Mysql – Created databases and inserted data on MySQL slaves in Master-Slave replication – how to fix

MySQLreplication

I got MySQL Master-Slave replication running on 1 master with 2 slaves. SHOW MASTER STATUS / SHOW SLAVE STATUS says they are in sync, but databases have been created on the slaves and filled with data which of course cannot be seen on the other slaves/master, because no replication from Slave to Master happened.

Is there an easy way to fix this situation? Two outcomes would be acceptable for me, but I'm not sure what is the best way to achieve this (sorry, DBA noob):

No replication at all, but no data lost on each server in its current state (replicated data stays in its current state, new data on the slave stays there, too)
Converting Master-Slave to Master-Master-Replication so every server has the same data.

Best Answer

You say:

databases have been created on the slaves and filled with data.

The easiest way of correcting this is to take a mysqldump of the specific databases on the slave, drop the database on the slave, and import the dumpfile onto the master. The slaves will then replicate the data.

This of course gets trickier if it is not whole databases or even tables (but specific rows inside a table).

PROBLEM

MySQL needs to be very explicit when flushing to disk in Windows. You have caught on to this when you did STOP SLAVE; and START SLAVE;

You said you are using sync-binlog = 1. That's great. That only addresses half the log file issues.

SOLUTION (or at least SUGGESTION)

You need to synchronize all other replication components

[mysqld]
sync-binlog = 1
sync-relay-log = 1
sync-relay-log-info = 1
sync-master-info = 1

The SQL thread reads binlog events of the master from the relay logs. Doing sync-binlog only flushes master logs. By flushing relay logs and the associated replication status files, this should make reading replication status and binlog events from the relay logs more accurate.

Here is the MySQL Documentation for these options

Give it a Try !!!

CAVEAT: There may be a small impact on disk I/O. Please monitor it.

Best Answer

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PROBLEM

SOLUTION (or at least SUGGESTION)

Give it a Try !!!

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