Hey Lars,
On Sat, Jan 21, 2012 at 05:52:28PM +0100, Lars Ellenberg wrote:
> On Fri, Jan 20, 2012 at 04:18:02AM +0100, Dejan Muhamedagic wrote:
> > Hi Lars,
> >
> > On Tue, Dec 13, 2011 at 10:55:57PM +0100, Lars Ellenberg wrote:
> > > Taking this to the mailing list to give it a wider audience.
> > >
> > > On Tue, Dec 13, 2011 at 09:59:11AM -0800, acqant wrote:
> > > > --- a/heartbeat/exportfs
> > > > +++ b/heartbeat/exportfs
> > > > @@ -181,9 +181,11 @@ END
> > > >
> > > > exportfs_monitor ()
> > > > {
> > > > + local clientspec_re
> > > > # "grep -z" matches across newlines, which is necessary as
> > > > # exportfs output wraps lines for long export directory names
> > > > - exportfs | grep -zqs
> > > > "${OCF_RESKEY_directory}[[:space:]]*${OCF_RESKEY_clientspec}"
> > > > + clientspec_re=`echo ${OCF_RESKEY_clientspec} | sed 's/*/[*]/'`
> > > > + exportfs | grep -zqs
> > > > "${OCF_RESKEY_directory}[[:space:]]*${clientspec_re}"
> > > >
> > > > #Adapt grep status code to OCF return code
> > > > case $? in
> > >
> > > > Or you can view, comment on it, or merge it online at:
> > > >
> > > > https://github.com/ClusterLabs/resource-agents/pull/45
> > >
> > > Thinking about it, I've got a problem with this whole grepping thing here.
> > >
> > > grep -z does not just "match accross newlines",
> > > it matches records separated by NUL in that file
> > > (which would be very unexpected).
> > >
> > > So it matches the full file.
> > >
> > > No anchors on the regex whatsoever.
> > >
> > > Client spec will typically have dots in them,
> > > both hostname and ip address form,
> > > which would also need to be matched literally.
> > >
> > > If you have two exports /bar and /foo/bar,
> > > to the same (or similar enough, see above) client spec,
> > > the grep for /bar will also match on /foo/bar.
> > >
> > > The mount point may also contain dots or other special chars.
> > >
> > > I don't like that, really :(
> > >
> > > Suggestion:
> > >
> > > Why not "unwrap" the exportfs output first,
> > > so we get one record per line,
> > > then match literal (grep -F)?
> >
> > That sounds good to me. I wonder if the author of the patch is
> > subscribed here.
>
> I first commented on his pull request on github, then basically
> forwarded what I said there slightly edited to the list here.
>
> > > That should cover most of these issues
> > > (appart from multiple consecutive blanks, or tabs, or newlines,
> > > in the mount point... would that even be "legal"?)
> >
> > I don't think we'd need to support that.
> >
> > > exportfs | fmt -w 1000 -t -u |
> > > grep -x -F "${OCF_RESKEY_directory} ${OCF_RESKEY_clientspec}"
> > >
> > > I'm not completely sure about the fmt trick:
> > > Availability should not be a problem (coreutils).
> > > But, is the exportfs output and fmt behaviour really consistent enough
> > > to have that work on all platforms?
> >
> > The original usage was probably just "fmt -1000" but that won't
> > do. IIRC, fmt on AIX was just like that.
> >
> > > But since both exportfs and fmt predate linux, maybe that just works?
> > >
> > > If necessary, we can pull off the unwrap with sed in a more "controlled"
> > > fashion as well.
> >
> > That'd be preferable (and you're a sed expert :) awk or perl
> > would also do.
>
> As you wish ;-)
>
> exportfs |
> sed -e '$! N; s/\n[[:space:]]\+/ /; t;
> s/[[:space:]]\+\([^[:space:]]\+\)\(\n\|$\)/ \1\2/g; P;D;' |
> grep -x -F "${OCF_RESKEY_directory} ${OCF_RESKEY_clientspec}"
>
> (please someone double check that gobbledygook!)
I think that it looks OK. Can you please also push this to the
repository.
Cheers,
Dejan
P.S. It would be good if sed had an option such as -E for grep,
so that one could reduce backslashism and at least slightly
improve expression readability :)
> --
> : Lars Ellenberg
> : LINBIT | Your Way to High Availability
> : DRBD/HA support and consulting http://www.linbit.com
>
> DRBD® and LINBIT® are registered trademarks of LINBIT, Austria.
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