Updated pg_rewind feature in PostgreSQL-9.6 for timeline switches

In this test case I am trying to make my previous Master as Master by rollbacking the changes happen into Standby.

Step 1:Install PostgreSQL-10 on both Master and Standby. Follow the Installation steps from Installation_Steps

Step 2: Now, Create Data Directory and make the changes to config files.

initdb -D /var/lib/pgsql/10/data/

vi /var/lib/pgsql/10/data/postgresql.conf

      port=5432
      listen_addresses = '*'
      wal_level = replica
      max_wal_senders = 10
      wal_keep_segments = 32
      wal_log_hints = on
      archive_mode    = on
      archive_command = 'cp %p /var/lib/pgsql/pg_archive/%f' 

vi /var/lib/pgsql/10/data/pg_hba.conf

host replication all 0.0.0.0 md5

Step 3: Start Master

pg_ctl -D /var/lib/pgsql/10/data/ start

Step 4: Upload the data in Master

/usr/pgsql-10/bin/pgbench -i -s 10

Step 5: Build the Streaming Replication

/usr/pgsql-10/bin/pg_basebackup -h 127.0.0.1 -p 5432 -U replication -D /var/lib/pgsql/10/slave-data/ -Xs -c fast -R

vi /var/lib/pgsql/10/slave-data/postgresql.conf

      port=6432
      listen_addresses = '*'
      hot_standby='on'

vi /var/lib/pgsql/10/slave-data/recovery.conf

         standby_mode = 'on'
         primary_conninfo = 'host=127.0.0.1 port=5432 dbname=postgres user=postgres'
         #recovery_target_timeline = 'latest'
         #restore_command = 'cp /var/lib/pgsql/pg_archive/%f %p'


Step 6:  Start the Standby by server and the promote it

/usr/pgsql-10/bin/pg_ctl -D /var/lib/pgsql/10/slave-data/ start
/usr/pgsql-10/bin/pg_ctl -D /var/lib/pgsql/10/slave-data/ promote

Step 7: Now load the data using pgbench into New Master(Which was earlier was standby) and Stop the New Master

/usr/pgsql-10/bin/pgbench -T 60 -p 6432 -d postgres
/usr/pgsql-10/bin/pg_ctl -D /var/lib/pgsql/10/slave-data/ -m fast stop

Step 8: Run pg_rewind to make the Previous Master and Rollback the changes happen in New Master

/usr/pgsql-10/bin/pg_rewind --target-pgdata /var/lib/pgsql/10/slave-data/ -n --source-server="port=5432 user=postgres dbname=postgres"
/usr/pgsql-10/bin/pg_rewind --target-pgdata /var/lib/pgsql/10/slave-data/ --source-server="port=5432 user=postgres dbname=postgres"

Step 9:  Edit postgres.conf file and create recovery.conf once it is done then start the server

vi /var/lib/pgsql/10/slave-data/postgresql.conf

      port=6432
      listen_addresses = '*'
      hot_standby='on'

vi /var/lib/pgsql/10/data/recovery.conf

    standby_mode = 'on'
    primary_conninfo = 'host=127.0.0.1 port=5432 dbname=postgres user=postgres'
    #recovery_target_timeline = 'latest'
    #restore_command = 'cp /var/lib/pgsql/pg_archive/%f %p'

/usr/pgsql-10/bin/pg_ctl -D /var/lib/pgsql/10/slave-data/ start

postgres=# select * from pg_stat_replication ;
 pid  | usesysid | usename  | application_name | client_addr | client_hostname | client_port |         backend_start         | bac
kend_xmin |   state   | sent_lsn  | write_lsn | flush_lsn | replay_lsn | write_lag | flush_lag | replay_lag | sync_priority | sync
_state
------+----------+----------+------------------+-------------+-----------------+-------------+-------------------------------+----
----------+-----------+-----------+-----------+-----------+------------+-----------+-----------+------------+---------------+-----
-------
 6011 |       10 | postgres | walreceiver      | 127.0.0.1   |                 |       55866 | 2019-03-21 11:50:00.193565+00 |
          | streaming | 0/D02BEE0 | 0/D02BEE0 | 0/D02BEE0 | 0/D02BEE0  |           |           |            |             0 | asyn
c
(1 row)

-bash-4.2$ psql
psql (10.7)
Type "help" for help.

postgres=# create table test(i int);
CREATE TABLE
postgres=# \q
-bash-4.2$ psql -p 6432    (Standby )
psql (10.7)
Type "help" for help.

postgres=# \dt
              List of relations
 Schema |       Name       | Type  |  Owner
--------+------------------+-------+----------
 public | pgbench_accounts | table | postgres
 public | pgbench_branches | table | postgres
 public | pgbench_history  | table | postgres
 public | pgbench_tellers  | table | postgres
 public | test             | table | postgres
(5 rows)

postgres=#