Filter Azure monitor logs when customer does not subscribe for the categories

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

@@ -29,7 +29,8 @@ public class AzureMonitorDiagnosticLogger : ILogger
         private readonly IEventGenerator _eventGenerator;
         private readonly IEnvironment _environment;
         private readonly IExternalScopeProvider _scopeProvider;
-        private AppServiceOptions _appServiceOptions;
+        private bool _isAzureMonitorLoggingEnabled;
+        private IOptionsMonitor<AppServiceOptions> _appServiceOptionsMonitor;
 
         public AzureMonitorDiagnosticLogger(string category, string hostInstanceId, IEventGenerator eventGenerator, IEnvironment environment, IExternalScopeProvider scopeProvider,
             HostNameProvider hostNameProvider, IOptionsMonitor<AppServiceOptions> appServiceOptionsMonitor)
@@ -40,10 +41,9 @@ public AzureMonitorDiagnosticLogger(string category, string hostInstanceId, IEve
             _environment = environment ?? throw new ArgumentNullException(nameof(environment));
             _scopeProvider = scopeProvider ?? throw new ArgumentNullException(nameof(scopeProvider));
             _hostNameProvider = hostNameProvider ?? throw new ArgumentNullException(nameof(hostNameProvider));
-            _ = appServiceOptionsMonitor ?? throw new ArgumentNullException(nameof(appServiceOptionsMonitor));
-
-            appServiceOptionsMonitor.OnChange(newOptions => _appServiceOptions = newOptions);
-            _appServiceOptions = appServiceOptionsMonitor.CurrentValue;
+            _appServiceOptionsMonitor = appServiceOptionsMonitor ?? throw new ArgumentNullException(nameof(appServiceOptionsMonitor));
+            UpdateAppServiceOptions(_appServiceOptionsMonitor.CurrentValue);
+            _appServiceOptionsMonitor.OnChange(UpdateAppServiceOptions);
 
             _roleInstance = _environment.GetInstanceId();
 
@@ -55,7 +55,7 @@ public AzureMonitorDiagnosticLogger(string category, string hostInstanceId, IEve
         public bool IsEnabled(LogLevel logLevel)
         {
             // We want to instantiate this Logger in placeholder mode to warm it up, but do not want to log anything.
-            return !string.IsNullOrEmpty(_hostNameProvider.Value) && !_environment.IsPlaceholderModeEnabled();
+            return _isAzureMonitorLoggingEnabled && !string.IsNullOrEmpty(_hostNameProvider.Value) && !_environment.IsPlaceholderModeEnabled();
         }
 
         public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception exception, Func<TState, Exception, string> formatter)
@@ -107,7 +107,7 @@ public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Except
             using (JsonTextWriter writer = new JsonTextWriter(sw) { Formatting = Formatting.None })
             {
                 writer.WriteStartObject();
-                WritePropertyIfNotNull(writer, "appName", _appServiceOptions.AppName);
+                WritePropertyIfNotNull(writer, "appName", _appServiceOptionsMonitor.CurrentValue.AppName);
                 WritePropertyIfNotNull(writer, "roleInstance", _roleInstance);
                 WritePropertyIfNotNull(writer, "message", formattedMessage);
                 WritePropertyIfNotNull(writer, "category", _category);
@@ -136,6 +136,11 @@ public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Except
             _eventGenerator.LogAzureMonitorDiagnosticLogEvent(logLevel, _hostNameProvider.Value, AzureMonitorOperationName, AzureMonitorCategoryName, _regionName, sw.ToString());
         }
 
+        private void UpdateAppServiceOptions(AppServiceOptions appServiceOptions)
+        {
+            _isAzureMonitorLoggingEnabled = !(_environment.IsConsumptionOnLegion() && !_appServiceOptionsMonitor.CurrentValue.IsAzureMonitorLoggingEnabled);
+        }
+
         private static void WritePropertyIfNotNull<T>(JsonTextWriter writer, string propertyName, T propertyValue)
         {
             if (propertyValue != null)

src/WebJobs.Script.WebHost/WebScriptHostBuilderExtension.cs

@@ -25,11 +25,13 @@
 using Microsoft.Azure.WebJobs.Script.WebHost.Management;
 using Microsoft.Azure.WebJobs.Script.WebHost.Middleware;
 using Microsoft.Azure.WebJobs.Script.WebHost.Storage;
+using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.DependencyInjection.Extensions;
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
+using static Microsoft.Azure.WebJobs.Script.Utility;
 
 namespace Microsoft.Azure.WebJobs.Script.WebHost
 {
@@ -91,6 +93,17 @@ public static IHostBuilder AddWebScriptHost(this IHostBuilder builder, IServiceP
                     loggingBuilder.AddWebJobsSystem<SystemLoggerProvider>();
                     if (environment.IsAzureMonitorEnabled())
                     {
+                        if (environment.IsConsumptionOnLegion())
+                        {
+                            loggingBuilder.Services.AddOptions<LoggerFilterOptions>()
+                                .Configure<IOptionsMonitor<AppServiceOptions>>((filters, options) =>
+                                {
+                                    filters.AddFilter<AzureMonitorDiagnosticLoggerProvider>((category, level) =>
+                                    {
+                                        return options.CurrentValue.IsAzureMonitorLoggingEnabled;
+                                    });
+                                });
+                        }
                         loggingBuilder.Services.AddSingleton<ILoggerProvider, AzureMonitorDiagnosticLoggerProvider>();
                     }
 

src/WebJobs.Script/Config/AppServiceOptions.cs

@@ -12,5 +12,7 @@ public class AppServiceOptions
         public string RuntimeSiteName { get; set; }
 
         public string SlotName { get; set; }
+
+        public bool IsAzureMonitorLoggingEnabled { get; set; }
     }
 }

src/WebJobs.Script/Config/AppServiceOptionsSetup.cs

@@ -2,6 +2,8 @@
 // Licensed under the MIT License. See License.txt in the project root for license information.
 
 using Microsoft.Extensions.Options;
+using static Microsoft.Azure.WebJobs.Script.EnvironmentSettingNames;
+using static Microsoft.Azure.WebJobs.Script.Utility;
 
 namespace Microsoft.Azure.WebJobs.Script.Configuration
 {
@@ -20,6 +22,7 @@ public void Configure(AppServiceOptions options)
             options.SubscriptionId = _environment.GetSubscriptionId() ?? string.Empty;
             options.RuntimeSiteName = _environment.GetRuntimeSiteName() ?? string.Empty;
             options.SlotName = _environment.GetSlotName() ?? string.Empty;
+            options.IsAzureMonitorLoggingEnabled = _environment.IsAzureMonitorEnabled();
         }
     }
 }

src/WebJobs.Script/Environment/EnvironmentExtensions.cs

@@ -11,6 +11,7 @@
 using Microsoft.Azure.WebJobs.Script.Description;
 using Microsoft.Azure.WebJobs.Script.Workers.Rpc;
 using static Microsoft.Azure.WebJobs.Script.EnvironmentSettingNames;
+using static Microsoft.Azure.WebJobs.Script.Utility;
 
 namespace Microsoft.Azure.WebJobs.Script
 {
@@ -69,13 +70,7 @@ public static bool IsEasyAuthEnabled(this IEnvironment environment)
         /// </summary>
         public static bool IsAzureMonitorEnabled(this IEnvironment environment)
         {
-            string value = environment.GetEnvironmentVariable(AzureMonitorCategories);
-            if (value == null)
-            {
-                return true;
-            }
-            string[] categories = value.Split(',');
-            return categories.Contains(ScriptConstants.AzureMonitorTraceCategory);
+            return IsAzureMonitorLoggingEnabled(environment.GetEnvironmentVariable(AzureMonitorCategories));
         }
 
         /// <summary>
@@ -337,7 +332,7 @@ public static bool IsLinuxConsumptionOnAtlas(this IEnvironment environment)
                    string.IsNullOrEmpty(environment.GetEnvironmentVariable(LegionServiceHost));
         }
 
-        private static bool IsConsumptionOnLegion(this IEnvironment environment)
+        public static bool IsConsumptionOnLegion(this IEnvironment environment)
         {
             return !environment.IsAppService() &&
                    (!string.IsNullOrEmpty(environment.GetEnvironmentVariable(ContainerName)) ||

src/WebJobs.Script/ScriptConstants.cs

@@ -227,6 +227,7 @@ public static class ScriptConstants
         public const string ExtendedPlatformChannelNameUpper = "EXTENDED";
 
         public const string AzureMonitorTraceCategory = "FunctionAppLogs";
+        public const string DefaultAzureMonitorCategories = "None";
 
         public const string KubernetesManagedAppName = "K8SE_APP_NAME";
         public const string KubernetesManagedAppNamespace = "K8SE_APP_NAMESPACE";

src/WebJobs.Script/Utility.cs

@@ -1145,6 +1145,22 @@ public static bool TryReadAsBool(IDictionary<string, object> properties, string
             return result = false;
         }
 
+        public static bool IsAzureMonitorLoggingEnabled(string azureMonitorcategoriesSubscribed)
+        {
+            if (azureMonitorcategoriesSubscribed == null)
+            {
+                return true;
+            }
+            if (string.Equals(ScriptConstants.DefaultAzureMonitorCategories, azureMonitorcategoriesSubscribed, StringComparison.Ordinal))
+            {
+                // Default value for the env variable is None.
+                // This is set when customer does not subscribe any category.
+                return false;
+            }
+            string[] categories = azureMonitorcategoriesSubscribed.Split(',');
+            return categories.Contains(ScriptConstants.AzureMonitorTraceCategory);
+        }
+
         private class FilteredExpandoObjectConverter : ExpandoObjectConverter
         {
             public override bool CanWrite => true;

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

@@ -206,35 +206,31 @@ public void Log_Sanitizes()
             Assert.True(JToken.DeepEquals(actual, expected), $"Actual: {actual.ToString()}{Environment.NewLine}Expected: {expected.ToString()}");
         }
 
-        [Fact]
-        public void Log_DisabledIfPlaceholder()
+        [Theory]
+        [InlineData(EnvironmentSettingNames.AzureWebsitePlaceholderMode, "1", false, false, false)] // Placeholder
+        [InlineData(EnvironmentSettingNames.AzureWebsitePlaceholderMode, "1", true, false, false)] // Placeholder
+        [InlineData(EnvironmentSettingNames.AzureWebsiteHostName, null, false, false, false)] // NoSiteName
+        [InlineData(EnvironmentSettingNames.AzureWebsiteHostName, null, true, false, false)] // NoSiteName
+        [InlineData(EnvironmentSettingNames.AzureWebsiteHostName, "host", false, false, true)]
+        [InlineData(EnvironmentSettingNames.AzureWebsiteHostName, "host", true, false, false)]
+        [InlineData(EnvironmentSettingNames.AzureWebsiteHostName, "host", true, true, true)]
+        public void Log_IsEnabled(string envVariableName, string envVariableVale, bool isConsumptionOnLegion, bool isAzureMonitorEnabled,  bool isDisabled)
         {
-            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(), _hostNameProvider, _appServiceOptionsWrapper);
+            _environment.SetEnvironmentVariable(envVariableName, envVariableVale);
+            if (isConsumptionOnLegion)
+            {
+                _environment.SetEnvironmentVariable(EnvironmentSettingNames.AzureWebsiteInstanceId, string.Empty);
+                _environment.SetEnvironmentVariable(EnvironmentSettingNames.ContainerName, "containername");
+                _environment.SetEnvironmentVariable(EnvironmentSettingNames.LegionServiceHost, "legionhost");
+            }
 
-            logger.LogInformation(message);
+            _appServiceOptionsWrapper.CurrentValue.IsAzureMonitorLoggingEnabled = isAzureMonitorEnabled;
+            _appServiceOptionsWrapper.InvokeChanged();
 
-            Assert.False(logger.IsEnabled(LogLevel.Information));
+            Assert.Equal(isDisabled, _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);
         }
 

test/WebJobs.Script.Tests/Extensions/EnvironmentExtensionsTests.cs

@@ -62,6 +62,8 @@ public void IsVMSS_RetrunsExpectedResult(string roleInstanceId, bool expected)
         [InlineData(null, true)]
         [InlineData("", false)]
         [InlineData("Foo,FunctionAppLogs,Bar", true)]
+        [InlineData("FunctionAppLogs", true)]
+        [InlineData("None", false)]
         [InlineData("Foo,Bar", false)]
         public void IsAzureMonitorEnabled_ReturnsExpectedResult(string value, bool expected)
         {