Date: Thu, 22 Apr 2021 10:16:42 +0700
From: Victor Sudakov <vas@sibptus.ru>
To: pgsql-admin@lists.postgresql.org
Subject: A streaming replica catching up
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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@fidonet