Automatically adjust the default ConnectRetryCount if targeting OnDemand endpoint (#1626)

Author: David-Engel

src/Microsoft.Data.SqlClient/netcore/src/Microsoft/Data/SqlClient/SqlConnection.cs

@@ -412,9 +412,15 @@ private void CacheConnectionStringProperties()
             if (connString != null)
             {
                 _connectRetryCount = connString.ConnectRetryCount;
+                // For Azure Synapse ondemand connections, set _connectRetryCount to 5 instead of 1 to greatly improve recovery
+                //  success rate. Note: Synapse should be detected first as it could be detected as a regular Azure SQL DB endpoint.
+                if (_connectRetryCount == 1 && ADP.IsAzureSynapseOnDemandEndpoint(connString.DataSource))
+                {
+                    _connectRetryCount = 5;
+                }
                 // For Azure SQL connection, set _connectRetryCount to 2 instead of 1 will greatly improve recovery
-                //   success rate
-                if (_connectRetryCount == 1 && ADP.IsAzureSqlServerEndpoint(connString.DataSource))
+                //  success rate
+                else if (_connectRetryCount == 1 && ADP.IsAzureSqlServerEndpoint(connString.DataSource))
                 {
                     _connectRetryCount = 2;
                 }

src/Microsoft.Data.SqlClient/netfx/src/Microsoft/Data/SqlClient/SqlConnection.cs

@@ -432,9 +432,15 @@ private void CacheConnectionStringProperties()
             if (connString != null)
             {
                 _connectRetryCount = connString.ConnectRetryCount;
+                // For Azure Synapse ondemand connections, set _connectRetryCount to 5 instead of 1 to greatly improve recovery
+                //  success rate. Note: Synapse should be detected first as it could be detected as a regular Azure SQL DB endpoint.
+                if (_connectRetryCount == 1 && ADP.IsAzureSynapseOnDemandEndpoint(connString.DataSource))
+                {
+                    _connectRetryCount = 5;
+                }
                 // For Azure SQL connection, set _connectRetryCount to 2 instead of 1 will greatly improve recovery
-                //   success rate
-                if (_connectRetryCount == 1 && ADP.IsAzureSqlServerEndpoint(connString.DataSource))
+                //  success rate
+                else if (_connectRetryCount == 1 && ADP.IsAzureSqlServerEndpoint(connString.DataSource))
                 {
                     _connectRetryCount = 2;
                 }

src/Microsoft.Data.SqlClient/src/Microsoft/Data/Common/AdapterUtil.cs

@@ -686,13 +686,26 @@ internal static Version GetAssemblyVersion()
         }
 
 
+        private const string ONDEMAND_PREFIX = "-ondemand";
+        private const string AZURE_SYNAPSE = "-ondemand.sql.azuresynapse.";
+
+        internal static bool IsAzureSynapseOnDemandEndpoint(string dataSource)
+        {
+            return IsEndpoint(dataSource, ONDEMAND_PREFIX) || dataSource.Contains(AZURE_SYNAPSE);
+        }
+
         internal static readonly string[] s_azureSqlServerEndpoints = { StringsHelper.GetString(Strings.AZURESQL_GenericEndpoint),
                                                                         StringsHelper.GetString(Strings.AZURESQL_GermanEndpoint),
                                                                         StringsHelper.GetString(Strings.AZURESQL_UsGovEndpoint),
                                                                         StringsHelper.GetString(Strings.AZURESQL_ChinaEndpoint)};
 
-        // This method assumes dataSource parameter is in TCP connection string format.
         internal static bool IsAzureSqlServerEndpoint(string dataSource)
+        {
+            return IsEndpoint(dataSource, null);
+        }
+
+        // This method assumes dataSource parameter is in TCP connection string format.
+        private static bool IsEndpoint(string dataSource, string prefix)
         {
             int length = dataSource.Length;
             // remove server port
@@ -715,10 +728,10 @@ internal static bool IsAzureSqlServerEndpoint(string dataSource)
                 length -= 1;
             }
 
-            // check if servername end with any azure endpoints
+            // check if servername ends with any endpoints
             for (int index = 0; index < s_azureSqlServerEndpoints.Length; index++)
             {
-                string endpoint = s_azureSqlServerEndpoints[index];
+                string endpoint = string.IsNullOrEmpty(prefix) ? s_azureSqlServerEndpoints[index] : prefix + s_azureSqlServerEndpoints[index];
                 if (length > endpoint.Length)
                 {
                     if (string.Compare(dataSource, length - endpoint.Length, endpoint, 0, endpoint.Length, StringComparison.OrdinalIgnoreCase) == 0)

src/Microsoft.Data.SqlClient/tests/FunctionalTests/SqlConnectionTest.cs

@@ -6,6 +6,7 @@
 using System.Data;
 using System.Collections.Generic;
 using Xunit;
+using System.Reflection;
 
 namespace Microsoft.Data.SqlClient.Tests
 {
@@ -1031,5 +1032,34 @@ public void ConnectionString_IPAddressPreference_Invalid(string value)
             Assert.Contains("'ip address preference'", ex.Message, StringComparison.OrdinalIgnoreCase);
             Assert.Null(ex.ParamName);
         }
+
+        [Fact]
+        public void ConnectionRetryForNonAzureEndpoints()
+        {
+            SqlConnection cn = new SqlConnection("Data Source = someserver");
+            FieldInfo field = typeof(SqlConnection).GetField("_connectRetryCount", BindingFlags.Instance | BindingFlags.NonPublic);
+            Assert.NotNull(field.GetValue(cn));
+            Assert.Equal(1, (int)field.GetValue(cn));
+        }
+
+        [Fact]
+        public void ConnectionRetryForAzureDbEndpoints()
+        {
+            SqlConnection cn = new SqlConnection("Data Source = someserver.database.windows.net");
+            FieldInfo field = typeof(SqlConnection).GetField("_connectRetryCount", BindingFlags.Instance | BindingFlags.NonPublic);
+            Assert.NotNull(field.GetValue(cn));
+            Assert.Equal(2, (int)field.GetValue(cn));
+        }
+
+        [Theory]
+        [InlineData("myserver-ondemand.sql.azuresynapse.net")]
+        [InlineData("someserver-ondemand.database.windows.net")]
+        public void ConnectionRetryForAzureOnDemandEndpoints(string serverName)
+        {
+            SqlConnection cn = new SqlConnection($"Data Source = {serverName}");
+            FieldInfo field = typeof(SqlConnection).GetField("_connectRetryCount", BindingFlags.Instance | BindingFlags.NonPublic);
+            Assert.NotNull(field.GetValue(cn));
+            Assert.Equal(5, (int)field.GetValue(cn));
+        }
     }
 }