warmup AzureMonitorDiagnosticLogger in placeholder mode

Author: brettsam

src/WebJobs.Script.WebHost/Diagnostics/AzureMonitorDiagnosticLogger.cs

@@ -40,7 +40,8 @@ public AzureMonitorDiagnosticLogger(string category, string hostInstanceId, IEve
 
         public bool IsEnabled(LogLevel logLevel)
         {
-            return true;
+            // We want to instantiate this Logger in placeholder mode to warm it up, but do not want to log anything.
+            return !string.IsNullOrEmpty(_websiteHostName) && !_environment.IsPlaceholderModeEnabled();
         }
 
         public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception exception, Func<TState, Exception, string> formatter)

src/WebJobs.Script.WebHost/WebScriptHostBuilderExtension.cs

@@ -15,8 +15,6 @@
 using Microsoft.Extensions.DependencyInjection.Extensions;
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
-using Microsoft.Extensions.Logging.Abstractions;
-using Microsoft.Extensions.Options;
 
 namespace Microsoft.Azure.WebJobs.Script.WebHost
 {
@@ -52,21 +50,7 @@ public static IHostBuilder AddWebScriptHost(this IHostBuilder builder, IServiceP
 
                     loggingBuilder.AddWebJobsSystem<SystemLoggerProvider>();
                     loggingBuilder.Services.AddSingleton<ILoggerProvider, UserLogMetricsLoggerProvider>();
-                    loggingBuilder.Services.AddSingleton<ILoggerProvider>(services =>
-                    {
-                        IEnvironment environment = services.GetService<IEnvironment>();
-                        IScriptWebHostEnvironment hostEnvironment = services.GetService<IScriptWebHostEnvironment>();
-
-                        if (!hostEnvironment.InStandbyMode &&
-                            !string.IsNullOrEmpty(environment.GetEnvironmentVariable(EnvironmentSettingNames.AzureWebsiteHostName)))
-                        {
-                            IEventGenerator eventGenerator = services.GetService<IEventGenerator>();
-                            IOptions<ScriptJobHostOptions> options = services.GetService<IOptions<ScriptJobHostOptions>>();
-                            return new AzureMonitorDiagnosticLoggerProvider(options, eventGenerator, environment);
-                        }
-
-                        return NullLoggerProvider.Instance;
-                    });
+                    loggingBuilder.Services.AddSingleton<ILoggerProvider, AzureMonitorDiagnosticLoggerProvider>();
 
                     ConfigureRegisteredBuilders(loggingBuilder, rootServiceProvider);
                 })

test/WebJobs.Script.Tests/Configuration/LoggingConfigurationTests.cs

@@ -11,7 +11,6 @@
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
-using Microsoft.Extensions.Logging.Abstractions;
 using Microsoft.Extensions.Logging.Console;
 using Microsoft.Extensions.Options;
 using Microsoft.WebJobs.Script.Tests;
@@ -183,7 +182,7 @@ public void LoggerProviders_Default()
             loggerProviders.OfType<HostFileLoggerProvider>().Single();
             loggerProviders.OfType<FunctionFileLoggerProvider>().Single();
             loggerProviders.OfType<UserLogMetricsLoggerProvider>().Single();
-            loggerProviders.OfType<NullLoggerProvider>().Single();
+            loggerProviders.OfType<AzureMonitorDiagnosticLoggerProvider>().Single();
         }
 
         [Fact]
@@ -202,7 +201,7 @@ public void LoggerProviders_ConsoleEnabled_IfDevelopmentEnvironment()
             loggerProviders.OfType<FunctionFileLoggerProvider>().Single();
             loggerProviders.OfType<ConsoleLoggerProvider>().Single();
             loggerProviders.OfType<UserLogMetricsLoggerProvider>().Single();
-            loggerProviders.OfType<NullLoggerProvider>().Single();
+            loggerProviders.OfType<AzureMonitorDiagnosticLoggerProvider>().Single();
         }
 
         [Fact]
@@ -227,7 +226,7 @@ public void LoggerProviders_ConsoleEnabled_InConfiguration()
             loggerProviders.OfType<FunctionFileLoggerProvider>().Single();
             loggerProviders.OfType<ConsoleLoggerProvider>().Single();
             loggerProviders.OfType<UserLogMetricsLoggerProvider>().Single();
-            loggerProviders.OfType<NullLoggerProvider>().Single();
+            loggerProviders.OfType<AzureMonitorDiagnosticLoggerProvider>().Single();
         }
 
         [Fact]
@@ -252,7 +251,7 @@ public void LoggerProviders_ApplicationInsights()
             loggerProviders.OfType<FunctionFileLoggerProvider>().Single();
             loggerProviders.OfType<ApplicationInsightsLoggerProvider>().Single();
             loggerProviders.OfType<UserLogMetricsLoggerProvider>().Single();
-            loggerProviders.OfType<NullLoggerProvider>().Single();
+            loggerProviders.OfType<AzureMonitorDiagnosticLoggerProvider>().Single();
         }
 
         [Fact]

test/WebJobs.Script.Tests/Eventing/DiagnosticLoggerTests.cs

@@ -163,6 +163,38 @@ public void Log_Sanitizes()
             Assert.True(JToken.DeepEquals(actual, expected), $"Actual: {actual.ToString()}{Environment.NewLine}Expected: {expected.ToString()}");
         }
 
+        [Fact]
+        public void Log_DisabledIfPlaceholder()
+        {
+            string message = "TestMessage";
+            string functionInvocationId = Guid.NewGuid().ToString();
+            string activityId = Guid.NewGuid().ToString();
+
+            _environment.SetEnvironmentVariable(EnvironmentSettingNames.AzureWebsitePlaceholderMode, "1");
+
+            _logger.LogInformation(message);
+
+            Assert.False(_logger.IsEnabled(LogLevel.Information));
+            _mockEventGenerator.Verify(m => m.LogAzureMonitorDiagnosticLogEvent(It.IsAny<LogLevel>(), It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>()), Times.Never);
+        }
+
+        [Fact]
+        public void Log_DisabledIfNoSiteName()
+        {
+            string message = "TestMessage";
+            string functionInvocationId = Guid.NewGuid().ToString();
+            string activityId = Guid.NewGuid().ToString();
+            _environment.SetEnvironmentVariable(EnvironmentSettingNames.AzureWebsiteHostName, null);
+
+            // Recreate the logger was we cache the site name in the constructor
+            ILogger logger = new AzureMonitorDiagnosticLogger(_category, _hostInstanceId, _mockEventGenerator.Object, _environment, new LoggerExternalScopeProvider());
+
+            logger.LogInformation(message);
+
+            Assert.False(logger.IsEnabled(LogLevel.Information));
+            _mockEventGenerator.Verify(m => m.LogAzureMonitorDiagnosticLogEvent(It.IsAny<LogLevel>(), It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>()), Times.Never);
+        }
+
         // Creates a scope based on the non-null values passed in. Allows us to test various permutations and make sure that the logger handles them.
         private IDisposable CreateScope(string functionName = null, string activityId = null, string functionInvocationId = null)
         {