[Beowulf] Concurrently open sockets limit on Linux system

[Galton, Simon]

Folks,

I ask here in anticipation that somebody out there in cluster-land has run
across this limitation and can advise me on moving past it...

We are looking at an application which uses a proprietary license manager.
The client connects to the license manager at start time and (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.  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.

Any thoughts?

Simon
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