FIX: Dynamic Caching may incorrectly delete recently cached objects from a caching server that is running Forefront Threat Management Gateway 2010 or Internet Security and Acceleration Server 2006

Symptoms

When you use Dynamic Caching for a web server, Dynamic Caching may incorrectly delete recently cached objects from a caching server that is running Forefront Threat Management Gateway 2010 or Internet Security and Acceleration Server 2006when concurrent requests are made for the same object and when the object is currently not cached.

For example, consider the following scenario:

• Two requests (request1 and request2) for the same object are made to a caching server that is running Forefront Threat Management Gateway 2010 or Internet Security and Acceleration Server 2006.

• The object is currently not cached on the caching server.

• The request is for a Dynamic URL that contains a special character such as a question mark (?).

• Dynamic Caching is enabled on a cache rule that applies to the destination URL for the object.

• Because the object does not exist in the cache of the caching server, both request1 and request2 are sent to the web server of the object.

• When the response for the object by request1 is received, the object is added to the cache of the caching server.

• If the response for for the object by request2 arrives while the cache is being updated for the object request1, the cache entry [?] is marked incorrectly for deletion.

• After the cache is updated by request1, the cache entry is deleted.

In this scenario, the next request for the same object may cause additional requests to the web server. However, you expect the request instead to be served from the cache.

Note The cache is updated and works as expected unless all the conditions in this scenario are met.

Resolution

To resolve this problem, apply one of the following fixes:

Forefront Threat Management Gateway 2010

Internet Security and Acceleration Server 2006After you apply the fix, run the following script to enable the fix:

Const SE_VPS_GUID = "{143F5698-103B-12D4-FF34-1F34767DEabc}"
Const SE_VPS_VALUE = "DeleteEntryForForceCache"

Sub SetValue()

' Create the root object.
Dim root ' The FPCLib.FPC root object
Set root = CreateObject("FPC.Root")

' Declare the other objects that are needed.
Dim array ' An FPCArray object
Dim VendorSets ' An FPCVendorParametersSets collection
Dim VendorSet ' An FPCVendorParametersSet object

' Obtain references to the array object
' and to the network rules collection.
Set array = root.GetContainingArray
Set VendorSets = array.VendorParametersSets

On Error Resume Next
Set VendorSet = VendorSets.Item( SE_VPS_GUID )

If Err.Number <> 0 Then
Err.Clear

' Add the item
Set VendorSet = VendorSets.Add( SE_VPS_GUID )
CheckError
WScript.Echo "New VendorSet added... " & VendorSet.Name

Else
WScript.Echo "Existing VendorSet found... value- " & VendorSet.Value(SE_VPS_VALUE)
End If

if VendorSet.Value(SE_VPS_VALUE) <> true Then

Err.Clear
VendorSet.Value(SE_VPS_VALUE) = true

If Err.Number <> 0 Then
CheckError
Else
VendorSets.Save false, true
CheckError

If Err.Number = 0 Then
WScript.Echo "Done with " & SE_VPS_VALUE & ", saved!"
End If
End If
Else
WScript.Echo "Done with " & SE_VPS_VALUE & ", no change!"
End If

End Sub

Sub CheckError()

If Err.Number <> 0 Then
WScript.Echo "An error occurred: 0x" & Hex(Err.Number) & " " & Err.Description
Err.Clear
End If

End Sub

SetValue

Status

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

References

For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:

824684 Description of the standard terminology that is used to describe Microsoft software updates