Re: Can master and slave on different PG versions?

Hi,

I was using pg_basebackup to rebuild slave, so pglogical is not in-built in
postgres and I have to install?

Thanks

On Nov 17, 2017 12:42 AM, <gparc(at)free(dot)fr> wrote:

Hello,

How did you create the slave ? with pg_basebackup or via rsync ?
In any case, the slave MUST have been built with a backup/rsync made AFTER
the master have been restarted when you changed
wal_level to logical.

Note, that you did so far, set wal_level=logical, is just a prerequisite to
use logical replication.
After that, you need a tool which will extract the changes in the WALs from
the master and will replay them on the slave.

Such tool is pg_logical : https://www.2ndquadrant.com/
en/resources/pglogical/

Regards

----- Mail original -----
De: "rammohan ganapavarapu" <rammohanganap(at)gmail(dot)com>
À: gparc(at)free(dot)fr, pgsql-admin(at)postgresql(dot)org
Envoyé: Jeudi 16 Novembre 2017 17:58:42
Objet: Re: [ADMIN] Can master and slave on different PG versions?

From Slave (9.6):

Database cluster state: shut down in recovery

wal_level setting: logical

From master (9.4) :

Database cluster state: in production

Current wal_level setting: logical

Quite frankly i couldn't find proper document on how to set logical
replication in 9.4, i think i am using pg_logical. All i did was set
wal_level to logical and add primary_slot_name in recovery.conf. Do i need
to install pglogical extension? i couldn't find one for amazon linux.

Thanks,
Ram

On Thu, Nov 16, 2017 at 6:12 AM, < gparc(at)free(dot)fr > wrote:

Hello again,

can you execute pg_controldata command on both Master and Slave
and check the following properties :
Database cluster state
wal_level setting

Also, if I understand correctly, you want to establish logical replication
between your 9.4 master
and your 9.6 slave but you don't explain how ? using pg_logical ?

Regards

----- Mail original -----
De: "rammohan ganapavarapu" < rammohanganap(at)gmail(dot)com >
À: "David G. Johnston" < david(dot)g(dot)johnston(at)gmail(dot)com >
Cc: pgsql-admin(at)postgresql(dot)org
Envoyé: Mercredi 15 Novembre 2017 22:23:57
Objet: Re: [ADMIN] Can master and slave on different PG versions?

Any one tried this before?

On Wed, Nov 8, 2017 at 8:17 AM, rammohan ganapavarapu <
rammohanganap(at)gmail(dot)com > wrote:

David,

So initially i have physical replication configured, so to upgrade slave to
9.6 version i did converted master slave to logical replication and then
try to upgrade the slave to 9.6. I am getting this error when i try to
start the slave. Any idea?

2017-11-08 05:08:49 UTC [20063]: [1-1] user= db= host= LOG: shutting down
2017-11-08 05:08:49 UTC [20063]: [2-1] user= db= host= LOG: database system
is shut down
2017-11-08 05:09:45 UTC [20322]: [1-1] user= db= host= LOG: database system
was shut down at 2017-11-08 05:08:55 UTC
2017-11-08 05:09:45 UTC [20322]: [2-1] user= db= host= LOG: entering
standby mode
2017-11-08 05:09:45 UTC [20322]: [3-1] user= db= host= WARNING: WAL was
generated with wal_level=minimal, data may be missing
2017-11-08 05:09:45 UTC [20322]: [4-1] user= db= host= HINT: This happens
if you temporarily set wal_level=minimal without taking a new base backup.
2017-11-08 05:09:45 UTC [20322]: [5-1] user= db= host= FATAL: hot standby
is not possible because wal_level was not set to "replica" or higher on the
master server
2017-11-08 05:09:45 UTC [20322]: [6-1] user= db= host= HINT: Either set
wal_level to "replica" on the master, or turn off hot_standby here.
2017-11-08 05:09:45 UTC [20312]: [3-1] user= db= host= LOG: startup process
(PID 20322) exited with exit code 1
2017-11-08 05:09:45 UTC [20312]: [4-1] user= db= host= LOG: aborting
startup due to startup process failure
2017-11-08 05:09:45 UTC [20312]: [5-1] user= db= host= LOG: database system
is shut down

Thanks,
Ram

On Mon, Oct 9, 2017 at 4:15 PM, David G. Johnston <
david(dot)g(dot)johnston(at)gmail(dot)com > wrote:

On Mon, Oct 9, 2017 at 4:06 PM, rammohan ganapavarapu <
rammohanganap(at)gmail(dot)com > wrote:

Hi,

Is it possible to add 9.6 version Slave to 9.4 master?

​Physical replication, no; Logical replication, yes - if the software you
are using is compatible with both versions.

David J.​