Spring4d custom BuilderInspector not called

I have many objects registered in Spring4d container,some as Singleton.When Application shutdown almost Singletons correct call own Destroy,but some no and FastMM reports Memory leaks. I'm looking for a way,how Log which objects have problem. I try experienced with Container Extension with this simple example:

unit Spring.Container.HCV.Extension;

interface

uses
  Spring.Container.Extensions, Spring.Container.Core, Spring.Container.Builder;

type
  THCVLoggerBuilderInspector = class(TInspectorBase)
  protected
    procedure DoProcessModel(const kernel: IKernel; const model: TComponentModel); override;
  end;

  TFakeBuilderInspector = class(TInspectorBase)
  protected
    procedure DoProcessModel(const kernel: IKernel; const model: TComponentModel);
        override;
  end;

  THCVLoggerExtension = class(TContainerExtension)
  protected
    procedure Initialize; override;
  end;

implementation
uses
  Spring.Container.Common;

procedure THCVLoggerBuilderInspector.DoProcessModel(const kernel: IKernel;
    const model: TComponentModel);
var
  lLT:string;
begin
  if model.ComponentType.IsInstance then
  begin
    case model.LifetimeType of
      TLifetimeType.Unknown:            lLT:='Unknown           ';
      TLifetimeType.Singleton:          lLT:='Singleton         ';
      TLifetimeType.Transient:          lLT:='Transient         ';
      TLifetimeType.PerResolve:         lLT:='PerResolve        ';
      TLifetimeType.SingletonPerThread: lLT:='SingletonPerThread';
      TLifetimeType.Pooled:             lLT:='Pooled            ';
      TLifetimeType.Custom:             lLT:='Custom            ';
    else
    end;
    kernel.Logger.Info('Builder: [%s] %s',[lLT,model.ComponentTypeName]);
  end;
end;

procedure THCVLoggerExtension.Initialize;
begin
  Kernel.Builder.AddInspector(THCVLoggerBuilderInspector.Create);
  Kernel.Builder.AddInspector(TFakeBuilderInspector.Create);
end;

procedure TFakeBuilderInspector.DoProcessModel(const kernel: IKernel; const
    model: TComponentModel);
begin
  kernel.Logger.Info('FakeBuilderInspector');
end;

end.

In Registration I have

container.AddExtension<THCVLoggerExtension>;

Container correct call THCVLoggerExtension.Initialize but in my inspectors is never called DoProcessModel.Why?

Possibly because you added the extension after you called Build on the container? Another reason could be simply not seeing any logging - did you place a breakpoint in the DoProcessModel to verify it's not called?

To the actual problem: Memory leaks with singletons are almost always a result of the container not figuring out the correct refcounting of those classes. Pass the correct TRefCounting value to AsSingleton when registering any classes that are not inherited from TInterfacedObject.