From b098f24c681f8943cdb1815392ef075f6b9e1141 Mon Sep 17 00:00:00 2001
From: mus65 <marius.thesing@gmail.com>
Date: Thu, 20 Feb 2025 18:56:39 +0100
Subject: [PATCH] Host: log exception if a service factory fails (#112534)

---
 .../src/Internal/Host.cs                      | 29 +++++++++----------
 .../tests/UnitTests/Internal/HostTests.cs     | 27 +++++++++++++++++
 2 files changed, 41 insertions(+), 15 deletions(-)

diff --git a/src/libraries/Microsoft.Extensions.Hosting/src/Internal/Host.cs b/src/libraries/Microsoft.Extensions.Hosting/src/Internal/Host.cs
index e84d2f3a646215..153bd31d4bc51e 100644
--- a/src/libraries/Microsoft.Extensions.Hosting/src/Internal/Host.cs
+++ b/src/libraries/Microsoft.Extensions.Hosting/src/Internal/Host.cs
@@ -85,28 +85,27 @@ public async Task StartAsync(CancellationToken cancellationToken = default)
                 cancellationToken.ThrowIfCancellationRequested();
 
                 List<Exception> exceptions = new();
-                _hostedServices ??= Services.GetRequiredService<IEnumerable<IHostedService>>();
-                _hostedLifecycleServices = GetHostLifecycles(_hostedServices);
                 _hostStarting = true;
                 bool concurrent = _options.ServicesStartConcurrently;
                 bool abortOnFirstException = !concurrent;
 
-                // Call startup validators.
-                IStartupValidator? validator = Services.GetService<IStartupValidator>();
-                if (validator is not null)
+                try
                 {
-                    try
-                    {
-                        validator.Validate();
-                    }
-                    catch (Exception ex)
-                    {
-                        exceptions.Add(ex);
+                    _hostedServices ??= Services.GetRequiredService<IEnumerable<IHostedService>>();
+                    _hostedLifecycleServices = GetHostLifecycles(_hostedServices);
 
-                        // Validation errors cause startup to be aborted.
-                        LogAndRethrow();
-                    }
+                    // Call startup validators.
+                    IStartupValidator? validator = Services.GetService<IStartupValidator>();
+                    validator?.Validate();
                 }
+                catch (Exception ex)
+                {
+                    // service factory or validation failed, abort startup.
+                    exceptions.Add(ex);
+                    LogAndRethrow();
+                    return; // unreachable
+                }
+
 
                 // Call StartingAsync().
                 if (_hostedLifecycleServices is not null)
diff --git a/src/libraries/Microsoft.Extensions.Hosting/tests/UnitTests/Internal/HostTests.cs b/src/libraries/Microsoft.Extensions.Hosting/tests/UnitTests/Internal/HostTests.cs
index 64f9dd8f904118..d5e03ebab1d08e 100644
--- a/src/libraries/Microsoft.Extensions.Hosting/tests/UnitTests/Internal/HostTests.cs
+++ b/src/libraries/Microsoft.Extensions.Hosting/tests/UnitTests/Internal/HostTests.cs
@@ -1426,6 +1426,33 @@ public async Task BackgroundServiceAsyncExceptionGetsLogged(
             }
         }
 
+        /// <summary>
+        /// Tests that an exception is logged if a hosted service factory fails.
+        /// </summary>
+        [Fact]
+        public async Task HostedServiceFactoryExceptionGetsLogged()
+        {
+            TestLoggerProvider logger = new TestLoggerProvider();
+
+            using IHost host = CreateBuilder()
+                .ConfigureLogging(logging =>
+                {
+                    logging.AddProvider(logger);
+                })
+                .ConfigureServices((hostContext, services) =>
+                {
+                    services.AddHostedService<WorkerTemplateService>(p => throw new InvalidOperationException("factory failed"));
+                })
+                .Build();
+
+            await Assert.ThrowsAsync<InvalidOperationException>(() => host.StartAsync());
+
+            LogEvent[] events = logger.GetEvents();
+            Assert.Single(events);
+            Assert.Equal(LogLevel.Error, events[0].LogLevel);
+            Assert.Equal("HostedServiceStartupFaulted", events[0].EventId.Name);
+        }
+
         /// <summary>
         /// Tests that when a BackgroundService is canceled when stopping the host,
         /// no error is logged.