BackgroundWorkers should be restartable to permit changes in Timer interval

[machonky]

As BackgroundWorkers are a Singleton, they should be restartable to permit changes in Timer interval without an application restart.

Description

When StopAsync is invoked followed by a StartAsync on a BackgroundWorker the StoppingTokenSource is not renewed and will throw if the BackgroundWorker is stopped a second time.

The change assigns a new CancellationTokenSource to the StoppingTokenSource property and assigns a new token from the new source.

Checklist

• I fully tested it as developer / designer and created unit / integration tests
• I documented it (or no need to document or I will create a separate documentation issue)

[CLAassistant]

All committers have signed the CLA.

[maliming]

hi

As BackgroundWorkers are a Singleton, they should be restartable to permit changes in Timer interval without an application restart.

Can you share some code to show this case?

The StopAsync is called on ApplicationShutdown. so it won't restart.

[machonky]

When the Host changes a system-wide polling interval setting a local message instructs the PerTenantBackgroundWorker to change as shown - Example code:

public class PerTenantBackgroundWorker : AsyncPeriodicBackgroundWorkerBase
{
...
    public async Task ChangePollingInterval(int newPollingInterval)
    {
        var oldValue = Timer.Period / Minutes;
        logger.LogInformation($"{ToString()} changing polling interval from {oldValue} to {newPollingInterval} (mins)");
        
        await StopAsync(StoppingToken);
        Timer.Period = newPollingInterval * Minutes;
        await StartAsync();

        logger.LogInformation($"{ToString()} Changed polling interval to: {newPollingInterval}");
    }
...
}

If the StopAsync is invoked after this without renewing the StoppingToken then an exception is thrown from the token source, as it has been used up already so it must be "renewed" after every stop call.

The change makes it routine to change the polling interval without needing an application restart,

[maliming]

ok, We can make these properties to protected, then you can change them in the sub-class.

protected CancellationTokenSource StoppingTokenSource { get; set; }

protected CancellationToken StoppingToken { get; set; }

We can drop the ResetStoppingCancellationTokenSource method.

What do you think?

[machonky]

Yes. Since StopAsync is overridable, this will work too.

[maliming]

Can you update your PR's code? Thanks

[machonky]

Updated: 9e051f6

[maliming]

Thanks.

Can you remove these spaces?

[machonky]

Done. https://github.com/macrobert-com/abp/commit/7efe0a4a628a19fa08fbf304538784064dade56f

[maliming]

Thanks!