Umbraco-CMS/src/Umbraco.Web/BatchedDatabaseServerMessenger.cs

using System;
using System.Collections.Generic;
using System.Web;
using Umbraco.Core;
using Umbraco.Core.Logging;
using Umbraco.Core.Sync;
using Umbraco.Web.Routing;

namespace Umbraco.Web
{
    public class BatchedDatabaseServerMessenger : Core.Sync.BatchedDatabaseServerMessenger
    {
        public BatchedDatabaseServerMessenger(ApplicationContext appContext, bool enableDistCalls, DatabaseServerMessengerOptions options)
            : base(appContext, enableDistCalls, options, GetBatch)
        {
            UmbracoApplicationBase.ApplicationStarted += Application_Started;
            UmbracoModule.EndRequest += UmbracoModule_EndRequest;
            UmbracoModule.RouteAttempt += UmbracoModule_RouteAttempt;
        }

        private void Application_Started(object sender, EventArgs eventArgs)
        {
            if (ApplicationContext.IsConfigured  == false 
                || ApplicationContext.DatabaseContext.IsDatabaseConfigured  == false
                || ApplicationContext.DatabaseContext.CanConnect == false)

                LogHelper.Warn<BatchedDatabaseServerMessenger>("The app is not configured or cannot connect to the database, this server cannot be initialized with " 
                    + typeof(BatchedDatabaseServerMessenger) + ", distributed calls will not be enabled for this server");

            // because .ApplicationStarted triggers only once, this is thread-safe
            Boot();
        }

        private void UmbracoModule_RouteAttempt(object sender, RoutableAttemptEventArgs e)
        {
            switch (e.Outcome)
            {
                case EnsureRoutableOutcome.IsRoutable:
                    Sync();
                    break;
                case EnsureRoutableOutcome.NotDocumentRequest:
                    //so it's not a document request, we'll check if it's a back office request
                    if (e.HttpContext.Request.Url.IsBackOfficeRequest(HttpRuntime.AppDomainAppVirtualPath))
                    {
                        //it's a back office request, we should sync!
                        Sync();
                    }
                    break;
                //case EnsureRoutableOutcome.NotReady:
                //case EnsureRoutableOutcome.NotConfigured:
                //case EnsureRoutableOutcome.NoContent:
                //default:
                //    break;
            }
        }

        private void UmbracoModule_EndRequest(object sender, EventArgs e)
        {
            // will clear the batch - will remain in HttpContext though - that's ok
            FlushBatch();
        }

        private static ICollection<RefreshInstructionEnvelope> GetBatch(bool ensure)
        {
            var httpContext = UmbracoContext.Current == null ? null : UmbracoContext.Current.HttpContext;
            if (httpContext == null)
            {
                if (ensure)
                    throw new NotSupportedException("Cannot execute without a valid/current UmbracoContext with an HttpContext assigned.");
                return null;
            }

            var key = typeof (BatchedDatabaseServerMessenger).Name;

            // no thread-safety here because it'll run in only 1 thread (request) at a time
            var batch = (ICollection<RefreshInstructionEnvelope>)httpContext.Items[key];
            if (batch == null && ensure)
                httpContext.Items[key] = batch = new List<RefreshInstructionEnvelope>();
            return batch;
        }
    }
}