| repmgr 4.3 Documentation | |||
|---|---|---|---|
| Prev | Up | Chapter 13. repmgrd setup and configuration | Next |
To use repmgrd, its associated function library must be included via postgresql.conf with:
shared_preload_libraries = 'repmgr'
Changing this setting requires a restart of PostgreSQL; for more details see the PostgreSQL documentation.
The following configuraton options apply to repmgrd in all circumstances:
The interval (in seconds, default: 2) to check the availability of the upstream node.
The option connection_check_type is used to select the method repmgrd uses to determine whether the upstream node is available.
Possible values are:
The number of attempts (default: 6) will be made to reconnect to an unreachable upstream node before initiating a failover.
There will be an interval of reconnect_interval seconds between each reconnection attempt.
Interval (in seconds, default: 10) between attempts to reconnect to an unreachable upstream node.
The number of reconnection attempts is defined by the parameter reconnect_attempts.
Interval (in seconds) after which repmgrd will terminate if either of the servers (local node and or upstream node) being monitored is no longer available (degraded monitoring mode).
-1 (default) disables this timeout completely.
See also repmgr.conf.sample for an annotated sample configuration file.
The following repmgrd options must be set in repmgr.conf:
Example:
failover=automatic
promote_command='/usr/bin/repmgr standby promote -f /etc/repmgr.conf --log-to-file'
follow_command='/usr/bin/repmgr standby follow -f /etc/repmgr.conf --log-to-file --upstream-node-id=%n'
Details of each option are as follows:
failover can be one of automatic or manual.
Note: If failover is set to manual, repmgrd will not take any action if a failover situation is detected, and the node may need to be modified manually (e.g. by executing repmgr standby follow).
The program or script defined in promote_command will be executed in a failover situation when repmgrd determines that the current node is to become the new primary node.
Normally promote_command is set as repmgr's repmgr standby promote command.
It is also possible to provide a shell script to e.g. perform user-defined tasks before promoting the current node. In this case the script must at some point execute repmgr standby promote to promote the node; if this is not done, repmgr metadata will not be updated and repmgr will no longer function reliably.
Example:
promote_command='/usr/bin/repmgr standby promote -f /etc/repmgr.conf --log-to-file'
Note that the --log-to-file option will cause output generated by the repmgr command, when executed by repmgrd, to be logged to the same destination configured to receive log output for repmgrd.
Note: repmgr will not apply pg_bindir when executing promote_command or follow_command; these can be user-defined scripts so must always be specified with the full path.
The program or script defined in follow_command will be executed in a failover situation when repmgrd determines that the current node is to follow the new primary node.
Normally follow_command is set as repmgr's repmgr standby follow command.
The follow_command parameter should provide the --upstream-node-id=%n option to repmgr standby follow; the %n will be replaced by repmgrd with the ID of the new primary node. If this is not provided, repmgr standby follow will attempt to determine the new primary by itself, but if the original primary comes back online after the new primary is promoted, there is a risk that repmgr standby follow will result in the node continuing to follow the original primary.
It is also possible to provide a shell script to e.g. perform user-defined tasks before promoting the current node. In this case the script must at some point execute repmgr standby follow to promote the node; if this is not done, repmgr metadata will not be updated and repmgr will no longer function reliably.
Example:
follow_command='/usr/bin/repmgr standby follow -f /etc/repmgr.conf --log-to-file --upstream-node-id=%n'
Note that the --log-to-file option will cause output generated by the repmgr command, when executed by repmgrd, to be logged to the same destination configured to receive log output for repmgrd.
Note: repmgr will not apply pg_bindir when executing promote_command or follow_command; these can be user-defined scripts so must always be specified with the full path.
The following configuraton options can be use to fine-tune automatic failover:
Indicates a preferred priority (default: 100) for promoting nodes; a value of zero prevents the node being promoted to primary.
Note that the priority setting is only applied if two or more nodes are determined as promotion candidates; in that case the node with the higher priority is selected.
User-defined script to execute for an external mechanism to validate the failover decision made by repmgrd.
Note: This option must be identically configured on all nodes.
One or both of the following parameter placeholders should be provided, which will be replaced by repmgrd with the appropriate value:
See also: Failover validation.
In a failover situation, disconnect the local node's WAL receiver.
This option is available from PostgreSQL 9.5 and later.
Note: This option must be identically configured on all nodes.
Additionally the repmgr user must be a superuser for this option.
repmgrd will refuse to start if this option is set but either of these prerequisites is not met.
See also: Standby disconnection on failover.
The following options can be used to further fine-tune failover behaviour. In practice it's unlikely these will need to be changed from their default values, but are available as configuration options should the need arise.
If failover_validation_command is set, and the command returns an error, pause the specified amount of seconds (default: 15) before rerunning the election.
If standby_disconnect_on_failover is true, the maximum length of time (in seconds, default: 30) to wait for other standbys to confirm they have disconnected their WAL receivers.
If using automatic failover, currently repmgrd will need to execute repmgr standby follow to restart PostgreSQL on standbys to have them follow a new primary.
To ensure this happens smoothly, it's essential to provide the appropriate system/service restart command appropriate to your operating system via service_restart_command in repmgr.conf. If you don't do this, repmgrd will default to using pg_ctl, which can result in unexpected problems, particularly on systemd-based systems.
For more details, see service command settings.
If you are intending to use the repmgr daemon start and repmgr daemon stop commands, the following parameters must be set in repmgr.conf:
Example (for repmgr with PostgreSQL 11 on CentOS 7):
repmgrd_service_start_command='sudo systemctl repmgr11 start' repmgrd_service_stop_command='sudo systemctl repmgr11 stop'
For more details see the reference page for each command.
To enable monitoring, set:
monitoring_history=yes
in repmgr.conf.
Monitoring data is written at the interval defined by the option monitor_interval_secs (see above).
For more details on monitoring, see Storing monitoring data.
To apply configuration file changes to a running repmgrd daemon, execute the operating system's repmgrd service reload command (see Package details for examples), or for instances which were manually started, execute kill -HUP, e.g. kill -HUP `cat /tmp/repmgrd.pid`.
Tip: Check the repmgrd log to see what changes were applied, or if any issues were encountered when reloading the configuration.
Note that only the following subset of configuration file parameters can be changed on a running repmgrd daemon:
The following set of configuration file parameters must be updated via repmgr standby register --force, as they require changes to the repmgr.nodes table so they are visible to all nodes in the replication cluster:
Note: After executing repmgr standby register --force, repmgrd must be restarted for the changes to take effect.