Mogilefs - many db connections causing performance problem
dormando at rydia.net
Thu Apr 10 23:04:09 UTC 2008
telnet to the tracker's management port and run !jobs.
you should have one DB connection per job type that exists. I figure
you're probably sending most of your traffic to one of the trackers?
If you have fewer workers than connections something else might be up.
Are those connections busy with queries? Can you tell what kind of
Fernando Gomes wrote:
> 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:
> http://davidrasch.com/2008/01/29/mogilefs-and-race-condition). 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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