maria-developers team mailing list archive
Mailing list archive
Re: Interaction between rpl_slave_state and rpl_binlog_state
Sachin Setiya <sachin.setiya@xxxxxxxxxxx> writes:
> I have some question related to rpl_slave_state. Suppose A circular
> async replication between A < -- > B (gtid_ignore_duplicates on)
Why do you set gtid_ignore_duplicates? This option is for multi-source
"When set, different master connections in multi-source replication are
allowed to receive and process event groups with the same GTID"
But you are not using multi-source connection here, there is only one master
connection (eg. connection to B on slave A).
Thus, the option will do nothing in this case.
> Now, we set some temp server_id on server A , lets say `X`. Now the
> problem is each event group which
> originates from A is executed 2 times. For example we insert into
> table t1 and gtid is 0-X-2. The event goes to slave B
> B applies it, And send it back to A, Since its server_is different
I think here you mean that A has server_id=1 (eg), B has server_id=2, but on
A you do
INSERT INTO t1 VALUES (1);
But there is no server with server_id=3 anywhere. In this case, you need to
break the circle yourself somewhere. For example by CHANGE MASTER ...
IGNORE_SERVER_IDS=3 on A.
To my knowledge, this has always been so for ring replication.
> Andrei suggested a solution of checking rpl_binlog_state in
> check_duplicate_gtid, This solution solves some problem but creates
It seems you think that --gtid-ignore-duplicates should magically ignore any
apply of duplicate GTID. But that is not the case, as the documentation
states (though admittedly rather briefly). --gtid-ignore-duplicates is
_only_ for multi-source replication (so perhaps unfortunately named).
In this case, the conflict is not between GTIDs replicated from different
master connections. It is a conflict between a transaction originated on a
master with a transaction replicated from another master.
> write gtid_event in log. But this does not make sense. rpl_slave_state
> should be used for slave replication usage.
Agree. rpl_binlog_state should not be involved in slave GTID processing.
There should be a clear separation: rpl_slave_state is what a slave has
applied from another master. rpl_binlog state is what a master has
The gtid_ignore_duplicates option is already very difficult for users to
understand and use correctly. It would be a mistake to make it even more
Also, this seems to originate from some Galera issue. It is well known that
Galera was merged prematurely into MariaDB with a broken design, and this
was never fixed. Galera issues must never influence how non-galera
replication (which at least attempts to have a proper design) works.
Hope this helps,