Troubleshooting "pre-login handshake failed" errors

  • To me, this is more of a Network Administrator issue, but the problem ONLY occurs in C# EntityFramework 6 code, and typically only occurs between 4AM and 6AM EST (we're located in Eastern time zone).

    However, since it is only happening in SQL parts of the code, it's straddling the lines of my DBA duties... and I have no idea how to troubleshoot what could cause this issue.

    Any tips?

    System.Data.SqlClient.SqlException: Connection Timeout Expired.  The timeout period elapsed while attempting to consume the pre-login handshake acknowledgement.  This could be because the pre-login handshake failed or the server was unable to respond back in time.  The duration spent while attempting to connect to this server was - [Pre-Login] initialization=17825; handshake=1;  ---> System.ComponentModel.Win32Exception: The wait operation timed out
       --- End of inner exception stack trace ---
       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 System.Data.Linq.SqlClient.SqlConnectionManager.UseConnection(IConnectionUser user)
       at System.Data.Linq.SqlClient.SqlProvider.get_IsSqlCe()
       at System.Data.Linq.SqlClient.SqlProvider.InitializeProviderMode()
       at System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query)

  • As this is a error that occurs only at times, mainly at particular periods it leads me to believe the most likely cause is something on the network temporarily blocking access or an overload on the network (or parts of) between the client and the server.

    To ensure it is not the Sql server causing the issue I would create a small powershell script to connect and get the version out of your server, and schedule it to run every minute on 2 other servers/workstations during the times where it occurs most often. Preferably on different networks segments from the client that is failing.
    If at all possible schedule it also on a server that is on the same switch - to avoid multiple hops.
    Also schedule it on the server itself.

    Can also be time synchronization or absence of AD domain controller to validate credentials.

    And can also be DNS - especially if your server is a cluster/AG group - Make sure that DNS is correctly setup with forward and reverse dns entries for all nodes

  • You may want to check what jobs are running in SQL Server between 4:00 am and 6:00 am. And what other maintenance is running on the server during those times.
    You could also try having the developers increase the timeout property in the connection string. You don't want to wait indefinitely though.


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