Run PostgreSQL streaming replication synchronous and asynchronous simultaneously - postgresql

Question

I am using PostgreSQL 14 and ubuntu as my OS.
I have done the database replication in synchronous mode
Now I want to add another server and the relationship between primary and new_standby node will be asynchronous.
Another problem, how to set application_name for different nodes? I have got same application_name=14/main for my two standby servers
Can anyone help me to solve these issues?

Answer 1

Yes, you can run it simultaneously.
You should have this configuration in your primary node:
listen_addresses = '*'
port = 5432
wal_level = hot_standby
max_wal_senders = 16
wal_keep_segments = 32
synchronous_commit = on
synchronous_standby_names = 'pgsql_0_node_0'
Restart the node to take the changes:
$ systemctl restart postgresql-14
Create the replication role:
$ CREATE ROLE replication_user WITH LOGIN PASSWORD 'PASSWORD' REPLICATION;
And configure this in your standby nodes:
Both:
wal_level = hot_standby
hot_standby = on
Sync:
standby_mode = 'on'
promote_trigger_file='/tmp/failover_5432.trigger'
recovery_target_timeline=latest
primary_conninfo='application_name=pgsql_0_node_0 host=PRIMARY_NODE port=5432 user=replication_user password=PASSWORD'
Replace PRIMARY_NODE, user, and password with the correct values.
Async:
promote_trigger_file='/tmp/failover_5432.trigger'
recovery_target_timeline=latest
primary_conninfo='application_name=pgsql_0_node_1 host=PRIMARY_NODE port=5432 user=replication_user password=PASSWORD'
Replace PRIMARY_NODE, user, and password with the correct values.
Restart the node to take the changes:
$ systemctl restart postgresql-14
Then, you can run this in your Primary node to see the replication nodes:
$ SELECT pid,usename,application_name,state,sync_state FROM pg_stat_replication;
pid | usename | application_name | state | sync_state
-------+------------------+------------------+-----------+------------
10951 | replication_user | pgsql_0_node_1 | streaming | async
10952 | replication_user | pgsql_0_node_0 | streaming | sync
(2 rows)