[Beowulf] Troubleshooting NFS stale file handles

Prentice Bisbal pbisbal at pppl.gov
Wed Apr 19 10:58:28 PDT 2017

Here's the sequence of events:

1. First job(s) run fine on the node and complete without error.

2. Eventually a job fails with a 'permission denied' error when it tries 
to access /l/hostname.

Since no jobs fail with a file I/O error, it's hard to confirm that the 
jobs themselves are causing the problem. However, if these particular 
jobs are the only thing running on the cluster and should be the only 
jobs accessing these NFS shares, what else could be causing them.

All these systems are getting their user information from LDAP. Since 
some jobs run before these errors appear, lack of, or inaccurate user 
info doesn't seem to be a likely source of this problem, but I'm not 
ruling anything out at this point.

Important detail: This is NFSv3.

Prentice Bisbal
Lead Software Engineer
Princeton Plasma Physics Laboratory

On 04/19/2017 12:20 PM, Ryan Novosielski wrote:
> Are you saying they can’t mount the filesystem, or they can’t write to a mounted filesystem? Where does this system get its user information from, if the latter?
> --
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> || \\UTGERS,  	 |---------------------------*O*---------------------------
> ||_// the State	 |         Ryan Novosielski - novosirj at rutgers.edu
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> ||  \\    of NJ	 | Office of Advanced Research Computing - MSB C630, Newark
>       `'
>> On Apr 19, 2017, at 12:09, Prentice Bisbal <pbisbal at pppl.gov> wrote:
>> Beowulfers,
>> I've been trying to troubleshoot a problem for the past two weeks with no luck. We have a cluster here that runs only one application (although the details of that application change significantly from run-to-run.). Each node in the cluster has an NFS export, /local, that can be automounted by every other node in the cluster as /l/hostname.
>> Starting about two weeks ago, when jobs would try to access /l/hostname, they would get permission denied messages. I tried analyzing this problem by turning on all NFS/RPC logging with rpcdebug and also using tcpdump while trying to manually mount one of the remote systems. Both approaches indicated state file handles were prevent the share from being mounted.
>> Since it has been 6-8 weeks since there were any seemingly relevant system config changes, I suspect it's an application problem (naturally). On the other hand, the application developers/users insist that they haven't made any changes, to their code, either. To be honest, there's no significant evidence indicating either is at fault. Any suggestions on how to debug this and definitively find the root cause of these stale file handles?
>> -- 
>> Prentice
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