Re: How to start slave after pg_basebackup. Why min_wal_size and wal_keep_segments are duplicated

From: "Andrus" <kobruleht2(at)hot(dot)ee>
To: "pgsql-general" <pgsql-general(at)postgresql(dot)org>, "Adrian Klaver" <adrian(dot)klaver(at)aklaver(dot)com>
Subject: Re: How to start slave after pg_basebackup. Why min_wal_size and wal_keep_segments are duplicated
Date: 2020-05-31 21:03:30
Message-ID: 102C5FA16F1549659B393B6A824B561F@dell2
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Hi!

>I'm guessing are looking for:
>https://www.postgresql.org/docs/12/runtime-config-replication.html
>26.2.6. Replication Slots
>Replication slots provide an automated way to ensure that the master
>does not remove WAL segments until they have been received by all
>standbys, and that the master does not remove rows which could cause a
>recovery conflict even when the standby is disconnected.

Using replication slot can cause pg_wal directoy to occupy all free disk space and after that server stop respondig.

>This is spelled out here:
> https://www.postgresql.org/docs/12/warm-standby.html#STREAMING-REPLICATION
>"If you use streaming replication without file-based continuous
>archiving, the server might recycle old WAL segments before the standby
>has received them. If this occurs, the standby will need to be
>reinitialized from a new base backup. You can avoid this by setting
>wal_keep_segments to a value large enough to ensure that WAL segments
>are not recycled too early, or by configuring a replication slot for the
>standby.

Will wal_keep_segments keep segments also if named replication slot is lot used ?

Andrus.

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