Automatic http failover base on Srv Dns (#442)

* Automatic http failover base on Srv Dns

* update failover condition

* Logging messages for auto failover

* Not use generic method

* Remove useless constructor

* Failover to TCP when response is truncated

* Error handling of TCP failover

* Resolve comments and add thrid party notice

* Fix the tests

* Fix the tess

* Fix the test

* Update to use DnsClient.NET

* Remove unecessary code

* Resolve conflict

* Stop once it has been auto failovered

* Update GetAvaliableClient method

* Resolve comments

* Resolve comments

* Internalize getting dynamic client in ConfigurationClientManager

* Fix format

* Fix format

* Resolve comments

* Resolve comments

* Resolve comments

* Resolve comments

* Resolve comments

* Resolve comments

* Resolve comments

* Not await RefreshFallbackClients when startup

* Revert non-await RefreshFallbackClients

* Validate domain of Srv endpoints (#489)

* Validate domain of Srv endpoints

* Resolve comments

* Resolve comments

* Create object in using

* Add the origin host to the srv lookup result

* Validate endpoint by domain name (#499)

* Validate endpoint by domain name

* Resolve comments

* Remove *-test

* Fix formatResolve conflict

* Use await using for IAsyncDisposible

* Replace IAsyncEumerable with ValueTask<IEnumerable>

* Resolve comments

* Remove cancallation token

* Resolve comments

Author: RichardChen820

NOTICE

@@ -0,0 +1,226 @@
+NOTICES AND INFORMATION
+Do Not Translate or Localize
+
+This software incorporates material from third parties. Microsoft makes certain
+open source code available at https://3rdpartysource.microsoft.com, or you may
+send a check or money order for US $5.00, including the product name, the open
+source component name, and version number, to:
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+Notwithstanding any other terms, you may reverse engineer this software to the
+extent required to debug changes to any libraries licensed under the GNU Lesser
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+---
+
+## [DnsClient.NET](https://github.com/MichaCo/DnsClient.NET)
+
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src/Microsoft.Extensions.Configuration.AzureAppConfiguration/AzureAppConfigurationOptions.cs

@@ -34,6 +34,11 @@ public class AzureAppConfigurationOptions
         // Since multiple prefixes could start with the same characters, we need to trim the longest prefix first.
         private SortedSet<string> _keyPrefixes = new SortedSet<string>(Comparer<string>.Create((k1, k2) => -string.Compare(k1, k2, StringComparison.OrdinalIgnoreCase)));
 
+        /// <summary>
+        /// Flag to indicate whether enable replica discovery.
+        /// </summary>
+        public bool ReplicaDiscoveryEnabled { get; set; } = true;
+
         /// <summary>
         /// The list of connection strings used to connect to an Azure App Configuration store and its replicas.
         /// </summary>

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

@@ -22,7 +22,7 @@
 
 namespace Microsoft.Extensions.Configuration.AzureAppConfiguration
 {
-    internal class AzureAppConfigurationProvider : ConfigurationProvider, IConfigurationRefresher
+    internal class AzureAppConfigurationProvider : ConfigurationProvider, IConfigurationRefresher, IDisposable
     {
         private bool _optional;
         private bool _isInitialLoadComplete = false;
@@ -63,7 +63,7 @@ public Uri AppConfigurationEndpoint
 
                     try
                     {
-                        return new Uri(ConnectionStringParser.Parse(_options.ConnectionStrings.First(), ConnectionStringParser.EndpointSection));
+                        return new Uri(ConnectionStringUtils.Parse(_options.ConnectionStrings.First(), ConnectionStringUtils.EndpointSection));
                     }
                     catch (FormatException) { }
                 }
@@ -85,6 +85,11 @@ public ILoggerFactory LoggerFactory
                 if (_loggerFactory != null)
                 {
                     _logger = new Logger(_loggerFactory.CreateLogger(LoggingConstants.AppConfigRefreshLogCategory));
+
+                    if (_configClientManager is ConfigurationClientManager clientManager)
+                    {
+                        clientManager.SetLogger(_logger);
+                    }
                 }
             }
         }
@@ -192,7 +197,7 @@ public async Task RefreshAsync(CancellationToken cancellationToken)
                         return;
                     }
 
-                    IEnumerable<ConfigurationClient> availableClients = _configClientManager.GetAvailableClients(utcNow);
+                    IEnumerable<ConfigurationClient> availableClients = _configClientManager.GetAvailableClients();
 
                     if (!availableClients.Any())
                     {
@@ -358,7 +363,6 @@ await CallWithRequestTracing(
                                 adapter.InvalidateCache(change.Current);
                             }
                         }
-
                     }
                     else
                     {
@@ -1126,5 +1130,10 @@ private void EnsureFeatureManagementVersionInspected()
                 }
             }
         }
+
+        public void Dispose()
+        {
+            (_configClientManager as ConfigurationClientManager)?.Dispose();
+        }
     }
 }

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

@@ -36,11 +36,11 @@ public IConfigurationProvider Build(IConfigurationBuilder builder)
                 }
                 else if (options.ConnectionStrings != null)
                 {
-                    clientManager = new ConfigurationClientManager(options.ConnectionStrings, options.ClientOptions);
+                    clientManager = new ConfigurationClientManager(options.ConnectionStrings, options.ClientOptions, options.ReplicaDiscoveryEnabled);
                 }
                 else if (options.Endpoints != null && options.Credential != null)
                 {
-                    clientManager = new ConfigurationClientManager(options.Endpoints, options.Credential, options.ClientOptions);
+                    clientManager = new ConfigurationClientManager(options.Endpoints, options.Credential, options.ClientOptions, options.ReplicaDiscoveryEnabled);
                 }
                 else
                 {