Your ASP.NET application uses connection pooling to connect to a database. You find that the following exception is logged repeatedly after the application runs for a few hours:
Exception: System.InvalidOperationException
Message: Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached.
Once this exception occurs, the application is no longer able to connect to the database. You find that when you restart the application, it can connect again for a few hours. You must fix the problem and make sure that it no longer occurs.

What should you do?