Port scala akka PR #26816 to Akka.NET (#4511)

* Port scala akka PR #26816 to Akka.NET

* Remove SynchronizationContext usage

* Use internal dispatcher in other part of Akka.NET, update documentation

* Port internal blocking dispatcher and default internal dispatcher for Akka.Stream

* Add circular dispatcher alias reference checking, unroll recursion

* Make ClusterSingletonManager and Proxy to use internal dispatchers

* Update API approver list

* Remove SynchronizationContext

* Clean up Pigeon.conf config file

Co-authored-by: Aaron Stannard <[email protected]>

Author: Arkatufus

docs/articles/actors/dispatchers.md

@@ -70,6 +70,7 @@ system.ActorOf(Props.Create<MyActor>().WithDispatcher("my-dispatcher"), "my-acto
 Some dispatcher configurations are available out-of-the-box for convenience. You can use them during actor deployment, [as described above](#configuring-dispatchers).
 
 * **default-dispatcher** - A configuration that uses the [ThreadPoolDispatcher](#threadpooldispatcher). As the name says, this is the default dispatcher configuration used by the global dispatcher, and you don't need to define anything during deployment to use it.
+* **internal-dispatcher** - To protect the internal Actors that is spawned by the various Akka modules, a separate internal dispatcher is used by default.
 * **task-dispatcher** - A configuration that uses the [TaskDispatcher](#taskdispatcher).
 * **default-fork-join-dispatcher** - A configuration that uses the [ForkJoinDispatcher](#forkjoindispatcher).
 * **synchronized-dispatcher** - A configuration that uses the [SynchronizedDispatcher](#synchronizeddispatcher).
@@ -174,3 +175,10 @@ The following configuration keys are available for any dispatcher configuration:
 
 > [!NOTE]
 > The throughput-deadline-time is used as a *best effort*, not as a *hard limit*. This means that if a message takes more time than the deadline allows, Akka.NET won't interrupt the process. Instead it will wait for it to finish before giving turn to the next actor.
+
+## Dispatcher aliases
+
+When a dispatcher is looked up, and the given setting contains a string rather than a dispatcher config block, 
+the lookup will treat it as an alias, and follow that string to an alternate location for a dispatcher config.
+If the dispatcher config is referenced both through an alias and through the absolute path only one dispatcher will
+be used and shared among the two ids.

src/contrib/cluster/Akka.Cluster.Sharding/ClusterSharding.cs

@@ -262,7 +262,7 @@ public ClusterSharding(ExtendedActorSystem system)
             {
                 var guardianName = system.Settings.Config.GetString("akka.cluster.sharding.guardian-name");
                 var dispatcher = system.Settings.Config.GetString("akka.cluster.sharding.use-dispatcher");
-                if (string.IsNullOrEmpty(dispatcher)) dispatcher = Dispatchers.DefaultDispatcherId;
+                if (string.IsNullOrEmpty(dispatcher)) dispatcher = Dispatchers.InternalDispatcherId;
                 return system.SystemActorOf(Props.Create(() => new ClusterShardingGuardian()).WithDispatcher(dispatcher), guardianName);
             });
         }

src/contrib/cluster/Akka.Cluster.Sharding/reference.conf

@@ -137,7 +137,7 @@ akka.cluster.sharding {
   coordinator-singleton = "akka.cluster.singleton"
 
   # The id of the dispatcher to use for ClusterSharding actors.
-  # If not specified default dispatcher is used.
+  # If not specified, the internal dispatcher is used.
   # If specified you need to define the settings of the actual dispatcher.
   # This dispatcher for the entity actors is defined by the user provided
   # Props, i.e. this dispatcher is not used for the entity actors.

src/contrib/cluster/Akka.Cluster.Tools/Client/ClusterClientReceptionist.cs

@@ -133,7 +133,7 @@ private IActorRef CreateReceptionist()
             {
                 var name = _config.GetString("name");
                 var dispatcher = _config.GetString("use-dispatcher", null);
-                if (string.IsNullOrEmpty(dispatcher)) dispatcher = Dispatchers.DefaultDispatcherId;
+                if (string.IsNullOrEmpty(dispatcher)) dispatcher = Dispatchers.InternalDispatcherId;
 
                 // important to use var mediator here to activate it outside of ClusterReceptionist constructor
                 var mediator = PubSubMediator;

src/contrib/cluster/Akka.Cluster.Tools/Client/reference.conf

@@ -24,7 +24,7 @@ akka.cluster.client.receptionist {
   response-tunnel-receive-timeout = 30s
 
   # The id of the dispatcher to use for ClusterReceptionist actors. 
-  # If not specified default dispatcher is used.
+  # If not specified, the internal dispatcher is used.
   # If specified you need to define the settings of the actual dispatcher.
   use-dispatcher = ""
 

src/contrib/cluster/Akka.Cluster.Tools/PublishSubscribe/DistributedPubSub.cs

@@ -102,7 +102,7 @@ private IActorRef CreateMediator()
             var name = _system.Settings.Config.GetString("akka.cluster.pub-sub.name");
             var dispatcher = _system.Settings.Config.GetString("akka.cluster.pub-sub.use-dispatcher", null);
             if (string.IsNullOrEmpty(dispatcher))
-                dispatcher = Dispatchers.DefaultDispatcherId;
+                dispatcher = Dispatchers.InternalDispatcherId;
 
             return _system.SystemActorOf(
                 Props.Create(() => new DistributedPubSubMediator(_settings))

src/contrib/cluster/Akka.Cluster.Tools/PublishSubscribe/reference.conf

@@ -30,7 +30,7 @@ akka.cluster.pub-sub {
   max-delta-elements = 3000
 
   # The id of the dispatcher to use for DistributedPubSubMediator actors. 
-  # If not specified default dispatcher is used.
+  # If not specified, the internal dispatcher is used.
   # If specified you need to define the settings of the actual dispatcher.
   use-dispatcher = ""
 

src/contrib/cluster/Akka.Cluster.Tools/Singleton/ClusterSingletonManager.cs

@@ -14,6 +14,7 @@
 using Akka.Actor;
 using Akka.Configuration;
 using Akka.Coordination;
+using Akka.Dispatch;
 using Akka.Event;
 using Akka.Pattern;
 using Akka.Remote;
@@ -604,7 +605,9 @@ public static Props Props(Props singletonProps, ClusterSingletonManagerSettings
         /// <returns>TBD</returns>
         public static Props Props(Props singletonProps, object terminationMessage, ClusterSingletonManagerSettings settings)
         {
-            return Actor.Props.Create(() => new ClusterSingletonManager(singletonProps, terminationMessage, settings)).WithDeploy(Deploy.Local);
+            return Actor.Props.Create(() => new ClusterSingletonManager(singletonProps, terminationMessage, settings))
+                .WithDispatcher(Dispatchers.InternalDispatcherId)
+                .WithDeploy(Deploy.Local);
         }
 
         private readonly Props _singletonProps;

src/contrib/cluster/Akka.Cluster.Tools/Singleton/ClusterSingletonProxy.cs

@@ -11,6 +11,7 @@
 using System.Linq;
 using Akka.Actor;
 using Akka.Configuration;
+using Akka.Dispatch;
 using Akka.Event;
 
 namespace Akka.Cluster.Tools.Singleton
@@ -70,7 +71,9 @@ public static Config DefaultConfig()
         /// <returns>TBD</returns>
         public static Props Props(string singletonManagerPath, ClusterSingletonProxySettings settings)
         {
-            return Actor.Props.Create(() => new ClusterSingletonProxy(singletonManagerPath, settings)).WithDeploy(Deploy.Local);
+            return Actor.Props.Create(() => new ClusterSingletonProxy(singletonManagerPath, settings))
+                .WithDispatcher(Dispatchers.InternalDispatcherId)
+                .WithDeploy(Deploy.Local);
         }
 
         private readonly ClusterSingletonProxySettings _settings;

src/contrib/cluster/Akka.DistributedData/ReplicatorSettings.cs

@@ -43,7 +43,7 @@ public static ReplicatorSettings Create(Config config)
                 throw ConfigurationException.NullOrEmptyConfig<ReplicatorSettings>();
 
             var dispatcher = config.GetString("use-dispatcher", null);
-            if (string.IsNullOrEmpty(dispatcher)) dispatcher = Dispatchers.DefaultDispatcherId;
+            if (string.IsNullOrEmpty(dispatcher)) dispatcher = Dispatchers.InternalDispatcherId;
 
             var durableConfig = config.GetConfig("durable");
             var durableKeys = durableConfig.GetStringList("keys");
@@ -63,7 +63,7 @@ public static ReplicatorSettings Create(Config config)
                 {
                     throw new ArgumentException($"`akka.cluster.distributed-data.durable.store-actor-class` is set to an invalid class {durableStoreType}.");
                 }
-                durableStoreProps = Props.Create(durableStoreType, durableConfig).WithDispatcher(durableConfig.GetString("use-dispatcher"));
+                durableStoreProps = Props.Create(durableStoreType, durableConfig).WithDispatcher(dispatcher);
             }
 
             // TODO: This constructor call fails when these fields are not populated inside the Config object:
@@ -212,7 +212,7 @@ private ReplicatorSettings Copy(string role = null,
         public ReplicatorSettings WithGossipInterval(TimeSpan gossipInterval) => Copy(gossipInterval: gossipInterval);
         public ReplicatorSettings WithNotifySubscribersInterval(TimeSpan notifySubscribersInterval) => Copy(notifySubscribersInterval: notifySubscribersInterval);
         public ReplicatorSettings WithMaxDeltaElements(int maxDeltaElements) => Copy(maxDeltaElements: maxDeltaElements);
-        public ReplicatorSettings WithDispatcher(string dispatcher) => Copy(dispatcher: string.IsNullOrEmpty(dispatcher) ? Dispatchers.DefaultDispatcherId : dispatcher);
+        public ReplicatorSettings WithDispatcher(string dispatcher) => Copy(dispatcher: string.IsNullOrEmpty(dispatcher) ? Dispatchers.InternalDispatcherId : dispatcher);
         public ReplicatorSettings WithPruning(TimeSpan pruningInterval, TimeSpan maxPruningDissemination) => 
             Copy(pruningInterval: pruningInterval, maxPruningDissemination: maxPruningDissemination);
         public ReplicatorSettings WithDurableKeys(IImmutableSet<string> durableKeys) => Copy(durableKeys: durableKeys);