perf(grain): lazily resolve grain runtime

src/Orleans.Core.Abstractions/Core/Grain.cs

@@ -14,6 +14,8 @@ namespace Orleans;
 /// </summary>
 public abstract partial class Grain : IGrainBase, IAddressable
 {
+    private IGrainRuntime? _grainRuntime;
+
     // Do not use this directly because we currently don't provide a way to inject it;
     // any interaction with it will result in non unit-testable code. Any behavior that can be accessed
     // from within client code (including subclasses of this class), should be exposed through IGrainRuntime.
@@ -23,7 +25,7 @@ public abstract partial class Grain : IGrainBase, IAddressable
 
     public GrainReference GrainReference { get { return GrainContext.GrainReference; } }
 
-    internal IGrainRuntime Runtime { get; }
+    internal IGrainRuntime Runtime => _grainRuntime ??= GetGrainRuntime()!;
 
     /// <summary>
     /// Gets an object which can be used to access other grains. Null if this grain is not associated with a Runtime, such as when created directly for unit testing.
@@ -54,9 +56,7 @@ protected Grain() : this(RuntimeContext.Current!, grainRuntime: null)
     protected Grain(IGrainContext grainContext, IGrainRuntime? grainRuntime = null)
     {
         GrainContext = grainContext;
-
-        // ! The runtime ensures that this is not null and Unit testing frameworks must make sure that this is not null.
-        Runtime = grainRuntime ?? grainContext?.ActivationServices.GetService<IGrainRuntime>()!;
+        _grainRuntime = grainRuntime;
     }
 
     /// <summary>
@@ -163,6 +163,22 @@ protected void DelayDeactivation(TimeSpan timeSpan)
     /// <param name="cancellationToken">A cancellation token which signals when deactivation should complete promptly.</param>
     public virtual Task OnDeactivateAsync(DeactivationReason reason, CancellationToken cancellationToken) => Task.CompletedTask;
 
+    private IGrainRuntime? GetGrainRuntime()
+    {
+        var grainContext = GrainContext;
+        if (grainContext is null)
+        {
+            return null;
+        }
+
+        if (grainContext.GetComponent(typeof(IGrainRuntime)) is IGrainRuntime grainRuntime)
+        {
+            return grainRuntime;
+        }
+
+        return grainContext.ActivationServices.GetService<IGrainRuntime>();
+    }
+
     internal void EnsureRuntime()
     {
         if (Runtime == null)

src/Orleans.Runtime/Catalog/GrainTypeSharedContext.cs

@@ -109,6 +109,11 @@ private static TimeSpan GetCollectionAgeLimit(GrainType grainType, Type grainCla
             return (TComponent)Logger;
         }
 
+        if (typeof(TComponent) == typeof(IGrainRuntime) && Runtime is TComponent runtime)
+        {
+            return runtime;
+        }
+
         if (_components is null) return default;
         _components.TryGetValue(typeof(TComponent), out var resultObj);
         return (TComponent?)resultObj;
@@ -131,6 +136,11 @@ private static TimeSpan GetCollectionAgeLimit(GrainType grainType, Type grainCla
             return Logger;
         }
 
+        if (componentType == typeof(IGrainRuntime))
+        {
+            return Runtime;
+        }
+
         if (_components is null) return default;
         _components.TryGetValue(componentType, out var resultObj);
         return resultObj;