NHibernate + MySql Intermittent TimeoutException - mysql

Question

I have just migrated my NHibernate app from SQL Server to MySql. All seems well except I am getting intermittent TimeoutExceptions. I can find a lot of info about this timeouts with MySql and even one blog post about timeouts with Hibernate + MySql + C3PO (whatever that is). But nothing about how to tweak NHib to stop this problem. Do you know?
Here is the stack trace:
NHibernate.TransactionException: Begin failed with SQL exception ---> System.TimeoutException: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond ---> System.IO.IOException: Unable to read data from the transport connection: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond. ---> System.Net.Sockets.SocketException: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond
at System.Net.Sockets.Socket.Receive(Byte[] buffer, Int32 offset, Int32 size, SocketFlags socketFlags)
at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)
--- End of inner exception stack trace ---
at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)
at MyNetworkStream.Read(Byte[] buffer, Int32 offset, Int32 count)
--- End of inner exception stack trace ---
at MyNetworkStream.HandleOrRethrowException(Exception e)
at MyNetworkStream.Read(Byte[] buffer, Int32 offset, Int32 count)
at MySql.Data.MySqlClient.TimedStream.Read(Byte[] buffer, Int32 offset, Int32 count)
at System.IO.BufferedStream.Read(Byte[] array, Int32 offset, Int32 count)
at MySql.Data.MySqlClient.MySqlStream.ReadFully(Stream stream, Byte[] buffer, Int32 offset, Int32 count)
at MySql.Data.MySqlClient.MySqlStream.LoadPacket()
at MySql.Data.MySqlClient.MySqlStream.ReadPacket()
at MySql.Data.MySqlClient.NativeDriver.ReadOk(Boolean read)
at MySql.Data.MySqlClient.NativeDriver.SetDatabase(String dbName)
at MySql.Data.MySqlClient.Driver.SetDatabase(String dbName)
at MySql.Data.MySqlClient.MySqlConnection.ChangeDatabase(String databaseName)
at MySql.Data.MySqlClient.MySqlConnection.Open()
at NHibernate.Connection.DriverConnectionProvider.GetConnection()
at NHibernate.AdoNet.ConnectionManager.GetConnection()
at NHibernate.Impl.SessionImpl.get_Connection()
at NHibernate.Transaction.AdoTransaction.Begin(IsolationLevel isolationLevel)
--- End of inner exception stack trace ---
at NHibernate.Transaction.AdoTransaction.Begin(IsolationLevel isolationLevel)
at NHibernate.Transaction.AdoTransaction.Begin()
at NHibernate.AdoNet.ConnectionManager.BeginTransaction()
at NHibernate.Impl.SessionImpl.BeginTransaction()

Answer 1

I run NHibernate on Rackspace cloud with a MYSQL database. I found I was getting timeouts due to the fact that connections were being left semi open due to sleeping. Eventually I was running out of connections and my web site timed out.
In the end I added Pooling=false; into my connection string. I am not sure if this is the ultimate fix but it has stopped my problem.
You can check for sleeping connections by using show processlist in a MySQL editor...