Switching Masters During Failover - Oracle 5.0 Reference Manual

• If your slaves are not acting as masters, and you have a potential solution in place to ensure
that you can bring up a master in the event of failure, then you can switch off
updates
their own binary log.

16.3.6. Switching Masters During Failover

There is currently no official solution for providing failover between master and slaves in the event
of a failure. With the currently available features, you would have to set up a master and a slave (or
several slaves), and to write a script that monitors the master to check whether it is up. Then instruct
your applications and the slaves to change master in case of failure.
Remember that you can tell a slave to change its master at any time, using the
statement. The slave will not check whether the databases on the master are compatible with the
slave, it will just start reading and executing events from the specified binary log coordinates on the
new master. In a failover situation, all the servers in the group are typically executing the same events
from the same binary log file, so changing the source of the events should not affect the database
structure or integrity providing you are careful.
Run your slaves with the
this way, the slave is ready to become a master as soon as you issue
and
CHANGE MASTER TO
structure shown in
Figure 16.4. Redundancy Using Replication, Initial Structure
In this diagram, the
replication slaves, and the
that issue only reads (and would normally be connected to the slaves) are not shown, as they do not
need to switch to a new server in the event of failure. For a more detailed example of a read/write
scale-out replication structure, see
Switching Masters During Failover
[1451]. This prevents "dumb" slaves from also logging events they have executed into
--log-bin
statement on the other slaves. For example, assume that you have the
Figure 16.4, "Redundancy Using Replication, Initial
MySQL Master
Web Client
[1467] option and without
holds the master database, the
machines are issuing database reads and writes. Web clients
Section 16.3.3, "Using Replication for
1493
--log-slave-
CHANGE MASTER TO
--log-slave-updates
STOP SLAVE; RESET
Structure".
hosts are
MySQL Slave
Scale-Out".
[1451]. In
MASTER,