Why PostgreSQL does not display the correct synchronization status

Issue

• An issue was found while configuring synchronous replication for PostgreSQL. The primary_conninfo parameter has been configured in the postgresql.conf file of the standby server, and the value application_name specified in the parameter is consistent with the synchronous_standby_names setting of the primary server.

• However, after the configuration is completed, it is confirmed through the pg_stat_replication view that the application_name does not display the value specified by primary_conninfo as expected, but instead displays the default value of 'walreceiver'. The sync_state is also displayed as 'async', rather than the expected 'sync'.

• Results on primary server side:

postgres=# select usename,application_name,state,sync_state from pg_stat_replication;
 usename | application_name |   state   | sync_state 
---------+------------------+-----------+------------
 replhr  | walreceiver      | streaming | async
(1 row)