Instance Hash Collisions for Large Service Registry

[jwoodmanbuildium]

When an application has a large service graph (thousands of services), instance hash collisions occur, causing the wrong implementations to be resolved at runtime.

Exception info:

ClassName: System.InvalidCastException
Message: Unable to cast object of type '{ImplentationType}' to type '{ServiceType}'.

Stack Trace:
   at (Closure`6 , Scope )
   at Lamar.IoC.Instances.GeneratedInstance.<>c__DisplayClass5_1.<BuildFuncResolver>b__0(Scope s)
   at Lamar.IoC.Instances.GeneratedInstance.Resolve(Scope scope)
   at (Closure`9 , Scope )
   at Lamar.IoC.Instances.GeneratedInstance.<>c__DisplayClass5_1.<BuildFuncResolver>b__0(Scope s)
   at Lamar.IoC.Instances.GeneratedInstance.Resolve(Scope scope)
   at (ArrayClosure , Scope )
   at Lamar.IoC.Instances.GeneratedInstance.<>c__DisplayClass5_1.<BuildFuncResolver>b__0(Scope s)
   at Lamar.IoC.Instances.GeneratedInstance.Resolve(Scope scope)
   at (ArrayClosure , Scope )
   at Lamar.IoC.Instances.GeneratedInstance.<>c__DisplayClass5_1.<BuildFuncResolver>b__0(Scope s)
   at Lamar.IoC.Instances.GeneratedInstance.Resolve(Scope scope)
   at (ArrayClosure , Scope )
   at Lamar.IoC.Instances.GeneratedInstance.<>c__DisplayClass5_1.<BuildFuncResolver>b__0(Scope s)
   at Lamar.IoC.Instances.GeneratedInstance.Resolve(Scope scope)
   at (ArrayClosure , Scope )
   at Lamar.IoC.Instances.GeneratedInstance.<>c__DisplayClass5_1.<BuildFuncResolver>b__0(Scope s)
   at Lamar.IoC.Instances.GeneratedInstance.Resolve(Scope scope)
   at (Closure`1 , Scope )
   at Lamar.IoC.Instances.GeneratedInstance.<>c__DisplayClass5_1.<BuildFuncResolver>b__0(Scope s)
   at Lamar.IoC.Instances.GeneratedInstance.Resolve(Scope scope)
   at (ArrayClosure , Scope )
   at Lamar.IoC.Instances.GeneratedInstance.<>c__DisplayClass5_1.<BuildFuncResolver>b__0(Scope s)
   at Lamar.IoC.Scope.GetInstance(Type serviceType)
   at Lamar.IoC.Scope.GetInstance[T]()

I've added a workaround to recalculate the hash duplicates at startup by updating the instance names, but it would be nice if these collisions could be avoided by Lamar.

e.g. workaround

void MitigateHashCollisions(ServiceRegistry serviceRegistry)
{
    var hashCollisions = serviceRegistry
        .Select(x => x.ImplementationInstance)
        .OfType<Instance>()
        .GroupBy(x => x.Hash)
        .Where(x => x.Select(y => y.ServiceType).Distinct().Count() > 1);

    foreach (var collisionGroup in hashCollisions)
    {
        foreach (var lamarInstance in collisionGroup.Where(x => !x.IsExplicitlyNamed))
        {
            // Updating the name will result in a new hash
            lamarInstance.Name = $"Default_{lamarInstance.ServiceType.Name}";
        }
    }
}

[jeremydmiller]

I'd be happy for a pull request on this one

[jwoodmanbuildium]

@jeremydmiller - Any chance the hashing implementation can be reworked with version 14 to avoid these collisions?