// *********
protected virtual void OnAllTasksCompleted(CompletedEventArgs e)
{
EventHandler <CompletedEventArgs> handler = AllTasksCompleted;
if (handler != null)
{
handler(this, e);
}
}
/*
* Bounding is also used to introduce artificial latency into the WithoutBlocking sample.
* One of the major differences between WithoutBlocking and WithBlocking are the TryAdd and TryTake statements.
* Examination of the parameters reveals timeout values in milliseconds or in a defined TimeSpan class.
* WithoutBlocking Tasks, block for small increments of time before continuing execution.
* The sample code utilizes seconds or half seconds, but given that a Timespan can be a small interval, a developer is not constrained to milliseconds.
* Because a method can return before the timeout interval, WithoutBlocking also excludes the try/catch code.
* This is an interesting sample to tinker with.
* Changing the Sleep values in Task1 and Task2 has some interesting effects and really demonstrates shifting bottlenecks in code.
*/
public void WithoutBlocking(int boundvalue, int stage1timeout, int stage2timeout, CancellationTokenSource tokenSource)
{
int[] items = { 1, 2, 3, 4, 5, 6, 7, 8 };
var startTime = DateTime.Now;
message += "Producer...Starting...WithoutBlocking" + Environment.NewLine;
var stage1 = new BlockingCollection <int>();
var stage2 = new BlockingCollection <int>(boundvalue); //Required to force the TryAdd delay
//Pulls numbers from the array
var task0 = Task.Factory.StartNew(() =>
{
foreach (int i in items)
{
if (tokenSource.IsCancellationRequested)
{
break;
}
stage1.Add(i);
message += ("T" + Thread.CurrentThread.ManagedThreadId.ToString()
+ "Producer - Add:" + i.ToString() + " Count=" + stage1.Count.ToString() + Environment.NewLine);
}
if (tokenSource.IsCancellationRequested)
{
message += "Producer - Cancellation requested, exiting..." + Environment.NewLine;
}
else
{
message += "Producer - Loaded all items into stage 1..." + Environment.NewLine;
stage1.CompleteAdding();
}
}, tokenSource.Token);
//Reads and passes data onto next stage
var task1 = Task.Factory.StartNew(() =>
{
int i = -1;
while (!stage1.IsCompleted)
{
if (tokenSource.IsCancellationRequested)
{
break;
}
if (stage1.TryTake(out i, stage1timeout))
{
message += ("T" + Thread.CurrentThread.ManagedThreadId.ToString()
+ " Consumer1 - Stage 1 Process: " + i.ToString() + " elapsed " + DateTime.Now.Subtract(startTime).TotalSeconds.ToString() + Environment.NewLine);
while (!stage2.TryAdd(i, new TimeSpan(0, 0, 0, 0, stage2timeout)))
{
message += ("T" + Thread.CurrentThread.ManagedThreadId.ToString()
+ " Consumer1 - Attempt to add " + i.ToString() + " expired elapsed " + DateTime.Now.Subtract(startTime).TotalSeconds.ToString() + Environment.NewLine);
}
//Pause X miliseconds simulating work
//change to as high as 2000 and low as 100
//to see impact
Thread.Sleep(new TimeSpan(0, 0, 0, 0, 2000));
}
else
{
message += ("T" + Thread.CurrentThread.ManagedThreadId.ToString()
+ " Consumer1 - TIMEOUT Stage1 - trytake: " + i.ToString() + " elapsed " + DateTime.Now.Subtract(startTime).TotalSeconds.ToString() + Environment.NewLine);
}
}
if (tokenSource.IsCancellationRequested)
{
message += "Consumer1 - Cancellation requested, exiting..." + Environment.NewLine;
}
else
{
message += "Consumer1 - Emptied all items from Stage 1..." + Environment.NewLine;
stage2.CompleteAdding();
}
}, tokenSource.Token);
//Reads prints data
var task2 = Task.Factory.StartNew(() =>
{
int i = -1;
while (!stage2.IsCompleted)
{
if (tokenSource.IsCancellationRequested)
{
break;
}
if (stage2.TryTake(out i, 300))
{
message += ("T" + Thread.CurrentThread.ManagedThreadId.ToString()
+ " Consumer2 - Stage 2 Process: " + i.ToString() + " elapsed " + DateTime.Now.Subtract(startTime).TotalSeconds.ToString() + Environment.NewLine);
//Pause a little over half second to simulate work
Thread.Sleep(new TimeSpan(0, 0, 0, 0, 600));
}
else
{
message += ("T" + Thread.CurrentThread.ManagedThreadId.ToString()
+ " Consumer2 - TIMEOUT Stage2 [Try take]: exceeded at " + DateTime.Now.Subtract(startTime).TotalSeconds.ToString() + Environment.NewLine);
}
}
}, tokenSource.Token)
.ContinueWith((prevtask) =>
{
message += "WithoutBlocking Example - Completed." + Environment.NewLine;
// Simple test for checking propagation of exceptions.
// This works fine, simply check the task.WhenAll result, it will say faulted with a list of the exceptions thrown...easy
//throw new System.NotImplementedException();
}, tokenSource.Token, TaskContinuationOptions.OnlyOnRanToCompletion, TaskScheduler.Default);
Task.WhenAll(task0, task1, task2)
.ContinueWith((prevTask) =>
{
CompletedEventArgs e = new CompletedEventArgs(prevTask);
OnAllTasksCompleted(e);
});
}
