Setting up a system that ensures ongoing database availability even in the case of a server or connection loss is usually involved in PostgreSQL failover with HAProxy. At Bobcares, with our PostgreSQL Support, we can handle your issues.

PostgreSQL Failover With HAProxy

With great efficiency, HAProxy is a widely used program for layer 4 and layer 7 (HTTP) session routing and load balancing. The failover occurs in situations like;

i. One or more primary instances.

It is common to refer to Citus coordinators, Postgres-XL coordinators, or completely similar multi-master nodes as multiple primary instances. The connection will be terminated and rejoined (session failover) if the backend database associated with the session detects an unexpected condition. A new RW node is used to replace the disconnected session on this node when the RW node is swapped.

ii. One or more instances that are read-only.

Load balancing (session-level) is enabled when there are many RO nodes in the backend. Following the changeover, this node’s session is detached and moved to the new RO node. It can implement various basic PostgreSQL access points (listening points) and session failover management features, but it cannot directly implement PostgreSQL’s read-write separation.

Database connections that have been established on a failing database node will likewise fail. HAProxy must make sure that incoming connection requests are not sent to the downed node.

HAProxy-based PostgreSQL Failover Setup

In the case of a failure, failover is the act of automatically rerouting traffic or services from one server or system to another. This refers to PostgreSQL failover, which makes sure that the system automatically switches to a secondary (backup) server in case the primary database server goes down in order to preserve database availability.

In a HAProxy-based PostgreSQL failover configuration:

1. A cluster of PostgreSQL servers is set up with one serving as the primary (active) server and the others as standbys or replicas.

2. HAProxy keeps an eye on these database servers’ condition. HAProxy recognises this failure if the primary server fails (for whatever reason—hardware malfunctions, network difficulties, etc.).

3. HAProxy starts a failover procedure when it detects a failure. In order to maintain uninterrupted database operations, it reroutes incoming database connection requests to one of the standby servers.

4. The failing server can be fixed or replaced without compromising the database’s availability, and the standby server that takes over becomes the new primary server.

This idea of changing the entries in pg_hba.conf may be applied to the failover/switchover process. So, if we are utilising any form of automation for failover or switchover, a callback script may simply do this kind of automation.

Failover is a problem for all HA database systems, regardless of configuration. With the pgsql-check option, HAProxy comes with an integrated PostgreSQL check.This suffices for rudimentary primary failover. However, it is less useful since it lacks the capabilities to identify and distinguish between the Primary and Hot-Standby nodes.

[Looking for a solution to another query? We are just a click away.]

Conclusion

To conclude, the article offers a solution to fix the PostgreSQL Failover With HAProxy.