Creating Job Processor Worker Assemblies Tutorial

Take the following steps to create a worker assembly for the Distributed Computing (Job Processor) SDK. Assume the Job Processor is to convert images from any supported format to PDF using one of the LEADTOOLS Imaging SDKs. This tutorial is meant to be used in conjunction with another tutorial (Adding Jobs to the Job Processor), which demonstrates how to add jobs to the Job Processor with a custom job type. This tutorial creates the worker assembly capable of actually processing these jobs. For the sake of simplicity, assume the client and worker are on the same machine.

  1. Start Visual Studio

  2. Choose File->New->Project from the menu

  3. In the New Project dialog box, choose either "Visual C# Projects" or "VB Projects" in the Projects Type List, and choose "Class Library" from the Templates List.

  4. Type the project name as "JobProcessorCreatingWorkersTutorial" in the Project Name field, and then click OK. If desired, type a new location for your project or select a directory using the Browse button, and then click OK.

  5. Change the project build configuration to x86. If this configuration does not exist, add it by performing the following steps:

    1. Open the configuration manager.

    2. Under 'Platform', choose 'New'.

    3. Choose 'x86' for 'New Platform' and click 'OK'.

  6. In the "Solution Explorer" window, right-click the "References" folder, and select "Add Reference..." from the context menu. In the "Add Reference" dialog box, select the ".NET" tab and browse to the "<LEADTOOLS_INSTALLDIR>\Bin\DotNet or DotNet4\Win32" folder, and select the following DLLs:

    • Leadtools.JobProcessor.Job
    • Leadtools.dll
    • Leadtools.Codecs.dll
    • Leadtools.Codecs.Bmp.dll
    • Leadtools.Codecs.Cmp.dll
    • Leadtools.Codecs.Tif.dll
    • Leadtools.Codecs.Fax.dll
    • Leadtools.Pdf.Dll
  7. Switch to Class1 code view (Double-click Class1.cs in the solution explorer) and add the following lines at the beginning of the file after any Imports or using statements if they exist.

VB
Imports Leadtools.JobProcessor.Job 
Imports System.IO 
Imports System.Xml.Serialization 
Imports Leadtools 
Imports Leadtools.Codecs 
Imports System.Threading 

C#
using Leadtools.JobProcessor.Job; 
using System.IO; 
using System.Xml.Serialization; 
using Leadtools; 
using Leadtools.Codecs; 
using System.Threading; 

  1. Change the name of the main class to 'MyCustomWorker', and have this class inherit from the JobBase class as shown below.

VB
Public Class MyCustomWorker : Inherits JobBase 
End Class 

C#
public class MyCustomWorker : JobBase 
{ 
} 

  1. Add the following methods, variables and structure to the MyCustomWorker class.

VB
Public Sub New(ByVal job As IJob) 
   MyBase.New(job) 
   'If using a licensed copy, add your license information below. 
   Dim MY_LICENSE_FILE As String = "d:\temp\TestLic.lic" 
   Dim MY_DEVELOPER_KEY As String = "xyz123abc" 
   RasterSupport.SetLicense(MY_LICENSE_FILE, MY_DEVELOPER_KEY); 
End Sub 
'This method will be used to store the conversion settings (source and target file in this simple demo). 
'The settings were serialized when the client submitted the job. Now, the worker assembly will deserialize it to obtain the settings. 
Public Structure JobMetadata 
   Public SourceFile As String 
   Public TargetFile As String 
                    
   Public Sub New(ByVal _sourceFile As String, ByVal _targetFile As String) 
      SourceFile = _sourceFile 
      TargetFile = _targetFile 
   End Sub 
End Structure 
Private jobID As String = String.Empty 
Private loadProgress As Integer = 0 
Private saveProgress As Integer = 0 
                    
'Deserialize the JobMetadata 
Public Function DeserializeFromString(ByVal serializedString As String) As JobMetadata 
   Dim serializedBytes As Byte() = Encoding.Unicode.GetBytes(serializedString) 
   Using ms As MemoryStream = New MemoryStream(serializedBytes) 
      Dim xmlSerializer As XmlSerializer = New XmlSerializer(GetType(JobMetadata)) 
      Return CType(xmlSerializer.Deserialize(ms), JobMetadata) 
   End Using 
End Function 
                       
Public Overrides Sub OnJobReceived(ByVal id As String, ByVal userToken As String, ByVal jobMetadata As String, ByVal jobType As String, ByVal progressRate As Integer) 
   Try 
      jobID = id 
      loadProgress = 0 
      saveProgress = 0 
                       
      ' Determine whether the job information and job metadata is valid 
      If String.IsNullOrEmpty(jobMetadata) Then 
         SetFailureStatus(id, CInt(RasterExceptionCode.InvalidParameter), Leadtools.RasterException.GetCodeMessage(RasterExceptionCode.InvalidParameter), Nothing) 
         Return 
      End If 
                       
      'Deserialize the jobMetadata in order to get the conversion settings 
      Dim conversionSettings As JobMetadata = DeserializeFromString(jobMetadata) 
      Using updateStatusTimer As Timer = New Timer(New TimerCallback(AddressOf UpdateStatusProc), Nothing, 0, progressRate * 1000) 
         Using codecs As RasterCodecs = New RasterCodecs() 
            codecs.Options.Save.RetrieveDataFromImage = true            
            AddHandler codecs.LoadImage, AddressOf Of CodecsLoadImageEventArgs 
            AddHandler codecs.SaveImage, AddressOf Of CodecsSaveImageEventArgs 
            Using img As RasterImage = codecs.Load(conversionSettings.SourceFile) 
               codecs.Save(img, conversionSettings.TargetFile, Leadtools.RasterImageFormat.RasPdfLzw, 0) 
               SetCompletedStatus(id, jobMetadata) 
            End Using 
         End Using 
      End Using 
   Catch ex As Exception 
      SetFailureStatus(id, 0, ex.Message, Nothing) 
   End Try 
End Sub 
                    
Private Sub codecs_SaveImage(ByVal sender As Object, ByVal e As CodecsSaveImageEventArgs) 
   'Update the save progress 
   saveProgress = e.TotalPercent 
End Sub 
                    
Private Sub codecs_LoadImage(ByVal sender As Object, ByVal e As CodecsLoadImageEventArgs) 
   'Update the load progress 
   loadProgress = e.TotalPercent 
End Sub 
                    
Private Sub UpdateStatusProc(ByVal stateInfo As Object) 
   Try 
      ' Always report status when the report status interval elapses: otherwise, 
      ' the windows service will assume the job has hung and kill the process. 
                    
      'The load and save progress are separate, so we must combine them as 1 
      Dim totalProgress As Integer = (loadProgress / 2) + (saveProgress / 2) 
      UpdatePercentage(jobID, totalProgress, String.Empty) 
   Catch ex As Exception 
      SetFailureStatus(jobID, 0, ex.Message, Nothing) 
   End Try 
End Sub 
                    

C#
public MyCustomWorker(IJob job) 
: base(job) 
{ 
   //If using a licensed copy, add your license information below. 
   string MY_LICENSE_FILE = "d:\\temp\\TestLic.lic"; 
   string MY_DEVELOPER_KEY = "xyz123abc"; 
   RasterSupport.SetLicense(MY_LICENSE_FILE, MY_DEVELOPER_KEY); 
} 
                     
//This method will be used to store the conversion settings (source and target file in this simple demo). 
//The settings were serialized when the client submitted the job. Now, the worker assembly will deserialize it to obtain the settings. 
public struct JobMetadata 
{ 
   public string SourceFile; 
   public string TargetFile; 
   public JobMetadata(string _sourceFile, string _targetFile) 
   { 
      SourceFile = _sourceFile; 
      TargetFile = _targetFile; 
   } 
} 
                     
string jobID = String.Empty; 
int loadProgress = 0; 
int saveProgress = 0; 
                     
//Deserialize the JobMetadata 
public JobMetadata DeserializeFromString(string serializedString) 
{ 
   byte[] serializedBytes = Encoding.Unicode.GetBytes(serializedString); 
   using (MemoryStream ms = new MemoryStream(serializedBytes)) 
   { 
      XmlSerializer xmlSerializer = new XmlSerializer(typeof(JobMetadata)); 
      return (JobMetadata)xmlSerializer.Deserialize(ms); 
   } 
} 
                     
public override void OnJobReceived(string id, string userToken, string jobMetadata, string jobType, int progressRate) 
{ 
   try 
   { 
      jobID = id; 
      loadProgress = 0; 
      saveProgress = 0; 
                           
      // Check if we have valid job information and job metadata 
      if (String.IsNullOrEmpty(jobMetadata)) 
      { 
         SetFailureStatus(id, (int)RasterExceptionCode.InvalidParameter, Leadtools.RasterException.GetCodeMessage(RasterExceptionCode.InvalidParameter), null); 
         return; 
      } 
                           
      //Deserialize the jobMetadata to get the conversion settings 
      JobMetadata conversionSettings = DeserializeFromString(jobMetadata); 
      using (Timer updateStatusTimer = new Timer(new TimerCallback(UpdateStatusProc), null, 0, progressRate * 1000)) 
      { 
         using (RasterCodecs codecs = new RasterCodecs()) 
         { 
            codecs.Options.Save.RetrieveDataFromImage = true; 
            codecs.LoadImage += new EventHandler<CodecsLoadImageEventArgs>(codecs_LoadImage); 
            codecs.SaveImage += new EventHandler<CodecsSaveImageEventArgs>(codecs_SaveImage); 
            using (RasterImage img = codecs.Load(conversionSettings.SourceFile)) 
            { 
               codecs.Save(img, conversionSettings.TargetFile, Leadtools.RasterImageFormat.RasPdfLzw, 0); 
               SetCompletedStatus(id, jobMetadata); 
            } 
         } 
      } 
   } 
   catch (Exception ex) 
   { 
      SetFailureStatus(id, 0, ex.Message, null); 
   } 
} 
void codecs_SaveImage(object sender, CodecsSaveImageEventArgs e) 
{ 
   //Update the save progress 
   saveProgress = e.TotalPercent; 
} 
void codecs_LoadImage(object sender, CodecsLoadImageEventArgs e) 
{ 
   //Update the load progress 
   loadProgress = e.TotalPercent; 
} 
                     
private void UpdateStatusProc(Object stateInfo) 
{ 
   try 
   { 
      // Always report status when the report status interval elapses: otherwise, 
      // the windows service will assume the job has hung and kill the process. 
                        
      //The load and save progress are separate, so we must combine them as 1 
      int totalProgress = (loadProgress / 2) + (saveProgress / 2); 
      UpdatePercentage(jobID, totalProgress, String.Empty); 
   } 
   catch (Exception ex) 
   { 
      SetFailureStatus(jobID, 0, ex.Message, null); 
   } 
} 

  1. The Workers.config file for the WorkerService WCF Service needs to be updated to handle this type of job. Perform the following steps to update the file.

    1. Open Workers.xml in the App_Data directory of the WorkerService WCF Service.

    2. Add the new job type under the machine that will be the worker (see below). In Adding Jobs to the Job Processor, we used a custom job type of 'ConvertToPDF' so we need to use that same job type here.

      <Workers> <Worker Name="MachineName" NewJobCheckPeriod="2"> <JobTypes> <JobType Name="ConvertToPDF" MaxNumberOfJobs="5" CpuThreshold="80" UseCpuThreshold="false" ProgressRate="10" AssumeHangAfter="60" Attempts="3"/> </JobTypes> </Worker> </Workers>

  2. Now we need to update the windows service configuration file on the worker (app.config) with the new job type, and add some information about our new assembly (see below for example). Perform the following steps to update the file.

    1. Open the windows service configuration file on the worker (app.config).

    2. Update the 'JobType' to 'ConvertToPDF'.

    3. Update the 'UserDllPath' so that it points to the location of your customer worker assembly.

    4. Update the 'UserClassTypeName' to the name of the namespace and class in your worker assembly that will do the work (JobProcessorCreatingWorkersTutorial.MyCustomWorker).

    <userSettings> <Leadtools.JobProcessor.WorkerService.Properties.Settings> <setting name="UserClassTypeName" serializeAs="String"> <value>JobProcessorCreatingWorkersTutorial.MyCustomWorker</value> </setting> <setting name="JobType" serializeAs="String"> <value>ConvertToPDF</value> </setting> <setting name="WorkerLayerPath" serializeAs="String"> <value>Path to Leadtools.JobProcessor.Workerlayer.exe</value> </setting> <setting name="UserDllPath" serializeAs="String"> <value>Path to your worker assembly</value> </setting> </Leadtools.JobProcessor.WorkerService.Properties.Settings> </userSettings>

  3. The worker assembly is now ready to process jobs. If you have not already done so, add jobs to the Job Processor using the project you created in Adding Jobs to the Job Processor. After jobs are added, start the windows service on the worker so that it can begin processing jobs.

    NOTE: If you encounter an "Invalid File Format" or "Feature Not Supported" exception, refer to the Invalid File Format/Feature Not Supported topic.

References

LEADTOOLS Job Processor Settings Understanding The LEADTOOLS Job Processor Database Creating Job Processor Worker Assemblies Deploying LEADTOOLS Distributed Computing (JobProcessor) Applications Unlocking Special LEAD Features

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