January 24, 2011 at 8:55 am
I am investigating whether an intermittant "connection failed" error in an SSIS task step could be a result of interaction between the SynAttackProtect setting (on) and SQL Server.
A Microsoft blog entry* makes reference to this scenario in the following terms:
In a SQL Server environment, when the number of simultaneous client connection requests is more than the system can handle and SQL Server backlog queue is full, the client will receive a 'connection failed' error from SQL Server
SQL Server backlog queue? Nope, you've got me there! When I Google for this phrase, I find 18 instances of it all of which have copied the above paragraph verbatim. And the blog has been dormant since June 2009.
What do other DBAs understand by the phrase "SQL Server backlog queue", and how would you go about monitoring it?
* Archive copy held at http://blogs.msdn.com/b/sqlprogrammability/archive/2008/05/27/sql-server-intermittent-connectivity-issue.aspx
January 25, 2011 at 1:17 pm
Graham_Day (1/24/2011)
I am investigating whether an intermittant "connection failed" error in an SSIS task step could be a result of interaction between the SynAttackProtect setting (on) and SQL Server.A Microsoft blog entry* makes reference to this scenario in the following terms:
In a SQL Server environment, when the number of simultaneous client connection requests is more than the system can handle and SQL Server backlog queue is full, the client will receive a 'connection failed' error from SQL Server
SQL Server backlog queue? Nope, you've got me there! When I Google for this phrase, I find 18 instances of it all of which have copied the above paragraph verbatim. And the blog has been dormant since June 2009.
What do other DBAs understand by the phrase "SQL Server backlog queue", and how would you go about monitoring it?
* Archive copy held at http://blogs.msdn.com/b/sqlprogrammability/archive/2008/05/27/sql-server-intermittent-connectivity-issue.aspx
oops i posted the definition of the backlog queue without reading the url.
anyway if you are opening many connections from SSIS at once then SynAttackProtect will kill your connections. you can disable it for testing purposes.
March 1, 2011 at 3:25 am
I am still none the wiser as to what the "SQL Server backlog queue" is.
However in case anyone else encounters the "Communication failed" when an SSIS Execute SQL task is running, what I found was that this occurred on a call to a very long running T-SQL stored procedure, and was always exactly on 120 seconds. The Execute SQL task in question had no timeout setting set, and after applying a setting of 10 minutes the problem has not occurred again.
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