Intermittent SQL connectivity issue with AWS RDS

问题

We are currently experiencing an intermittent issue with our ASP.NET website (built on Sitecore) where the website cannot connect to SQL server for seemingly random periods of 15 minutes. After 15 minutes, the issue resolves itself and the website comes back up.

The error message is:

Exception: System.Data.SqlClient.SqlException
Message: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)
Source: .Net SqlClient Data Provider
   at System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData, DbConnectionPool pool, String accessToken, Boolean applyTransientFaultHandling)
   at System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions)
   at System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnection owningObject, DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions)
   at System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
   at System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
   at System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 retry)
   at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)
   at System.Data.SqlClient.SqlConnection.Open()
   at Sitecore.Data.DataProviders.Sql.DataProviderCommand..ctor(IDbCommand command, DataProviderTransaction transaction, Boolean openConnection)
   at Sitecore.Data.DataProviders.Sql.SqlDataApi.<>c__DisplayClass4.<CreateCommand>b__3()
   at Sitecore.Data.DataProviders.NullRetryer.Execute[T](Func`1 action, Action recover)
   at Sitecore.Data.DataProviders.Sql.SqlDataApi.<>c__DisplayClass12.<CreateReader>b__10()
   at Sitecore.Data.DataProviders.NullRetryer.Execute[T](Func`1 action, Action recover)
   at Sitecore.Data.DataProviders.Sql.SqlDataApi.CreateReader(String sql, Object[] parameters)
   at Sitecore.Data.DataProviders.Sql.SqlDataApi.<CreateObjectReader>d__6`1.MoveNext()
   at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source)
   at Sitecore.Eventing.EventQueue.ProcessEvents(Action`2 handler)
   at Sitecore.Eventing.EventProvider.RaiseQueuedEvents()

Nested Exception

Exception: System.ComponentModel.Win32Exception
Message: The network path was not found


6420 16:53:53 ERROR Exception processing remote events from database: web
Exception: System.Data.SqlClient.SqlException
Message: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)
Source: .Net SqlClient Data Provider
   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
   at System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 retry)
   at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)
   at System.Data.SqlClient.SqlConnection.Open()
   at Sitecore.Data.DataProviders.Sql.DataProviderCommand..ctor(IDbCommand command, DataProviderTransaction transaction, Boolean openConnection)
   at Sitecore.Data.DataProviders.Sql.SqlDataApi.<>c__DisplayClass4.<CreateCommand>b__3()
   at Sitecore.Data.DataProviders.NullRetryer.Execute[T](Func`1 action, Action recover)
   at Sitecore.Data.DataProviders.Sql.SqlDataApi.<>c__DisplayClass12.<CreateReader>b__10()
   at Sitecore.Data.DataProviders.NullRetryer.Execute[T](Func`1 action, Action recover)
   at Sitecore.Data.DataProviders.Sql.SqlDataApi.CreateReader(String sql, Object[] parameters)
   at Sitecore.Data.DataProviders.Sql.SqlDataApi.<CreateObjectReader>d__6`1.MoveNext()
   at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source)
   at Sitecore.Eventing.EventQueue.ProcessEvents(Action`2 handler)
   at Sitecore.Eventing.EventProvider.RaiseQueuedEvents()

Nested Exception

Exception: System.ComponentModel.Win32Exception
Message: The network path was not found

This error message, seems to be the same error you'd get if you had a typo in the connection string, but the site functions fine for 99% of the time.

If the error message was a timeout, I could imagine the cause being that the application is causing excessive load and SQL cannot respond - however, the SQL RDS logs show no heavy load and just a drop off of connections for a period of 15 minutes.

Is there anything from an application/code perspective that could cause this?

Is the period of 15 minutes significant? Is that a clue to something in particular?