bug#768: 23.0.60; vc-bzr.el re-reads metadata files in an endless loop

bug#768: 23.0.60; vc-bzr.el re-reads metadata files in an endless loop

[Torsten Bronger]

I load a remote file in a Bazaar repository using Emacs Tramp through an ssh
connection.  Sometimes, this means that every five seconds, four remote files
belonging to Bazaar's metadata are read.  These are "dirstate" twice, then
"format" and "last-revision".  After five seconds, this procedure starts again.
I haven't yet figured out when it happens, however, I was once blocked by a
firewall because the repetive ssh connection were considered an attack.

See also http://thread.gmane.org/gmane.emacs.tramp/6641/focus=6641 for a bug
report to the tramp mailing list because I first thought it was a Tramp bug.

The remote Bazaar version is 1.3.1, the local one is 1.5.  The remote
repository is "Bazaar Branch Format 6 (bzr 0.15)".



In GNU Emacs 23.0.60.10 (x86_64-unknown-linux-gnu)
 of 2008-08-20 on wilson
Windowing system distributor `The X.Org Foundation', version 11.0.10400090
configured using `configure  '--prefix=/usr/local/' '--mandir=/usr/local/share/man/' '--infodir=/usr/local/share/info/' '--with-x-toolkit=no' '--with-xpm' '--with-jpeg' '--with-tiff' '--with-gif' '--with-png' '--with-x''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: de_DE.UTF-8
  value of $XMODIFIERS: nil
  locale-coding-system: utf-8-unix
  default-enable-multibyte-characters: t

Major mode: Emacs-Lisp

Minor modes in effect:
  diff-auto-refine-mode: t
  shell-dirtrack-mode: t
  global-auto-revert-mode: t
  savehist-mode: t
  display-time-mode: t
  desktop-save-mode: t
  mouse-wheel-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  global-auto-composition-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t

bug#768: 23.0.60; vc-bzr.el re-reads metadata files in an endless loop

[Torsten Bronger]

Hallöchen!

Torsten Bronger writes:

> I load a remote file in a Bazaar repository using Emacs Tramp
> through an ssh connection.  Sometimes, this means that every five
> seconds, four remote files belonging to Bazaar's metadata are
> read.  These are "dirstate" twice, then "format" and
> "last-revision".  After five seconds, this procedure starts again.
> I haven't yet figured out when it happens, however, I was once
> blocked by a firewall because the repetive ssh connection were
> considered an attack.

I think I know what happens: I set (auto-revert-check-vc-info t)
which probably means that Emacs re-reads VC metadata every five
seconds.  However, it is questionable whether this makes sense for
remote files through Tramp.

Tschö,
Torsten.

-- 
Torsten Bronger, aquisgrana, europa vetus
                   Jabber ID: torsten.bronger@jabber.rwth-aachen.de

bug#768: 23.0.60; vc-bzr.el re-reads metadata files in an endless loop

[Lars Magne Ingebrigtsen]

Torsten Bronger <bronger@physik.rwth-aachen.de> writes:

> I think I know what happens: I set (auto-revert-check-vc-info t)
> which probably means that Emacs re-reads VC metadata every five
> seconds.  However, it is questionable whether this makes sense for
> remote files through Tramp.

I think special-casing the action of that variable for tramp files
sounds non-optimal.  If your files are too slow to be read in that way,
then you shouldn't switch that on, but Emacs has no way of determining
that.

So I don't think this is a bug, and I'm closing the report.

-- 
(domestic pets only, the antidote for overdose, milk.)
  bloggy blog http://lars.ingebrigtsen.no/

bug#768: 23.0.60; vc-bzr.el re-reads metadata files in an endless loop

[Torsten Bronger]

Hallöchen!

Lars Magne Ingebrigtsen writes:

> Torsten Bronger <bronger@physik.rwth-aachen.de> writes:
>
>> I think I know what happens: I set (auto-revert-check-vc-info t)
>> which probably means that Emacs re-reads VC metadata every five
>> seconds.  However, it is questionable whether this makes sense
>> for remote files through Tramp.
>
> I think special-casing the action of that variable for tramp files
> sounds non-optimal.  If your files are too slow to be read in that
> way, then you shouldn't switch that on, but Emacs has no way of
> determining that.

But tramp files are special-cased also when it comes to restoring
the desktop after an Emacs start: They are not restored (at least
not by default).  I think it is fair to assume that probing a file
every five seconds through SSH is more critical than probing a local
file.

Moreover, I have dozens of local version-controlled files open but I
open a remote file only seldomly.  Without special-casing, the whole
workflow suffered due to a rare use case.

Tschö,
Torsten.

-- 
Torsten Bronger    Jabber ID: torsten.bronger@jabber.rwth-aachen.de
                                  or http://bronger-jmp.appspot.com