Switchover and Switchback in PostgreSQL10

 

postgres=# select application_name, state, sync_priority, sync_state from pg_stat_replication;

 application_name |   state   | sync_priority | sync_state
------------------+-----------+---------------+------------
 walreceiver      | streaming |             0 | async

If Return  false so the server is running in Primary mode or Master

/u02/PostgreSQL/10/data

cat recovery.conf

standby_mode = 'on'

primary_conninfo = 'user=replicator password=replicator host=192.168.0.106 port=5432 sslmode=prefer sslcompression=1 krbsrvname=postgres target_session_attrs=any'

recovery_target_timeline = 'latest'

trigger_file = '/u02/PostgreSQL/10/data/recovery.stop'

Now run the touch the file  (2nd step main)

touch /u02/PostgreSQL/10/data/recovery.stop

Standby has been promoted as master and a new timeline followed which you can notice in logs.

 2020-03-26 20:46:34 IST    LOG:  trigger file found: /u02/PostgreSQL/10/data/recovery.stop

 2020-03-26 20:46:34 IST    LOG:  redo done at 0/2B000028

 2020-03-26 20:46:34 IST    LOG:  last completed transaction was at log time 2020-03-25 19:45:14.642094+05:30

 2020-03-26 20:46:34 IST    LOG:  selected new timeline ID: 2

 2020-03-26 20:46:34 IST    LOG:  archive recovery complete

 2020-03-26 20:46:34 IST    LOG:  checkpoint starting: force

 2020-03-26 20:46:34 IST    LOG:  database system is ready to accept connections

 2020-03-26 20:46:34 IST    LOG:  checkpoint complete: wrote 0 buffers (0.0%); 0 WAL file(s) added, 0 removed, 0 recycled; write=0.000 s, sync=0.000 s, total=0.028 s; sync files=0, longest=0.000 s, average=0.000 s; distance=0 kB, estimate=14702 kB

cat recovery.conf

recovery_target_timeline = 'latest'

standby_mode = 'on'

primary_conninfo = 'user=replicator password=replicator host=192.168.0.107 port=5432 sslmode=prefer sslcompression=1 krbsrvname=postgres target_session_attrs=any'

trigger_file = '/u02/PostgreSQL/10/data/recovery.stop'

Check the data in primary and standby:-