After alot of tests we concluded that Planet Lab nodes highly unpredictable in nature in terms of availability. For every access by TULIP we log the response for landmark. With the help of this logging information we generate a list containing of nodes with corresponding success or failure percentages and reasons of their failsures. These percentages are generated by /afs/slac/package/netmon/tulip/tulip-log-analyze.pl and results can be seen here.
There are two ways in which we can disable the landmarks which are not responding.
1) Manual Process
2) Automate Process (updated by cronjob)
Manual disable of hosts
This can be done by tulip data base. In tulip database table landmarks has a parameter "enabled" which is used to decide which host is to be added to sites.xml. This XML file is latter used by reflector to query the landmarks for the results. Sites.xml is generated by cron job so if we change the value of enabled to '0' it would automatically not appear in Sites.xml after it has re-run after the cronjob. We can also update Sites.xml manually. The process is discussed below.
- Login to tulip database (username and password available in escrow)
- Change the database to tulip by cmd
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mysql> use tulip;
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- Now update the value of enabled using the following sql cmd; in this instance we are using ipv4Addr = 141.22.213.35; generally ipv4Addr is the primary key but we can also use hostName as an identifier to disable landmarks
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update landmarks set enabled = '0' where ipv4Addr = '141.22.213.35';
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tulip tulip-tuning.pl
Now with the help of this results from analysis script we can very well identify the hosts and thier success percentage. We opted to disable all the hosts which were having success less than 20%. The above mentioned script is in $tulipdir and it performs the listed functions. It use LWP package to access the webpage, download the file and then parse the output to get the faulty landmarks.
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