SQL Azure - Transient "ExecuteReader requires an open connection" exception - sql

Question

I'm using SQL Azure in a Windows Azure app running as a cloud service. Most of the time my database actions works completely fine (that is, after handling all sorts of timeouts and what not), however i'm running into a problem that seems
using (var connection = new SqlConnection(m_connectionString))
{
m_ConnectionRetryPolicy.ExecuteAction(() => connection.Open());
using (var command = connection.CreateCommand())
{
command.CommandText = "SELECT * FROM X WHERE Y = Z";
var reader = m_CommandRetryPolicy.ExecuteAction(() => command.ExecuteReader());
return LoadData(reader).FirstOrDefault();
}
}
The line that fails is the Command.ExecuteReader with an:
ExecuteReader requires an open and available Connection. The connection's current state is closed
Things that i have already considered
I'm not "reusing" an old connection or saving a connection is a member variable
There should be no concurrency issues - the repository class that these methods belong to is created each time it is needed
Have anyone else experienced this? I could of course just add this to the list of exception which would yield a retry, but I'm not very comfortable with that as

Answer 1

I had a bunch of these errors a few days ago (West Europe) on my production deployment, but they went away by themselves. At the same time I was seeing timeouts, throttling and other errors from SQL Azure. I assume that there was a temporary problem with the platform (or at least the server that I am running on).
You probably aren't doing anything wrong in your code, but are suffering from degraded performance on SQL Azure. Try and handle the errors, perform retries, exponential back-off, queues (to reduce concurrency), splitting your load across databases — that sort of thing.

Answer 2

write every thing within try and catch,finally block.
as follows:
try
{
con.open();
m_ConnectionRetryPolicy.ExecuteAction(() => connection.Open());
using (var command = connection.CreateCommand())
{
command.CommandText = "SELECT * FROM X WHERE Y = Z";
var reader = m_CommandRetryPolicy.ExecuteAction(() => command.ExecuteReader());
return LoadData(reader).FirstOrDefault();
}
con.close();
}
catch(exception ex)
{
}
finally
{
con.close();
}
Remember to close connection in finally block as well.

Answer 3

There is an Enterprise Library that MS has produced specifically for SQL Azure, here are some examples from their patterns and Practice.
It's similar to what you are doing, however it does more on the reliability (and these examples show how to get a reliable connection)
http://msdn.microsoft.com/en-us/library/hh680899(v=pandp.50).aspx

Answer 4

Are you sure it's the reader that's failing and not the opening of the connection? I'm encountering an exception when I wrap the connection.Open() in the m_ConnectionRetryPolicy.ExecuteAction().
However it works just fine for me if I skip the ExecuteAction wrapper and open the connection using connection.OpenWithRetry(m_ConnectionRetryPolicy).
And I'm also using command.ExecuteReaderWithRetry(m_ConnectionRetryPolicy) which is working for me.
I have no idea though why it's not working when wrapped in ExecuteAction though.

Answer 5

I believe this means that Azure has closed the connection behind the scenes, without telling the connection pooler. This is by design. So, the connection pooler gives you what it thinks is an available, open connection, but when you try to use it, it finds out it's not open after all.
This seems very clunky to me, but it's the way Azure is at the moment.