Better report Kestrel crashing errors

src/Microsoft.AspNetCore.Server.Kestrel/Internal/Infrastructure/KestrelThread.cs

@@ -142,17 +142,16 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal
                             Post(t => t.OnStopImmediate());
                             if (!await WaitAsync(_threadTcs.Task, stepTimeout).ConfigureAwait(false))
                             {
-                                _log.LogError(0, null, "KestrelThread.StopAsync failed to terminate libuv thread.");
+                                _log.LogCritical("KestrelThread.StopAsync failed to terminate libuv thread.");
                             }
                         }
                     }
                     catch (ObjectDisposedException)
                     {
-                        // REVIEW: Should we log something here?
                         // Until we rework this logic, ODEs are bound to happen sometimes.
                         if (!await WaitAsync(_threadTcs.Task, stepTimeout).ConfigureAwait(false))
                         {
-                            _log.LogError(0, null, "KestrelThread.StopAsync failed to terminate libuv thread.");
+                            _log.LogCritical("KestrelThread.StopAsync failed to terminate libuv thread.");
                         }
                     }
                 }
@@ -343,8 +342,8 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal
             }
             finally
             {
-                thisHandle.Free();
                 _threadTcs.SetResult(null);
+                thisHandle.Free();
             }
         }
 

src/Microsoft.AspNetCore.Server.Kestrel/Internal/KestrelEngine.cs

@@ -51,7 +51,22 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Internal
 
         public void Dispose()
         {
-            Task.WaitAll(Threads.Select(thread => thread.StopAsync(TimeSpan.FromSeconds(2.5))).ToArray());
+            try
+            {
+                Task.WaitAll(Threads.Select(thread => thread.StopAsync(TimeSpan.FromSeconds(2.5))).ToArray());
+            }
+            catch (AggregateException aggEx)
+            {
+                // An uncaught exception was likely thrown from the libuv event loop.
+                // The original error that crashed one loop may have caused secondary errors in others.
+                // Make sure that the stack trace of the original error is logged.
+                foreach (var ex in aggEx.InnerExceptions)
+                {
+                    Log.LogCritical("Failed to gracefully close Kestrel.", ex);
+                }
+
+                throw;
+            }
 
             Threads.Clear();
 #if DEBUG

test/Microsoft.AspNetCore.Server.KestrelTests/KestrelServerTests.cs

@@ -23,7 +23,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
         [InlineData(-1337)]
         public void StartWithNonPositiveThreadCountThrows(int threadCount)
         {
-            var testLogger = new TestApplicationErrorLogger();
+            var testLogger = new TestApplicationErrorLogger { ThrowOnCriticalErrors = false };
             var server = CreateServer(new KestrelServerOptions() { ThreadCount = threadCount }, testLogger);
 
             var exception = Assert.Throws<ArgumentOutOfRangeException>(() => StartDummyApplication(server));
@@ -35,7 +35,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
         [Fact]
         public void StartWithInvalidAddressThrows()
         {
-            var testLogger = new TestApplicationErrorLogger();
+            var testLogger = new TestApplicationErrorLogger { ThrowOnCriticalErrors = false };
             var server = CreateServer(new KestrelServerOptions(), testLogger);
             server.Features.Get<IServerAddressesFeature>().Addresses.Add("http:/asdf");
 
@@ -72,7 +72,7 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
         [InlineData(int.MaxValue - 1, int.MaxValue)]
         public void StartWithMaxRequestBufferSizeLessThanMaxRequestLineSizeThrows(long maxRequestBufferSize, int maxRequestLineSize)
         {
-            var testLogger = new TestApplicationErrorLogger();
+            var testLogger = new TestApplicationErrorLogger { ThrowOnCriticalErrors = false };
             var options = new KestrelServerOptions();
             options.Limits.MaxRequestBufferSize = maxRequestBufferSize;
             options.Limits.MaxRequestLineSize = maxRequestLineSize;

test/shared/TestApplicationErrorLogger.cs

@@ -14,6 +14,8 @@ namespace Microsoft.AspNetCore.Testing
         // Application errors are logged using 13 as the eventId.
         private const int ApplicationErrorEventId = 13;
 
+        public bool ThrowOnCriticalErrors { get; set; } = true;
+
         public ConcurrentBag<LogMessage> Messages { get; } = new ConcurrentBag<LogMessage>();
 
         public int TotalErrorsLogged => Messages.Count(message => message.LogLevel == LogLevel.Error);
@@ -34,9 +36,17 @@ namespace Microsoft.AspNetCore.Testing
 
         public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception exception, Func<TState, Exception, string> formatter)
         {
-#if false
+#if true
-            Console.WriteLine($"Log {logLevel}[{eventId}]: {formatter(state, exception)} {exception?.Message}");
+            if (logLevel == LogLevel.Critical && ThrowOnCriticalErrors)
 #endif
+            {
+                Console.WriteLine($"Log {logLevel}[{eventId}]: {formatter(state, exception)} {exception?.Message}");
+
+                if (logLevel == LogLevel.Critical && ThrowOnCriticalErrors)
+                {
+                    throw new Exception("Unexpected critical error.", exception);
+                }
+            }
 
             Messages.Add(new LogMessage
             {