Avoiding deadlocks from higher default isolation level

Default isolation level of TransactionScope is higher than default isolation
of a transaction. This change makes the desired isolation level explicit.

Also adds a feature to experimental which logs additional Sql CE lock
information when an exception is thrown from a web request.

--HG--
branch : dev
extra : rebase_source : 0d9456873e475d87da6e97ae12db0faf5a93232b

src/Orchard.Web/Modules/Orchard.Experimental/LockLogging.cs

@@ -0,0 +1,35 @@
+using System.Linq;
+using System.Web.Mvc;
+using Orchard.Data;
+using Orchard.Environment;
+using Orchard.Environment.Extensions;
+using Orchard.Logging;
+using Orchard.Mvc.Filters;
+
+namespace Orchard.Experimental {
+    [OrchardFeature("Orchard.Experimental.LockLogging")]
+    public class LockLogging : FilterProvider, IExceptionFilter {
+        private readonly Work<ISessionLocator> _sessionLocator;
+        private readonly ITransactionManager _transactionManager;
+
+        public LockLogging(Work<ISessionLocator> sessionLocator) {
+            _sessionLocator = sessionLocator;
+            Logger = NullLogger.Instance;
+        }
+
+        public ILogger Logger { get; set; }
+
+        public void OnException(ExceptionContext filterContext) {
+            var connection = _sessionLocator.Value.For(null).Connection;
+            var command = connection.CreateCommand();
+            command.CommandText = "SELECT * FROM sys.lock_information";
+            var reader = command.ExecuteReader();
+            while (reader.Read()) {
+                var fields = Enumerable.Range(0, reader.FieldCount)
+                    .Select(i => new { Key = reader.GetName(i), Value = reader.GetValue(i) });
+                var message = fields.Aggregate("sys.lock_information", (sz, kv) => sz + " " + kv.Key + ":" + kv.Value);
+                Logger.Debug(message);
+            }
+        }
+    }
+}

src/Orchard.Web/Modules/Orchard.Experimental/Module.txt

@@ -21,3 +21,7 @@ Features:
         Description: Adds some content definitions to help test lists
         Dependencies: Orchard.Lists
         Category: Developer
+    Orchard.Experimental.LockLogging:
+        Name: Lock Logging
+        Description: Logs extra diagnostic information for Sql CE if a deadlock timeout occurs
+        Category: Developer

src/Orchard.Web/Modules/Orchard.Experimental/Orchard.Experimental.csproj

@@ -39,10 +39,12 @@
       <HintPath>..\..\..\..\lib\autofac\Autofac.dll</HintPath>
     </Reference>
     <Reference Include="Microsoft.CSharp" />
+    <Reference Include="NHibernate, Version=2.1.2.4000, Culture=neutral, PublicKeyToken=aa95f207798dfdb4, processorArchitecture=MSIL" />
     <Reference Include="System" />
     <Reference Include="System.Core">
       <RequiredTargetFramework>3.5</RequiredTargetFramework>
     </Reference>
+    <Reference Include="System.Data" />
     <Reference Include="System.Web.Mvc, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35, processorArchitecture=MSIL">
       <SpecificVersion>False</SpecificVersion>
       <HintPath>..\..\..\..\lib\aspnetmvc\System.Web.Mvc.dll</HintPath>
@@ -62,6 +64,7 @@
     <Compile Include="Controllers\MetadataController.cs" />
     <Compile Include="DebugFilter.cs" />
     <Compile Include="Handlers\DebugLinkHandler.cs" />
+    <Compile Include="LockLogging.cs" />
     <Compile Include="Migrations.cs" />
     <Compile Include="Models\ShowDebugLink.cs" />
     <Compile Include="Models\Simple.cs" />

src/Orchard/Data/TransactionManager.cs

@@ -23,7 +23,11 @@ namespace Orchard.Data {
         void ITransactionManager.Demand() {
             if (_scope == null) {
                 Logger.Debug("Creating transaction on Demand");
-                _scope = new TransactionScope(TransactionScopeOption.Required);
+                _scope = new TransactionScope(
+                    TransactionScopeOption.Required, 
+                    new TransactionOptions { 
+                        IsolationLevel = IsolationLevel.ReadCommitted 
+                    });
             }
         }