NullReferenceException on Code First Migrations when Glimpse is installed

[rikrak]

Hi,

ref: https://github.com/rikrak/EF6_2_InitialisationError

I've just upgraded to EF6.2 and I receive a NullReferenceException on startup. I've done a bit of digging around and I think it's results from having Glimpse.EF6 installed.

The exception appears to come from a call to DbMigrator.GetPendingMigrations().
After a bit of debugging, it looks like a DbConnection is disposed of, which causes the GlimpseDbConnection to set the InnerConnection to null. I think another call is then made to the same connection after disposal, which then causes a NullReferenceException.

The same code worked with EF 6.1.3

source Error:

Line 46:             var migrator = new DbMigrator(_configuration);
Line 47: 
Line 48:             if (migrator.GetPendingMigrations().Any())
Line 49:             {
Line 50:                 migrator.Update();

Source File: D:\Dev\Src\EF6_2_InitialisationError\UI.Web\UnitOfWork\DbInitialiser.cs Line: 48

Stack Trace:

[NullReferenceException: Object reference not set to an instance of an object.]
   Glimpse.Ado.AlternateType.GlimpseDbConnection.get_State() +6
   System.Data.Entity.Internal.RepositoryBase.CreateConnection() +25
   System.Data.Entity.Migrations.History.HistoryRepository.QueryExists(String contextKey) +82
   System.Data.Entity.Migrations.History.HistoryRepository.Exists(String contextKey) +39
   System.Data.Entity.Migrations.History.HistoryRepository.GetPendingMigrations(IEnumerable`1 localMigrations) +46
   System.Data.Entity.Migrations.DbMigrator.GetPendingMigrations() +29
   UI.Web.UnitOfWork.CreateAndMigrateDatabaseInitializer`2.System.Data.Entity.IDatabaseInitializer<TContext>.InitializeDatabase(TContext context) in D:\Dev\Src\EF6_2_InitialisationError\UI.Web\UnitOfWork\DbInitialiser.cs:48
   System.Data.Entity.Internal.<>c__DisplayClassf`1.<CreateInitializationAction>b__e() +76
   System.Data.Entity.Internal.InternalContext.PerformInitializationAction(Action action) +60
   System.Data.Entity.Internal.InternalContext.PerformDatabaseInitialization() +357
   System.Data.Entity.Internal.LazyInternalContext.<InitializeDatabase>b__4(InternalContext c) +7
   System.Data.Entity.Internal.RetryAction`1.PerformAction(TInput input) +111
   System.Data.Entity.Internal.LazyInternalContext.InitializeDatabaseAction(Action`1 action) +198
   System.Data.Entity.Internal.LazyInternalContext.InitializeDatabase() +73
   System.Data.Entity.Internal.InternalContext.Initialize() +30
   System.Data.Entity.Internal.InternalContext.ForceOSpaceLoadingForKnownEntityTypes() +48
   System.Data.Entity.DbContext.System.Data.Entity.Infrastructure.IObjectContextAdapter.get_ObjectContext() +25
   UI.Web.UnitOfWork.SampleContext..ctor() in D:\Dev\Src\EF6_2_InitialisationError\UI.Web\UnitOfWork\SampleContext.cs:13
   UI.Web.MvcApplication.Application_Start() in D:\Dev\Src\EF6_2_InitialisationError\UI.Web\Global.asax.cs:23

[HttpException (0x80004005): Object reference not set to an instance of an object.]
   System.Web.HttpApplicationFactory.EnsureAppStartCalledForIntegratedMode(HttpContext context, HttpApplication app) +477
   System.Web.HttpApplication.RegisterEventSubscriptionsWithIIS(IntPtr appContext, HttpContext context, MethodInfo[] handlers) +118
   System.Web.HttpApplication.InitSpecial(HttpApplicationState state, MethodInfo[] handlers, IntPtr appContext, HttpContext context) +176
   System.Web.HttpApplicationFactory.GetSpecialApplicationInstance(IntPtr appContext, HttpContext context) +350
   System.Web.Hosting.PipelineRuntime.InitializeApplication(IntPtr appContext) +303

[HttpException (0x80004005): Object reference not set to an instance of an object.]
   System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +678
   System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +90
   System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) +188

[ajcvickers]

Looks like this might have been introduced by some of the changes made around connection managemenrt: fad188c#diff-a45479295396de842101deaaf8b212dd
8e1e169#diff-a45479295396de842101deaaf8b212dd

Assigning this to @AndriySvyryd for further investigation.

[AndriySvyryd]

Confirmed that this is a regression in 6.2

As a workaround you can supply the connection to the context:

public SampleContext() : base(new GlimpseDbConnection(new SqlConnection("Data Source=...")), contextOwnsConnection: false)
{
    ((IObjectContextAdapter)this).ObjectContext.ObjectMaterialized += ObjectContextOnObjectMaterialized;
}

Alternatively Glimpse could modify their code so GlimpseDbConnection.State returns Closed or Broken when the connection has been disposed.

[rikrak]

Is it worth me reporting this on the Glimpse project too?

[ajcvickers]

Clearing milestone to consider patch.

[ajcvickers]

@rikrak Yes, please do report this to Glimpse.

[ajcvickers]

Notes from triage: as of now, we are planning to put this in 6.3.0 and not into a patch. This is because:

• There is a workaround
• It only seems to impact people using Glimpse when Migrator is being used, which we don't think is super common.

However, we will reconsider this if enough people are hitting the issue; so please comment if this is impacting you.

@rikrak When you have filed an issue with Glimpse, can you post a link here?