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In order to ensure response in case of problems, use the Global Grid User Support (GGUS) and/or your VO support rather than private e-mail contacts or internal mailing lists.


Loadbalancing of WMS using Poise

Server Nodes

Each poise client has a metric. The Poise server checks these metrices every two minutes, and sets the DNS entry to the machine with the lowest metric. The DNS entry has a TTL of 120 seconds.

Each client needs a user mpoise. The user itself if installed via Quattor, and the necessary poise files are pushed to the server via

>cd /afs/desy.de/group/it/grid/tools/POISE/
>./wms_poise.install 
usage: ./wms_poise.install 
This will basically do for you the following:
  /opt/misc/poise/WMS/WMS_install.sh



  grep mpoise /etc/passwd /etc/shadow /etc/group
/etc/passwd:mpoise:x:13417:0:POISE user (contact Yves):/home/mpoise:/home/mpoise/public/metricwrapper.pl
/etc/shadow:mpoise:!!:14057:0:99999:7:::

  mkdir -p /home/mpoise/.ssh
  cp /opt/misc/poise/authorized_keys /home/mpoise/.ssh/authorized_keys
  chown -R mpoise /home/mpoise/.ssh

  mkdir -p /home/mpoise/public
  cp /opt/misc/poise/metric.Linux_RHEL /home/mpoise/public/metric.Linux_RHEL
  cp /opt/misc/poise/metric.config /etc/metric.config
  cp /opt/misc/poise/WmsMetric.pl /home/mpoise/public/WmsMetric.pl
  cp /opt/misc/poise/metricwrapper.pl /home/mpoise/public/metricwrapper.pl
  chown -R mpoise /home/mpoise/public

This script also installs the main script /home/mpoise/public/metricwrapper.pl. This script uses the following config file metric.config

  > cat /etc/metric.config
/home/mpoise/public/SomeMetricScript.sh

So, the actual metric computation is done using SomeMetricScript.sh in this example. The script should simply return an integer value. We have different metric scripts, the most simple one is

>cat metric.Offline
echo 9999
This returns always a very high number. If you want a node to be never chosen by POISE, put the location to this script into /etc/metric.config
Another more sophisticated script is WmsMetric.pl which (currently) checks the load and the space consumtion in the sandbox dir. In addition, the value is set to 1000 in case the WMS is drained.

Further tests and configuration on the WMS

Try su poise to see whether the metric works. If some problem occurs, run the executable described in /etc/metric.config. This will give you error messages.

One thing that will not be installed on a pristine WMS are the WMS selfs tests. Please follow:

  cd ~
  ln -s /opt/misc/tools/POISE/WMSTests .
  cp ~/WMSTests/cronjob /etc/cron.d/WMSTest
  /root/WMSTests/WMSTests_match.sh
In order for the selftest to be able to run, the WMS must be authorized to query itself. Check the following file:
> head /opt/glite/etc/glite_wms_wmproxy.gacl

  
    
      /C=DE/O=GermanGrid/OU=DESY/CN=host/grid-wms14.desy.de
    
    
  

Poise Server, version 2

The new version of Poise is managed by a web interface.

Testing

With Poise2, the miss.pl commands do not work anymore. However, you can easily write your own scripts using the command line, e.g.:

wget -O - -q http://it-dns-lb02.desy.de/cgi-bin/misstable.cgi
Now also images can be generated:
wget -O - -q http://it-dns-lb.desy.de/cgi-bin/make_images.cgi
There is a build-in throttle, if images are too new, they are not generated. Images can be viewed from inside DESY using a syntax like http://it-dns-lb.desy.de/html2/atlas.naf.desy.de-1day.png
Last modified: 02/14/2007
by the DESY Grid Team: http://grid.desy.de/