Release notes for repmgr 3.0: repmgr - Replication Manager for PostgreSQL

repmgr 3.0 released

What is repmgr?

repmgr is an open source package which greatly simplifies the process of setting up and managing replication using streaming replication within a cluster of PostgreSQL servers. Taking advantage of features introduced since PostgreSQL 9.3, repmgr builds on PostgreSQL's core functionality to provide a smooth, user-friendly way of working with the complexities of replication and failover management in high-availability environments.

repmgr consists of two core tools - the repmgr command line interface, which provides functionality for adminstering replication such as cloning standby servers, and repmgrd, a background daemon which monitors nodes in a replication cluster and provides automatic failover support.

The latest repmgr release, version 3.0, introduces a number of new features which further simplify replication administration:

Standby cloning with pg_basebackup
Timeline following:
- a standby can be promoted to a master without requiring a restart
- other standbys can connect to the new master without being resynced
Cascading standby support
- Standbys not directly connected to the master node are not affected during failover of the master to another standby mode
Replication slot support (PostgreSQL 9.4 and later), simplifying WAL retention management

Additionally many usability improvements have been made based on user feedback, including better error reporting, removing the requirement to set pg_bindir if PostgreSQL binaries are in the default path, and a command line option to examine a server's configuration and report any changes required for setting up replication.

Note that repmgr 3.0 supports PostgreSQL 9.3 and later only.

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New features

Supports cloning of a standby using pg_basebackup (rsync still available as an option)
Supports cascaded standbys
No server restart needed when promoting a standby to a master
Supports replication slots (PostgreSQL 9.4 and later)
Supports tablespace remapping with pg_basebackup (PostgreSQL 9.4 and later) and rsync
Events of interest (e.g. failovers) logged to a new log table `repl_events` and can be optionally passed to an external program to provide notifications by email etc.

New or altered configuration options

Config option pg_bindir is no longer mandatory; repmgr will use the default path by default, or alternatively the new --pg_bindir command line option
New config option: pg_basebackup_options
New config option: tablespace_mapping
New config option: upstream_node
New config option: use_replication_slots
New config option: event_notification_command
New config option: event_notifications

New or altered command line options (repmgr)

New command line option --check-upstream-config to report issues with the upstream server configuration
New command line option --fast-checkpoint (forces a fast checkpoint when cloning a standby)
New command line option --rsync-only (use rsync only to clone a standby)
New command line option --pg_bindir
New command line option --ignore-external-config-files

Compatibility with repmgr 2.x

The configuration file format and options in repmgr 3 are backwards compatible with repmgr 2.x, so existing configuration files can be used largely as-is. However please be aware that the priority setting now defaults to 100 and that a setting of 0 (or less) indicates that the node should not be promoted to master, so any priority in existing repmgr.conf files should be adjusted accordingly.

Note that the metadata stored by repmgr 3 has changed and the existing metadata table (repl_nodes) will need to be upgraded; a script has been provided for this (repmgr2_repmgr3.sql).

The following minor compatibility changes have been made:

The text of many log messages has been revised for brevity and clarity
A valid value for config option failover must be provided (previously it defaulted to manual if an unrecognized value was provided)
The config option pg_bindir is no longer mandatory

Community and development

repmgr is free and open source software and is licensed under the GPLv3.

Contributions to repmgr are welcome. See the README.md file for information about how to contribute.