We recently migrated a client to the SQL Azure platform during the course of a production deployment. By all outward signs, it was successful: the web apps connected to it are all working.

However, when we look at the Azure monitor, we see many failed connections. We haven't been able to find much documentation explaining what constitutes a failed connection. And none of our users have been reporting problems. Does anyone know how this could be?

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Using the sample query from this article (View Connection Issues on an SQL Azure Instance)

SELECT      
            [Date From] = EL.[start_time],
            [Date To] = EL.[end_time],
            [Database Name] = EL.[database_name],
            [Event Type] = EL.[event_type],
            [Event Sub Type] = EL.[event_subtype_desc],
            [Description] = EL.[description],
            [Additional Data] = EL.additional_data
FROM sys.event_log EL
WHERE EL.event_type != 'connection_successful'
AND EL.event_subtype_desc != 'idle_connection_timeout'
ORDER BY [Date From] DESC

We see results like this:

2013-04-19 16:40:00.0000000 2013-04-19 16:45:00.0000000 [DATABASE]  connection_failed   blocked_by_firewall Client IP address is not allowed to access the server.  NULL
2013-04-19 16:40:00.0000000 2013-04-19 16:45:00.0000000             connection_failed   blocked_by_firewall Client IP address is not allowed to access the server.  NULL
2013-04-19 16:35:00.0000000 2013-04-19 16:40:00.0000000 [DATABASE]  connection_failed   blocked_by_firewall Client IP address is not allowed to access the server.  NULL
2013-04-19 16:35:00.0000000 2013-04-19 16:40:00.0000000             connection_failed   blocked_by_firewall Client IP address is not allowed to access th
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