Fix IIS/Windows Service console race condition (#7691)

src/core/Akka.Tests/Loggers/StandardOutWriterSpec.cs

@@ -0,0 +1,94 @@
+//-----------------------------------------------------------------------
+// <copyright file="StandardOutWriterSpec.cs" company="Akka.NET Project">
+//     Copyright (C) 2009-2022 Lightbend Inc. <http://www.lightbend.com>
+//     Copyright (C) 2013-2025 .NET Foundation <https://github.com/akkadotnet/akka.net>
+// </copyright>
+//-----------------------------------------------------------------------
+
+using System;
+using System.IO;
+using System.Threading.Tasks;
+using Akka.TestKit;
+using Akka.Util;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace Akka.Tests.Loggers
+{
+    /// <summary>
+    /// Tests for StandardOutWriter to ensure it handles IIS/Windows Service environments correctly
+    /// where Console.Out and Console.Error may be redirected to StreamWriter.Null
+    /// </summary>
+    public class StandardOutWriterSpec : AkkaSpec
+    {
+        public StandardOutWriterSpec(ITestOutputHelper output) : base(output)
+        {
+        }
+
+        [Fact]
+        public void StandardOutWriter_should_handle_concurrent_writes_without_race_conditions()
+        {
+            // This test simulates the concurrent access pattern that causes issues in IIS
+            // In normal test environments this won't reproduce the issue, but it ensures
+            // our fix doesn't break normal console operation
+
+            var tasks = new Task[100];
+
+            for (int i = 0; i < tasks.Length; i++)
+            {
+                var taskId = i;
+                tasks[i] = Task.Run(() =>
+                {
+                    for (int j = 0; j < 10; j++)
+                    {
+                        // These calls should not throw even under concurrent access
+                        StandardOutWriter.WriteLine($"Task {taskId} - Line {j}");
+                        StandardOutWriter.Write($"Task {taskId} - Write {j} ");
+                    }
+                });
+            }
+
+            // Should complete without throwing IndexOutOfRangeException
+            Assert.True(Task.WaitAll(tasks, TimeSpan.FromSeconds(5)));
+        }
+
+        [Fact]
+        public void StandardOutWriter_should_not_throw_when_console_is_redirected()
+        {
+            // Save original streams
+            var originalOut = Console.Out;
+            var originalError = Console.Error;
+
+            try
+            {
+                // Simulate IIS/Windows Service environment by redirecting to null
+                Console.SetOut(StreamWriter.Null);
+                Console.SetError(StreamWriter.Null);
+
+                // These should not throw even when console is redirected to null
+                StandardOutWriter.WriteLine("This should not throw");
+                StandardOutWriter.Write("Neither should this");
+
+                // Test with colors (which would normally fail in IIS)
+                StandardOutWriter.WriteLine("Colored output", ConsoleColor.Red);
+                StandardOutWriter.Write("Colored write", ConsoleColor.Blue, ConsoleColor.Yellow);
+            }
+            finally
+            {
+                // Restore original streams
+                Console.SetOut(originalOut);
+                Console.SetError(originalError);
+            }
+        }
+
+        [Fact]
+        public void StandardOutWriter_should_handle_null_and_empty_messages()
+        {
+            // Should not throw
+            StandardOutWriter.WriteLine(null);
+            StandardOutWriter.WriteLine("");
+            StandardOutWriter.Write(null);
+            StandardOutWriter.Write("");
+        }
+    }
+}

src/core/Akka/Event/DefaultLogger.cs

@@ -46,7 +46,11 @@ protected override bool Receive(object message)
         protected virtual void Print(LogEvent logEvent)
         {
             if (_stdoutLogger == null)
-                throw new Exception("Logger has not been initialized yet.");
+            {
+                // Include context about the failed log event to help with debugging
+                var logDetails = $"[{logEvent.LogLevel()}] {logEvent.LogSource}: {logEvent.Message}";
+                throw new Exception($"Logger has not been initialized yet. Failed to log: {logDetails}");
+            }
 
             _stdoutLogger.Tell(logEvent);
         }

src/core/Akka/Util/StandardOutWriter.cs

@@ -6,6 +6,7 @@
 //-----------------------------------------------------------------------
 
 using System;
+using System.IO;
 
 namespace Akka.Util
 {
@@ -16,6 +17,34 @@ namespace Akka.Util
     public static class StandardOutWriter
     {
         private static readonly object _lock = new();
+        private static readonly bool _isConsoleAvailable = DetectConsoleAvailability();
+
+        /// <summary>
+        /// Detects whether a real console is available for output.
+        /// In environments like IIS and Windows Services, console output is redirected to StreamWriter.Null,
+        /// which is a singleton. When multiple threads write to both Console.Out and Console.Error
+        /// (which point to the same StreamWriter.Null instance), it causes race conditions.
+        /// 
+        /// Since console output goes nowhere in these environments anyway, we skip it entirely
+        /// to prevent the race condition and improve performance.
+        /// </summary>
+        private static bool DetectConsoleAvailability()
+        {
+            // Specifically detect the IIS/Windows Service scenario where both Console.Out 
+            // and Console.Error point to the SAME StreamWriter.Null singleton instance.
+            // This is the exact condition that causes the race condition.
+            // Note: We check both because in these environments, both are always set to the same instance
+            if (Console.Out == StreamWriter.Null && Console.Error == StreamWriter.Null)
+                return false;
+
+            // Also check Environment.UserInteractive for additional safety
+            // This returns false for Windows Services and IIS in .NET Framework
+            // (though less reliable in .NET Core, the StreamWriter.Null check above is the key)
+            if (!Environment.UserInteractive)
+                return false;
+
+            return true;
+        }
 
         /// <summary>
         /// Writes the specified <see cref="string"/> value to the standard output stream. Optionally 
@@ -46,6 +75,16 @@ public static void WriteLine(string message, ConsoleColor? foregroundColor = nul
         private static void WriteToConsole(string message, ConsoleColor? foregroundColor = null,
             ConsoleColor? backgroundColor = null, bool line = true)
         {
+            // Skip console output in IIS, Windows Services, and other non-console environments.
+            // In these environments:
+            // 1. Console output is redirected to StreamWriter.Null (goes nowhere anyway)
+            // 2. Both Console.Out and Console.Error point to the same StreamWriter.Null singleton
+            // 3. Concurrent writes to both streams cause race conditions and IndexOutOfRangeException
+            // 4. Skipping output entirely prevents the race condition and improves performance
+            // See: https://github.com/akkadotnet/akka.net/issues/7691
+            if (!_isConsoleAvailable)
+                return;
+
             lock (_lock)
             {
                 ConsoleColor? fg = null;