[Xymon] df hanging will cause xymon-client to hang.

[Richard L. Hamilton]

A “hard” NFS mount will not give up on an access, but retry until the server comes back up (contrasted to a “soft” mount which will eventually give up, but can cause program crashes or even data loss on write operations when it gives up).  “soft” mounts are almost always Evil (TM).

An NFS mount with BOTH “hard” and “intr” options is as robust as a regular “hard” mount, but programs hung in an access to an unresponsive server can be killed.


> On Jun 18, 2015, at 09:45, Novosielski, Ryan <novosirj at ca.rutgers.edu> wrote:
> 
> I wouldn't be certain that would work. Hangs on NFS tend not to respond to CTRL-C or kill. I'm working from memory here, but it would be interesting to try.
> 
> --
> ____ *Note: UMDNJ is now Rutgers-Biomedical and Health Sciences*
> || \\UTGERS      |---------------------*O*---------------------
> ||_// Biomedical | Ryan Novosielski - Senior Technologist
> || \\ and Health | novosirj at rutgers.edu - 973/972.0922 (2x0922)
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> ________________________________________
> From: Steve Anderson [steve.anderson at bipsolutions.com]
> Sent: Thursday, June 18, 2015 9:23 AM
> To: Novosielski, Ryan; Cédric BRINER; xymon at xymon.com
> Subject: RE: [Xymon] df hanging will cause xymon-client to hang.
> 
> If you don't care about the nfs mounted volumes, you may get away with replacing the df with something like
> 
> df -l
> or
> df -x nfs
> 
> Those /should/ (depending on implementation) just skip the testing of the nfs volumes.
> 
> timeout 5s df
> 
> is another option, which should kill the df if it takes more than 5 seconds.
> 
> 
> Steve
> 
> 
> -----Original Message-----
> From: Xymon [mailto:xymon-bounces at xymon.com] On Behalf Of Novosielski, Ryan
> Sent: 18 June 2015 14:16
> To: Cédric BRINER; xymon at xymon.com
> Subject: Re: [Xymon] df hanging will cause xymon-client to hang.
> 
> You do eventually find out when the status turns purple.
> 
> This is a pretty hard one to deal with, from my experience. A hang on something NFS-related is pretty difficult to get out of. I've seen that mounting NFS with the "bg" option can improve this somewhat, but that might create other problems.
> 
> --
> ____ *Note: UMDNJ is now Rutgers-Biomedical and Health Sciences*
> || \\UTGERS      |---------------------*O*---------------------
> ||_// Biomedical | Ryan Novosielski - Senior Technologist
> || \\ and Health | novosirj at rutgers.edu - 973/972.0922 (2x0922)
> ||  \\  Sciences | OIRT/High Perf & Res Comp - MSB C630, Newark
>      `'
> ________________________________________
> From: Xymon [xymon-bounces at xymon.com] On Behalf Of Cédric BRINER [Cedric.BRINER at UniGE.ch]
> Sent: Thursday, June 18, 2015 9:11 AM
> To: xymon at xymon.com
> Subject: [Xymon] df hanging will cause xymon-client to hang.
> 
> Hello,
> 
> I'm running a xymon-client on a Debian Jessie.
> 
> OS: Debian
> OS-Release: 8 (Jessie)
> xymon-client version : 4.3.17
> 
> The error happend due to a nfs ressource not responding. I suppose that
> as xymon launch "df" to get information and as the nfs was hanging, the
> xymon-client is no able to detect that the df hangs and it does not send
> any data to the server. Worst, the xymon-client is not verbose at all,
> it does not tell this test (df) takes too long to accomplish.
> 
> Many thanks for xymon.
> 
> Regards.
> 
> Cédric BRINER
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