When to run collect-like extensions

[Kenneth Pronovici <kenneth.pronovici@cedar-solutions.com>]

I have been debugging a backup problem where the collect and stage
actions seemed to succeed but only part of the collected data appeared
to be staged to the master.  

The odd part was that when I ran the collect action by hand, it seemed
to work with no problems.  I was running something like this:

   cback collect mbox sysinfo

Eventually, I realized that the problem was related to the mbox action,
which was taking a really long time to run (due to a large file and an
old, slow box).

I had configured the extensions with indices 101 and 102, so they
would run immediately after collect (which has index 100).

Under this configuration, there is a potential for a problem, because
the "collect action finished" marker file is written by the collect
action.  That means that the marker file gets written before the mbox
and sysinfo extensions are even run.

In this case, what happened was that -- even though the backup was still
running -- the master saw the marker file, thought everything was OK,
and happily staged a partial backup.

Moral of the story: collect-like extensions should ALWAYS be configured
to run BEFORE the collect action itself.  I now use something like this:

      <action>
         <name>mbox</name>
         <module>CedarBackup2.extend.mbox</module>
         <function>executeAction</function>
         <index>99</index> <!-- just before collect -->
      </action>

I will update the documentation for the next release.

KEN

-- 
Kenneth J. Pronovici <pronovic@ieee.org>
http://www.cedar-solutions.com/


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