Replace lifecycle SystemTarget scheduling with Task.Run

Co-authored-by: ReubenBond <203839+ReubenBond@users.noreply.github.com>

Author: Copilot

src/Orleans.Core/Runtime/Constants.cs

@@ -16,7 +16,6 @@ internal static class Constants
         public static readonly GrainType CatalogType = SystemTargetGrainId.CreateGrainType("catalog");
         public static readonly GrainType MembershipServiceType = SystemTargetGrainId.CreateGrainType("clustering");
         public static readonly GrainType SystemMembershipTableType = SystemTargetGrainId.CreateGrainType("clustering.dev");
-        public static readonly GrainType LifecycleSchedulingSystemTargetType = SystemTargetGrainId.CreateGrainType("lifecycle");
         public static readonly GrainType DeploymentLoadPublisherSystemTargetType = SystemTargetGrainId.CreateGrainType("load-publisher");
         public static readonly GrainType TestHooksSystemTargetType = SystemTargetGrainId.CreateGrainType("test.hooks");
         public static readonly GrainType TransactionAgentSystemTargetType = SystemTargetGrainId.CreateGrainType("txn.agent");
@@ -46,7 +45,6 @@ internal static class Constants
             {ClientDirectoryType, "ClientDirectory"},
             {CatalogType,"Catalog"},
             {MembershipServiceType,"MembershipService"},
-            {LifecycleSchedulingSystemTargetType, "LifecycleSchedulingSystemTarget"},
             {DeploymentLoadPublisherSystemTargetType, "DeploymentLoadPublisherSystemTarget"},
             {StreamProviderManagerAgentSystemTargetType,"StreamProviderManagerAgent"},
             {TestHooksSystemTargetType,"TestHooksSystemTargetType"},

src/Orleans.Runtime/Hosting/DefaultSiloServices.cs

@@ -93,7 +93,6 @@ internal static void AddDefaultServices(ISiloBuilder builder)
             services.TryAddSingleton<OverloadDetector>();
 
             services.AddSingleton<SystemTargetShared>();
-            services.AddSingleton<LifecycleSchedulingSystemTarget>();
 
             services.TryAddSingleton<ITimerRegistry, TimerRegistry>();
 

src/Orleans.Runtime/Silo/Silo.cs

@@ -53,8 +53,6 @@ public sealed partial class Silo : IAsyncDisposable, IDisposable
         /// </summary>
         public Task SiloTerminated { get { return this.siloTerminatedTask.Task; } } // one event for all types of termination (shutdown, stop and fast kill).
 
-        private LifecycleSchedulingSystemTarget lifecycleSchedulingSystemTarget;
-
         /// <summary>
         /// Initializes a new instance of the <see cref="Silo"/> class.
         /// </summary>
@@ -142,12 +140,9 @@ public Silo(ILocalSiloDetails siloDetails, IServiceProvider services)
         /// <returns>A <see cref="Task"/> representing the operation.</returns>
         public async Task StartAsync(CancellationToken cancellationToken)
         {
-            // SystemTarget for provider init calls
-            this.lifecycleSchedulingSystemTarget = Services.GetRequiredService<LifecycleSchedulingSystemTarget>();
-
             try
             {
-                await this.lifecycleSchedulingSystemTarget.WorkItemGroup.QueueTask(() => this.siloLifecycle.OnStart(cancellationToken), lifecycleSchedulingSystemTarget);
+                await Task.Run(() => this.siloLifecycle.OnStart(cancellationToken), cancellationToken);
             }
             catch (Exception exc)
             {
@@ -344,7 +339,7 @@ public async Task StopAsync(CancellationToken cancellationToken)
 
             try
             {
-                await this.lifecycleSchedulingSystemTarget.QueueTask(() => this.siloLifecycle.OnStop(cancellationToken)).ConfigureAwait(false);
+                await Task.Run(() => this.siloLifecycle.OnStop(cancellationToken), cancellationToken).ConfigureAwait(false);
             }
             finally
             {
@@ -427,8 +422,7 @@ private async Task OnActiveStop(CancellationToken ct)
             {
                 try
                 {
-                    await lifecycleSchedulingSystemTarget
-                        .QueueTask(() => this.messageCenter.Gateway.SendStopSendMessages(this.grainFactory)).WaitAsync(ct);
+                    await Task.Run(() => this.messageCenter.Gateway.SendStopSendMessages(this.grainFactory), ct).WaitAsync(ct);
                 }
                 catch (Exception exception)
                 {
@@ -679,14 +673,4 @@ private readonly struct SiloAddressConsistentHashCodeLogValue(SiloAddress siloAd
         )]
         private static partial void LogDebugGrainServiceStopped(ILogger logger, string grainServiceType, GrainId grainServiceId);
     }
-
-    // A dummy system target for fallback scheduler
-    internal sealed class LifecycleSchedulingSystemTarget : SystemTarget
-    {
-        public LifecycleSchedulingSystemTarget(SystemTargetShared shared)
-            : base(Constants.LifecycleSchedulingSystemTargetType, shared)
-        {
-            shared.ActivationDirectory.RecordNewTarget(this);
-        }
-    }
 }