galera multi-master support

[jsalmeron]

Multi-master mysql is developing as the a horizontal scalability solution for mysql. Galera based mysqls, such as Percona's XC, Maria DB's galera, Codership's, even Oracle's answer to these guys.

If maxwell could use the positions table to store more than one server - file - binlog position, it could de facto give it HA support for this type of cluster. This is because different multi-masters will (surely in time) have different binlog files and positions. It would avoid having to manually adjust maxwell binlog positions with a procedure, say like:

maxwell producer recovery for galera multimaster dbs (as maxwell atm can only depend on one server):

1) identify last commited transaction id (xid)
2) determine binlog file for each galera node:
eg.

show master status;
mysql> show master status;
 +---------------+-----------+--------------+------------------+
 | File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
 +---------------+-----------+--------------+------------------+
 | binlog.000003 | 195545158 | | |
 +---------------+-----------+--------------+------------------+
 1 row in set (0.00 sec)

3) find out position from binlog file corresponding to xid:

eg.
mysql -uroot -ptemporal -h172.16.215.19 -e "show binlog events in 'binlog.000003'" | grep "xid=421484"
output:
binlog.000003 195543779 Xid 4 195543806 COMMIT /* xid=421484 */
or:
mysqlbinlog /var/lib/mysql/binlog.000003 | grep "Xid = 421484"
output:
#160714 9:40:09 server id 4 end_log_pos 195543806 Xid = 421484
binlog position for xid 421484 after commit is 195543806 for file binlog.000003

Not an issue but an enhancement request. Easy testing with these guys.