fix pool router start in case of failing routee props (#1715)

Author: marcinbudny

src/Proto.Actor/Router/RouterActor.cs

@@ -3,8 +3,8 @@
 //      Copyright (C) 2015-2022 Asynkron AB All rights reserved
 // </copyright>
 // -----------------------------------------------------------------------
+using System;
 using System.Linq;
-using System.Threading;
 using System.Threading.Tasks;
 using Proto.Router.Messages;
 using Proto.Router.Routers;
@@ -15,21 +15,28 @@ public class RouterActor : IActor
 {
     private readonly RouterConfig _config;
     private readonly RouterState _routerState;
-    private readonly AutoResetEvent _wg;
+    private readonly RouterStartNotification _startNotification;
 
-    public RouterActor(RouterConfig config, RouterState routerState, AutoResetEvent wg)
+    public RouterActor(RouterConfig config, RouterState routerState, RouterStartNotification startNotification)
     {
         _config = config;
         _routerState = routerState;
-        _wg = wg;
+        _startNotification = startNotification;
     }
 
     public Task ReceiveAsync(IContext context)
     {
         if (context.Message is Started)
         {
-            _config.OnStarted(context, _routerState);
-            _wg.Set();
+            try
+            {
+                _config.OnStarted(context, _routerState);
+                _startNotification.NotifyStarted();
+            }
+            catch (Exception e)
+            {
+                _startNotification.NotifyFailed(e);
+            }
             return Task.CompletedTask;
         }
 

src/Proto.Actor/Router/Routers/RouterConfig.cs

@@ -20,8 +20,8 @@ public abstract record RouterConfig
     private PID SpawnRouterProcess(ActorSystem system, string name, Props props, PID? parent, Action<IContext>? callback)
     {
         var routerState = CreateRouterState();
-        var wg = new AutoResetEvent(false);
-        var p = props.WithProducer(() => new RouterActor(this, routerState, wg));
+        var notifyStarted = new RouterStartNotification();
+        var p = props.WithProducer(() => new RouterActor(this, routerState, notifyStarted));
 
         var mailbox = props.MailboxProducer();
         var dispatcher = props.Dispatcher;
@@ -35,7 +35,42 @@ private PID SpawnRouterProcess(ActorSystem system, string name, Props props, PID
         mailbox.RegisterHandlers(ctx, dispatcher);
         mailbox.PostSystemMessage(Started.Instance);
         mailbox.Start();
-        wg.WaitOne();
+
+        var (startSuccess, startException) = notifyStarted.Wait();
+
+        if (!startSuccess)
+        {
+            system.Root.Stop(self);
+            throw new RouterStartFailedException(startException!);
+        }
+
         return self;
     }
+}
+
+public class RouterStartNotification
+{
+    private readonly ManualResetEvent _wg = new(false);
+    private Exception? _exception;
+
+    public void NotifyStarted() => _wg.Set();
+
+    public void NotifyFailed(Exception exception)
+    {
+        _exception = exception;
+        _wg.Set();
+    }
+
+    public (bool StartSuccess, Exception? Exception) Wait()
+    {
+        _wg.WaitOne();
+        return (_exception is null, _exception);
+    }
+}
+
+public class RouterStartFailedException : Exception
+{
+    public RouterStartFailedException(Exception inner) : base("Router failed to start", inner)
+    {
+    }
 }

tests/Proto.Actor.Tests/Router/PoolRouterTests.cs

@@ -1,6 +1,8 @@
 using System;
 using System.Threading.Tasks;
+using FluentAssertions;
 using Proto.Router.Messages;
+using Proto.Router.Routers;
 using Proto.TestFixtures;
 using Xunit;
 
@@ -58,4 +60,16 @@ public async Task RandomPool_CreatesRoutees()
         var routees = await system.Root.RequestAsync<Routees>(router, new RouterGetRoutees(), _timeout);
         Assert.Equal(3, routees.Pids.Count);
     }
+
+    [Fact]
+    public async Task If_routee_props_then_router_creation_fails()
+    {
+        await using var system = new ActorSystem();
+
+        var failingProps = Props.FromProducer(() => throw new Exception("Failing props"));
+
+        system.Invoking(s => s.Root.Spawn(s.Root.NewRandomPool(failingProps, 3, 0)))
+            .Should().Throw<RouterStartFailedException>()
+            .WithInnerException<Exception>().WithMessage("Failing props");
+    }
 }