RavenDB - An Introduction

using System;
using log4net;
using Raven.Database.Extensions;
using Raven.Database.Storage;
using Raven.Database.Tasks;

namespace Raven.Database.Indexing
{
	public class TaskExecuter
	{
		private readonly WorkContext context;
		private readonly ILog log = LogManager.GetLogger(typeof (TaskExecuter));
		private readonly TransactionalStorage transactionalStorage;

		public TaskExecuter(TransactionalStorage transactionalStorage, WorkContext context)
		{
			this.transactionalStorage = transactionalStorage;
			this.context = context;
		}

		public void Execute()
		{
			while (context.DoWork)
			{
				var foundWork = false;
				transactionalStorage.Batch(actions =>
				{
					log.Debug("Trying to find a task to execute");
					var taskAsJson = actions.GetFirstTask();
					if (taskAsJson == null)
					{
						log.Debug("Could not find any task to execute, will wait for more work");
						actions.Commit();
						return;
					}
					log.DebugFormat("Executing {0}", taskAsJson);
					foundWork = true;

					ExecuteTask(taskAsJson);

					actions.CompleteCurrentTask();
					actions.Commit();
				});
				if (foundWork == false)
					context.WaitForWork();
			}
		}

		private void ExecuteTask(string taskAsJson)
		{
			try
			{
				var task = Task.ToTask(taskAsJson);
				try
				{
					task.Execute(context);
				}
				catch (Exception e)
				{
					log.WarnFormat(e, "Task {0} has failed and was deleted without completing any work", taskAsJson);
				}
			}
			catch (Exception e)
			{
				log.ErrorFormat(e, "Could not create instance of a task: {0}", taskAsJson);
			}
		}
	}
}