
Настройка мастера для потоковой репликации
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Изменяем параметры.

    psql -h localhost -p 5432 -U postgres

    => alter system set wal_level = hot_standby;
    ALTER SYSTEM

    => alter system set archive_mode = off;
    ALTER SYSTEM

    => alter system set max_standby_streaming_delay = '10s';
    ALTER SYSTEM

    => alter system set max_replication_slots = 5;
    ALTER SYSTEM

    => alter system set max_wal_senders = 5;
    ALTER SYSTEM

    => alter system set port = 5432;
    ALTER SYSTEM

    => alter system set hot_standby = off;
    ALTER SYSTEM

    => alter system set hot_standby_feedback = off;
    ALTER SYSTEM

    => alter system set wal_receiver_status_interval = 0;
    ALTER SYSTEM

Файл pg_hba.conf должен содержать строку для базы данных replication:

postgres> sed -i s/#\(\w\+\s\+replication\)/\1/ /usr/local/pgsql/data/pg_hba.conf 



postgres> tail -n 5 /usr/local/pgsql/data/pg_hba.conf 
# Allow replication connections from localhost, by a user with the
# replication privilege.
local   replication     postgres                                trust
host    replication     postgres        127.0.0.1/32            trust
host    replication     postgres        ::1/128                 trust

Перезапустим сервер.

    => \q

postgres> pg_ctl restart -w -l /home/postgres/logfile 
waiting for server to shut down.... done
server stopped
waiting for server to start.... done
server started

Слот репликации.

    psql -h localhost -p 5432 -U postgres

    => select pg_create_physical_replication_slot('slot_a');
     pg_create_physical_replication_slot 
    -------------------------------------
     (slot_a,)
    (1 row)
    


Создание базовой резервной копии
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


postgres2> bash -c "rm -rf /usr/local/pgsql2/data/*" 
postgres2> pg_basebackup -U postgres -p 5432 -D /usr/local/pgsql2/data -X stream -R 


Настройка реплики
~~~~~~~~~~~~~~~~~

Изменение файла postgresql.auto.conf:

postgres2> sed -i "s/port = .*/port = 5433/" /usr/local/pgsql2/data/postgresql.auto.conf 
postgres2> sed -i "s/hot_standby = .*/hot_standby = on/" /usr/local/pgsql2/data/postgresql.auto.conf 
postgres2> sed -i "s/hot_standby_feedback = .*/hot_standby_feedback = on/" /usr/local/pgsql2/data/postgresql.auto.conf 
postgres2> sed -i "s/wal_receiver_status_interval = .*/wal_receiver_status_interval = 1s/" /usr/local/pgsql2/data/postgresql.auto.conf 



postgres2> cat /usr/local/pgsql2/data/postgresql.auto.conf 
# Do not edit this file manually!
# It will be overwritten by ALTER SYSTEM command.
wal_level = 'hot_standby'
archive_mode = 'off'
max_standby_streaming_delay = '10s'
max_replication_slots = '5'
max_wal_senders = '5'
port = 5433
hot_standby = on
hot_standby_feedback = on
wal_receiver_status_interval = 1s

Добавляем слот репликации и триггерный файл в recovery.conf.


postgres2> bash -c "echo primary_slot_name = \\'\'slot_a\\'\' >> /usr/local/pgsql2/data/recovery.conf" 
postgres2> bash -c "echo trigger_file = \\'\'promote_me\\'\' >> /usr/local/pgsql2/data/recovery.conf" 



postgres2> cat /usr/local/pgsql2/data/recovery.conf 
standby_mode = 'on'
primary_conninfo = 'user=postgres port=5432 sslmode=disable sslcompression=1'
primary_slot_name = 'slot_a'
trigger_file = 'promote_me'


Запуск реплики и проверка
~~~~~~~~~~~~~~~~~~~~~~~~~


postgres2> pg_ctl start -w -l /home/postgres2/logfile 
waiting for server to start..... done
server started

    => create database db12;
    CREATE DATABASE

    => \c db12
    You are now connected to database "db12" as user "postgres".

    => create table replica_test(t text);
    CREATE TABLE

    |    psql -h localhost -p 5433 -U postgres

    |    => \c db12
    |    You are now connected to database "db12" as user "postgres".

    |    => select * from replica_test;
    |     t 
    |    ---
    |    (0 rows)
    |    

Репликация работает.

Сбой мастера и повышение реплики
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


    => \q

postgres> pg_ctl stop -m immediate 
waiting for server to shut down... done
server stopped
postgres2> touch /usr/local/pgsql2/data/promote_me 

    |    => select pg_is_in_recovery();
    |     pg_is_in_recovery 
    |    -------------------
    |     f
    |    (1 row)
    |    

Бывшая реплика стала новым мастером.
Слот репликации на новом мастере:

    |    => select pg_create_physical_replication_slot('slot_a');
    |     pg_create_physical_replication_slot 
    |    -------------------------------------
    |     (slot_a,)
    |    (1 row)
    |    


Восстановление мастера из резервной копии
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


postgres> bash -c "rm -rf /usr/local/pgsql/data/*" 
postgres> pg_basebackup -U postgres -p 5433 -D /usr/local/pgsql/data -X stream -R 

Изменение файла postgresql.auto.conf:

postgres> sed -i "s/port = .*/port = 5432/" /usr/local/pgsql/data/postgresql.auto.conf 
postgres> sed -i "s/hot_standby = .*/hot_standby = on/" /usr/local/pgsql/data/postgresql.auto.conf 
postgres> sed -i "s/hot_standby_feedback = .*/hot_standby_feedback = on/" /usr/local/pgsql/data/postgresql.auto.conf 
postgres> sed -i "s/wal_receiver_status_interval = .*/wal_receiver_status_interval = 1s/" /usr/local/pgsql/data/postgresql.auto.conf 



postgres> cat /usr/local/pgsql/data/postgresql.auto.conf 
# Do not edit this file manually!
# It will be overwritten by ALTER SYSTEM command.
wal_level = 'hot_standby'
archive_mode = 'off'
max_standby_streaming_delay = '10s'
max_replication_slots = '5'
max_wal_senders = '5'
port = 5432
hot_standby = on
hot_standby_feedback = on
wal_receiver_status_interval = 1s

Добавляем слот репликации в recovery.conf.


postgres> bash -c "echo primary_slot_name = \\'\'slot_a\\'\' >> /usr/local/pgsql/data/recovery.conf" 



postgres> cat /usr/local/pgsql/data/recovery.conf 
standby_mode = 'on'
primary_conninfo = 'user=postgres port=5433 sslmode=disable sslcompression=1'
primary_slot_name = 'slot_a'


Запуск новой реплики и проверка
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


postgres> pg_ctl start -w -l /home/postgres/logfile 
waiting for server to start..... done
server started

Слот репликации инициализировался и используется:

    |    => \x
    |    Expanded display is on.

    |    => select * from pg_replication_slots;
    |    -[ RECORD 1 ]+-----------
    |    slot_name    | slot_a
    |    plugin       | 
    |    slot_type    | physical
    |    datoid       | 
    |    database     | 
    |    active       | t
    |    active_pid   | 21391
    |    xmin         | 165086
    |    catalog_xmin | 
    |    restart_lsn  | 0/62000000
    |    

Проверим передачу данных.

    |    => insert into replica_test values ('Привет!');
    |    INSERT 0 1

    psql -h localhost -p 5432 -U postgres

    => \c db12
    You are now connected to database "db12" as user "postgres".

    => select * from replica_test;
        t    
    ---------
     Привет!
    (1 row)
    

Повышаем старый мастер, восстанавливаем параметры, останавливаем старую реплику.

postgres2> pg_ctl stop -D /usr/local/pgsql2/data 
waiting for server to shut down.... done
server stopped

    |    => \q

postgres> pg_ctl -w promote 
server promoting

    => alter system reset all;
    ALTER SYSTEM

    => \q

postgres> pg_ctl restart -w -l /home/postgres/logfile 
waiting for server to shut down.... done
server stopped
waiting for server to start.... done
server started
