Sasha, thanks for your help!
But I'm not sure we're in agreement about what
is happening yet:
Sasha Pachev wrote:
> On Wednesday 26 December 2001 01:24 pm, Venu wrote:
>
>>Since replication is only one-way, there really shouldn't be any updates
>>happening on the slave, but in the failover case, I've got no choice.
NOTE the failover happens automatically when the master fails for some
reason.
>>
>>So how do I isolate those updates and reapply them to the master,
>>and switch back?
>>
>
> Steve:
>
> Here is how you can do the above:
>
> * make sure slave runs with log-bin.
>
> * before you direct updates to the slave, record the binlog offset and
> position on the slave by running SHOW MASTER STATUS ( on the slave not on the
> master!)
Whoops! When the failover occurs, there is nobody at the console to
record the offset! It's an automatic failover when the master fails!
It might have happened at 4 in the morning yesterday.
How do we automatically know the master has failed and record that offset?
>
> * when you bring back the master, do CHANGE MASTER TO
> MASTER_HOST='slave.mycompany.com', MASTER_USER='rpluser_on_slave',
> MASTER_PASSWORD='rpl_pass_on_slave', MASTER_LOG_FILE='recorded_log_name',
> MASTER_LOG_POS=recorded_log_pos; SLAVE START
>
> * on slave, FLUSH TABLES WITH READ LOCK; SHOW MASTER STATUS;
>
> * record log_name and log_pos
>
> * on master SELECT MASTER_POS_WAIT('log_name',log_pos)
>
> * redirect updates to the old master when the above returns ( this will
> happen when master fully synced up with the slave
>
> * on slave UNLOCK TABLES
>
> Depending on the nature of your queries you may have some conflicts. most
> likely, queries that cause the conflict in this case can be skipped, so if
> you can just add --slave-skip-errors=1062 ( to skip duplicate key errors) in
> the master my.cnf
>
> I will put the above in the manual...
>
>
--
Steve Rapaport
World Citizen
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