Postgres Data Backup with Continuous Archiving and Point-in-time-recovery

This blog is an alternative method to the SQL dump method for Postgresql data backup. This method has some advantages over methods for instance it does not need a perfectly consistent file system backup as the starting point.
Understanding Continuous Archiving
Continuous Archiving is a feature in PostgreSQL that enables the continuous streaming of transaction log files (WAL files) to an archive directory. This ensures that a complete history of changes to the database is maintained, allowing for point-in-time recovery.
Steps to Set Up Continuous Archiving
1.Configure PostgreSQL.conf
Modify the PostgreSQL configuration file (postgresql.conf) to enable continuous archiving. Set the wal_level to replica and define the archive_mode and archive_command parameters.

wal_level = replica
archive_mode = on
archive_command = 'cp %p /path/to/archive/%f'

2.Create Archive Directory
Create the specified archive directory and ensure that the PostgreSQL user has the necessary permissions to write to it.

mkdir /path/to/archive
chown postgres:postgres /path/to/archive

3.Restart PostgreSQL
Restart the PostgreSQL service to apply the changes made in the configuration file.

systemctl restart postgresql

Implementing Point-in-time Recovery (PITR)
Point-in-time Recovery allows you to restore your database to any specific point in time by replaying the transaction logs. This is invaluable in scenarios where you need to recover from a critical error or data corruption.

Steps for Point-in-time Recovery
1.Create a Base Backup
Initiate a base backup of the PostgreSQL cluster, which serves as the starting point for the recovery process.

pg_basebackup -D /path/to/backup

2.Restore the Base Backup
To perform a point-in-time recovery, restore the base backup to a new location.

pg_ctl stop -D /path/to/restore
rm -rf /path/to/restore/*
cp -r /path/to/backup/* /path/to/restore

3.Apply Transaction Logs
Copy the necessary archived WAL files to the new PostgreSQL cluster and start the server in recovery mode.

cp /path/to/archive/* /path/to/restore/pg_wal
pg_ctl -D /path/to/restore -l /path/to/restore/logfile start

4.Point-in-time Recovery
Use the pg_wal_replay_resume function to specify the desired recovery target time.

psql -c "SELECT pg_wal_replay_resume('target_time')"

Conclusion:
By implementing Continuous Archiving and Point-in-time Recovery in PostgreSQL, you can enhance the resilience of your data management system. Regularly creating base backups and archiving transaction logs ensures that you have a reliable backup strategy in place, minimizing the risk of data loss and allowing for precise recovery to any desired point in time.