A streaming replica catching up

From: Victor Sudakov <vas(at)sibptus(dot)ru>
To: pgsql-admin(at)lists(dot)postgresql(dot)org
Subject: A streaming replica catching up
Date: 2021-04-22 03:16:42
Message-ID: YIDqmtsUEpTK8Krp@admin.sibptus.ru
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Dear Colleagues,

After a streaming standby has been down for a time, I know of two
options for it to catch up with the master:

1. The replica can fetch all the necessary WAL records via the
replication protocol from the master (unless max_slot_wal_keep_size is
not the default -1, all the required WAL archives should be available from
the master).

2. The replica can be provided with a restore_command and will fetch
all WAL files from the WAL archive before starting streaming WAL from
the master.

Which is the preferred way?

Of course if max_slot_wal_keep_size is limited, the second options seems
the only safe one.

OTOH, if the master does not write to a WAL archive, only the first
option is left to us.

--
Victor Sudakov VAS4-RIPE
http://vas.tomsk.ru/
2:5005/49(at)fidonet

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