Postgres中的WAL归档不起作用

Question

I have enabled WAL archiving in postgres configuration file. When I restarted Postgres service WAL recovery is not working. There was no wal recovery entries in logs.

Steps I followed:

Created directory for wal:
mkdir -p  /var/lib/pgsql/wals/
mkdir -p  /var/lib/pgsql/backups/
chown postgres:postgres -R /var/lib/pgsql/backups/
chown postgres:postgres -R /var/lib/pgsql/wals/

Edited the postgresql.conf with the below changes:
wal_level=archive
archive_mode=on
archive_command = 'test ! -f /var/lib/pgsql/wals/%f && cp %p /var/lib/pgsql/wals/%f'

sudo service postgresql restart 10
sudo su - postgres
pg_basebackup -D /var/lib/pgsql/data #created base backup
tar -C /var/lib/pgsql/data/ -czvf /var/lib/pgsql/backups/pg_basebackup_backup.tar.gz .

Deleted two rows of data in my database and stopped the postgres service

sudo service postgresql stop 10

Extracted the Basebackup

tar xvf /var/lib/pgsql/backups/pg_basebackup_backup.tar.gz -C /var/lib/pgsql/data

Created recovery.conf with the below content and restarted postgres service

echo "restore_command = 'cp /var/lib/pgsql/wals/%f %p'">/var/lib/pgsql/recovery.conf
cp /var/lib/pgsql/recovery.conf /var/lib/pgsql/data/
sudo service postgresql stop 10
sudo service postgresql start 10

There was no wal recovery entries in logs and the two rows which I deleted didn't get restored.

Answer 1

pg_basebackup can catch all WAL segments during backup. I use basebackup into tar format with "-X stream" option and all works well. See here - pg_basebackup – bash script for backup and archiving on Google storage It works excellent - I backup database 4.5+ TB big which takes almost 2 days.

Restoration is described here - pg_basebackup / pg-barman – restore tar backup

All works - we already had incidents when we had to restore from these backups.

Answer 2

The WAL containing the two deleted rows probably hasn't been archived yet.

archive_command is run whenever a 16 MB WAL segment is full or something forces a log switch.

To be able to recover the latest changes that have not been archived yet, you have to copy the contents of pg_wal to the pg_wal directory in the restored base backup.

You can also consider streaming replication or pg_receivewal if you cannot afford to lose transactions.