Mogilefs - many db connections causing performance problem

Fernando Gomes f.m.gomes at
Thu Apr 10 22:40:04 UTC 2008


I'm using MogileFS with mysql DB, with two trackers and two storage
nodes. There are around 65000 files stored, and as they are replicated,
about 130000 total, distributed by the different devices.

All was working as expected until recently I noticed two problems 
(perhaps related). One is that from time to time the files I got from
the client (java) wasn't the requested file (I suppose that might be
something like reported here: I'll try
to look to the client java code in order to see what can be done.

The other problem is that today the trackers started creating a lot of
database connections (one tracker more than the other), almost taking
the database down. After finding that the database performance problem
was caused by one of the trackers I restarted it and things got a bit
better, but I still see many connections on the database from the

When trying to diagnose the problem also found something that seems
strange to me (perhaps caused by the hours spent on this problem) - the
number of connections from one tracker to the database, evaluated by
netstat -n |grep 3306, is not the same if I execute netstat on the
tracker server or on the database server (I am now having 8 connections
from tracker 2 to the database server if I run netstat on the tracker,
but I see 68 connections from tracker2 to the database if i run it on
the database server. 

If you can give me some tip about what might be the problem it will be
very useful to me!



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