PostgreSQL Replication Skill Skill

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")

Agent Skills: PostgreSQL Replication Skill

Skill Files