Re: [ADMIN] Can master and slave on different PG versions? - Mailing list pgsql-admin

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@gmail.com>

À: gparc@free.fr, pgsql-admin@postgresql.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@free.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@gmail.com >
À: "David G. Johnston" < david.g.johnston@gmail.com >
Cc: pgsql-admin@postgresql.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@gmail.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.g.johnston@gmail.com > wrote:




On Mon, Oct 9, 2017 at 4:06 PM, rammohan ganapavarapu < rammohanganap@gmail.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.​