Postgressql stream replication active / standby switchover primary database no read / write downtime scenario

Catalog

One Scenario introduction

Two Based on the environment

3、 ... and Status check

Four Active standby switching

5、 ... and other

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One Scenario introduction

PostgreSQL Stream replication primary and standby environments , There is no read / write in the main database , Database down , The original and standby databases are switched to the primary database , Switch from the original primary database to the standby database . The main database downtime methods are smart、fast、immediate, The main library downtime based on these three methods , How to switch between active and standby .

Two Based on the environment

Main library ：192.168.5.128

For the library ：192.168.5.129

3、 ... and Status check

1. Active / standby status check

pg_controldata -D /data/dbdata/pgsql/14/5432/data/

128：Database cluster state:               in production
129：Database cluster state:               in archive recovery

2. Stream replication synchronization check

select * from pg_stat_replication;

Four Active standby switching

1. Main library down

# 128 The host simulation database is closed 
pg_ctl -D /data/dbdata/pgsql/14/5432/data stop -m smart

2. Active standby switching

# 129 The host switches to the main library 
pg_ctl promote -D /data/dbdata/pgsql/14/5432/data

3. Adjust the original primary warehouse to standby warehouse

# 128 Switch the host to the standby database 
touch /data/dbdata/pgsql/14/5432/data/standby.signal
echo "primary_conninfo = 'host=192.168.5.129 port=5432 user=repl password=repl'" >> /data/dbdata/pgsql/14/5432/data/postgresql.conf
pg_ctl -D /data/dbdata/pgsql/14/5432/data start

4. Active / standby status check

pg_controldata -D /data/dbdata/pgsql/14/5432/data/

128：Database cluster state:               in archive recovery
129：Database cluster state:               in production

5. Stream replication synchronization check

select * from pg_stat_replication;

 6. data validation

#  Now the main library 129 Update data 
pgbench=#  select * from t1 where id=1;   
 id |  t   | mod_time 
----+------+----------
  1 |  test  | 
(1 row)
pgbench=# update t1 set t=' test 1' where id=1;
pgbench=# select * from t1 where id=1;  
 id |   t   | mod_time 
----+-------+----------
  1 |  test 1 | 
(1 row)

#  Ready to use warehouse 128 Query data 
pgbench=# select * from t1 where id=1;  
 id |   t   | mod_time 
----+-------+----------
  1 |  test 1 | 
(1 row)

7. result

After the active standby switch , The active and standby status is normal , Data update is normal .

8. Active / standby switchback

Just switch back according to the above steps

5、 ... and other

in addition , Main library fast and immediate Downtime mode , The main and standby switching mode is the same as .