Threading and Loops

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Jan 6th, 2003, 02:57 PM
VB-Mike

Threading and Loops

I need to loop through a data reader and spawn a seperate thread for each item within the set. You can see my code below, but it does not appear to work as I thought. This application is running as windows service and this block of code executes via a timer. Any help or ideas would be GREATLY appreciated...

Dim oDataReader As SqlDataReader
Dim BootClass As New BootClass()

Try
If SQLCheck() Then
Dim oCmd As New SqlCommand("BootGet", SQLConnObj)

oDataReader = oCmd.ExecuteReader()

While oDataReader.Read()
Dim bootThread As New Thread(AddressOf BootClass.Reboot)

BootClass.Server = oDataReader("Server")
BootClass.Key = oDataReader("PKey")
BootClass.Notify = oDataReader("Notify")

bootThread.IsBackground = True
bootThread.Name = "thd_" & Rnd()

bootThread.Start()

End While

oDataReader.Close()
Catch ex as exception
'Do nothing in example
End try

Try this:

VB Code:

Dim oDataReader As SqlDataReader 
Dim iCounter As Integer  'For naming the threads
 
'Start the counter at zero
iCounter = 0
 
Try 
   If SQLCheck() Then 
      Dim oCmd As New SqlCommand("BootGet", SQLConnObj) 
 
      oDataReader = oCmd.ExecuteReader() 
 
      While oDataReader.Read()
         'Create a new instance of your bootclass for each thread.
         'You don't want to share the same object on each thread.
         Dim myBootClass As New BootClass()
         Dim bootThread As New Thread(AddressOf myBootClass.Reboot) 
 
         myBootClass.Server = oDataReader("Server") 
         myBootClass.Key = oDataReader("PKey") 
         myBootClass.Notify = oDataReader("Notify") 
 
         bootThread.IsBackground = True 
         bootThread.Name = "thd_" & iCounter.ToString() 'Use the counter to name it uniquely
 
         bootThread.Start() 
 
         'Increase counter by one
         iCounter++
      End While 
 
      oDataReader.Close() 
Catch ex as exception 
      'Do nothing in example 
End try

Jan 7th, 2003, 06:56 AM
VB-Mike

Looks like I was going down the correct path, but just not close enough. So far my testing looks good and I am seeing none of the problems that I was before. THANK YOU SOOOOO MUCH, hellswraith!

I apparently spoke to soon. For the most part I am seeing the same issue as before. Essentially, all this app does is read server names, times, etc from a SQL db and reboot servers. The service checks the db every 10 seconds for new servers. Once it finds one or many it loops through the dataset and spawns a seperate thread to manage each reboot. The problem comes when I throw a server name that does not exist. My code knows how to account for this, tries 5 times, then exits the sub-routine. If I give it two servers that do not exist it works fine. If I give it 3 servers that do not exist, it loops through each one, creates a thread for each then does nothing. The only thing it does do is create more and more threads and consumes more and more memory until it blows up. I know that these threads are not coming from my loop because I write them to a log file. So, the big question is, where are these extraneous threads being created from and why does it handle 2 but not 3. Here is some more code:

VB Code:

Protected Overrides Sub OnStart(ByVal args() As String)
 
        Dim Timer As New Timers.Timer()
 
        OpenLog()
 
        AddLog("-----------------------------------------")
        AddLog(Me.ServiceName & " Started [" & GetVersion() & "]")
        AddLog("Log Open")
        AddLog("Database Open : " & OpenSQL())
 
        AddHandler Timer.Elapsed, AddressOf OnTimedEvent
        Timer.Interval = (GetDataFromXML("/config/chkinterval") * 1000)
        Timer.Start()
 
        AddLog("Timer Started : " & (Timer.Interval / 1000) & " second loop interval")
    End Sub
 
Private Sub OnTimedEvent(ByVal source As Object, ByVal e As Timers.ElapsedEventArgs)
 
        Dim oDataReader As SqlDataReader
        Dim iCounter As Integer
 
        iCounter = 0
 
        Try
            If SQLCheck() Then
                Dim oCmd As New SqlCommand("BootGet", SQLConnObj)
 
                oDataReader = oCmd.ExecuteReader()
 
                While oDataReader.Read()
                    Dim myBootClass As New BootClass()
                    Dim bootThread As New Thread(AddressOf myBootClass.Reboot)
 
                    myBootClass.Server = oDataReader("Server")
                    myBootClass.Key = oDataReader("PKey")
                    myBootClass.Notify = oDataReader("Notify")
 
                    bootThread.IsBackground = True
                    bootThread.Name = "thd_" & iCounter.ToString()
 
                    bootThread.Start()
 
                    iCounter += 1
 
                    'ThreadPool.QueueUserWorkItem(AddressOf BootClass.Reboot, "Running") ', oDataReader("Server") & "|" & oDataReader("PKey") & "|" & oDataReader("Notify"))
                    AddLog("Reboot thread initialized [" & oDataReader("Server") & "-" & bootThread.Name & "]")
                End While
 
                oDataReader.Close()
 
                TimeErrCnt = 0
            End If
        Catch ex As Exception
 
            If oDataReader.IsClosed = False Then
                oDataReader.Close()
            End If
 
            TimeErrCnt += 1
 
            If TimeErrCnt >= 5 Then
                AddLog("Timer Error : " & TimeErrCnt & " : Critical error level exceeded, service shutting down.  Error Detail: BootManager:OnTimedEvent")
                SendNotify(ex.Message, GetDataFromXML("/config/adminnotify"))
                End
            End If
 
            Thread.CurrentThread.Sleep(10000)
 
            AddLog("Timer Error : " & TimeErrCnt & " : " & ex.Message & " Error Detail: BootManager:OnTimedEvent")
        End Try
 
    End Sub
 
Public Class BootClass
 
    Public Server As String
    Public Key As Integer
    Public Notify As String
 
    Public Sub Reboot()
 
        Dim BootErrCnt As Integer = 1
 
        If SQLCheck() Then
 
            Dim Path As New ManagementPath()
 
            Path.Server = Server
            Path.NamespacePath = "root\CIMV2"
 
            Dim Scope As New ManagementScope(Path)
 
            Scope.Options.Username = UserName
            Scope.Options.Password = Password
 
            Scope.Options.Impersonation = ImpersonationLevel.Impersonate
            Scope.Options.EnablePrivileges = True
 
            Do While BootErrCnt <= 5
                Try
                    Scope.Connect()
                    Exit Do
                Catch ex As Exception
                    If BootErrCnt = 5 Then
                        If SQLCheck() Then
                            Dim oFCmd As New SqlCommand("BootLogInsert " & Key & ",'" & ex.Message & "(Error Count:" & BootErrCnt & " : Exiting thread)'", SQLConnObj)
                            oFCmd.ExecuteNonQuery()
                        End If
 
                        AddLog("Boot Error : " & Server & " : " & BootErrCnt & " : " & ex.Message & " : Exiting thread")
 
                        If Not Notify = "" Then
                            SendNotify(Server & " reboot failure", Notify)
                        End If
 
                        Exit Sub
                    Else
                        Thread.CurrentThread.Sleep(10000)
 
                        If SQLCheck() Then
                            Dim oECmd As New SqlCommand("BootLogInsert " & Key & ",'" & ex.Message & "(Error Count:" & BootErrCnt & ")'", SQLConnObj)
                            oECmd.ExecuteNonQuery()
                        End If
 
                        AddLog("Boot Error : " & Server & " : " & BootErrCnt & " : " & ex.Message)
 
                        BootErrCnt += 1
                    End If
                End Try
            Loop
 
            Dim Query As New ObjectQuery("SELECT * FROM Win32_OperatingSystem")
            Dim Searcher As New ManagementObjectSearcher(Scope, Query)
            Dim myObject As New ManagementObject()
            Dim InParams As ManagementBaseObject()
 
            For Each myObject In Searcher.Get
                myObject.Scope.Options.EnablePrivileges = True
                myObject.InvokeMethod("Reboot", InParams)
            Next
 
            If SQLCheck() Then
                Dim oSCmd As New SqlCommand("BootLogInsert " & Key & ", 'Successfull'", SQLConnObj)
                oSCmd.ExecuteNonQuery()
            End If
 
            AddLog("Reboot Success : " & Server)
 
            If Not Notify = "" Then
                SendNotify(Server & " successfully rebooted", Notify)
            End If
        End If
    End Sub
 
End Class

Jan 7th, 2003, 08:25 AM
VB-Mike

Ok, here is the other wierd thing. Put some output in the loop that calls the thread and the thread code itself:

[1/7/2003 8:22:06 AM] - Thread initialized [TEST-thd_0]
[1/7/2003 8:22:06 AM] - Thread initialized [ME-thd_1]
[1/7/2003 8:22:06 AM] - Thread initialized [G-thd_2]

[1/7/2003 8:22:06 AM] - Thread started [TEST - thd_0]
[1/7/2003 8:22:06 AM] - Thread started [TEST - thd_0]
[1/7/2003 8:22:06 AM] - Thread started [ME - thd_1]
[1/7/2003 8:22:06 AM] - Thread started [TEST - thd_0]
[1/7/2003 8:22:06 AM] - Thread started [ME - thd_1]
[1/7/2003 8:22:06 AM] - Thread started [G - thd_2]

The "thread initialized" comes from the loop and the thread call. The "thread started" comes from the actual thread class itself. Notice that TEST shows up 3 times, ME 2 times, and G one time. Cannot figure this out, specially when each thread was only called once.
Jan 7th, 2003, 08:40 AM
VB-Mike

Ok, think I have it figured out. Looks as if I need to sleep the application thread for a moment within the loop. I believe the loop was moving to fast and not allowing enough time for the thread to get created....

thread.currentthread.slee(500)