In this chapter, we will learn about High Availability (HA) clusters and how to achieve them with PostgreSQL. HA database clusters (also known as failover clusters) are a group of computers that support server applications that can be reliably utilized with a minimum of downtime in case something happens, such as a disaster, or we simply need to carry out an upgrade of the hardware or software.
As we have seen in the preceding definition, when we talk about high availability, this will always mean more than two servers, where one of them functions as the master and another one as the standby. This kind of architecture is the minimum that will be needed to comply with zero or near-zero downtime.
In the PostgreSQL world, it is common for architectures such as HA to use streaming replication as a base. Failover is managed is through an application...
