TransactionScope Prematurely Completed

Question

I have a block of code that runs within a TransactionScope and within this block of code I make several calls to the DB. Selects, Updates, Creates, and Deletes, the whole gamut. When I execute my delete I execute it using an extension method of the SqlCommand that will automatically resubmit the query if it deadlocks as this query could potentially hit a deadlock.

I believe the problem occurs when a deadlock is hit and the function tries to resubmit the query. This is the error I receive:

The transaction associated with the current connection has completed but has not been disposed. The transaction must be disposed before the connection can be used to execute SQL statements.

This is the simple code that executes the query (all of the code below executes within the using of the TransactionScope):

using (sqlCommand.Connection = new SqlConnection(ConnectionStrings.App))
{
    sqlCommand.Connection.Open();
    sqlCommand.ExecuteNonQueryWithDeadlockHandling();
}

Here is the extension method that resubmits the deadlocked query:

public static class SqlCommandExtender
{
    private const int DEADLOCK_ERROR = 1205;
    private const int MAXIMUM_DEADLOCK_RETRIES = 5;
    private const int SLEEP_INCREMENT = 100;

    public static void ExecuteNonQueryWithDeadlockHandling(this SqlCommand sqlCommand)
    {
        int count = 0;
        SqlException deadlockException = null;

        do
        {
            if (count > 0) Thread.Sleep(count * SLEEP_INCREMENT);
            deadlockException = ExecuteNonQuery(sqlCommand);
            count++;
        }
        while (deadlockException != null && count < MAXIMUM_DEADLOCK_RETRIES);

        if (deadlockException != null) throw deadlockException;
    }

    private static SqlException ExecuteNonQuery(SqlCommand sqlCommand)
    {
        try
        {
            sqlCommand.ExecuteNonQuery();
        }
        catch (SqlException exception)
        {
            if (exception.Number == DEADLOCK_ERROR) return exception;
            throw;
        }

        return null;
    }
}

The error occurs on the line:

sqlCommand.ExecuteNonQuery();

Answer 1

Don't forget to supress your select statements from your TransactionScope. In SQL Server 2005 and above, even when you use with(nolock), locks are still created on those tables the select touches. Check this out, it shows you how to setup and use TransactionScope.

using(TransactionScope ts = new TransactionScope 
{ 
  // db calls here are in the transaction 
  using(TransactionScope tsSuppressed = new TransactionScope (TransactionScopeOption.Suppress)) 
  { 
    // all db calls here are now not in the transaction 
  } 
} 

Answer 2

I've found that this message can occur when a transaction runs for a longer period than the maxTimeout for System.Transactions. It doesn't matter that TransactionOptions.Timeout is increased, it can't exceed maxTimeout.

The default value of maxTimeout is set to 10 minutes and its value can only be modified in the machine.config

Add the following (in the configuration level) to the machine.config to modify the timeout:

<configuration>
    <system.transactions>
        <machineSettings maxTimeout="00:30:00" />
    </system.transactions>
</configuration>

The machine.config can be found at: %windir%\Microsoft.NET\Framework\[version]\config\machine.config

You can read more about it in this blog post: http://thecodesaysitall.blogspot.se/2012/04/long-running-systemtransactions.html

Answer 3

I can reproduce the problem. It is a transaction timeout.

using (new TransactionScope(TransactionScopeOption.Required, new TimeSpan(0, 0, 0, 1)))
{
    using (SqlConnection connection = new SqlConnection(connectionString))
    {
        connection.Open();
        using (var sqlCommand = connection.CreateCommand())
        {
            for (int i = 0; i < 10000; i++)
            {
                sqlCommand.CommandText = "select * from actor";
                using (var sqlDataReader = sqlCommand.ExecuteReader())
                {
                    while (sqlDataReader.Read())
                    {
                    }
                }
            }
        }
    }
}

Throws System.InvalidOperationException with this message:

The transaction associated with the current connection has completed but has not been disposed. The transaction must be disposed before the connection can be used to execute SQL statements.

To solve the problem make your query run faster or increase the timeout.