Mysql – Database replication without locking tables

Replication is always serialized to prevent the race-conditions you are speaking about. See this stackoverflow post for my explanation of InnoDB locking. Some important notes:

• RBR with row-based replication and read-committed isolation level sets fewer locks than InnoDB would have previously.

• We should be moving to a world with RBR anyway, because this will open more doors for parallel replication threads (by working out dependencies between transactions).

To answer your last question, I use RBR in production, and I haven't seen any major performance hit. We do generate a lot more binary log data however, since the events logged contain whole rows.

Surprisingly, that's not gibberish.

That indeed appears at the top of binlogs whenever you do mysqlbinlog to a binary log generated using MySQL 5.1 and MySQL 5.5. You will not see that gibberish in binary logs for MySQL 5.0 and back.

This is why the start point for replication from an empty binary log is

• 107 for MySQL 5.5
• 106 for MySQL 5.1
• 98 for MySQL 5.0 and back

This is good to remember if you do MySQL Replication where the Master if MySQL 5.1 and the slave is MySQL 5.0. This could present a really big headache.

Replication from Master using 5.0 and Slave using 5.1 works fine, not the other way around.(According to MySQL Documentation, it is generally not supported for 3 reasons: 1) Binary Log Format, 2) Row-based Replication, 3) SQL Incompatibility).

Anyway, do a mysqlbinlog on the offending binary log on the master. If the resulting dump produces gibberish in the middle of the dump (which I have seen a couple of times in my DBA career) you may have to skip to position 98 (MySQL 5.0) or 106 (MySQL 5.1) or 107 (MySQL 5.5) of the master's next binary log and start replicating from there (SOB :( you may need to use MAATKIT tools mk-table-checksum and mk-table-sync to reload master changes not on the slave [if you want to be a hero]; even worse, mysqldump the master and reload the slave and start replication totally over [if you don't want to be a hero])

If the mysqlbinlog of the master is completely readable after the top gibberish you saw, it is possible the master's binary log is fine but the relay log on the slave is corrupt (due to transmission/CRC errors). If that's the case, just reload the relay logs by issuing the CHANGE MASTER TO command as follows:

STOP SLAVE;
CHANGE MASTER TO
MASTER_HOST='< master-host ip or DNS >',
MASTER_PORT=3306,
MASTER_USER='< usernmae >',
MASTER_PASSWORD='< password >',
MASTER_LOG_FILE='< MMMM >',
MASTER_LOG_POS=< PPPP >;
START SLAVE;

Where

• MMMM is the last file used from the Master that was last processed on the Slave
• PPPP is the last position used from the Master that was last processed on the Slave

You can get MMMM and PPPP by doing SHOW SLAVE STATUS\G and using

• Relay_Master_Log_File for MMMM
• Exec_Master_Log_Pos for PPPP

Try it out and let me know !!!

BTW running CHANGE MASTER TO command erases the slave's current relay logs and starts fresh.