Each time ltcluster or ltclusterd perform a significant event, a record of that event is written into the ltcluster.events table together with a timestamp, an indication of failure or success, and further details if appropriate. This is useful for gaining an overview of events affecting the replication cluster. However note that this table has advisory character and should be used in combination with the ltcluster and LightDB logs to obtain details of any events.

Example output after a primary was registered and a standby cloned and registered:

    ltcluster=# SELECT * from ltcluster.events ;
     node_id |      event       | successful |        event_timestamp        |                                       details
    ---------+------------------+------------+-------------------------------+-------------------------------------------------------------------------------------
           1 | primary_register | t          | 2016-01-08 15:04:39.781733+09 |
           2 | standby_clone    | t          | 2016-01-08 15:04:49.530001+09 | Cloned from host 'ltcluster_node1', port 5432; backup method: lt_basebackup; --force: N
           2 | standby_register | t          | 2016-01-08 15:04:50.621292+09 |
    (3 rows)

Alternatively, use ltcluster cluster event to output a formatted list of events.

Additionally, event notifications can be passed to a user-defined program or script which can take further action, e.g. send email notifications. This is done by setting the event_notification_command parameter in ltcluster.conf.

The following format placeholders are provided for all event notifications:

The values provided for %t and %d may contain spaces, so should be quoted in the provided command configuration, e.g.:

    event_notification_command='/path/to/some/script %n %e %s "%t" "%d"'

The following parameters are provided for a subset of event notifications:

The values provided for %c and %a will probably contain spaces, so should always be quoted.

By default, all notification types will be passed to the designated script; the notification types can be filtered to explicitly named ones using the event_notifications parameter, e.g.:

    event_notifications='primary_register,standby_register,witness_register'

Events generated by the ltcluster command:

Events generated by ltclusterd (streaming replication mode):

Note that under some circumstances (e.g. when no replication cluster primary could be located), it will not be possible to write an entry into the ltcluster.events table, in which case executing a script via event_notification_command can serve as a fallback by generating some form of notification.