Multi-threaded Parallel Processing

Many times you come across a situation when you have to execute the same logic across different clients or batch. While running them in simplest manner without multi-threading, your records will be sequentially processed means your process will take longer time to finish. 

You can speed up the above process by implementing multi-threaded parallel processing in few lines of code. To keep it simple in this example, you have to make sure that you have distinct batches or set of records which will not interfere or overlap during this processing. Here is how you can implement in quickest possible manner, make sure your machine has enough processing and threading capabilities.

Step 1

Create a property of method so that you can dynamically set the no of threads if needed

Private ReadOnly Property MaxAllowableThreadCount() As Integer

        Get

            'You can define this value in config file 

            Dim maxThreadCount As Integer = 15

            Return maxThreadCount

        End Get

    End Property

Step 2

Following is the example of multi threading or parallel processing code. Assuming each client will have unique set of records.

Private Function ProcessAllClients() As Integer

      Dim clientList As New List(Of String)

      Dim exceptionMessages As New List(Of String)

      Dim totalNoOfRecProcessed As Integer = 0

      'Add some Test Clients

      clientList.Add("A1")

      clientList.Add("A2")

      clientList.Add("A3")

      If clientList IsNot Nothing AndAlso clientList.Count > 0 Then

          'Customize No of Threads you may want to use as per need or you can simply use a value

          Dim noOfThreadCounts As Integer = MaxAllowableThreadCount

          Dim noOfClients As Integer = clientList.Count

          Dim noOfThreadsGroup As Integer = 0

          'Adjust No of Loops as per max allowable thread

          If (noOfClients Mod noOfThreadCounts = 0) Then

              noOfThreadsGroup = CInt(Math.Floor(noOfClients / noOfThreadCounts))

          Else

              noOfThreadsGroup = CInt(Math.Floor(noOfClients / noOfThreadCounts)) + 1

          End If

          'Set clients in each group/loop 

          For threadGroup As Integer = 0 To noOfThreadsGroup - 1

              Dim processingTaskCounter As Integer = noOfThreadCounts

              If threadGroup = (noOfThreadsGroup - 1) AndAlso (noOfClients Mod noOfThreadCounts > 0) Then

                  processingTaskCounter = noOfClients Mod noOfThreadCounts

              End If

              Dim allProcessingTasks(processingTaskCounter - 1) As Task(Of Integer)

              Dim clinetsToProcess As New List(Of String)

              Dim taskCounter As Integer = 0

              For i = 0 To processingTaskCounter - 1

                  clinetsToProcess.Add(clientList(CInt(threadGroup * noOfThreadCounts) + i))

              Next

              For Each clientCode As String In clinetsToProcess

                  Try

                      Dim currentClient As String = clientCode

                      allProcessingTasks(taskCounter) = New Task(Of Integer)(Function()

                                                                                 Dim pHelper As New ProcessHelper

                                                                                 Return pHelper.ClientProcessingLogic(currentClient)

                                                                             End Function)

                      taskCounter = taskCounter + 1

                  Catch ex As Exception

                      exceptionMessages.Add("Sorry! Error Occurred." & ex.Message)

                      totalNoOfRecProcessed = 0

                  End Try

              Next

              'Now Execute all client's tasks as once but in seperate thread

              Array.ForEach(allProcessingTasks, Sub(tx) tx.Start())

              'Wait till all finishes processing

              Task.WaitAll(allProcessingTasks)

              For Each tsk In allProcessingTasks

                  Select Case True

                      Case tsk.IsCanceled

                          exceptionMessages.Add("Task ID" & tsk.Id & " was canceled.")

                      Case tsk.IsFaulted

                          exceptionMessages.Add("Task ID" & tsk.Id & " was faulted.")

                      Case tsk.IsCompleted

                          totalNoOfRecProcessed += tsk.Result

                      Case Else

                          exceptionMessages.Add("Task ID" & tsk.Id & " was in unknown status.")

                  End Select

              Next

          Next

      End If

      Return totalNoOfRecProcessed

  End Function

Step 3

Call the Step 2 from wherever you want to call it

Dim allItemsProcessedCount As Integer = ProcessAllClients()

Now you can see the difference in processing time and no of records processed during one call.