xtrabackup_slave_info does not contain GTID purge lists

Reported by Sheeri K. Cabral on 2013-10-14
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
Percona XtraBackup
Status tracked in 2.2
2.0
Undecided
Unassigned
2.1
High
Alexey Kopytov
2.2
High
Alexey Kopytov

Bug Description

xtrabackup_slave_info does not contain any GTID information. Shouldn't it contain the purge list(s)? Otherwise master_auto_position will not work properly.

Version info:
xtrabackup version 2.1.3 for Percona Server 5.1.59 unknown-linux-gnu (x86_64) (revision id: 608)

(xtrabackup_binlog_info does have GTID position, but xtrabackup_slave_info does not)

Alexey Kopytov (akopytov) wrote :

Sheeri,

I don't' understand this report, but my GTID knowledge is limited. Can you provide any examples of cases where master_auto_position would not work when cloning a slave, and what GTID information could fix that?

Thanks!

Changed in percona-xtrabackup:
status: New → Incomplete
Sheeri K. Cabral (awfief) wrote :

master_auto_position relies on GTIDs to know what transactions have been applied and what transactions have not, so they are essential to be able to actually use a cloned slave to replicate. GTIDs are a replacement for binlog and position, which spells out which transactions have been applied. Thus, MySQL knows that it does not need to apply those transactions, but will apply everything else not in the purge list.

So here's an example:

master -> slave1

If you want to spin up slave2, but don't want to take up resources on the master, you would run innobackupex --slave-info against slave1, and restore to slave2. However, without the GTID information, slave2 would try to reapply ALL the transactions in the master's binary logs, because there is nothing in the purge list. This will cause duplicate key errors and duplicate data when there are no unique keys on data.

In summary - think of it as like not having binlog information - you have a good clone, but you can't easily figure out where to start replication from.

Alexey Kopytov (akopytov) wrote :

Sheeri,

Thanks for clarifications.

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