Writing wrong values to log files after concurrent calls of a script - vbscript

Question

This code sample is part of a vbscript script that
is making HTTP POST requests for sending SMS through an API. For each SMS, I need a unique random ID. A description of the functions:
WriteLog (Create log files)
MoveLogFiles (Archiving old log files)
CreateGUID (Generate GUIDs for each SMS)
The problem here is when I write to the log file. I tried apache benchmark to stress test my script. In the log file, the smsID is not stored correctly. It is supposed to be unique for each http request. Instead I see the same ID written in many entries in the log file. How can I protect the variable so that it writes the appropriate value in the log file when the script is called multiple times?
Private smsID
smsID = CreateGUID(12)
'HTTP Request & Response
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WriteLog smsID, "[SMS ID:" & smsID & "] Starting HTTP Request..."
WriteLog smsID, "[SMS ID:" & smsID & "] JSON to be sent: " & JSONStringNoPIN
WriteLog smsID, "[SMS ID:" & smsID & "] Sending HTTP Request..."
ASPPostJSON(smsID)
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set JSONString = Nothing
set JSONStringNoPIN = Nothing
set JSONRequest = Nothing
logFilesDic.RemoveAll
Set logFilesDic = Nothing
WriteLog smsID, "[SMS ID:" & smsID & "] Finished..." & vbCrLf
Set smsID=Nothing
Function WriteLog(ByVal smsID_, ByVal psMessage)
Dim fs: Set fs = Server.CreateObject("Scripting.FileSystemObject")
' Check if the log file and folder exists
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dim f, logSize, logDic
On Error Resume Next
Set f = fs.GetFile(logFile)
Set logDic = CreateObject("Scripting.Dictionary")
'logDic.Add "1", Now() & vbTab & "[SMS ID:" & smsID_ & "] Opening Log file: " & logFile
If Err.Number <> 0 Then
logDic.Add "1", Now() & vbTab & "[SMS ID:" & smsID_ & "] An error occured while opening the log file. Error #" & Err.Number & ": " & Err.Description
If Err.Number = 53 And Not fs.FileExists(logFile) Then
if Not fs.FolderExists Then
fs.CreateFolder logDirectory
End if
if Not fs.FileExists(logFile) Then
fs.CreateTextFile logFile
logDic.Add "2", Now() & vbTab & "[SMS ID:" & smsID_ & "] Log file was created: " & logFile
End if
Set f = fs.GetFile(logFile)
End if
End if
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' Check if the log size exceeds the log size limit
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logSize = f.Size
if logSize >= logMaxSize Then
logDic.Add "3", Now() & vbTab & "[SMS ID:" & smsID_ & "] Log file is exceeding the maximum file size allowed:" & logMaxSize & " Bytes. Archiving the current log file: " & logFile
MoveLogFiles()
fs.CreateTextFile logFile
logDic.Add "4", Now() & vbTab & "[SMS ID:" & smsID_ & "] Log file was archived: " & logTemp
End if
set f=nothing
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' Write to the log file
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Application.Lock
dim log, logDicItems
Set log = fs.OpenTextFile(logFile, 8, True) '1=ForReading, 2=ForWriting, 8=ForAppending
If logDic.Exists("1") Then log.WriteLine logDic.Item("1")
If logDic.Exists("2") Then log.WriteLine logDic.Item("2")
If logDic.Exists("3") Then log.WriteLine logDic.Item("3")
If logDic.Exists("4") Then log.WriteLine logDic.Item("4")
log.WriteLine Now() & vbTab & psMessage
log.Close
Application.UnLock
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Set log = Nothing
fs.Close()
Set fs = Nothing
logDic.RemoveAll
Set logDic = Nothing
WriteLog = True
End Function
Function MoveLogFiles()
Dim fs: Set fs = Server.CreateObject("Scripting.FileSystemObject")
For i = logMaxArchives To 1 Step -1
if fs.FileExists(logFile & "." & CStr(i)) Then
if i = logMaxArchives Then
fs.DeleteFile logDirectory & logFilesDic.Item(logMaxArchives)
Else
fs.MoveFile logDirectory & logFilesDic.Item(i), logDirectory & logFilesDic.Item(i+1)
End if
End if
Next
fs.MoveFile logDirectory & logFilesDic.Item(0), logDirectory & logFilesDic.Item(1)
fs.Close()
End Function
' Generate unique identifier for SMS
Function CreateGUID(tmpLength)
Application.Lock
if tmpLength >= 64 or tmpLength < 0 Then
WriteLog "Error when generating SMS ID. Maximum length of characters allowed: 64. Value given: " & tmpLength
Elseif tmpLength < 4 Then
WriteLog "Error when generating SMS ID. Minimum length of characters allowed: 4. Value given: " & tmpLength
Else
Randomize Timer
Dim tmpCounter,tmpGUID
Const strValid = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
For tmpCounter = 1 To tmpLength
tmpGUID = tmpGUID & Mid(strValid, Int(Rnd(1) * Len(strValid)) + 1, 1)
Next
CreateGUID = tmpGUID
End if
Application.UnLock
End Function

Answer 1

Eventually the problem was caused by the Randomize Timer. Instead I used this:
Function CreateGUID()
Dim TypeLib: Set TypeLib = CreateObject("Scriptlet.TypeLib")
CreateGUID = TypeLib.Guid
CreateGUID = Left(CreateGUID, Len(CreateGUID)-3)
CreateGUID = Mid(CreateGUID,2)
Response.Write CreateGUID
End Function