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132 lines
4.5 KiB
Markdown
132 lines
4.5 KiB
Markdown
repmgr: Replication Manager for PostgreSQL
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==========================================
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`repmgr` is a suite of open-source tools to manage replication and failover
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within a cluster of PostgreSQL servers. It enhances PostgreSQL's built-in
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replication capabilities with utilities to set up standby servers, monitor
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replication, and perform administrative tasks such as failover or switchover
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operations.
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`repmgr 4` is a complete rewrite of the existing `repmgr` codebase.
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Supports PostgreSQL 9.6 and later; support for 9.3 has been dropped, 9.4/9.5
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may be supported if feasible.
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Building from source
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--------------------
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Simply:
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./configure && make install
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Ensure `pg_config` for the target PostgreSQL version is in `$PATH`.
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Commands
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--------
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Currently available:
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repmgr primary register
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repmgr primary unregister
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repmgr standby clone
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repmgr standby register
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repmgr standby unregister
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repmgr standby promote
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repmgr standby follow
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repmgr bdr register
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repmgr cluster event [--all] [--node-id] [--node-name] [--event] [--event-matching]
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Backwards compatibility
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-----------------------
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See also: doc/changes-in-repmgr4.md
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`repmgr` is now implemented as a PostgreSQL extension. NOTE: no need to
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install the extension, this will be done automatically by `repmgr primary register`.
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Metadata tables have been revised and are not backwards-compatible
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with 3.x. (however future DDL updates will be easier as they can be
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carried out via the ALTER EXTENSION mechanism.
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TODO: extension upgrade script for pre-4.0
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Some configuration items have had their names changed for consistency
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and clarity e.g. `node` => `node_id`. `repmgr` will issue a warning
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about deprecated/altered options.
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Some configuration items have been changed to command line options,
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and vice-versa, e.g. to avoid hard-coding things like a node's
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upstream ID which might change.
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TODO: possibly add a config file conversion script/function.
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Generating event notifications with repmgr/repmgrd
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--------------------------------------------------
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Each time `repmgr` or `repmgrd` perform a significant event, a record
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of that event is written into the `repl_events` table together with
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a timestamp, an indication of failure or success, and further details
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if appropriate. This is useful for gaining an overview of events
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affecting the replication cluster. However note that this table has
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advisory character and should be used in combination with the `repmgr`
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and PostgreSQL logs to obtain details of any events.
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Example output after a master was registered and a standby cloned
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and registered:
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repmgr=# SELECT * from repmgr_test.repl_events ;
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node_id | event | successful | event_timestamp | details
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---------+------------------+------------+-------------------------------+-------------------------------------------------------------------------------------
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1 | master_register | t | 2016-01-08 15:04:39.781733+09 |
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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
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2 | standby_register | t | 2016-01-08 15:04:50.621292+09 |
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(3 rows)
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Additionally, event notifications can be passed to a user-defined program
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or script which can take further action, e.g. send email notifications.
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This is done by setting the `event_notification_command` parameter in
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`repmgr.conf`.
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This parameter accepts the following format placeholders:
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%n - node ID
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%e - event type
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%s - success (1 or 0)
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%t - timestamp
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%d - details
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The values provided for "%t" and "%d" will probably contain spaces,
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so should be quoted in the provided command configuration, e.g.:
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event_notification_command='/path/to/some/script %n %e %s "%t" "%d"'
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Additionally the following format placeholders are available for the even
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type `bdr_failover`:
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%c - conninfo string of the next available node
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%a - name of the next available node
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These should always be quoted.
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By default, all notification type will be passed to the designated script;
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the notification types can be filtered to explicitly named ones:
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event_notifications=master_register,standby_register
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The following event types are available:
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...
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* `bdr_failover`
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* `bdr_register`
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* `bdr_unregister`
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Note that under some circumstances (e.g. no replication cluster master could
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be located), it will not be possible to write an entry into the `repl_events`
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table, in which case `event_notification_command` can serve as a fallback.
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