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

On 5/31/20 2:03 PM, Andrus wrote:
> 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 ?

In addition to my most recent questions:

What are you trying to achieve?

In other words why do a pg_basebackup if you have a standby receiving WALs?

>
> Andrus.

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com