% CPU is not an issue if it is performing the required jobs. Cancelling a thread because you have high CPU just means you aren't performing the jobs you expected it to perform.

[rhubarb-geek-nz]

@kasini3000 Are you able to implement timed thread cancellation in your own code?

For example when you create a thread also create a CancellationToken and call CancellationTokenSource.CancelAfter to set your timeout. Then each thread has a cancellation token, use a static ThreadLocal<> to associate the thread token with each thread when they start.

Where ever you have a loop, then also check the state of the CancellationToken associated with the current thread and if cancelled throw an exception. Likewise anywhere that you Thread.Sleep(timeout), do cancellationToken.WaitHandle.WaitOne(timeout) and again throw an exception if the cancellation has occurred.

This could be implemented in a small C# class that you use in your PowerShell project.

[rhubarb-geek-nz]

Likewise, in the same module you can do

        Thread current = Thread.CurrentThread;
        current.Priority = ThreadPriority.BelowNormal;

To adjust the priority.

[rhubarb-geek-nz]

The priority range is 1-9, and the default is 5,priority 1 will be executed first.

Suggest use existing ThreadPriority enum

[rhubarb-geek-nz]

This is a pattern you can use now and also on original non-core PowerShell.exe

$cancellationTokenSource = New-Object -Type System.Threading.CancellationTokenSource

try
{
	$cancellationTokenSource.CancelAfter(5000)
	$cancellationToken = $cancellationTokenSource.Token

	[Threading.Thread]::CurrentThread.Priority = [Threading.ThreadPriority]::BelowNormal

	Write-Host $cancellationToken.IsCancellationRequested

	$result = $cancellationToken.WaitHandle.WaitOne(10000)

	Write-Host $result
}
finally
{
	$cancellationTokenSource.Dispose()
}

[kasini3000]

timeoutseconds can make the ps1 script in the thread more robust.
The example you share is very important to the powershell community and USERS !!!
thanks @rhubarb-geek-nz !!!

I hope ANYONE can provide PR as soon as possible to realize this function

[kborowinski]

@rhubarb-geek-nz Could you show a small example how to use ThreadLocal with cancelation token inside of the Start-ThreadJob scriptblock?

[rhubarb-geek-nz]

The more I look at PowerShell threads the more I think it is better to forget about them actually being threads. I may be completely wrong about this but PowerShell threads are completely isolated from other threads, this is unlike a traditional threading system where threads share memory. Here it appears that threads use their own runspace and are isolated from others. From my tests, even $Global are not global, they seem effectively visible only with that thread/runspace.
So within a thread script block you might as well just pass the token around as a variable or put it in $Global.
This does mean you can use exactly the same mechanism for jobs that run in other processes or on other machines.
Rather than think about it as job cancellation or job timeout, think of it in terms of what are the conditions under which my job will terminate. The token is then just part of the calculation.

[rhubarb-geek-nz]

That said, if they are threads running in the same process you might be able to pass a cancellation token created in the main thread or any other thread onto another thread via argument list into the parameters of a script block. This would not work for jobs in other process or remote jobs.

[kasini3000]

@stevenebutler
I saw you adding a cancellation token to IWR. Do you have time to address this issue?

[kasini3000]

news：asp.net8 pr3 add timeout for per request

https://devblogs.microsoft.com/dotnet/asp-net-core-updates-in-dotnet-8-preview-3/

You can set request timeouts for individual endpoints, controllers, or dynamically per request.

To apply request timeouts, first add the request timeout services:

builder.Services.AddRequestTimeouts();
You can then apply request timeouts using middleware by calling :UseRequestTimeouts()

[stevenebutler]

@stevenebutler I saw you adding a cancellation token to IWR. Do you have time to address this issue?

I don't really know much about this side of PowerShell so I don't think I can help here. If I read the issue correctly (and I may not) you are looking for something to cancel jobs that are running after a timeout.

If that's the case I don't think cancellation tokens are going to help you because they rely on the code being cancelled being co-operative in that it must periodically check for cancellation. If you're stuck inside third party code that does not use/check a cancellation token then it will not take any notice of the cancellation of the token and will continue to process until it finishes. The fix I applied was to make the code base in IWR (which we control) more co-operative by checking the cancellation token in places where it was not.