ltcluster standby promote

ltcluster standby promote — promote a standby to a primary


Promotes a standby to a primary if the current primary has failed. This command requires a valid ltcluster.conf file for the standby, either specified explicitly with -f/--config-file or located in a default location; no additional arguments are required.


If ltclusterd is active, you must execute ltcluster service pause (ltcluster 4.2 - 4.4: ltcluster service pause) to temporarily disable ltclusterd while making any changes to the replication cluster.

If the standby promotion succeeds, the server will not need to be restarted. However any other standbys will need to follow the new primary, and will need to be restarted to do this.

Beginning with ltcluster 5, the option --siblings-follow can be used to have all other standbys (and a witness server, if in use) follow the new primary.


If using ltclusterd, when invoking ltcluster standby promote (either directly via the promote_command, or in a script called via promote_command), --siblings-follow must not be included as a command line option for ltcluster standby promote.

ltcluster will wait for up to promote_check_timeout seconds (default: 60) to verify that the standby has been promoted, and will check the promotion every promote_check_interval seconds (default: 1 second). Both values can be defined in ltcluster.conf.


      $ ltcluster -f /etc/ltcluster.conf standby promote
      NOTICE: promoting standby to primary
      DETAIL: promoting server "node2" (ID: 2) using "lt_ctl -l /var/log/lightdb/startup.log -w -D '/var/lib/lightdb/data' promote"
      server promoting
      NOTICE: STANDBY PROMOTE successful
      DETAIL: server "node2" (ID: 2) was successfully promoted to primary

User permission requirements

pg_promote() (LightDB 21 and later)

From LightDB 21, ltcluster will attempt to use the built-in pg_promote() function to promote a standby to primary.

By default, execution of pg_promote() is restricted to superusers. If the ltcluster user does not have permission to execute pg_promote(), ltcluster will fall back to using "lt_ctl promote".


Execute ltcluster standby promote with the --dry-run to check whether the ltcluster user has permission to execute pg_promote().

If the ltcluster user is not a superuser, execution permission for this function can be granted with e.g.:

    GRANT EXECUTE ON FUNCTION pg_catalog.pg_promote TO ltcluster

Note that permissions are only effective for the database they are granted in, so this must be executed in the ltcluster database to be effective.

For more details on pg_promote(), see the LightDB documentation.



Check if this node can be promoted, but don't carry out the promotion.


Have all sibling nodes (nodes formerly attached to the same upstream node as the promotion candidate) follow this node after it has been promoted.

Note that a witness server, if in use, is also counted as a "sibling node" as it needs to be instructed to synchronise its metadata with the new primary.


Do not provide this option when configuring ltclusterd's promote_command.


Ignore warnings and continue anyway.

This option is relevant in the following situations if --siblings-follow was specified:

  • If one or more sibling nodes was not reachable via SSH, the standby will be promoted anyway.
  • If the promotion candidate has insufficient free walsenders to accomodate the standbys which will be attached to it, the standby will be promoted anyway.
  • If replication slots are in use but the promotion candidate has insufficient free replication slots to accomodate the standbys which will be attached to it, the standby will be promoted anyway.

Note that if the -F/--force option is used when any of the above situations is encountered, the onus is on the user to manually resolve any resulting issues.

Configuration file settings

The following parameters in ltcluster.conf are relevant to the promote operation:

  • promote_check_interval: interval (in seconds, default: 1 second) to wait between each check to determine whether the standby has been promoted.

  • promote_check_timeout: time (in seconds, default: 60 seconds) to wait to verify that the standby has been promoted before exiting with ERR_PROMOTION_FAIL.

  • service_promote_command: a command which will be executed instead of lt_ctl promote or (in LightDB 21 and later) pg_promote().

    This is intended for systems which provide a package-level promote command, such as Debian's pg_ctlcluster, to promote the LightDB from standby to primary.

Exit codes

Following exit codes can be emitted by ltcluster standby promote:


The standby was successfully promoted to primary.


ltcluster was unable to connect to the local LightDB node.

LightDB must be running before the node can be promoted.


The node could not be promoted to primary for one of the following reasons:

  • there is an existing primary node in the replication cluster
  • the node is not a standby
  • WAL replay is paused on the node
  • execution of the LightDB promote command failed

Event notifications

A standby_promote event notification will be generated.