How do you detect if a SqlConnection's "blocking period" is active?

Question

According to Microsoft's article (SQL Server Connection Pooling (ADO.NET)),

When connection pooling is enabled, and if a timeout error or other login error occurs, an exception will be thrown and subsequent connection attempts will fail for the next five seconds, the "blocking period". If the application attempts to connect within the blocking period, the first exception will be thrown again. After the blocking period ends, another connection failure by the application will result in a blocking period that is twice as long as the previous blocking period. Subsequent failures after a blocking period ends will result in a new blocking periods that is twice as long as the previous blocking period, up to a maximum of five minutes.

How would you detect that the blocking period is active? I would assume that there is some property to check before attempting the connection so that you could avoid extending the blocking period.

Answer 1

There shouldn't be a need to check if you're in a blocking period to avoid extending it. As it says in the excerpt above, any attempts to connect during the blocking period will re-throw the first exception, it says nothing about extending the blocking period. However, each new blocking period will be twice as long as the previous.

In my experience, the exceptions that get thrown (due to timeouts, connection leaks, etc.) are either environmental issues or failing to properly close/dispose connections. It's a good idea to log these exceptions so that you can track down the real issue.

If you do keep coming across a timeout exception, you could catch it and try to clear all the pools, but it's likely due to a connection leak. You'll want to make sure you're wrapping your connections with a using statement, which will help to close/dispose of your connections when you're done with them or if an exception occurs.

using(SqlConnection connection = new SqlConnection("connection_string"))
{
    using(SqlCommand command = new SqlCommand())
    {

        SqlCommand command = new SqlCommand();
        command.Connection = connection;
        command.CommandType = CommandType.Text;
        command.CommandTimeout = [some timeout value]; 
        command.CommandText = "Update SomeTable Set Value = 1";

        connection.Open();

        command.ExecuteNonQuery();
    }
}

Answer 2

In addition to the ClientConnectionId field,

The SqlException.Message will also be reference-equal. That is, the cached string will be returned for connections that fail within the "blocking period".

However, this is also an implementation detail and may change.