I am using DryIoc (last release version) for Dependency Injection.
In my application (Asp.net Core 3.1), I am using Entity Framework.
My AppDbContext hinerits DbContext and implements IDisposable
I also use UnitOfWork pattern and the class is disposable.
These two objects are declared as Transient.
I follow the documentation of DryIoc that explains the context with Transient Disposable objects:
https://github.com/dadhi/DryIoc/blob/master/docs/DryIoc.Docs/ReuseAndScopes.md
For my AppDbContext, I resolve this service manually. Same thing for my UnitOfWork. At the end I call Dispose method.
But these two instances are not destroyed and are stored in the Singleton Scope of the DryIoc Container.
I did some tests and use JetBrain dotMemory.
My test is to call 100 times a method
Call controler
open UnitOfWork
create AppDbContext
call database to get my data
close / dispose objects.
At the end, I have 100 times my AppDbContext and my UnitOfWork in the scope of the container:
I tried a lot of combinations of creation of container but each time, it is the same thing:
var container = new Container(rules =>
rules.With(propertiesAndFields: request => request.ServiceType.Name.EndsWith("Controller") ? PropertiesAndFields.Auto(request) : null)
// .WithoutThrowOnRegisteringDisposableTransient()
// .WithTrackingDisposableTransients()
.WithoutThrowIfDependencyHasShorterReuseLifespan())
.WithDependencyInjectionAdapter(services);
Result: memory is growing up fast because of these two kind of objects stored in the scope.
If I comment .WithoutThrowOnRegisteringDisposableTransient(), my code is still working (I thought an exception would be thrown)
I tried also to declare these services as Scoped (for each http request) but it does not work because I don't create scope for each query. (Exception thrown and a scope is automatically opened per each web request by Asp .Net Core framework).
Maybe I need to dispose scope at the end of each request?
How could I force destruction of objects?
Thanks to the author of the lib, I found solution:
https://github.com/dadhi/DryIoc/issues/261
Related
We have migrated from a windows Framework 4.7 application to .NET 6.0. Lamar is added for Dependency Injection. We are trying to finalize a refactor to the latest "one-file" program.cs but are getting unexpected System.ObjectDisposedException: 'Cannot access a disposed object'. In all cases, the error is against a Func<T> during object creation.
All our tests are running correctly using the same environment, except to start the tests we (a) create the DI container and (b) use the container to create an object that loads the singletons (from MongoDB):
Container = new Container(registry);
var start = Container.GetInstance<HomeService>();
In the program.cs, we configure the container, but do not get to see it created, or access it inside program.cs. Instead we create HomeService from IServiceProvider during the first use of a controller. Here we were trying to limit the lifecyle scope during creation:
using (var scope = _container.CreateScope())
{
scope.ServiceProvider.GetService<INewHomeService>();
}
For test, we use the same loading steps, except for adding controllers/mvc, of course (i.e. NOT using builder.Services.AddControllers(); and builder.Services.AddMvc() for (integration) testing).
We have tried a lot of different things, like creating our object independently to the startup, but that did not align the singletons. We can get functionality by using static instead, but then we lose dynamic change access.
Some great tips like Resolving instances with ASP.NET Core DI from within ConfigureServices and https://andrewlock.net/exploring-dotnet-6-part-10-new-dependency-injection-features-in-dotnet-6/ but I can't see the specific example to get the live container just after initial creation.
Is it possible that the issue is just the difference between the lifecycle management of the new .NET DI implementation? As this is configuration at the composition root, if we can configure as per our testing approach, it should solve our problem. Other solutions welcome!
The problem 'Cannot access a disposed object' was being caused by a lifecycle mismatch between retained context and the controller access. The code retained a handle on the state object, that had a handle on the factory using FUNC. As we did not configure the Func as anything, it was transient during the controller graph creation, and so was disposed when the controller request ended.
To solve, we tried registering ALL of the FUNC, per How to use Func<T> in built-in dependency injection which was a large task as we had a few factories throughout an old codebase.
The better solution was to create a factory in the composition root, and use an injected IserviceProvider (or with Lamar an IContainer). This is a simple workaround.
With our creation concern, the creation of our object after the completion of the startup process is working correctly as a lazy validation of the first controller access.
I've configured my DbContext with services.AddDbContext() in the Startup class and constructor injection in my controllers works very well.
By default it's a scoped service, but I have one place in the app where I want to update a single property of an entity in a separate scope of work. So I need to create a new DbContext in the controller, but I'm not sure how. I want it to be created by the DI so I don't have to manually call the constructor and provide all the options needed. Is there a way to do that? Maybe there's a way to get the db context options from the DI? Then I could construct the DbContext easily.
The normal method of injecting a DbContext into your Controller works fine, as long as you are doing a small amount of work during an HTTP request. However, you might want to create a DbContext for a long-running a operation that queries/modifies a lot of records (causing SaveChangesAsync() to get bogged down because DbContext.ChangeTracker is tracking a lot of objects). In that case, you can create a scoped DbContext for each operation ("unit of work"). Here is an example ASP.NET Core Controller method:
/// <summary>
/// An endpoint that processes a batch of records.
/// </summary>
/// <param name="provider">The service provider to create scoped DbContexts.
/// This is injected by DI per the FromServices attribute.</param>
/// <param name="records">The batch of records.</param>
public async Task<IActionResult> PostRecords(
[FromServices] IServiceProvider provider,
Record[] records)
{
// The service scope factory is used to create a scope per iteration
var serviceScopeFactory =
provider.GetRequiredService<IServiceScopeFactory>();
foreach (var record in records)
{
// At the end of the using block, scope.Dispose() will be called,
// releasing the DbContext so it can be disposed/reset.
using (var scope = serviceScopeFactory.CreateScope())
{
var context = scope.ServiceProvider.GetService<MainDbContext>();
// Query and modify database records as needed
await context.SaveChangesAsync();
}
}
return Ok();
}
Also, I would recommend switching from AddDbContext() to AddDbContextPool() in Startup.cs to avoid creating/destroying DbContext objects for each request. The DbContextPool will reset the DbContext objects to a clean state after they go out of scope. (In case you were interested, DbContextPool calls DbContext.ResetState() and DbContext.Resurrect(), but I wouldn't recommend calling those directly from your code, as they will probably change in future releases.)
https://github.com/aspnet/EntityFrameworkCore/blob/v2.2.1/src/EFCore/Internal/DbContextPool.cs#L157
Finally, be aware that there are a few pitfalls of creating multiple DbContexts:
Using a large number of DbContexts in parallel may cause the database server to run out of active connections, since many EF database providers open a database connection per DbContext. (Requesting and releasing pooled DbContext objects in a loop should be fine.)
There may be more efficient ways to do the same thing. On my project, I tested and found that running a single "upsert" on a single DbContext was significantly faster than running a SELECT and INSERT/UPDATE on a separate DbContext for each record. There are a number of implementations of upsert for EF Core. For example, here are two that I have used:
FlexLabs.Upsert: https://github.com/artiomchi/FlexLabs.Upsert
EF Extensions BulkMerge: https://entityframework-extensions.net/bulk-merge
One option is to inject IDbContextFactory into your comtroller to create contexts within using blocks.
https://msdn.microsoft.com/en-us/library/hh506876(v=vs.113).aspx
I have an issue with my datacontext getting disposed every once in a while in one of my filters attached to my web api controllers. Is this the correct way to setup a filter for my Web API controllers and why does my datacontext get disposed sometimes?
The operation cannot be completed because the DbContext has been disposed.
Global.asax
GlobalConfiguration.Configuration.Filters
.Add(new ApiValidationFilter(kernel.Get<IApiAuthenticationService>()));
kernel.Bind<IDatabaseFactory>()
.To<DatabaseFactory>()
.InScope(q => HttpContext.Current ?? StandardScopeCallbacks.Thread(q));
ApiValidationFilter.cs
public class ApiValidationFilter : System.Web.Http.Filters.IActionFilter
{
private readonly IApiAuthenticationService _apiAuthenticationService;
public ApiValidationFilter(
IApiAuthenticationService apiAuthenticationService)
{
_apiAuthenticationService = apiAuthenticationService;
}
You should be using the Filter binding syntax, then Ninject will handle the the filter lifetime, and it will also handle the constructor injection of the filter.
https://github.com/ninject/ninject.web.mvc/wiki/Filter-configurations
I would also let Ninject handle managing the lifetime of the data conext as well, instead of using a factory.
kernel.Bind<MyContext>().ToSelf().InRequestScope();
Alternatively, if you want better testability you can derive your context from an interface and bind to that. The InRequestScope makes sure the context lives for the entire web request, and it will automatically get disposed when the request is done. You don't have to remember to do so, and there won't be any memory leaks by holding onto a request longer than a single request.
You can see an example here:
ASP.NET MVC 3 and Global Filter Injection
I eventually had to resort to the following, nothing worked.
var apiRepository = new ApiRepository(new DatabaseFactory());
var apiAuthenticationService = new ApiAuthenticationService(apiRepository, new UnitOfWork(new DatabaseFactory()), new ValidationProvider(null));
I am using Wcf in Sharp Architecture. I have configured my project following northwind sample using WcfSessionStorage etc. I have a method in the wcf service that gets a list of business object using Repository<>.GetAll(). I am testing the service method using WcfTestClient. When the method is called the very first time, everything works fine. However on the subsequent call, I get the following exception on the Repository<>.GetAll() method
[System.ObjectDisposedException]
Session is closed!
Object name: 'ISession'
It seems like the NHibernate session gets disposed after each call. I have got around this problem by decorating my service with the following attribute
[ServiceBehavior( InstanceContextMode = InstanceContextMode.PerCall )]
public class WcfService : IWcfService
{
}
However this means, an instance of the service will be created on each call that in turn will create a new nhibernate session etc. In my scenario there is no need of creating a new service instance per call and I think its an expensive process and not the right solution. I would like to know what is the best practice in my scenario and how to get this thing work with creating a new service instace per call.
Thanks
Nabeel
The easiest way is to create a new instance every time and it's not an expensive process, because creating a new object in .NET is like 0.00000000000000001 second (I read that on Ayande's blog or somewhere).
I use Autofac DI in my projects and I usually make ISession as container scoped (one per request). And then every class that uses (directly or indirectly) ISession has to be container scoped or lower (factory scoped == every class usage get's a new instance). If a class that uses ISession is higer scoped (session scoped == singleton) you'll run into problems that you currently have.
If your service is singleton service:
At first run the service is created, this service uses ISession, which should be container scoped, and it is on the first run.
The next request to service (service is now created) has still a reference to created ISession (which was closed on previous end request), so now it's closed.
I don't recomend using the same ISession that you'll open/close (it's not recomended in the NHibernate documentation), just use container scoped (I do and I don't have any performance issues), or you should create ISession manually in every method in your service like:
using(ISession s = ISessionFactory.OpenSession())
using(ITransaction t = .....)
....
But that isn't nice at all...
Please take a look at my answer to my own similar question: WCF/S#arpArch: underlying ISession is closed after the first call within a request.
#dmonlord is right that the creation of additional session instances within the same request is very cheap in this case.
Does anyone have any tips or best practices regarding how Autofac can help manage the NHibernate ISession Instance (in the case of an ASP.NET MVC application)?
I'm not overly familiar with how NHibernate sessions should be handled. That said, Autofac have excellent instance lifetime handling (scoping and deterministic disposal). Some related resources are this article and this question. Since you're in ASP.Net MVC land make sure you also look into the MVC integration stuff.
To illustrate the point, here's a quick sample on how you can use Autofac factory delegates and the Owned generic to get full control over instance lifetime:
public class SomeController
{
private readonly Func<Owned<ISession>> _sessionFactory;
public SomeController(Func<Owned<ISession>> sessionFactory)
{
_sessionFactory = sessionFactory;
}
public void DoSomeWork()
{
using (var session = _sessionFactory())
{
var transaction = session.Value.BeginTransaction();
....
}
}
}
The container setup to get this to work is quite simple. Notice that we don't have to do anything to get the Func<> and Owned<> types, these are made available automatically by Autofac:
builder.Register(c => cfg.BuildSessionFactory())
.As<ISessionFactory>()
.SingleInstance();
builder.Register(c => c.Resolve<ISessionFactory>().OpenSession());
Update: my reasoning here is that, according to this NHibernate tutorial, the lifetime of the session instance should be that of the "unit of work". Thus we need some way of controlling both when the session instance is created and when the session is disposed.
With Autofac we get this control by requesting a Func<> instead of the type directly. Not using Func<> would require that the session instance be created upfront before the controller instance is created.
Next, the default in Autofac is that instances have the lifetime of their container. Since we know that we need the power to dispose this instance as soon as the unit of work is done, we request an Owned instance. Disposing the owned instance will in this case immediately dispose the underlying session.
Edit: Sounds like Autofac and probably other containers can scope the lifetime correctly. If that's the case, go for it.
It isn't a good idea to use your IoC container to manage sessions directly. The lifetime of your session should correspond to your unit of work (transaction boundary). In the case of a web application, that should almost certainly be the lifetime of a web request.
The most common way to achieve this is with an HttpModule that both creates your session and starts your transaction when a request begins, then commits when the request has finished. I would have the HttpModule register the session in the HttpContext.Items collection.
In your IoC container, you could register something like HttpContextSessionLocator against ISessionLocator.
I should mention that your generic error handling should locate the current session and roll back the transaction automatically, or you could end up committing half a unit of work.