Closed Ryujose closed 5 months ago
What's wrong with the handler being a transient exactly?
The particular reason here is for this point.
Context pooling works by reusing the same context instance across requests; this means that it's effectively registered as a Singleton, and the same instance is reused across multiple requests (or DI scopes). This means that special care must be taken when the context involves any state that may change between requests.
In A DDD structure for domain events we usually have some sequence like this.
-> Endpoint
-> Command handler
-> Domain events registered
-> UnitOfWork SaveChanges
-> DomainEventDispatcher
-> INotification publish
-> Entity Framework Core SaveChanges
Looking on this sequence the issue happens because we've the following on DI
What were the issues we were having?
An unhandled exception has occurred while executing the request. System.InvalidOperationException: Cannot resolve 'System.Collections.Generic.IEnumerable
1[MediatR.INotificationHandler1[Event registered]]' from root provider because it requires scoped service 'Random.Domain.Aggregates.RandomAggregate.IRandomRepository'. at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteValidator.ValidateResolution(ServiceCallSite callSite, IServiceScope scope, IServiceScope rootScope) at Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService(ServiceIdentifier serviceIdentifier, ServiceProviderEngineScope serviceProviderEngineScope) at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService(Type serviceType) at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType) at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService[T](IServiceProvider provider) at MediatR.Wrappers.NotificationHandlerWrapperImpl
1.Handle(INotification notification, IServiceProvider serviceFactory, Func4 publish, CancellationToken cancellationToken)
Turning into the core question
There's some possible impact if we choose the path of trying to use scoped instead of transient for those calls?
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Issue
We're having an issue with INotification event for domain events. The thing is that we were trying to use DbContextPooling but it seems that this throw an exception because a captive dependency https://blog.ploeh.dk/2014/06/02/captive-dependency/
App structure
Possible solution
We were thinking to resolve this registering the INotification on hand as a scoped service.
Possible impacts
You know if there could be some extra impact on this possible solution?