2006/7/5, Daniel Kinzler daniel@brightbyte.de:
Hi
When monitoring activity on the toolserver, I often notice your script wikicnt_daemon.pl - it seems to be started every few hours, run for quite a while, and there are often many instances running at once (33 at the moment). I suspect (but I'm not sure) that it may be one of the reasons the toolserver often falls behind with replicating from the master db. Critical resources are RAM and Disk-I/O, and thus SQL queries, of course.
Please tell me what that script does, and why there are so many instances at once. Please send a copy of your response to toolserver-l@Wikipedia.org. Thanks!
Regards, Daniel aka Duesentrieb
Hi Daniel,
This script is articles counter installed by admins of Russian Wikipedia. It must make 5-100 inserts into database per second. Now I'm going to move this from MySQL to GDBM database (this should reduce load) but this is not yet done.
Currently running this as daemon is quite a good optimization because of persistent connections to MySQL and usage of prepared statements.
Unfortunately, there's no threads support in Perl version installed and one thread can't dispatch all 5-100 requests per second because it's waiting too many time for MySQL server reply. So this script simply forks five times (so there're 32, not 33 threads) after making listening socket and before connecting to database.
Another optimization was caching results of 'page_title -> page_id' requests in memory (cron task restarted daemon each hour to clear it). Here I made a mistake: full cache (with info about all pages) takes 14 Mb. But after you report I realized that it can take 14*32 = 448 Mb. Now I moved this into GDBM database which is updated only one time per day. Please check, RAM usage should be now not more than 1-2 Mb.
I'm now working on future optimizations. But the counter should be on before this is done (it collects no info about time of requests, only hits from the moment it was launched first).
P.S. There're no required libraries installed (gdbm, sqlite) and perl modules (GDBM_FILE and DBD::SQLite).