Orleans Grain Long Running Reminder

LongRunningReminderGrain.cs

#nullable enable
using Orleans.Runtime;

namespace MyGrains;

public class MyLongRunningReminderGrain : Grain, IRemindable
{
    private readonly CancellationTokenSource _shutdownCancellation = new();
    private Task? _backgroundTask;

    public Task ReceiveReminder(string reminderName, TickStatus status)
    {
        if (_backgroundTask is null or { IsCompleted: true })
        {
            _backgroundTask = ProcessBackgroundTask();
        }

        return Task.CompletedTask;
    }

    private async Task ProcessBackgroundTask()
    {
        // It's polite to yield immediately, since we're starting background work.
        await Task.Yield();

        while (!_shutdownCancellation.IsCancellationRequested)
        {
            // Do work here...
            await Task.Delay(1_000);
        }
    }

    public override async Task OnDeactivateAsync(DeactivationReason reason, CancellationToken cancellationToken)
    {
        _shutdownCancellation.Cancel();
        if (_backgroundTask is { } task && !task.IsCompleted)
        {
            // Wait for the background task to complete, but don't wait indefinitely.
            await task.WaitAsync(cancellationToken);
        }
    }
}