Details
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Bug
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Status: Closed (View Workflow)
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Major
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Resolution: Fixed
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10.1.37, 10.2.21, 10.3.12
Description
Currently, gtid_binlog_pos can be manually updated by changing gtid_binlog_state.
https://mariadb.com/kb/en/library/gtid/#gtid_binlog_state
Since gtid_current_pos is a union of gtid_binlog_pos and gtid_slave_pos, this also updates gtid_current_pos. For example:
MariaDB [db1]> SHOW GLOBAL VARIABLES WHERE Variable_name IN( 'log_bin', 'server_id', 'gtid_binlog_pos', 'gtid_binlog_state', 'gtid_slave_pos', 'gtid_current_pos' );
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+-------------------+------------------+
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| Variable_name | Value |
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+-------------------+------------------+
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| gtid_binlog_pos | 1-1-101,2-1-2002 |
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| gtid_binlog_state | 1-1-101,2-1-2002 |
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| gtid_current_pos | 1-1-101,2-1-2002 |
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| gtid_slave_pos | |
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| log_bin | ON |
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| server_id | 1 |
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+-------------------+------------------+
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6 rows in set (0.001 sec)
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|
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MariaDB [db1]> RESET MASTER;
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Query OK, 0 rows affected (0.005 sec)
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|
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MariaDB [db1]> SHOW GLOBAL VARIABLES WHERE Variable_name IN( 'log_bin', 'server_id', 'gtid_binlog_pos', 'gtid_binlog_state', 'gtid_slave_pos', 'gtid_current_pos' );
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+-------------------+-------+
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| Variable_name | Value |
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+-------------------+-------+
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| gtid_binlog_pos | |
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| gtid_binlog_state | |
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| gtid_current_pos | |
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| gtid_slave_pos | |
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| log_bin | ON |
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| server_id | 1 |
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+-------------------+-------+
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6 rows in set (0.001 sec)
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MariaDB [db1]> SET GLOBAL gtid_binlog_state='1-1-101,2-1-2002';
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Query OK, 0 rows affected (0.005 sec)
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|
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MariaDB [db1]> SHOW GLOBAL VARIABLES WHERE Variable_name IN( 'log_bin', 'server_id', 'gtid_binlog_pos', 'gtid_binlog_state', 'gtid_slave_pos', 'gtid_current_pos' );
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+-------------------+------------------+
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| Variable_name | Value |
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+-------------------+------------------+
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| gtid_binlog_pos | 1-1-101,2-1-2002 |
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| gtid_binlog_state | 1-1-101,2-1-2002 |
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| gtid_current_pos | 1-1-101,2-1-2002 |
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| gtid_slave_pos | |
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| log_bin | ON |
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| server_id | 1 |
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+-------------------+------------------+
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6 rows in set (0.001 sec)
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However, there seems to be a bug where gtid_current_pos is not updated if gtid_binlog_state is updated with GTIDs that contain non-local server_id values. Compare the above behavior to the following:
MariaDB [db1]> SHOW GLOBAL VARIABLES WHERE Variable_name IN( 'log_bin', 'server_id', 'gtid_binlog_pos', 'gtid_binlog_state', 'gtid_slave_pos', 'gtid_current_pos' );
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+-------------------+------------------+
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| Variable_name | Value |
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+-------------------+------------------+
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| gtid_binlog_pos | 1-1-101,2-1-2002 |
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| gtid_binlog_state | 1-1-101,2-1-2002 |
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| gtid_current_pos | 1-1-101,2-1-2002 |
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| gtid_slave_pos | |
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| log_bin | ON |
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| server_id | 1 |
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+-------------------+------------------+
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6 rows in set (0.001 sec)
|
|
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MariaDB [db1]> RESET MASTER;
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Query OK, 0 rows affected (0.005 sec)
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|
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MariaDB [db1]> SHOW GLOBAL VARIABLES WHERE Variable_name IN( 'log_bin', 'server_id', 'gtid_binlog_pos', 'gtid_binlog_state', 'gtid_slave_pos', 'gtid_current_pos' );
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+-------------------+-------+
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| Variable_name | Value |
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+-------------------+-------+
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| gtid_binlog_pos | |
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| gtid_binlog_state | |
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| gtid_current_pos | |
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| gtid_slave_pos | |
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| log_bin | ON |
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| server_id | 1 |
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+-------------------+-------+
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6 rows in set (0.001 sec)
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|
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MariaDB [db1]> SET GLOBAL gtid_binlog_state='1-2-101,2-2-2002';
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Query OK, 0 rows affected (0.005 sec)
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MariaDB [db1]> SHOW GLOBAL VARIABLES WHERE Variable_name IN( 'log_bin', 'server_id', 'gtid_binlog_pos', 'gtid_binlog_state', 'gtid_slave_pos', 'gtid_current_pos' );
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+-------------------+------------------+
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| Variable_name | Value |
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+-------------------+------------------+
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| gtid_binlog_pos | 1-2-101,2-2-2002 |
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| gtid_binlog_state | 1-2-101,2-2-2002 |
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| gtid_current_pos | |
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| gtid_slave_pos | |
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| log_bin | ON |
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| server_id | 1 |
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+-------------------+------------------+
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6 rows in set (0.001 sec)
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I think that if an update to gtid_binlog_state causes gtid_binlog_pos to be updated, then gtid_current_pos should also be updated--even if the GTIDs didn't contain the local server_id.
Attachments
Issue Links
- relates to
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MDEV-18405 Add Mariabackup option to set gtid_slave_pos to original server's gtid_current_pos during prepare
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- Stalled
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Activity
Hi knielsen,
No, this is wrong. See the documentation of @@gtid_current_pos:
https://mariadb.com/kb/en/library/gtid/#gtid_current_pos
gtid_current_pos is documented to only take from the binlog position those GTIDs with the server's own server_id.
To be specific, it says this:
For each replication domain, if the server ID of the corresponding GTID in @@gtid_binlog_pos is equal to the servers own server_id, and the sequence number is higher than the corresponding GTID in @@gtid_slave_pos, then the GTID from @@gtid_binlog_pos will be used. Otherwise the GTID from @@gtid_slave_pos will be used for that domain.
Based on this, it wasn't entirely clear what gtid_current_pos would contain for a given domain if gtid_binlog_pos contained a GTID from a different server for that domain, and if gtid_slave_pos contained no GTID for that domain. I assumed that gtid_current_pos would use the GTID from gtid_binlog_pos for that domain. I just did a test, and I can see that gtid_current_pos actually does not use any GTID for that domain.
For example:
MariaDB [(none)]> SHOW GLOBAL VARIABLES WHERE Variable_name IN('server_id', 'gtid_binlog_pos', 'gtid_slave_pos', 'gtid_current_pos');
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+------------------+--------------+
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| Variable_name | Value |
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+------------------+--------------+
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| gtid_binlog_pos | 1-1-95,3-1-1 |
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| gtid_current_pos | |
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| gtid_slave_pos | |
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| server_id | 2 |
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+------------------+--------------+
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4 rows in set (0.001 sec)
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So I've clarified the documentation by adding this:
GTIDs from gtid_binlog_pos in which the server_id of the GTID is not equal to the server's own server_id are effectively ignored. If gtid_binlog_pos contains a GTID for a given replication domain, but the server_id of the GTID is not equal to the server's own server_id, and gtid_slave_pos does not contain a GTID for that given replication domain, then gtid_current_pos will not contain any GTID for that replication domain.
Fixed with improving documentation https://mariadb.com/kb/en/library/gtid/#gtid_current_pos. GeoffMontee, thanks.
No, this is wrong. See the documentation of @@gtid_current_pos:
https://mariadb.com/kb/en/library/gtid/#gtid_current_pos
gtid_current_pos is documented to only take from the binlog position those GTIDs with the server's own server_id.
If you want GTIDs from a different server to affect the slave position, just update the gtid_slave_pos at the same time as updating gtid_binlog_state.