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Re: Backup on the replication server getting affected


Howyd Ragul,

> Hi team,
> I have facing a replication issue in my DB setup where we have a master-slave server and replication is ON between
> the servers.
> Environment: MariaDB 10.6.11
> DB size: approx. 1TB
> While taking mariabackup, at the stage of preparing backup I see some interpretation in replication which I can see
> in MySQL logs. Backup was successful but the replication is not catching up with the master and able to see the
> slave worker are getting stuck forever (as per Processlist). Even if we stop the slave SQL thread or stop slave not
> fixing the issue. (WIthout backup process the replication is working
> fine without any delays)

By the show-processlist I could suspect
  MDEV-30780 optimistic parallel slave hangs after hit an error

If you can reproduce it, could you please file a Jira
https://jira.mariadb.org/ ticket to include
1. mysqlbinlog output of the replication events (you may need a master
   binlog for that) being executed by all workers at that
   time (find the last executed through Show-Slave-Status, or
2. slave error log
3. execute on slave
     gdb -ex 'set height 0' -ex 'thread apply all backtrace' -p "find yourself mariadb-pid"

> | 704638 | system user |                      | NULL | Slave_worker | 113000 | Waiting for prior transaction to commit       | NULL                  |    0.000 |
> | 704639 | system user |                      | NULL | Slave_worker | 113000 | closing tables                                | NULL                  |    0.000 |
> | 704641 | system user |                      | NULL | Slave_worker | 113000 | Waiting for prior transaction to commit       | NULL                  |    0.000 |


> Replication as a Backup Solution - MariaDB Knowledge Base as per the page "Running the backup from a slave has the
> advantage of being able to shutdown or lock the slave and perform a backup without any impact on the primary
> server."
> Does it mean running a backup in a slave might impact the replication?

Not really. The sentance merely says the master server performance
won't be affected when one takes backup on the slave.

> If this is expected behavior, do we have any
> proper way to achieve a backup on a daily basis in the replication server?
> Or The backup is not the problem and some other factor (like a deadlock) is affecting the slave thread to lock?

I would think of deadlock.



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