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>From: Harry Edmon <address@hidden> >Organization: University of Washington >Keywords: 200303041956.h24Jus327228 IDD LDM-6 Hi Harry, >Can you explain the very large latencies I see in the following graph: >http://www.unidata.ucar.edu/cgi-bin/rtstats/iddstats?IDS|DDPLUS+sunny.atmos.washington.edu Yes. Oh, so you want the explanation ;-) Here is what was going on: o the LDM on the IDD relay node in SSEC, unidata2.ssec.wisc.edu is running with a 2 GB queue, but it is not moving a lot of data. Therefore, there is some really old data in its queue. o the LDM on thelma was not updating the timestamp for the latest product received for products that were rejected as being duplicates. o unidata2.ssec.wisc.edu was rebooted last night (as per request from Mike Schmidt who had installed system patches) o upon once again being able to get to unidata2, the LDM on thelma requested IDS|DDPLUS products that were newer than the last one it received - from unidata2 for the particular feedtype -, that was rejected as being a duplicate. The time used for the reconnect request, was, therefore very old (like 20000) seconds. So, unidata2 started sending thelma very old products in IDS|DDPLUS even though thelma had received those products a long time ago. The products were not rejected since their MD5 checksum did not match any product in the queue. At the same time, thelma is receiving real-time products from our NOAAPORT ingest machine, jackie, so their latencies are near nothing. The result of having old products from unidata2 and new products from jackie was the graph you note above that looked like it was color filled. Steve noticed the problem above this morning (before your email) from latency plots for thelma: http://www.unidata.ucar.edu/cgi-bin/rtstats/iddstats?IDS|DDPLUS+thelma.ucar.edu He implemented a code modification and we rebuilt the LDM on thelma (for good measure, we rebooted to install a boot time mod that Mike S. had made). After the LDM restart on thelma, the old products from unidata2 were correctly not requested, so the latencies in the plots dropped to zero. Onto another point: The request lines you have in the ldmd.conf file on sunny are incorrect. You are apparently requesting products from 'thelma.unidata.ucar.edu.' instead of 'thelma.ucar.edu'. Two things to note here: 1) leave the trailing '.' off of the upstream machine name 2) use thelma.ucar.edu and _not_ thelma.unidata.ucar.edu Please make the above changes and stop and restart the LDM on sunny. As soon as you have done this, let us know. We want to disable thelma.unidata.ucar.edu as a valid name, but we can't do this until you have changed sunny (and any other machines you have that request data from thelma.unidata.ucar.edu). Thanks in advance. One last thing. There is a new ldm-6.0.tar.Z file in the pub/ldm/test directory on ftp.unidata.ucar.edu. This recut of LDM 6.0 contains the mod to correctly update the time for duplicate products that are rejected so that a request to an upstream site will not get really old products after the upstream's LDM is restarted. This mod shouldn't affect anything on leaf node IDD machines, but it can have consequences on relays as we learned from thelma this morning. You may want to regrab ldm-6.0.tar.Z and rebuild your distributions, but it is not critical. Tom From: Harry Edmon <address@hidden> Date: Tue, 4 Mar 2003 14:41:51 -0800 (PST) To: address@hidden Subject: Re: 20030304: latencies on sunny and a small mod made to LDM 6.0 sunny has been rebooted with the latest 6.0 and with the changes to ldmd.conf you suggested. I will now work on the other systems. -- Dr. Harry Edmon E-MAIL: address@hidden 206-543-0547 address@hidden Dept of Atmospheric Sciences FAX: 206-543-0308 University of Washington, Box 351640, Seattle, WA 98195-1640