SQL_THREAD left in stopped state of safe-slave-backup-timeout is reached

Bug #1037379 reported by Jervin R on 2012-08-16
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
Percona XtraBackup
Fix Released
Medium
Alexey Kopytov
2.0
Fix Released
Medium
Alexey Kopytov
2.1
Fix Released
Medium
Alexey Kopytov

Bug Description

When using safe-slave-backup and safe-slave-backup-timeout is reached, SQL_THREAD is left in stopped state causing the slave thread to lag behind.

Related to https://bugs.launchpad.net/percona-xtrabackup/+bug/1016714 but that one has few other things discussed, figured this one should be separate instead.

Here is a quick patch to restart the slave before the script dies on 2.0.1

2587a2588,2589
> mysql_send 'START SLAVE SQL_THREAD;';
>

Related branches

tags: added: contribution
Jervin R (revin) wrote :

Can we get this up on next release? Thanks!

See internal i25625

tags: added: i25625
tags: removed: i25625
Vadim Tkachenko (vadim-tk) wrote :

well,
the fix is not full, we need to check if SQL_THREAD was running at the start of backup, and only in that case to send "START SQL_THREAD"

tags: added: i25625
Alexey Kopytov (akopytov) wrote :

It's safe to send "START SLAVE SQL_THREAD" unconditionally when the timeout is reached, as innobackupex runs START/STOP SLAVE SQL_THREAD in a loop in wait_for_safe_slave before the timeout anyway.

Alexey Kopytov (akopytov) wrote :

On a second thought, we do need to check, because the slave thread indeed might be stopped with a non-zero slave_open_temp_tables before taking a backup.

markus_albe (markus-albe) wrote :

Will the check and conditional START SLAVE SQL_THREAD be implemented? I got this behavior with 2.1.5... If not, documentation here http://www.percona.com/doc/percona-xtrabackup/2.1/innobackupex/innobackupex_option_reference.html#cmdoption-innobackupex--safe-slave-backup should make it explicit that is possible for failed backup to leave SQL thread stopped.

Alexey Kopytov (akopytov) wrote :

Markus,

This bug was about leaving the SQL thread stopped when safe-slave-backup-timeout. If innobackupex fails between SQL thread stop and restart, it will still be left in the stopped state even in 2.1.5.

Reported separately as bug #1248835. Please let me know if I should prioritize it in case it is affecting a customer.

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PXB-598

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