repmgr: Replication Manager for PostgreSQL

repmgr is a suite of open-source tools to manage replication and failover within a cluster of PostgreSQL servers. It enhances PostgreSQL's built-in replication capabilities with utilities to set up standby servers, monitor replication, and perform administrative tasks such as failover or switchover operations.

repmgr 4 is a complete rewrite of the existing repmgr codebase.

Supports PostgreSQL 9.6 and later; support for 9.3 has been dropped, 9.4/9.5 may be supported if feasible.

Building from source

Simply:

./configure && make install

Ensure pg_config for the target PostgreSQL version is in $PATH.

Reference

repmgr commands

The following commands are available:

repmgr primary register
repmgr primary unregister

repmgr standby clone
repmgr standby register
repmgr standby unregister
repmgr standby promote
repmgr standby follow

repmgr bdr register
repmgr bdr unregister

repmgr cluster show
repmgr cluster event [--all] [--node-id] [--node-name] [--event] [--event-matching]

• primary register

  Registers a primary in a streaming replication cluster, and configures it for use with repmgr. This command needs to be executed before any standby nodes are registered.

  master register can be used as an alias for primary register.

• cluster show

  Displays information about each active node in the replication cluster. This command polls each registered server and shows its role (master / standby / bdr) and status. It polls each server directly and can be run on any node in the cluster; this is also useful when analyzing connectivity from a particular node.

  This command requires either a valid repmgr.conf file or a database connection string to one of the registered nodes; no additional arguments are needed.

  Example:

    $ repmgr -f /etc/repmgr.conf cluster show
  
     ID | Name  | Role    | Status    | Upstream | Connection string
    ----+-------+---------+-----------+----------+-----------------------------------------
     1  | node1 | primary | * running |          | host=db_node1 dbname=repmgr user=repmgr
     2  | node2 | standby |   running | node1    | host=db_node2 dbname=repmgr user=repmgr
     3  | node3 | standby |   running | node1    | host=db_node3 dbname=repmgr user=repmgr
  

  To show database connection errors when polling nodes, run the command in --verbose mode.

  The cluster show command accepts an optional parameter --csv, which outputs the replication cluster's status in a simple CSV format, suitable for parsing by scripts:

    $ repmgr -f /etc/repmgr.conf cluster show --csv
    1,-1,-1
    2,0,0
    3,0,1
  

  The columns have following meanings:

    - node ID
    - availability (0 = available, -1 = unavailable)
    - recovery state (0 = not in recovery, 1 = in recovery, -1 = unknown)
  

  Note that the availability is tested by connecting from the node where repmgr cluster show is executed, and does not necessarily imply the node is down.

Backwards compatibility

See also: doc/changes-in-repmgr4.md

repmgr is now implemented as a PostgreSQL extension. NOTE: no need to install the extension, this will be done automatically by repmgr primary register.

Metadata tables have been revised and are not backwards-compatible with 3.x. (however future DDL updates will be easier as they can be carried out via the ALTER EXTENSION mechanism.

TODO: extension upgrade script for pre-4.0

Some configuration items have had their names changed for consistency and clarity e.g. node => node_id. repmgr will issue a warning about deprecated/altered options.

Some configuration items have been changed to command line options, and vice-versa, e.g. to avoid hard-coding things like a node's upstream ID which might change.

TODO: possibly add a config file conversion script/function.

Generating event notifications with repmgr/repmgrd

Each time repmgr or repmgrd perform a significant event, a record of that event is written into the repl_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 repmgr and PostgreSQL logs to obtain details of any events.

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

repmgr=# SELECT * from repmgr_test.repl_events ;
 node_id |      event       | successful |        event_timestamp        |                                       details
---------+------------------+------------+-------------------------------+-------------------------------------------------------------------------------------
       1 | master_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 'repmgr_node1', port 5432; backup method: pg_basebackup; --force: N
       2 | standby_register | t          | 2016-01-08 15:04:50.621292+09 |
(3 rows)

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 repmgr.conf.

This parameter accepts the following format placeholders:

%n - node ID
%e - event type
%s - success (1 or 0)
%t - timestamp
%d - details

The values provided for "%t" and "%d" will probably 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"'

Additionally the following format placeholders are available for the even type bdr_failover:

%c - conninfo string of the next available node
%a - name of the next available node

These should always be quoted.

By default, all notification type will be passed to the designated script; the notification types can be filtered to explicitly named ones:

event_notifications=master_register,standby_register

The following event types are available:

...

• bdr_failover
• bdr_register
• bdr_unregister

Note that under some circumstances (e.g. no replication cluster master could be located), it will not be possible to write an entry into the repl_events table, in which case event_notification_command can serve as a fallback.