PostgreSQL Replication Skill

Atomic skill for streaming replication

Overview

Production-ready patterns for streaming replication, monitoring, and failover with Patroni.

Prerequisites

• PostgreSQL 16+
• Multiple server nodes
• Network connectivity

Parameters

parameters:
  operation:
    type: string
    required: true
    enum: [setup_primary, setup_replica, monitor, failover]
  replication_mode:
    type: string
    enum: [async, sync]
    default: async

Quick Reference

Primary Setup

-- postgresql.conf
wal_level = replica
max_wal_senders = 10
max_replication_slots = 10

-- Create replication user
CREATE ROLE replicator WITH REPLICATION LOGIN PASSWORD 'secret';

-- Create slot
SELECT pg_create_physical_replication_slot('replica1');

Replica Setup

pg_basebackup -h primary -D /data -U replicator -v -P -R

Monitor Lag

-- On primary
SELECT client_addr, state,
    pg_size_pretty(pg_wal_lsn_diff(sent_lsn, replay_lsn)) as lag
FROM pg_stat_replication;

-- On replica
SELECT pg_is_in_recovery(), pg_last_wal_replay_lsn();

Patroni HA

scope: cluster
bootstrap:
  dcs:
    ttl: 30
    maximum_lag_on_failover: 1048576

Replication Modes

Mode	Data Safety	Latency
async	Possible loss	Low
sync	No loss	Higher

Troubleshooting

Problem	Cause	Solution
Lag increasing	Slow replica	Check I/O
Slot inactive	Replica down	Drop old slot
Failover failed	etcd issue	Check cluster

Usage

Skill("postgresql-replication")