On 08/28/2015 03:02 AM, Benjamin Kaduk wrote:
On Thu, 27 Aug 2015, Gunnar Krull wrote:

Hi,

when I have a backup Volume Set defined in this order, the volume
"user.backup" is not included into the backup:

Volume set userbackup:
     Entry 1: server .*, partition .*, volumes: user\..*\.backup
     Entry 2: server .*, partition .*, volumes: user\.backup

But when I change the order of the two Volume Set entries, the volume
"user.backup" is included:

Volume set userbackup:
     Entry   1: server .*, partition .*, volumes: user\.backup
     Entry   2: server .*, partition .*, volumes: user\..*\.backup


It's strange, but the order is irrelevant for another Volume Set. The
difference to the example above is, that the resulting volume list to be
backuped only consists of two volumes. Namely: "svn.backup" and
"svn.test.backup".

I couldn't find an explanation for this behavior.
Is there something wrong in my understanding of the volume set definitions?

Most likely, there is a bug.

Unfortunately, the backup code is some of the least-maintained and worst
code in the tree that we still have some expectation of people actually
using (which excludes kauth, among other things), so the reason is
unlikely to be clear solely from code examination.  To make matters worse,
there are a few codepaths that could be taken; in what I think is the
common case, the regex is actually evaluated on the vlserver, not on the
machine running the backup utility.  (Note that this means that different
calls may get different results, if the vlservers are not homogeneous and
have different regex libraries on them!)

All servers are running on Debian Wheezy. So it should be quite homogeneous.
I observed this behavior with OpenAFS 1.6.9 and now also with 1.6.14.


As a first debugging step, I would suggest using wireshark or similar to
capture traffic between the backup utility and the vlserver(s) to confirm
whether the problem exists in the vlserver code or on the client side.

The Wireshark records show that the backup client gets the complete volume list from the vlserver correctly, independent of the order in the volume set definition. I can see the two requests to the vlserver for both volume set entries and their corresponding responses including the volumes correctly.

But the output and execution of the backup client depends on the order, like I described above.

So, it seems to be the backup client that skips the volume and doesn't consider it for the actual backup.

Regards,
Gunnar



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