Creating custom web farm synchronization tasks

Web farm tasks are code executed by web farm servers. Create custom web farm tasks if you extended Kentico with functions that work directly with the application's memory or file storages. For example, if your custom function writes files to the file system and you want these files to be synchronized across all servers in your web farm, you need to write a custom web farm task that handles the synchronization.

Add the code of your tasks into a class placed in the App_Code folder of your web project (or CMSApp_AppCode -> Old_App_Code if you installed Kentico as a web application).

 

Example

The following example shows how to create a custom synchronization task that logs information events into the event log of all servers in the web farm:

  1. Open your web project in Visual Studio, expand the App_Code folder and add a new class named WebFarmTaskLoader.cs.
  2. Add the following references:

    using CMS.Base;
    using CMS.EventLog;
    using CMS.WebFarmSync;
  3. Delete the default class declaration and its content.
  4. Extend the CMSModuleLoader partial class and define a new attribute as shown below:

    [WebFarmTaskLoader]
    public partial class CMSModuleLoader
    {
    	/// <summary>
    	/// Custom attribute class.
    	/// </summary>
    	private class WebFarmTaskLoaderAttribute : CMSLoaderAttribute
    	{
    	
    	}
    }
  5. Override the Init method inside the WebFarmTaskLoaderAttribute class, and assign a handler method to the OnProcessCustomTask event:

    /// <summary>
    /// Called automatically when the application starts.
    /// </summary>
    public override void Init()
    {
    	// Assigns a handler to the OnProcessCustomTask event	
    	WebSyncHelper.OnProcessCustomTask += WebSyncHelper_OnProcessCustomTask;
    }
    
    /// <summary>
    /// Handles the processing of custom web farm tasks.
    /// </summary>
    static void WebSyncHelper_OnProcessCustomTask(string taskType, string target, string data, int taskId)
    {
    	// Logs a record into the system's event log, with 'Execute' as the event code
    	EventLogProvider.LogInformation("CustomTask", "Execute", data);
    }
  6. Repeat steps 1-5 for all web servers in the web farm. Build the projects if they are installed as web applications.

Each server in the web farm can now process custom tasks. You can create the tasks through the API anywhere in your custom code.

For example, select one web farm server and expand the Init method in the WebFarmTaskLoaderAttribute class:

/// <summary>
/// Called automatically when the application starts
/// </summary>
public override void Init()
{
	// Assigns a handler to the OnProcessCustomTask event
	WebSyncHelper.OnProcessCustomTask += WebSyncHelper_OnProcessCustomTask;

	// Prepares the data parameter of the custom task
	string data = "Task from " + WebSyncHelper.ServerName;

	// Creates the custom web farm synchronization task
	if (WebSyncHelper.CreateTask(SystemTaskType.Custom, "MyTask", data, null))
	{
		// Runs if the custom task was created successfully
		// Logs a record in the event log on the server that created the web farm task
		EventLogProvider.LogInformation("CustomTask", "Create", data);
	}
}

The selected web farm server creates the custom task when the application starts. If successful, the given server also logs a record into the event log, with Create as the event code. You can see the results by checking the event log for all web farm servers in the Event log application.