Re: pg_xlog on a hot_stanby slave

From: Guillaume Lelarge <guillaume(at)lelarge(dot)info>
To: Xavier 12 <maniatux(at)gmail(dot)com>
Cc: PostgreSQL General <pgsql-general(at)postgresql(dot)org>
Subject: Re: pg_xlog on a hot_stanby slave
Date: 2015-06-16 10:41:06
Message-ID: CAECtzeV9_OLz2ViBvTuR8gCYP91-aKneD7QiL_6WB4=Ho9go2w@mail.gmail.com
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Le 16 juin 2015 10:57 AM, "Xavier 12" <maniatux(at)gmail(dot)com> a écrit :
>
> Hi everyone,
>
> Questions about pg_xlogs again...
> I have two Postgresql 9.1 servers in a master/slave stream replication
> (hot_standby).
>
> Psql01 (master) is backuped with Barman and pg_xlogs is correctly
> purged (archive_command is used).
>
> Hower, Psql02 (slave) has a huge pg_xlog (951 files, 15G for 7 days
> only, it keeps growing up until disk space is full). I have found
> documentation and tutorials, mailing list, but I don't know what is
> suitable for a Slave. Leads I've found :
>
> - checkpoints
> - archive_command
> - archive_cleanup
>
> Master postgresq.conf :
>
> [...]
> wal_level = 'hot_standby'
> archive_mode = on
> archive_command = 'rsync -az /var/lib/postgresql/9.1/main/pg_xlog/%f
> barman(at)nas(dot)lan:/data/pgbarman/psql01/incoming/%f'
> max_wal_senders = 5
> wal_keep_segments = 64
> autovacuum = on
>
> Slave postgresql.conf :
>
> [...]
> wal_level = minimal
> wal_keep_segments = 32
> hot_standby = on
>
> Slave recovery.conf :
>
> standby_mode = 'on'
> primary_conninfo = 'host=10.0.0.1 port=5400 user=postgres'
> trigger_file = '/var/lib/postgresql/9.1/triggersql'
> restore_command='cp /var/lib/postgresql/9.1/wal_archive/%f "%p"'
> archive_cleanup_command =
> '/usr/lib/postgresql/9.1/bin/pg_archivecleanup
> /var/lib/postgresql/9.1/wal_archive/ %r'
>
>
>
>
>
> How can I reduce the number of WAL files on the hot_stanby slave ?
>

Depends on what you're talking about. If they are archived wal,
pg_archive_cleanup is what you're looking for.

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