Add lock

Author: yim-lee

Sources/ActorSingletonPlugin/ActorSingleton.swift

@@ -13,6 +13,7 @@
 //===----------------------------------------------------------------------===//
 
 import DistributedActors
+import DistributedActorsConcurrencyHelpers
 
 // ==== ----------------------------------------------------------------------------------------------------------------
 // MARK: Actor singleton
@@ -28,7 +29,14 @@ internal final class ActorSingleton<Message> {
     let behavior: Behavior<Message>?
 
     /// The `ActorSingletonProxy` ref
-    internal private(set) var proxy: ActorRef<Message>?
+    private var _proxy: ActorRef<Message>?
+    private let proxyLock = Lock()
+
+    internal var proxy: ActorRef<Message>? {
+        self.proxyLock.withLock {
+            self._proxy
+        }
+    }
 
     init(settings: ActorSingletonSettings, props: Props?, _ behavior: Behavior<Message>?) {
         self.settings = settings
@@ -39,11 +47,13 @@ internal final class ActorSingleton<Message> {
     /// Spawns `ActorSingletonProxy` and associated actors (e.g., `ActorSingletonManager`).
     func spawnAll(_ system: ActorSystem) throws {
         let allocationStrategy = self.settings.allocationStrategy.make(system.settings.cluster, self.settings)
-        self.proxy = try system._spawnSystemActor(
-            "singletonProxy-\(self.settings.name)",
-            ActorSingletonProxy(settings: self.settings, allocationStrategy: allocationStrategy, props: self.props, self.behavior).behavior,
-            props: ._wellKnown
-        )
+        try self.proxyLock.withLock {
+            self._proxy = try system._spawnSystemActor(
+                "singletonProxy-\(self.settings.name)",
+                ActorSingletonProxy(settings: self.settings, allocationStrategy: allocationStrategy, props: self.props, self.behavior).behavior,
+                props: ._wellKnown
+            )
+        }
     }
 }
 

Sources/ActorSingletonPlugin/ActorSingletonPlugin.swift

@@ -13,6 +13,7 @@
 //===----------------------------------------------------------------------===//
 
 import DistributedActors
+import DistributedActorsConcurrencyHelpers
 
 // ==== ----------------------------------------------------------------------------------------------------------------
 // MARK: Actor singleton plugin
@@ -31,26 +32,29 @@ import DistributedActors
 ///            and <a href="https://doc.akka.io/docs/akka/current/cluster-singleton.html">`ClusterSingleton` in Akka</a>.
 public final class ActorSingletonPlugin {
     private var singletons: [String: BoxedActorSingleton] = [:]
+    private let singletonsLock = Lock()
 
     public init() {}
 
     func ref<Message>(of type: Message.Type, settings: ActorSingletonSettings, system: ActorSystem, props: Props? = nil, _ behavior: Behavior<Message>? = nil) throws -> ActorRef<Message> {
-        if let existing = self.singletons[settings.name] {
-            guard let proxy = existing.unsafeUnwrapAs(Message.self).proxy else {
-                fatalError("Singleton [\(settings.name)] not yet initialized")
+        try self.singletonsLock.withLock {
+            if let existing = self.singletons[settings.name] {
+                guard let proxy = existing.unsafeUnwrapAs(Message.self).proxy else {
+                    fatalError("Singleton [\(settings.name)] not yet initialized")
+                }
+                return proxy
             }
-            return proxy
-        }
 
-        let singleton = ActorSingleton<Message>(settings: settings, props: props, behavior)
-        try singleton.spawnAll(system)
-        self.singletons[settings.name] = BoxedActorSingleton(singleton)
+            let singleton = ActorSingleton<Message>(settings: settings, props: props, behavior)
+            try singleton.spawnAll(system)
+            self.singletons[settings.name] = BoxedActorSingleton(singleton)
 
-        guard let proxy = singleton.proxy else {
-            fatalError("Singleton[\(settings.name)] not yet initialized")
-        }
+            guard let proxy = singleton.proxy else {
+                fatalError("Singleton[\(settings.name)] not yet initialized")
+            }
 
-        return proxy // FIXME: Worried that we never synchronize access to proxy...
+            return proxy
+        }
     }
 
     func actor<Act: Actorable>(of type: Act.Type, settings: ActorSingletonSettings, system: ActorSystem, props: Props? = nil, _ makeInstance: ((Actor<Act>.Context) -> Act)? = nil) throws -> Actor<Act> {
@@ -92,8 +96,10 @@ extension ActorSingletonPlugin: Plugin {
 
     // TODO: Future
     public func stop(_ system: ActorSystem) -> Result<Void, Error> {
-        for (_, singleton) in self.singletons {
-            singleton.stop(system)
+        self.singletonsLock.withLock {
+            for (_, singleton) in self.singletons {
+                singleton.stop(system)
+            }
         }
         return .success(())
     }

Sources/DistributedActors/ActorSystem.swift

@@ -50,8 +50,6 @@ public final class ActorSystem {
 
     internal let _root: _ReceivesSystemMessages
 
-    private let terminationLock = Lock()
-
     /// Allows inspecting settings that were used to configure this actor system.
     /// Settings are immutable and may not be changed once the system is running.
     public let settings: ActorSystemSettings