Managing a cluster

Cluster information

To get information about the cluster, use the list or topology endpoints:

patronictl -c /etc/patroni.yml list

Output

+ Cluster: demo-cluster-1 (7106835957012965359) ----+----+-----------+
| Member      | Host            | Role    | State   | TL | Lag in MB |
+-------------+-----------------+---------+---------+----+-----------+
| pg-patroni1 | xxx.xxx.xxx.xxx | Leader  | running |  1 |           |
| pg-patroni2 | xxx.xxx.xxx.xxx | Replica | running |  1 |         0 |
+-------------+-----------------+---------+---------+----+-----------+

patronictl -c /etc/patroni.yml topology

Output

+ Cluster: demo-cluster-1 (7106835957012965359) ------+----+-----------+
| Member        | Host            | Role    | State   | TL | Lag in MB |
+---------------+-----------------+---------+---------+----+-----------+
| pg-patroni1   | xxx.xxx.xxx.xxx | Leader  | running |  1 |           |
| + pg-patroni2 | xxx.xxx.xxx.xxx | Replica | running |  1 |         0 |
+---------------+-----------------+---------+---------+----+-----------+

Patroni logs

Patroni logs are sent to system logs by systemd. Use the journalctl system utility to fetch it:

sudo journalctl -u patroni.service -n 100 -f

Output

Jun 08 12:26:29 pg-patroni1 patroni[26589]: 2022-06-08 12:26:29,000 INFO: no action. I am (pg-patroni1), a secondary, and following a leader (pg-patroni2)
...

Maintenance mode

To pause or resume cluster management, use:

patronictl -c /etc/patroni.yml pause

Output

Success: cluster management is paused

patronictl -c /etc/patroni.yml list

Output

+ Cluster: demo-cluster-1 (7106835957012965359) ----+----+-----------+
| Member      | Host            | Role    | State   | TL | Lag in MB |
+-------------+-----------------+---------+---------+----+-----------+
| pg-patroni1 | xxx.xxx.xxx.xxx | Leader  | running |  1 |           |
| pg-patroni2 | xxx.xxx.xxx.xxx | Replica | running |  1 |         0 |
+-------------+-----------------+---------+---------+----+-----------+
 Maintenance mode: on

patronictl -c /etc/patroni.yml resume

Output

Success: cluster management is resumed

Manual failover or switchover

The failover endpoint allows you to perform a manual failover when there are no healthy nodes. It doesn't allow you to schedule a switchover.

Usage: patronictl failover [OPTIONS] [CLUSTER_NAME]

  Failover to a replica

Options:
  --master TEXT     The name of the current master
  --candidate TEXT  The name of the candidate
  --force           Do not ask for confirmation at any point
  --help            Show this message and exit.

The switchover endpoint works only when the cluster is healthy, that is, there's a leader. It allows you to schedule a switchover.

Usage: patronictl switchover [OPTIONS] [CLUSTER_NAME]

  Switchover to a replica

Options:
  --master TEXT     The name of the current master
  --candidate TEXT  The name of the candidate
  --scheduled TEXT  Timestamp of a scheduled switchover in unambiguous format
                    (e.g. ISO 8601)
  --force           Do not ask for confirmation at any point
  --help            Show this message and exit.

Example:

patronictl -c /etc/patroni.yml switchover --candidate pg-patroni2

Output

Master [pg-patroni1]: 
When should the switchover take place (e.g. 2022-06-08T13:14 )  [now]: 
Current cluster topology
+ Cluster: demo-cluster-1 (7106835957012965359) ----+----+-----------+
| Member      | Host            | Role    | State   | TL | Lag in MB |
+-------------+-----------------+---------+---------+----+-----------+
| pg-patroni1 | xxx.xxx.xxx.xxx | Leader  | running |  1 |           |
| pg-patroni2 | xxx.xxx.xxx.xxx | Replica | running |  1 |         0 |
+-------------+-----------------+---------+---------+----+-----------+
Are you sure you want to switchover cluster demo-cluster-1, demoting current master pg-patroni1? [y/N]: y
2022-06-08 12:14:48.01625 Successfully switched over to "pg-patroni2"
+ Cluster: demo-cluster-1 (7106835957012965359) ----+----+-----------+
| Member      | Host            | Role    | State   | TL | Lag in MB |
+-------------+-----------------+---------+---------+----+-----------+
| pg-patroni1 | xxx.xxx.xxx.xxx | Replica | stopped |    |   unknown |
| pg-patroni2 | xxx.xxx.xxx.xxx | Leader  | running |  1 |           |
+-------------+-----------------+---------+---------+----+-----------+

patronictl -c /etc/patroni.yml list

Output

+ Cluster: demo-cluster-1 (7106835957012965359) ----+----+-----------+
| Member      | Host            | Role    | State   | TL | Lag in MB |
+-------------+-----------------+---------+---------+----+-----------+
| pg-patroni1 | xxx.xxx.xxx.xxx | Replica | running |  2 |         0 |
| pg-patroni2 | xxx.xxx.xxx.xxx | Leader  | running |  2 |           |
+-------------+-----------------+---------+---------+----+-----------+

patronictl -c /etc/patroni.yml history

Output

+----+----------+------------------------------+----------------------------------+-------------+
| TL |      LSN | Reason                       | Timestamp                        | New Leader  |
+----+----------+------------------------------+----------------------------------+-------------+
|  1 | 67109024 | no recovery target specified | 2022-06-08T12:14:47.785857+00:00 | pg-patroni2 |
+----+----------+------------------------------+----------------------------------+-------------+

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