5.1. Cloning a standby from Barman

repmgr standby clone can use 2ndQuadrant's Barman application to clone a standby (and also as a fallback source for WAL files).

Tip: Barman (aka PgBarman) should be considered as an integral part of any PostgreSQL replication cluster. For more details see: https://www.pgbarman.org/.

Barman support provides the following advantages:

5.1.1. Prerequisites for cloning from Barman

In order to enable Barman support for repmgr standby clone, following prerequisites must be met:

Note: Barman support is automatically enabled if barman_server is set. Normally it is good practice to use Barman, for instance when fetching a base backup while cloning a standby; in any case, Barman mode can be disabled using the --without-barman command line option.

Tip: If you have a non-default SSH configuration on the Barman server, e.g. using a port other than 22, then you can set those parameters in a dedicated Host section in ~/.ssh/config corresponding to the value ofbarman_host in repmgr.conf. See the Host section in man 5 ssh_config for more details.

It's now possible to clone a standby from Barman, e.g.:

    NOTICE: using configuration file "/etc/repmgr.conf"
    NOTICE: destination directory "/var/lib/postgresql/data" provided
    INFO: connecting to Barman server to verify backup for test_cluster
    INFO: checking and correcting permissions on existing directory "/var/lib/postgresql/data"
    INFO: creating directory "/var/lib/postgresql/data/repmgr"...
    INFO: connecting to Barman server to fetch server parameters
    INFO: connecting to upstream node
    INFO: connected to source node, checking its state
    INFO: successfully connected to source node
    DETAIL: current installation size is 29 MB
    NOTICE: retrieving backup from Barman...
    receiving file list ...
    NOTICE: standby clone (from Barman) complete
    NOTICE: you can now start your PostgreSQL server
    HINT: for example: pg_ctl -D /var/lib/postgresql/data start

5.1.2. Using Barman as a WAL file source

As a fallback in case streaming replication is interrupted, PostgreSQL can optionally retrieve WAL files from an archive, such as that provided by Barman. This is done by setting restore_command in recovery.conf to a valid shell command which can retrieve a specified WAL file from the archive.

barman-wal-restore is a Python script provided as part of the barman-cli package (Barman 2.0 and later; for Barman 1.x the script is provided separately as barman-wal-restore.py) which performs this function for Barman.

To use barman-wal-restore with repmgr and assuming Barman is located on the barmansrv host and that barman-wal-restore is located as an executable at /usr/bin/barman-wal-restore, repmgr.conf should include the following lines:

    restore_command=/usr/bin/barman-wal-restore barmansrv somedb %f %p

Note: barman-wal-restore supports command line switches to control parallelism (--parallel=N) and compression ( --bzip2, --gzip).

Note: To use a non-default Barman configuration file on the Barman server, specify this in repmgr.conf with barman_config: