add AlwaysHealthy health check when provider is disabled

Author: zhiyuanliang-ms

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/AlwaysHealthyHealthCheck.cs

@@ -0,0 +1,17 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+//
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+using System.Threading.Tasks;
+using System.Threading;
+
+namespace Microsoft.Extensions.Configuration.AzureAppConfiguration
+{
+    internal class AlwaysHealthyHealthCheck : IHealthCheck
+    {
+        public Task<HealthCheckResult> CheckHealthAsync(HealthCheckContext context, CancellationToken cancellationToken = default)
+        {
+            return Task.FromResult(HealthCheckResult.Healthy());
+        }
+    }
+}

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/AzureAppConfigurationExtensions.cs

@@ -7,7 +7,6 @@
 using Microsoft.Extensions.DependencyInjection.Extensions;
 using System;
 using System.Collections.Generic;
-using System.Security;
 
 namespace Microsoft.Extensions.Configuration
 {
@@ -16,19 +15,7 @@ namespace Microsoft.Extensions.Configuration
     /// </summary>
     public static class AzureAppConfigurationExtensions
     {
-        private const string DisableProviderEnvironmentVariable = "AZURE_APP_CONFIGURATION_PROVIDER_DISABLED";
-        private static readonly bool _isProviderDisabled = IsProviderDisabled();
-
-        private static bool IsProviderDisabled()
-        {
-            try
-            {
-                return bool.TryParse(Environment.GetEnvironmentVariable(DisableProviderEnvironmentVariable), out bool disabled) ? disabled : false;
-            }
-            catch (SecurityException) { }
-
-            return false;
-        }
+        private static readonly bool _isProviderDisabled = Utils.IsProviderDisabled();
 
         /// <summary>
         /// Adds key-value data from an Azure App Configuration store to a configuration builder using its connection string.

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/AzureAppConfigurationHealthChecksBuilderExtensions.cs

@@ -14,6 +14,8 @@ namespace Microsoft.Extensions.DependencyInjection
     /// </summary>
     public static class AzureAppConfigurationHealthChecksBuilderExtensions
     {
+        private static readonly bool _isProviderDisabled = Utils.IsProviderDisabled();
+
         /// <summary>
         /// Add a health check for Azure App Configuration to given <paramref name="builder"/>.
         /// </summary>
@@ -32,6 +34,17 @@ public static IHealthChecksBuilder AddAzureAppConfiguration(
             IEnumerable<string> tags = default,
             TimeSpan? timeout = default)
         {
+            if (_isProviderDisabled)
+            {
+                // If the provider is disabled, register a health check that always reports healthy.
+                return builder.Add(new HealthCheckRegistration(
+                    name ?? HealthCheckConstants.HealthCheckRegistrationName,
+                    sp => new AlwaysHealthyHealthCheck(),
+                    failureStatus,
+                    tags,
+                    timeout));
+            }
+
             return builder.Add(new HealthCheckRegistration(
                 name ?? HealthCheckConstants.HealthCheckRegistrationName,
                 sp => new AzureAppConfigurationHealthCheck(

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/EnvironmentVariables.cs

@@ -21,5 +21,11 @@ internal static class EnvironmentVariables
         /// The value of this variable is a boolean string, e.g. "true" or "false".
         /// </summary>
         public const string DisableRequestTracing = "AZURE_APP_CONFIGURATION_TRACING_DISABLED";
+
+        /// <summary>
+        /// Environment variable to disable Azure App Configuration provider.
+        /// The value of this variable is a boolean string, e.g. "true" or "false".
+        /// </summary>
+        public const string DisableAppConfigurationProvider = "AZURE_APP_CONFIGURATION_PROVIDER_DISABLED";
     }
 }

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/Utils.cs

@@ -0,0 +1,23 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+//
+
+using System;
+using System.Security;
+
+namespace Microsoft.Extensions.Configuration.AzureAppConfiguration
+{
+    internal static class Utils
+    {
+        public static bool IsProviderDisabled()
+        {
+            try
+            {
+                return bool.TryParse(Environment.GetEnvironmentVariable(EnvironmentVariables.DisableAppConfigurationProvider), out bool disabled) ? disabled : false;
+            }
+            catch (SecurityException) { }
+
+            return false;
+        }
+    }
+}