On Jul 23, 2010, at 8:01 PM, der.hans wrote:
Am 23. Jul, 2010 schwätzte Alex Dean so:
Hm. Are users on the slave modifying tables which get replicated
from the master? That's grandma's recipe for data stew. You can't
do that if you
Yeah and yeah. I'm going to change that.
have any interest in data integrity. If the slave has some tables
which only exist on the slave, that's probably not a huge issue.
If you want to describe the situation in a little more detail we
can help comment further on how bad/not-bad it all is. :)
Engineering is doing some reporting off the slave. To do so, they've
been
mucking with slave data. There was also some temporary restoral of old
data.
I think you should consider replicating to multiple slaves. 1 is for
backup, and is totally read-only.
http://dev.mysql.com/doc/refman/5.1/en/server-system-variables.html#sysvar_read_only
Another slave, for reporting, can have more relaxed rules. If people
want to mess with the data there, no harm. If they screw it up too
horribly, restore a backup onto the reporting database and continue as
before. You need to get them to script any changes they're making, so
they're easy to re-apply after you restore the testing database. (If
there are certain columns they add, or aggregating tables they find
useful, they should be able to run 1 script to re-create them. This
removes the "we can't restore, it'll ruin all my custom work!"
complaint.)
Plan to periodically take a backup from your live database, and use
that re-init your slaves. MySQL replication is quite good, but I
still have seen some odd situations where replication can mess up.
Since a full live diff of the 2 servers (which would check all data
and verify you're in sync) isn't really feasible, I think it's safest
to take backups from the prod server on a somewhat-infrequent basis.
alex
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