[Beowulf] Concurrently open sockets limit on Linux system

Galton, Simon galtons at aecl.ca
Sun Jun 17 14:30:25 PDT 2007


Joe - good ideas!

As a debugging step we even ran the LM daemon as root, ulimit -a reports a
file limit of 65535...

It's a permanently running daemon, not going through xinetd and it,
annoyingly, produces no logs or sends anything to syslog.

Thanks for your thoughts...
Simon



-----Original Message-----
From: Joe Landman [mailto:landman at scalableinformatics.com]
Sent: 2007 Jun 17 2:52 PM
To: Galton, Simon
Cc: 'beowulf at beowulf.org'
Subject: Re: [Beowulf] Concurrently open sockets limit on Linux system


Hi Simon

Galton, Simon wrote:

> (according lsof on the system running the license manager) seems to hold 
> a socket open during the duration of the job.
> 
> We want to run a couple of hundred of these jobs on our cluster, but 
> after job 126 the client can no longer connect to the license manager.  

This seems to suggest somewhere that there is a 128 socket limit on the 
service.  How is the license manager run?  What does

	limit

or

	ulimit -a

tell you for the user that the license manager runs as?   Any notes in 
system logs?

> The server hosting the license manager is otherwise fine, and you can 
> continue to perform network-based operations on and against it...
> 
> The vendor feels that they have not coded a specific limit; I'm 
> wondering if it's file descriptors or somesuch.  I raised the limit of 
> FDs on the system to 65000+ and verified that the change took effect; no 
> change to the applications behaviour.  It's a c-based app, compiled with 
> gcc on a Fedora Core 6 system, I believe.

Doesn't sound like an FD limit, but as a socket limit.  Older inetd's 
had something like 20-40 connections per process.  If you are serving 
this through xinetd or similar, you might be able to raise these limits.

Joe

> 
> Any thoughts?
> 
> Simon
> 
> 
> 
> 
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-- 

Joseph Landman, Ph.D
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Scalable Informatics LLC,
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