bgw_replstatus

bgw_replstatus : Small PostgreSQL background worker to report whether a node is a replication master or standby

Overview

Packages

Source

Install

Make sure PGDG repo available:

pig repo add pgdg -u    # add pgdg repo and update cache

Install this extension with pig:

pig install bgw_replstatus;		# install via package name, for the active PG version

pig install bgw_replstatus -v 18;   # install for PG 18
pig install bgw_replstatus -v 17;   # install for PG 17
pig install bgw_replstatus -v 16;   # install for PG 16
pig install bgw_replstatus -v 15;   # install for PG 15
pig install bgw_replstatus -v 14;   # install for PG 14

Config this extension to shared_preload_libraries:

shared_preload_libraries = 'bgw_replstatus';

This extension does not need CREATE EXTENSION DDL command

Usage

bgw_replstatus: lightweight replication status checker for load balancers

bgw_replstatus is a background worker that listens on a TCP port and immediately reports whether the node is a MASTER or STANDBY. Designed for load balancer health checks without requiring a full PostgreSQL connection.

How It Works

Any TCP connection to the configured port receives an immediate text response (MASTER or STANDBY) and the connection is closed. No request is needed.

Quick Test

nc localhost 5400
# Output: MASTER (or STANDBY)

HAProxy Configuration Example

frontend test
    bind 127.0.0.1:5999
    default_backend pgcluster

backend pgcluster
    mode tcp
    option tcp-check
    tcp-check expect string MASTER
    server s1 127.0.0.1:5500 check port 5400
    server s2 127.0.0.1:5501 check port 5401 backup
    server s3 127.0.0.1:5502 check port 5402 backup

Configuration

Security note: There is no source verification. Protect the port with a host firewall.