A quick fix when saving to DSS takes a bit too much time

In a project I’m currently working on I need to update some DSS tables when a user is viewing a page. This is not a problem, but sometimes the save method takes a bit to much time.

Since the saving part of the data not necessarily need to be done in that user thread, I have created a Lazy saver class that do the saving in a different thread.

All I needed to do is to implement my DDS classes with an interface ISaveMe and then save the item like this

Code Snippet
 public void SaveMe()
{
    Store.Save(this);
}
public void Save()
{
    LazyDSSSave.Current.AddToSave(this);
}
public static void Save(T item)
{
    LazyDSSSave.Current.AddToSave(item);
}
public static DynamicDataStore Store
{
    get
    {
        return DynamicDataStoreFactory.Instance.GetStore(typeof(T));
    }
}
 

Then the code bellow will start a new thread if needed an do the saving there.

It is important to remember that all exceptions in a thread that is not suppressed will make the app pool to restart. Therefore is very important to catch all errors.

Code Snippet
 using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections;
using System.Threading;
 
namespace Itera.Data
{
    public interface ISaveMe
    {
        void SaveMe();
    }
    public class LazyDSSSave
    {
        protected Queue ActiveQueue = new Queue();
        ThreadStart backgroundJob;
        Thread thread;
        #region Current
        private static LazyDSSSave _current = new LazyDSSSave();
        public static LazyDSSSave Current
        {
            get
            {
                if (_current == null)
                    _current = new LazyDSSSave();
                return _current;
            }
        }
        #endregion
 
        public void AddToSave(object action)
        {
 
            lock (ActiveQueue.SyncRoot)
            {
                if (!ActiveQueue.Contains(action))
                {
                    ActiveQueue.Enqueue(action);
                }
            }
            EnsureBackgroundJob();
        }
 
        object lockObject = new object();
        #region EnsureBackgroundJob
        public void EnsureBackgroundJob()
        {
            lock (lockObject)
            {
                if (thread == null || backgroundJob == null || !thread.IsAlive)
                {
                    if (this.backgroundJob == null)
                    {
                        this.backgroundJob = new ThreadStart(this.Worker);
                        
                    }
                    if (this.thread == null || !thread.IsAlive)
                    {
                        this.thread = new Thread(this.backgroundJob);
                        this.thread.IsBackground = true;
                        this.thread.Start();
                    }
                }
            }
        }
        #endregion
      
        #region Worker
 
        private void Worker()
        {
            try
            {
                while (true)
                {
                    object item = null;
                    lock (ActiveQueue.SyncRoot)
                    {
                        if (ActiveQueue.Count == 0)
                            return;
                        item = ActiveQueue.Dequeue();
                        
                    }
                    try
                    {
                        if (item is ISaveMe)
                            (item as ISaveMe).SaveMe();
                    }
                    catch (Exception exception)
                    {
                       
                        //log.Error("", exception);
                    }
                }
            }
            catch (System.Exception error)
            {
                //log.Error("", exception);
            }
            finally
            {
                lock (lockObject)
                {
                    if (backgroundJob != null)
                        backgroundJob = null;
                }
            }
        }
        #endregion
    }
}
 

This saves me sometimes as much as 70-100ms on each page request.

Oct 12, 2011

Comments

Magnus Rahl Oct 12, 2011 01:15 PM

Any special reason you decided to build your own queueing/thread solution instead of using the ThreadPool?

Anders Hattestad Oct 12, 2011 01:21 PM

Its based on the EPiServer.LazyIndexer code (at least some time ago)
I have used that way of handling this type of problems before, but I see your point :)
Its imo easier to add some statistics and logging here that can be viewed in a report later since you have one place to store these kind of data.

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