/// <summary>
/// Procedure represents the notification callback provided by the
/// TaskProxy. This callback is invoked whenever a task the TaskProxy
/// is waiting on has been serviced by the TaskPool. When all the tasks the
/// proxy is waiting on have been serviced it will signal external clients
/// using the condition variable reference passed from the client at
/// TaskProxy construction.
/// </summary>
/// <param name="tceArg"></param>
private void OnTPTaskComplete(TPTaskCompleteEventArgs tceArg)
{
lock (m_results.SyncRoot)
{
// Index results by TaskID
m_results.Add(tceArg.TaskID, tceArg);
m_nTasksPending--;
if (m_nTasksPending == 0)
{
// Indicate results are ready by changing state
m_status = enuTaskProxyStatus.ResultsReady;
// Signal to any waiting client
m_condition.Set();
}
}
}
/// <summary>
/// TaskPool subscribes to the TPTaskComplete event. When a TPTask
/// thread is finished servicing a request, locate the
/// subscription of the client that queued the request and
/// notify them via the callback they provided as part of
/// their subscription.
/// <seealso cref="TPTask"/>
/// <seealso cref="TPTaskCompleteEventArgs"/>
/// </summary>
/// <param name="tceArg">TPTask completion event arguement</param>
private static void OnTPTaskComplete(TPTaskCompleteEventArgs tceArg)
{
try
{
lock (ClientNotification.SyncRoot)
{
if (ClientNotification.ContainsKey(tceArg.TaskID))
{
TaskRequest.NotificationCallback objNotify = (TaskRequest.NotificationCallback)ClientNotification[tceArg.TaskID];
if (objNotify != null)
{
// Notifiy specific client
objNotify(tceArg);
// Remove subscription
ClientNotification.Remove(tceArg.TaskID);
}
}
}
}
catch (Exception /*e*/)
{}
}
/// <summary>
/// Procedure enforces the leader-followers behavior of TPTask threads
/// </summary>
/// <remarks></remarks>
public void Service()
{
// Every thread that comes thru here ups the thread count
Interlocked.Increment(ref nNumTasks);
while (true)
{
// Begin critical section
lock (this)
{
Console.WriteLine("Checking for leader");
// While a leader has been selected...wait around
while (bLeaderAvailable)
{
Console.WriteLine("Waiting to be leader");
m_leaderSignal.WaitOnSignal();
Console.WriteLine("Received leader signal");
}
// Assert self as leader before leaving critical section
bLeaderAvailable = true;
// Leave critical section
Console.WriteLine("Leaving as leader");
}
// Only one thread active at this point
Console.WriteLine("Waiting on work");
// waiting on work
m_workSignal.WaitOnSignal();
Console.WriteLine("Got work");
bool bExitLoop = false;
// Nothing else to do so this thread can exit or be recycled
if (requestQ.Count == 0)
{
// No work to do so let other threads (next leader) wait on work
m_workSignal.Reset();
bExitLoop = true;
}
// Begin critical section
lock (this)
{
// Signal self is no longer the leader
bLeaderAvailable = false;
// Signal a follower to become the new leader
m_leaderSignal.Signal();
// Leave critical section
}
if (bExitLoop)
{
// If this task is not marked as recyclable
// then it must exit if no requests are
// pending
if (!m_bRecycleTask)
{
// Thread on its way out so decrease thread count
Interlocked.Decrement(ref nNumTasks);
break;
}
}
else
{
try
{
// Dequeue Service request
TaskRequest req = (TaskRequest)requestQ.Dequeue();
// Set taskID
this.TaskID = req.TaskID;
// Execute Callback
object objRes = req.TaskCb(req.Context);
// If any one subscribed, then fire LFTaskDone event
if (TPTaskComplete != null)
{
TPTaskCompleteEventArgs tceArg = new TPTaskCompleteEventArgs();
tceArg.TaskID = req.TaskID;
tceArg.Result = objRes;
TPTaskComplete(tceArg);
}
}
catch (Exception e) // Catch any exceptions thrown
{
// If any one subscribed, then fire LFTaskFailed event
if (TPTaskComplete != null)
{
TPTaskCompleteEventArgs tceArg = new TPTaskCompleteEventArgs();
tceArg.TaskID = this.TaskID;
// Signal that we had errors so that
// clients can check the
// ExceptionMessage property
tceArg.HasErrors = true;
tceArg.Result = e.Message;
TPTaskComplete(tceArg);
}
}
finally
{
// Reset task ID
this.TaskID = Guid.Empty;
}
}
} // End-while(true)
} // End-Method Service()
