bug#21952: 24.5; auto-revert-tail-mode doesn't work (perhaps because of nfs)

bug#21952: 24.5; auto-revert-tail-mode doesn't work (perhaps because of nfs)

[dan.dever]

I'm accustomed to monitoring the log files of running jobs with emacs
using auto-revert-tail-mode.  This no longer works on Emacs 24, but 
works fine on previous versions of Emacs.  I don't know if the fact
that our disks are mounted via NFS is the problem or not, but I ran one
trial on a local disk in which auto-revert-tail-mode did work.

Regards,
Dan


Standard form below:
----------------------------------------------------------------

emacs -Q logfile
M->
M-x auto-revert-tail-mode



In GNU Emacs 24.5.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.20.1)
 of 2015-04-13 on ln-ddever
Windowing system distributor `Scientific Linux', version 11.0.11300000
System Description:	Red Hat Enterprise Linux Client release 6 (Carbon Update 4)

Configured using:
 `configure --prefix=/ddever/emacs/emacs-24.5'

Important settings:
  value of $LC_ALL: en_US
  locale-coding-system: iso-latin-1-unix

Major mode: Fundamental

Minor modes in effect:
  auto-revert-tail-mode: t
  tooltip-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Mark set
File changed on disk, content may be missing.  Perform a full revert? (y or n) y
Reverting buffer `logfile'.

Load-path shadows:
None found.

Features:
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easymenu mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util help-fns mail-prsvr mail-utils autorevert filenotify
vc-dispatcher vc-svn time-date tooltip electric uniquify ediff-hook
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Memory information:
((conses 16 72844 7584)
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bug#21952: 24.5; auto-revert-tail-mode doesn't work (perhaps because of nfs)

[Eli Zaretskii]

> From: dan.dever@cavium.com
> Date: Wed, 18 Nov 2015 10:00:15 -0500
> 
> I'm accustomed to monitoring the log files of running jobs with emacs
> using auto-revert-tail-mode.  This no longer works on Emacs 24, but 
> works fine on previous versions of Emacs.  I don't know if the fact
> that our disks are mounted via NFS is the problem or not, but I ran one
> trial on a local disk in which auto-revert-tail-mode did work.
> 
> Regards,
> Dan
> 
> 
> Standard form below:
> ----------------------------------------------------------------
> 
> emacs -Q logfile
> M->
> M-x auto-revert-tail-mode

Does it help to set auto-revert-use-notify to nil?

bug#21952: 24.5; auto-revert-tail-mode doesn't work (perhaps because of nfs)

[Michael Albinus]

Eli Zaretskii <eliz@gnu.org> writes:

>> I'm accustomed to monitoring the log files of running jobs with emacs
>> using auto-revert-tail-mode.  This no longer works on Emacs 24, but 
>> works fine on previous versions of Emacs.  I don't know if the fact
>> that our disks are mounted via NFS is the problem or not, but I ran one
>> trial on a local disk in which auto-revert-tail-mode did work.

> Does it help to set auto-revert-use-notify to nil?

When autorevert detects a file on a known mount location,
`auto-revert-use-notify' is set to nil per default. See
`auto-revert-notify-exclude-dir-regexp', which uses

(regexp-opt '("/afs/" "/media/" "/mnt" "/net/" "/tmp_mnt/"))

Perhaps, the file Dan wants to watch is mounted somewhere else. In this
case I recommend to extend that variable.

Dan, could you check whether this works for you?

Best regards, Michael.

bug#21952: 24.5; auto-revert-tail-mode doesn't work (perhaps because of nfs)

[Dan Dever]

On 08/23/2016 04:22 AM, Michael Albinus wrote:
> When autorevert detects a file on a known mount location,
> `auto-revert-use-notify' is set to nil per default. See
> `auto-revert-notify-exclude-dir-regexp', which uses
>
> (regexp-opt '("/afs/" "/media/" "/mnt" "/net/" "/tmp_mnt/"))
>
> Perhaps, the file Dan wants to watch is mounted somewhere else. In this
> case I recommend to extend that variable.
>
> Dan, could you check whether this works for you?

This does work (tried it on emacs-25.0.95).

I prefer just setting auto-revert-use-notify to nil, however, since we'd never be using auto-revert on locally mounted files anyways.  But thanks for mentioning the alternative.

What also works is the configuration switch that we recently discovered (and have used to build 25.1-rc1/-rc2): "--with-file-notification=no".

I'm not sure I understand the preference for using a file notification utility by default for auto-revert when that utility only works on locally mounted files.  I haven't worked in an environment where our storage has been locally mounted in decades, and I've never had a reason to use auto-revert at home.

Thanks,
Dan

bug#21952: 24.5; auto-revert-tail-mode doesn't work (perhaps because of nfs)

[Michael Albinus]

Dan Dever <dan.dever@caviumnetworks.com> writes:

Hi Dan,

> On 08/23/2016 04:22 AM, Michael Albinus wrote:
>> When autorevert detects a file on a known mount location,
>> `auto-revert-use-notify' is set to nil per default. See
>> `auto-revert-notify-exclude-dir-regexp', which uses
>>
>> (regexp-opt '("/afs/" "/media/" "/mnt" "/net/" "/tmp_mnt/"))
>>
>> Perhaps, the file Dan wants to watch is mounted somewhere else. In this
>> case I recommend to extend that variable.
>>
>> Dan, could you check whether this works for you?
>
> This does work (tried it on emacs-25.0.95).
>
> I prefer just setting auto-revert-use-notify to nil, however, since
> we'd never be using auto-revert on locally mounted files anyways.  But
> thanks for mentioning the alternative.

Thanks for checking. So I will close this bug.

> What also works is the configuration switch that we recently
> discovered (and have used to build 25.1-rc1/-rc2):
> "--with-file-notification=no".
>
> I'm not sure I understand the preference for using a file notification
> utility by default for auto-revert when that utility only works on
> locally mounted files.  I haven't worked in an environment where our
> storage has been locally mounted in decades, and I've never had a
> reason to use auto-revert at home.

There are good reasons for file notifications. Think about working in a
git-controlled directory of source files, where file changes could
happen outside Emacs. You want to be informed about, immediately.

But if you don't need it, it is totally OK to compile without file
notification support.

> Thanks,
> Dan

Best regards, Michael.