Connection causing IDS to do reverse DNS lookups
So far, I've mostly posted questions and problems to this list and many times I've received lots of help and suggestions. Well, this time I thought I would just give something back and maybe save someone of anything from hours of harmless head-scratching to days of production system problems. I just experienced an upgrade of the Informix JDBC driver from 2.21 to 3.00 which caused major connection problems. There were other things changed at the same time, so it took us a while before we could determine the actual cause of the problem. Seems that the new JDBC driver connected in such a way that IDS needed to perform a reverse DNS lookup on the client. Some clients did not have a valid reverse lookup which caused the connection time to go from 0.01 sec to 4.5 sec. Also, some of the clients (appserver connection pools) were connecting with INFORMIXCONTIME set to 5 seconds and when the IDS system were under high load, the connection time increased above 5 seconds which in turn caused a lot of connection retries. The problem occurred both with IDS 7.31.TD6 and 10.00.TC6. It seems that this reverse DNS lookup affected all connections. When the "bad" clients did a lot of connects, not even "good" clients could connect within reasonable time (typically they could wait 60-90 seconds before getting in). So, the simple solution to this problem was to make sure all client IP's could be reversed to a name - in our case, we just added them to the IDS server host file - and the connect time was improved drastically. cheers Johan
I had that problem so far. Delays are present when DNS server is failing or is not tunned to give a fast response of failed search. Now we dont have to have all of the reverse ip resolution in DNS. El vie, 28-03-2008 a las 05:06 -0400, un remitente desconocido escribió: > So far, I've mostly posted questions and problems to this list and many times > I've received lots of help and suggestions. Well, this time I thought I would > just give something back and maybe save someone of anything from hours of > harmless head-scratching to days of production system problems. > > I just experienced an upgrade of the Informix JDBC driver from 2.21 to 3.00 > which caused major connection problems. There were other things changed at the > same time, so it took us a while before we could determine the actual cause of > the problem. > > Seems that the new JDBC driver connected in such a way that IDS needed to > perform a reverse DNS lookup on the client. Some clients did not have a valid > reverse lookup which caused the connection time to go from 0.01 sec to 4.5 > sec. Also, some of the clients (appserver connection pools) were connecting > with INFORMIXCONTIME set to 5 seconds and when the IDS system were under high > load, the connection time increased above 5 seconds which in turn caused a lot > of connection retries. > > The problem occurred both with IDS 7.31.TD6 and 10.00.TC6. > > It seems that this reverse DNS lookup affected all connections. When the "bad" > clients did a lot of connects, not even "good" clients could connect within > reasonable time (typically they could wait 60-90 seconds before getting in). > > So, the simple solution to this problem was to make sure all client IP's could > be reversed to a name - in our case, we just added them to the IDS server host > file - and the connect time was improved drastically. > > cheers > > Johan > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > See you at the IIUG Informix 2008 Conference > The Power Conference for Informix Professionals > April 27 - 30, 2008 Marriott Overland Park (Kansas City), Kansas > http://www.iiug.org/conf > Registration Now Open!!