Bereitstellen von Unterstützung für das Debuggen in einem benutzerdefinierten Task

IDTSBreakpointSite-Schnittstelle und BreakpointManager

Tasks erstellen Haltepunktziele durch Aufruf der CreateBreakpointTarget-Methode des BreakpointManager, indem sie eine ganzzahlige ID und eine Zeichenfolgenbeschreibung als Parameter bereitstellen. Wenn ein Task den Punkt im Code erreicht, der ein Haltepunktziel enthält, überprüft er mithilfe der IsBreakpointTargetEnabled-Methode, ob der Haltepunkt aktiviert ist. Falls der Wert true lautet, benachrichtigt der Task das Laufzeitmodul, indem er das OnBreakpointHit-Ereignis auslöst.

Die IDTSBreakpointSite-Schnittstelle definiert eine Methode, AcceptBreakpointManager, die vom Laufzeitmodul während der Taskerstellung aufgerufen wird. Diese Methode stellt als Parameter das BreakpointManager-Objekt bereit, das anschließend vom Task zur Erstellung und Verwaltung der Haltepunkte verwendet wird. Tasks sollten den BreakpointManager zur Verwendung während der Validate- und Execute-Methoden lokal speichern.

Im folgenden Codebeispiel wird das Erstellen eines Haltepunktziels mithilfe des BreakpointManager veranschaulicht. Im Beispiel wird die OnBreakpointHit-Methode aufgerufen, um das Ereignis auszulösen.

public void AcceptBreakpointManager( BreakpointManager breakPointManager )
{
   //   Store the breakpoint manager locally.
   this.bpm  = breakPointManager;
}
public override DTSExecResult Execute( Connections connections,
  Variables variables, IDTSComponentEvents events,
  IDTSLogging log, DtsTransaction txn)
{
   //   Create a breakpoint.
   this.bpm.CreateBreakPointTarget( 1 , "A sample breakpoint target." );
...
   if( this.bpm.IsBreakpointTargetEnabled( 1 ) == true )
      events.OnBreakpointHit( this.bpm.GetBreakpointTarget( 1 ) );
}

Public Sub AcceptBreakpointManager(ByVal breakPointManager As BreakpointManager)

   ' Store the breakpoint manager locally.
   Me.bpm  = breakPointManager

End Sub

Public Overrides Function Execute(ByVal connections As Connections, _
  ByVal variables As Variables, ByVal events As IDTSComponentEvents, _
  ByVal log As IDTSLogging, ByVal txn As DtsTransaction) As DTSExecResult

   ' Create a breakpoint.
   Me.bpm.CreateBreakPointTarget(1 , "A sample breakpoint target.")

   If Me.bpm.IsBreakpointTargetEnabled(1) = True Then
      events.OnBreakpointHit(Me.bpm.GetBreakpointTarget(1))
   End If

End Function

IDTSSuspend-Schnittstelle

Die IDTSSuspend-Schnittstelle definiert die Methoden, die vom Laufzeitmodul aufgerufen werden, um den Task anzuhalten oder seine Ausführung fortzusetzen. Die IDTSSuspend-Schnittstelle wird von der IDTSBreakpointSite-Schnittstelle implementiert, und ihre Suspend- und ResumeExecution-Methoden werden meist durch den benutzerdefinierten Task außer Kraft gesetzt. Wenn das Laufzeitmodul ein OnBreakpointHit-Ereignis von einem Task empfängt, ruft es die Suspend-Methode für alle derzeit ausgeführten Tasks auf und veranlasst sie, die Ausführung anzuhalten. Wenn der Client die Ausführung fortsetzt, ruft das Laufzeitmodul die ResumeExecution-Methode der angehaltenen Tasks auf.

Das Anhalten und Fortsetzen der Taskausführung schließt das Anhalten und Fortsetzen des Ausführungsthreads des Tasks ein. In verwaltetem Code erreichen Sie dies mit der ManualResetEvent-Klasse im System.Threading-Namespace von .NET Framework.

Im folgenden Codebeispiel wird die Unterbrechung und Wiederaufnahme der Taskausführung veranschaulicht. Beachten Sie dabei, dass sich die Execute-Methode gegenüber dem letzten Codebeispiel geändert hat und der Ausführungsthread angehalten wird, wenn der Haltepunkt ausgelöst wird.

private ManualResetEvent m_suspended = new ManualResetEvent( true );
private ManualResetEvent m_canExecute = new ManualResetEvent( true );
private int   m_suspendRequired = 0;
private int   m_debugMode = 0;

public override DTSExecResult Execute( Connections connections, Variables variables, IDTSComponentEvents events, IDTSLogging log, DtsTransaction txn)
{
   // While a task is not executing, it is suspended.  
   // Now that we are executing,
   // change to not suspended.
   ChangeEvent(m_suspended, false);
   
   // Check for a suspend before doing any work, 
   // in case the suspend and execute calls
   // were initiated at virtually the same time.
   CheckAndSuspend();
   CheckAndFireBreakpoint( componentEvents, 1);
}
private void CheckAndSuspend()
{
   // Loop until we can execute.  
   // The loop is required rather than a simple If
   // because there is a time between the return from WaitOne and the
   // reset that we might receive another Suspend call.  
   // Suspend() will see that we are suspended
   // and return.  So we need to rewait.
   while (!m_canExecute.WaitOne(0, false))
   {
      ChangeEvent(m_suspended, true);
      m_canExecute.WaitOne();
      ChangeEvent(m_suspended, false);
   }
}
private void CheckAndFireBreakpoint(IDTSComponentEvents events, int breakpointID)
{
   // If the breakpoint is enabled, fire it.
   if (m_debugMode != 0 &&    this.bpm.IsBreakpointTargetEnabled(breakpointID))
   {
      //   Enter a suspend mode before firing the breakpoint.  
      //   Firing the breakpoint will cause the runtime 
      //   to call Suspend on this task.  
      //   Because we are blocked on the breakpoint, 
      //   we are suspended.
      ChangeEvent(m_suspended, true);
      events.OnBreakpointHit(this.bpm.GetBreakpointTarget(breakpointID));
      ChangeEvent(m_suspended, false);
   }
   // Check for a suspension for two reasons: 
   //   1. If we are at a point where we could fire a breakpoint, 
   //      we are at a valid suspend point.  Even if we didn't hit a
   //      breakpoint, the runtime may have called suspend, 
   //      so check for it.     
   //   2. Between the return from OnBreakpointHit 
   //      and the reset of the event, it is possible to have
   //      received a suspend call from which we returned because 
   //      we were already suspended.  We need to be sure it is okay
   //      to continue executing now.
   CheckAndSuspend();
}
static void ChangeEvent(ManualResetEvent e, bool shouldSet)
{
   bool succeeded;
   if (shouldSet)
      succeeded = e.Set();
   else
      succeeded = e.Reset();

   if (!succeeded)
      throw new Exception("Synchronization object failed.");
            
}
public bool SuspendRequired
{
   get   {return m_suspendRequired != 0;}
   set
   {
      // This lock is also taken by Suspend().  
      // Because it is possible for the package to be
      // suspended and resumed in quick succession, 
      // this property might be set before
      // the actual Suspend() call.  
      // Without the lock, the Suspend() might reset the canExecute
      // event after we set it to abort the suspension.
      lock (this)
      {
         Interlocked.Exchange(ref m_suspendRequired, value ? 1 : 0);
         if (!value)
            ResumeExecution();
      }
   }
}
public void ResumeExecution()
{
   ChangeEvent( m_canExecute,true );
}
public void Suspend()
{
   // This lock is also taken by the set SuspendRequired method.  
   // It prevents this call from overriding an 
   // aborted suspension.  See comments in set SuspendRequired.
   lock (this)
   {
      // If a Suspend is required, do it.
      if (m_suspendRequired != 0)
         ChangeEvent(m_canExecute, false);
   }
   // We can't return from Suspend until the task is "suspended".
   // This can happen one of two ways: 
   // the m_suspended event occurs, indicating that the execute thread
   // has suspended, or the canExecute flag is set, 
   // indicating that a suspend is no longer required.
   WaitHandle [] suspendOperationComplete = {m_suspended, m_canExecute};
   WaitHandle.WaitAny(suspendOperationComplete);
}

Private m_suspended As ManualResetEvent = New ManualResetEvent(True)
Private m_canExecute As ManualResetEvent = New ManualResetEvent(True)
Private m_suspendRequired As Integer = 0
Private m_debugMode As Integer = 0

Public Overrides Function Execute(ByVal connections As Connections, _
ByVal variables As Variables, ByVal events As IDTSComponentEvents, _
ByVal log As IDTSLogging, ByVal txn As DtsTransaction) As DTSExecResult

   ' While a task is not executing it is suspended.  
   ' Now that we are executing,
   ' change to not suspended.
   ChangeEvent(m_suspended, False)

   ' Check for a suspend before doing any work, 
   ' in case the suspend and execute calls
   ' were initiated at virtually the same time.
   CheckAndSuspend()
   CheckAndFireBreakpoint(componentEvents, 1)

End Function

Private Sub CheckAndSuspend()

   ' Loop until we can execute.  
   ' The loop is required rather than a simple if
   ' because there is a time between the return from WaitOne and the
   ' reset that we might receive another Suspend call.  
   ' Suspend() will see that we are suspended
   ' and return.  So we need to rewait.
   Do While Not m_canExecute.WaitOne(0, False)
              ChangeEvent(m_suspended, True)
              m_canExecute.WaitOne()
              ChangeEvent(m_suspended, False)
   Loop

End Sub

Private Sub CheckAndFireBreakpoint(ByVal events As IDTSComponentEvents, _
ByVal breakpointID As Integer)

   ' If the breakpoint is enabled, fire it.
   If m_debugMode <> 0 AndAlso Me.bpm.IsBreakpointTargetEnabled(breakpointID) Then
              '   Enter a suspend mode before firing the breakpoint.  
              '   Firing the breakpoint will cause the runtime 
              '   to call Suspend on this task.  
              '   Because we are blocked on the breakpoint, 
              '   we are suspended.
              ChangeEvent(m_suspended, True)
              events.OnBreakpointHit(Me.bpm.GetBreakpointTarget(breakpointID))
              ChangeEvent(m_suspended, False)
   End If

   ' Check for a suspension for two reasons: 
   '   1. If we are at a point where we could fire a breakpoint, 
   '         we are at a valid suspend point.  Even if we didn't hit a
   '         breakpoint, the runtime may have called suspend, 
   '         so check for it.   
   '   2. Between the return from OnBreakpointHit 
   '         and the reset of the event, it is possible to have
   '         received a suspend call from which we returned because 
   '         we were already suspended.  We need to be sure it is okay
   '         to continue executing now.
   CheckAndSuspend()

End Sub

Shared Sub ChangeEvent(ByVal e As ManualResetEvent, ByVal shouldSet As Boolean)

   Dim succeeded As Boolean
   If shouldSet Then
              succeeded = e.Set()
   Else
              succeeded = e.Reset()
   End If

   If (Not succeeded) Then
              Throw New Exception("Synchronization object failed.")
   End If
 
End Sub

Public Property SuspendRequired() As Boolean
   Get
               Return m_suspendRequired <> 0
  End Get
  Set
    ' This lock is also taken by Suspend().  
     '   Because it is possible for the package to be
     '   suspended and resumed in quick succession, 
     '   this property might be set before
     '   the actual Suspend() call.  
     '   Without the lock, the Suspend() might reset the canExecute
     '   event after we set it to abort the suspension.
              SyncLock Me
                         Interlocked.Exchange(m_suspendRequired,IIf(Value, 1, 0))
                         If (Not Value) Then
                                    ResumeExecution()
                         End If
              End SyncLock
   End Set
End Property

Public Sub ResumeExecution()
   ChangeEvent(m_canExecute,True)
End Sub

Public Sub Suspend()

   ' This lock is also taken by the set SuspendRequired method.  
   ' It prevents this call from overriding an 
   ' aborted suspension.  See comments in set SuspendRequired.
   SyncLock Me
   ' If a Suspend is required, do it.
              If m_suspendRequired <> 0 Then
                         ChangeEvent(m_canExecute, False)
              End If
   End SyncLock
   ' We can't return from Suspend until the task is "suspended".
   ' This can happen one of two ways: 
   ' the m_suspended event occurs, indicating that the execute thread
   ' has suspended, or the canExecute flag is set, 
   ' indicating that a suspend is no longer required.
   Dim suspendOperationComplete As WaitHandle() = {m_suspended, m_canExecute}
   WaitHandle.WaitAny(suspendOperationComplete)

End Sub

Siehe auch

Aufgaben