INT 21h

Hi, I am Vladimir Smagin, SysAdmin and Kaptain. Telegram Email / GIT / Thingiverse / RSS / GPG

wal-g for Postgresql replication

№ 10938 В разделе "Sysadmin" от March 20th, 2020,
В подшивках: , ,

Initials

Master database: postgresql-10, in production
Backup storage: minio with empty pg-walg-backup bucket

Task: Create slave postgresql-10 server with recovery

Preparing for both servers

Install wal-g binary manually or use my Ubuntu repository (install walg-lzo).

Create special script for wal-g with variables, save to /var/lib/postgresql/walg-postgresql

#!/bin/bash
source /etc/profile

export AWS_ENDPOINT=http://minio.myserv.com:9000
export AWS_ACCESS_KEY_ID="KEYNAMEKEYNAMEKEYNAME"
export AWS_SECRET_ACCESS_KEY="SECRETSECRETSECRETSECRETSECRETSECRET"
export WALE_S3_PREFIX="s3://pg-walg-backup/"
export AWS_S3_FORCE_PATH_STYLE="true"
export AWS_REGION=us-east-1
export PGHOST=/var/run/postgresql
export PGUSER=postgres
export PGPORT=5433

wal-g $@

It is not secure to store this file global readable. Best choice to place it in postgres home directory without read by others:

chmod 500 /var/lib/postgresql/walg-postgresql
chown postgres:postgres /var/lib/postgresql/walg-postgresql

Master server

Add to postgresql.conf:

archive_mode = on
archive_command = '/var/lib/postgresql/walg-postgresql wal-push %p'

Ok, now run backup-push to create full backup:

/var/lib/postgresql/walg-postgresql backup-push /pg_data/10/main

Slave server

Stop postgresql and remove data directory, wal-g requires empty directory before restore.

Now run:

/var/lib/postgresql/walg-postgresql backup-fetch /pgdata/10/main LATEST

Create /pgdata/10/main/recovery.conf:

standby_mode = 'on'
restore_command = 'walg-postgresql wal-fetch "%f" "%p"'

Now see logfile for wal restoring, database in recovery mode.

Postgresql 12: recovery settings moved to postgresql.conf. To start infinite recovery create flag file /var/lib/postgresql/12/main/standby.signal.

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