Q271787: PRB: Application.Lock and Application.UnLock Hangs IIS 5.0

Article: Q271787
Product(s): Internet Information Server
Version(s): 5.0
Operating System(s): 
Keyword(s): kbASP kbCOMPlus kbMTS kbVBp kbGrpDSASP kbDSupport
Last Modified: 26-JUL-2001

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The information in this article applies to:

- Microsoft Internet Information Server 5.0 
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SYMPTOMS
========

When you modify Application variables from within a component that is called
from an Active Server Pages (ASP) page, your server may stop responding (hang).
The code in the component that causes the problem resembles the following:

  Application.Lock
  Application("myvar") = "hello world"
  Application.UnLock

CAUSE
=====

Code that is embedded in the Application.Lock and Application.UnLock methods
provides protection in a multi-user environment. With the introduction of COM+,
Internet Information Server (IIS) 5.0 takes advantage of the Thread-Neutral
Apartment (NA) when accessing the Application object. As a result, when you
explicitly call Application.Lock and Application.UnLock from within a component,
under certain scenarios you might encounter a deadlock scenario that causes the
server to stop responding. This problem is most commonly seen when ASP
intrinsics are marshalled back and forth between the IIS server and the COM+
Application server. The following two scenarios may cause the server to hang:

- When you debug a Microsoft Visual Basic component from the Visual Basic
  Integrated Development Envrionment (IDE).

- When you call a component that is running as a Server application in COM+.

RESOLUTION
==========

The Application.Lock and Application.UnLock methods are not needed to assign a
single Application variable because the methods are called internally.

If you need to assign multiple Application variables within the same
Application.Lock and Application.UnLock methods from your component, your
component must run in the same process as the caller, or you must modify your
logic to only include a single assignment. For example, the following code

  Application.Lock
  Application("myvar1") = "hello"
  Application("myvar2") = "world"
  Application.UnLock

could be modified to work around this issue as follows:

  Dim array(1)
  array(0) = "hello"
  array(1) = "world"
  Application("myvar") = array

NOTE: This is only one example. There are numerous ways that you can change your
logic to work around this issue.

MORE INFORMATION
================

Steps to Reproduce Behavior
---------------------------

1. In Visual Basic, create a new ActiveX DLL project.

2. Add a reference to the following libraries:

  COM+ Services Type Library
  Microsoft Active Server Pages Object Library

3. Add the following code to the class module:

  Implements ObjectControl

  Private oContext As ObjectContext
  Private oApplication As ASPTypeLibrary.Application

  Private Sub ObjectControl_Activate()
      Set oContext = GetObjectContext()
      Set oApplication = oContext("Application")
  End Sub

  Private Sub ObjectControl_Deactivate()
      Set oContext = Nothing
      Set oApplication = Nothing
  End Sub

  Private Function ObjectControl_CanBePooled() As Boolean
      ObjectControl_CanBePooled = False
  End Function

  Public Sub IISHang()

      oApplication.Lock
          oApplication("test") = "World"  '<= App HANGS here
      oApplication.UnLock

  End Sub

4. Compile the DLL and register the component with COM+. Make sure that the COM+
  package's Activation type is set to Server application.

5. Create a new ASP page and paste the following code:

  <%
      Dim obj
      Set obj = Server.CreateObject("Project1.Class1")
      Call obj.IISHang()
      Set obj = nothing
  %>

6. Run the ASP page to cause the server to stop responding.


Additional query words: IIS5 HANG Application LOCK UNLOCK VB COM+

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Keywords          : kbASP kbCOMPlus kbMTS kbVBp kbGrpDSASP kbDSupport 
Technology        : kbiisSearch kbiis500
Version           : :5.0
Issue type        : kbprb

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