Обсуждение: PG 10 streaming replication pg_wal question

Hi LIst,
I am testing PG10 streaming replication ,  with archiving off, I have 
pg_wal on separate directory  to monitor the growth , I had the slave 
offline yesterday  for  more than 20h while I was restoring one of db 
(60GB) with pg_restore from a backup taken with pg_dump, today I brought 
the slave PG host online and replication catch up  nicely , master and 
slave are in sync now, but  on master host the pg_wal is still same  
large size ( as yesterday)  even after all the wal files had been 
applied to salve, would replication process not suppose to removed the 
wal files  on master after being applied to salve ?
( do I need to manually implement a cleanup job of this wal files, as 
mentioned archiving is off on  both servers)
see bellow:

master:  pg_current_wal_lsn
-------------------- C5/D82DDD68

and slave:  pg_last_wal_receive_lsn
------------------------- C5/D82DDD68


and master :
4.0K    ./wal/archive_status
166G    ./wal
last wal file  :
w------- 1 postgres postgres 16777216 Nov 29 16:05 00000007000000C5000000D8

 ans slave :
12K    ./wal/archive_status
1.1G    ./wal

last wal file:
rw------- 1 postgres postgres 16777216 Nov 30 08:56 00000007000000C5000000D8

ghiureai wrote:
> I am testing PG10 streaming replication ,  with archiving off, I have 
> pg_wal on separate directory  to monitor the growth , I had the slave 
> offline yesterday  for  more than 20h while I was restoring one of db 
> (60GB) with pg_restore from a backup taken with pg_dump, today I brought 
> the slave PG host online and replication catch up  nicely , master and 
> slave are in sync now, but  on master host the pg_wal is still same  
> large size ( as yesterday)  even after all the wal files had been 
> applied to salve, would replication process not suppose to removed the 
> wal files  on master after being applied to salve ?
> ( do I need to manually implement a cleanup job of this wal files, as 
> mentioned archiving is off on  both servers)

Never remove WAL files yourself.

pg_wal will shrink eventually.
At the next checkpoint, PostgreSQL will remove all WAL files
that were completed and archived successfully since the
previous checkpoint, thus reducing WAL size a little.

If there is activity on the databases, pg_wal will eventually
shrink back to max_wal_size.

Yours,
Laurenz Albe

Thank you Laurenz,
can I  run a checkpoint manually in master host than ?

 On 11/30/2017 09:35 AM, Laurenz Albe wrote:
> ghiureai wrote:
>> I am testing PG10 streaming replication ,  with archiving off, I have
>> pg_wal on separate directory  to monitor the growth , I had the slave
>> offline yesterday  for  more than 20h while I was restoring one of db
>> (60GB) with pg_restore from a backup taken with pg_dump, today I brought
>> the slave PG host online and replication catch up  nicely , master and
>> slave are in sync now, but  on master host the pg_wal is still same
>> large size ( as yesterday)  even after all the wal files had been
>> applied to salve, would replication process not suppose to removed the
>> wal files  on master after being applied to salve ?
>> ( do I need to manually implement a cleanup job of this wal files, as
>> mentioned archiving is off on  both servers)
> Never remove WAL files yourself.
>
> pg_wal will shrink eventually.
> At the next checkpoint, PostgreSQL will remove all WAL files
> that were completed and archived successfully since the
> previous checkpoint, thus reducing WAL size a little.
>
> If there is activity on the databases, pg_wal will eventually
> shrink back to max_wal_size.
>
> Yours,
> Laurenz Albe
>

ghiureai wrote:
> can I  run a checkpoint manually in master host than ?

Yes, but that will only remove WAL files if there has
been enough activity to cause one or more WAL switches.

You just have to wait.

Yours,
Laurenz Albe