Restart the task if it fails
I am trying to restart one of several tasks if it fails. I'm using .ContinueWith(t => { HandleException(t); }, TaskContinuationOptions.OnlyOnFaulted);
where the method is HandleException(t)
to find the task in the excisting array of tasks and create a new one in its place. Only the task passed to my method HandleException(t)
is different from the original task, so I cannot find it in my tasks. Also the exclusive task is still running while the exception is being handled.
Example:
using System;
using System.Threading.Tasks;
using System.Threading;
static Task[] tasks;
static void Main(string[] args)
{
tasks = new Task[2];
for (int i = 0; i < tasks.Count(); i++)
{
tasks[i] = Task.Run(() => { Thread.Sleep(1000); throw new Exception("BOOM"); })
.ContinueWith(t => { HandleException(t); }
, TaskContinuationOptions.OnlyOnFaulted);
Console.WriteLine(String.Format("Task {0} started", tasks[i].Id));
}
Console.ReadLine();
}
static void HandleException(Task task)
{
Console.WriteLine(String.Format("Task {0} stopped", task.Id));
// Check task status
for (int i = 0; i < tasks.Count(); i++)
{
Console.WriteLine(String.Format("Task {0} status = {1}", i, tasks[i].Status));
}
// fFind and restart the task here
if (tasks.Contains(task))
{
int index = Array.IndexOf(tasks, task);
tasks[index] = Task.Run(() => { Thread.Sleep(1000); throw new Exception("BOOM"); })
.ContinueWith(t => { HandleException(t); }
, TaskContinuationOptions.OnlyOnFaulted);
Console.WriteLine(String.Format("Task {0} started", tasks[index].Id));
}
}
My application results in:
Task 3 started
Task 6 started
Task 5 stopped
Task 0 status = Running
Task 2 stopped
Task 1 status = Running
Task 0 status = Running
Task 1 status = Running
Since the task passed to HandleException(t)
is different from the original task, it is not found in tasks[]
and thus does not restart. Also looking at the states tasks[]
, it hasn't stopped yet. How can I properly restart my task?
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This is because you are storing the continuation task in your array, not the original task (that is - you are storing the result ContinueWith
). To fix, save the original task instead:
var task = Task.Run(() => { Thread.Sleep(1000); throw new Exception("BOOM");});
task.ContinueWith(t => { HandleException(t); }
, TaskContinuationOptions.OnlyOnFaulted);
tasks[i] = task;
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