Re: How to start slave after pg_basebackup. Why min_wal_size andwal_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 ?

Well if you are using a replication slot there is no point in using 
wal_keep_segments. Slots where created in, part at least, so you did not 
have to guess at a wal_keep_segments number.

To really answer this we will need to see the exact commands you are 
using and the sequence they are done in.

> 
> Andrus.


-- 
Adrian Klaver
adrian.klaver@aklaver.com