Code review comment for lp:~akopytov/percona-xtrabackup/read-server-options-with-show-variables

Hi Alexey,

The patch itself looks good, but

I am concerned of "Bug #1343722: Too easy to backup wrong datadir with
multiple instances". Not only datadir but every other important option
can be different if we read options from my.cnf which doesn't belong
to MySQL instance.

This patch makes following change:

innobackupex reads options from running MySQL.
xtrabackup reads options from my.cnf.

Now instead of single source we have two sources which can be out of
sync. We making sure that xtrabackup and innobackupex agree about
"datadir" but we don't take proper care of other options. Wouldn't it
be better to make both innobackupex and xtrabackup to use runtime
options (innobackupex could simply pass all sensitive options to
xtrabackup or even dump them into tmp-my.cnf).