more LoggerFactory disposal improvements

Author: brettsam

src/WebJobs.Script.WebHost/App_Start/AutofacBootstrap.cs

@@ -29,7 +29,7 @@ internal static void Initialize(ScriptSettingsManager settingsManager, Container
             builder.Register<ISwaggerDocumentManager>(ct => ct.Resolve<WebHostResolver>().GetSwaggerDocumentManager(settings)).ExternallyOwned();
             builder.Register<WebScriptHostManager>(ct => ct.Resolve<WebHostResolver>().GetWebScriptHostManager(settings)).ExternallyOwned();
             builder.Register<WebHookReceiverManager>(ct => ct.Resolve<WebHostResolver>().GetWebHookReceiverManager(settings)).ExternallyOwned();
-            builder.Register<ILoggerFactory>(ct => ct.Resolve<WebHostResolver>().GetScriptHostConfiguration(settings).HostConfig.LoggerFactory).ExternallyOwned();
+            builder.Register<ILoggerFactory>(ct => ct.Resolve<WebHostResolver>().GetLoggerFactory(settings)).ExternallyOwned();
         }
     }
 }

src/WebJobs.Script.WebHost/App_Start/WebHostResolver.cs

@@ -9,6 +9,7 @@
 using Microsoft.Azure.WebJobs.Script.Eventing;
 using Microsoft.Azure.WebJobs.Script.WebHost.Properties;
 using Microsoft.Azure.WebJobs.Script.WebHost.WebHooks;
+using Microsoft.Extensions.Logging;
 
 namespace Microsoft.Azure.WebJobs.Script.WebHost
 {
@@ -28,13 +29,31 @@ public sealed class WebHostResolver : IDisposable
 
         private static ScriptSettingsManager _settingsManager;
 
+        private static ILoggerFactory _emptyLoggerFactory = new LoggerFactory();
+
         public WebHostResolver(ScriptSettingsManager settingsManager, ISecretManagerFactory secretManagerFactory, IScriptEventManager eventManager)
         {
             _settingsManager = settingsManager;
             _secretManagerFactory = secretManagerFactory;
             _eventManager = eventManager;
         }
 
+        public ILoggerFactory GetLoggerFactory(WebHostSettings settings)
+        {
+            WebScriptHostManager manager = GetWebScriptHostManager(settings);
+
+            if (!manager.CanInvoke())
+            {
+                // The host is still starting and the LoggerFactory cannot be used. Return
+                // an empty LoggerFactory rather than waiting. This will mostly affect
+                // calls to /admin/host/status, which do not block on CanInvoke. It allows this
+                // API to remain fast with the side effect of occassional missed logs.
+                return _emptyLoggerFactory;
+            }
+
+            return GetScriptHostConfiguration(settings).HostConfig.LoggerFactory;
+        }
+
         public ISwaggerDocumentManager GetSwaggerDocumentManager(WebHostSettings settings)
         {
             return GetWebScriptHostManager(settings).SwaggerDocumentManager;

src/WebJobs.Script/Host/ScriptHost.cs

@@ -1780,8 +1780,6 @@ protected override void Dispose(bool disposing)
                     (function.Invoker as IDisposable)?.Dispose();
                 }
 
-                _loggerFactory?.Dispose();
-
                 if (_traceMonitor != null)
                 {
                     _hostConfig.Tracing.Tracers.Remove(_traceMonitor);
@@ -1796,9 +1794,16 @@ protected override void Dispose(bool disposing)
                 }
             }
 
-            // dispose base last to ensure that errors there don't
+            // dispose base here to ensure that errors there don't
             // cause us to not dispose ourselves
             base.Dispose(disposing);
+
+            if (disposing)
+            {
+                // The LoggerFactory can be used by the host up until it's disposed,
+                // so make sure that it's disposed last.
+                _loggerFactory?.Dispose();
+            }
         }
     }
 }