# on NODE_1
e_host=(
  /opt/tantor/usr/bin/etcdctl
  --endpoints=https://<HOST_1_IP>:2379,https://<HOST_2_IP>:2379,https://<HOST_N_IP>:2379
  --cacert=/opt/tantor/etc/patroni/ca.pem
  --cert=/opt/tantor/etc/patroni/<NODE1_HOSTNAME>.pem  
  --key=/opt/tantor/etc/patroni/<NODE1_HOSTNAME>-key.pem
)

# list etcd members
ETCDCTL_API=3 "${e_host[@]}" member list --debug

# check version
ETCDCTL_API=3  "${e_host[@]}" version

# get key value ("main" is "patroni_scope")
ETCDCTL_API=3  "${e_host[@]}" get /service/main/config

# cleanup patroni cluster configuration
ETCDCTL_API=3  "${e_host[@]}" del /service/main --prefix

# create user
su - postgres -c "psql -A -t -d postgres -c \"CREATE ROLE replicator WITH REPLICATION LOGIN PASSWORD 'repuserpasswd'\""
# check user
su - postgres -c "psql -A -t -d postgres -c \"select * from pg_roles where rolname = 'replicator'\""

Patroni включает команду под названием patronictl, которая может использоваться для управления кластером. Давайте проверим статус кластера:

root@node1:~# patronictl -c /opt/tantor/etc/patroni/<NODE1_HOSTNAME>.yml list
+ Cluster: main (7351350415269982209) --+---------+-----------+----+-----------+
| Member  | Host            | Role    | State     | TL | Lag in MB |
+---------+-----------------+---------+-----------+----+-----------+
| node1   | xxx.xxx.xxx.xxx | Leader  | running   |  1 |           |
| node2   | yyy.yyy.yyy.yyy | Replica | streaming |  1 |         0 |
| node3   | zzz.zzz.zzz.zzz | Replica | streaming |  1 |         0 |
+---------+-----------------+---------+-----------+----+-----------+

patronictl -c /opt/tantor/etc/patroni/<NODE1_HOSTNAME>.yml edit-config следует использовать только для управления глобальной конфигурацией кластера. Он не должен содержать никаких настроек, специфичных для узлов, таких как connect_address, listen, data_dir и так далее.

Обновить настройки DCS pg_hba:

cat > pg_hba.conf << EOL
host replication replicator 0.0.0.0/0 md5
local all all  trust
host all all 127.0.0.1/32 trust
host all all localhost trust
EOL

cat pg_hba.conf | jq -R -s 'split("\n") | .[0:-1] | {"postgresql": {"pg_hba": .}}' | \
patronictl -c /opt/tantor/etc/patroni/<NODE1_HOSTNAME>.yml edit-config --apply - --force main

patronictl -c /opt/tantor/etc/patroni/<NODE1_HOSTNAME>.yml show-config

Изменить настройки postgresql.conf:

cat > postgresql.conf << EOL
"postgresql": {
"parameters": {
    "max_connections" : 101
}
}
EOL

cat postgresql.conf | patronictl -c /opt/tantor/etc/patroni/<NODE1_HOSTNAME>.yml edit-config --apply - --force main
patronictl -c /opt/tantor/etc/patroni/<NODE1_HOSTNAME>.yml list
patronictl -c /opt/tantor/etc/patroni/<NODE1_HOSTNAME>.yml restart main

Сделать переключение switchover:

root@node1:~# patronictl -c /opt/tantor/etc/patroni/<NODE1_HOSTNAME>.yml switchover
Current cluster topology
+ Cluster: main (7351350415269982209) --+---------+-----------+----+-----------+
| Member| Host            | Role    | State     | TL | Lag in MB |
+-------+-----------------+---------+-----------+----+-----------+
| node1 | xxx.xxx.xxx.xxx | Leader  | running   |  1 |           |
| node2 | yyy.yyy.yyy.yyy | Replica | streaming |  1 |         0 |
| node3 | zzz.zzz.zzz.zzz | Replica | streaming |  1 |         0 |
+-------+-----------------+---------+-----------+----+-----------+
Primary [node1]:
Candidate ['node2', 'node3'] []: node2
When should the switchover take place (e.g. 2024-04-02T13:51 )  [now]:
Are you sure you want to switchover cluster main, demoting current leader node1? [y/N]: y
2024-04-02 12:51:28.04774 Successfully switched over to "node2"
+ Cluster: main (7351350415269982209) --+---------+-----------+----+-----------+
| Member| Host            | Role    | State     | TL | Lag in MB |
+-------+-----------------+---------+-----------+----+-----------+
| node1 | xxx.xxx.xxx.xxx | Leader  | streaming |  2 |           |
| node2 | yyy.yyy.yyy.yyy | Replica | running   |  2 |         0 |
| node3 | zzz.zzz.zzz.zzz | Replica | streaming |  2 |         0 |
+-------+-----------------+---------+-----------+----+-----------+

Переключиться в асинхронный режим (режим по умолчанию):

cat > postgresql.conf << EOL
"postgresql": {
"parameters": {
    "synchronous_commit" : "local"
}
}
"synchronous_mode": false
"synchronous_mode_strict": false
EOL
cat postgresql.conf | patronictl -c /opt/tantor/etc/patroni/<NODE1_HOSTNAME>.yml edit-config --apply - --force main

Переключиться в синхронный режим:

cat > postgresql.conf << EOL
"postgresql": {
"parameters": {
    "synchronous_commit" : "remote_apply"
}
}
"synchronous_mode": true
"synchronous_mode_strict": true
EOL
cat postgresql.conf | patronictl -c /opt/tantor/etc/patroni/<NODE1_HOSTNAME>.yml edit-config --apply - --force main

Диаграмма H.2. synchronous_commit

Повторная инициализация неудавшегося узла, в случае если вывод patronictl -c /opt/tantor/etc/patroni/<NODE1_HOSTNAME>.yml list предоставляет информацию о неудачном состоянии узла:

patronictl -c /opt/tantor/etc/patroni/<NODE1_HOSTNAME>.yml list
>>
root@node1:~# patronictl -c /opt/tantor/etc/patroni/<NODE1_HOSTNAME>.yml list
+ Cluster: main (7351350415269982209) --+------------+-----------+----+-----------+
| Member  | Host            | Role    | State        | TL | Lag in MB |
+---------+-----------------+---------+--------------+----+-----------+
| node1   | xxx.xxx.xxx.xxx | Leader  | running      |  1 |           |
| node2   | yyy.yyy.yyy.yyy | Replica | streaming    |  1 |         0 |
| node3   | zzz.zzz.zzz.zzz | Replica | start failed |  1 |         0 |
+---------+-----------------+---------+--------------+----+-----------+

Вышедший из строя узел можно перенастроить для присоединения к кластеру с помощью:

patronictl -c /opt/tantor/etc/patroni/<NODE1_HOSTNAME>.yml reinit node3
>>
root@node1:~# patronictl -c /opt/tantor/etc/patroni/<NODE1_HOSTNAME>.yml list
+ Cluster: main (7351350415269982209) --+---------+-----------+----+-----------+
| Member  | Host            | Role    | State     | TL | Lag in MB |
+---------+-----------------+---------+-----------+----+-----------+
| node1   | xxx.xxx.xxx.xxx | Leader  | running   |  1 |           |
| node2   | yyy.yyy.yyy.yyy | Replica | streaming |  1 |         0 |
| node3   | zzz.zzz.zzz.zzz | Replica | streaming |  1 |         0 |
+---------+-----------------+---------+-----------+----+-----------+