CentOS 7
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PostgreSQL 9.6 : Replication
2017/10/31
 
Configure PostgreSQL Replication settings. This configuration is Master-Slave settings.
[1]
Install PostgreSQL 9.6 Server on all Nodes, refer to here.
[1] Configure Master Host.
[root@www ~]#
postgresql-setup --initdb --unit rh-postgresql96-postgresql

* Initializing database in '/var/opt/rh/rh-postgresql96/lib/pgsql/data'
* Initialized, logs are in /var/lib/pgsql/initdb_rh-postgresql96-postgresql.log
[root@www ~]#
vi /var/opt/rh/rh-postgresql96/lib/pgsql/data/postgresql.conf
# line 59: uncomment and change

listen_addresses = '
*
'
# line 178: uncomment and change

wal_level =
hot_standby
# line 183: uncomment and change

# on ⇒ sync

# remote_write ⇒ memory sync

# local ⇒ slave is asynchronous

# off ⇒ asynchronous

synchronous_commit =
local
# line 215: uncomment and change (enable archive_mode)

archive_mode =
on
# line 217: uncomment and change (command to get archives)

archive_command = '
cp %p /var/opt/rh/rh-postgresql96/lib/pgsql/archive/%f
'
# line 233: uncomment and change (slave servers + 1)

max_wal_senders =
2
# line 235: uncomment and change

wal_keep_segments =
10
# line 247: uncomment and change (any name you like)

synchronous_standby_names = '
slave01
'
[root@www ~]#
vi /var/opt/rh/rh-postgresql96/lib/pgsql/data/pg_hba.conf
# add to the end

# host replication [replication user] [allowed IP addresses] password

host    replication     replica          127.0.0.1/32            md5
host    replication     replica          10.0.0.30/32            md5
host    replication     replica          10.0.0.51/32            md5
[root@www ~]#
systemctl start rh-postgresql96-postgresql

[root@www ~]#
systemctl enable rh-postgresql96-postgresql

# create a user for replication

[root@www ~]#
su - postgres
-bash-4.2$
createuser --replication -P replica

Enter password for new role:
Enter it again:
[2] If Firewalld is running, allow PostgreSQL service.
[root@www ~]#
firewall-cmd --add-service=postgresql --permanent

success
[root@www ~]#
firewall-cmd --reload

success
[3] Configure Slave Host.
[root@node01 ~]#
su - postgres
# get backup from Master Server

-bash-4.2$
pg_basebackup -h www.srv.world -U replica -D /var/opt/rh/rh-postgresql96/lib/pgsql/data -P --xlog

Password:    
# [replica] user's password

39211/39211 kB (100%), 1/1 tablespace
-bash-4.2$
vi /var/opt/rh/rh-postgresql96/lib/pgsql/data/postgresql.conf
# line 256: uncomment and change

hot_standby =
on
-bash-4.2$
cp /opt/rh/rh-postgresql96/root/usr/share/pgsql/recovery.conf.sample /var/opt/rh/rh-postgresql96/lib/pgsql/data/recovery.conf

-bash-4.2$
vi /var/opt/rh/rh-postgresql96/lib/pgsql/data/recovery.conf
# line 44: uncomment and change (command to get archives)

restore_command = '
scp 10.0.0.31:/var/opt/rh/rh-postgresql96/lib/pgsql/archive/%f %p
'
# line 116: uncomment and change

standby_mode =
on
# line 123: uncomment and change (connection info to Master Server)

primary_conninfo = '
host=10.0.0.31 port=5432 user=replica password=password application_name=slave01
'
-bash-4.2$
exit

logout
[root@node01 ~]#
systemctl start rh-postgresql96-postgresql

[root@node01 ~]#
systemctl enable rh-postgresql96-postgresql

[4] It's OK all if result of the command below is like follows. Make sure the setting works normally to create databases on Master Server.
-bash-4.2$
psql -c "select application_name, state, sync_priority, sync_state from pg_stat_replication;" 

 application_name |   state   | sync_priority | sync_state
------------------+-----------+---------------+------------
 slave01          | streaming |             1 | sync
(1 row)
 
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