Performing failovers

Once you have learned how to replicate tables and add them to sets, it is time to learn about failover. Basically, we can distinguish between two types of failovers:

• Planned failovers

• Unplanned failovers and crashes

In this section, you will learn about both scenarios.

Planned failovers

Having planned failovers might be more of a luxury scenario. In some cases, you will not be so lucky and you will have to rely on automatic failovers or face unplanned outages.

Basically, a planned failover can be seen as moving a set of tables to some other node. Once that node is in charge of those tables, you can handle things accordingly.

In our example, we want to move all tables from node 1 to node 2. In addition to this, we want to drop the first node. Here is the code required:

#!/bin/sh

MASTERDB=db1
SLAVEDB=db2
HOST1=localhost
HOST2=localhost
DBUSER=hs

slonik<<_EOF_
cluster name = first_cluster;

node 1 admin conninfo = 'dbname=$MASTERDB host=$HOST1 user=$DBUSER';
node 2 admin...