title: provider: Session Provider, error: 19 - Physical connection is not usable - Azure SQL database
body: <p>I get the error <code>provider: Session Provider, error: 19 - Physical connection is not usable</code> intermittently when making Entity Framework requests to a database in Azure. </p>
  
  <p>When the problem occurs it affects a little under 1% of requests. But it doesn't occur often or predictably. It happened for a few hours last week and this week, but now everything is fine. </p>
  
  <p>I've checked my connection string db pool size, it is using the default. I tried reducing the pool to 2 connections and this causes a different error. </p>
  
  <p>What else could it be? </p>