recovery: optional restore_command & allow custom command if needed

Right now the role assumes you always want to use barman-wal-restore
script as a restore command to recover WAL files at startup time of a
standby server.

This PR adds a new `primary.restore_command` option which lets you
override the command to use.

⚠️ Breaking change: the PR renames the existing
`primary.restore_directory` option to
`primary.restore_barman_directory` ⚠️ in order to give more context to
this option which will automatically use the `barman-wal-restore`
script as a restore command.

Finally if none of the two options specified above are specified in
the `primary:` object then the `restore_command` is left commented out
in the PG configuration (which is totally fine as it will try to
recover WALs from the primary server directly see
[documentation](https://www.postgresql.org/docs/12/warm-standby.html#STANDBY-SERVER-OPERATION))

1 files changed, 5 insertions, 7 deletions

diff --git a/templates/postgresql.12.conf.j2 b/templates/postgresql.12.conf.j2
index b49b836..3598319 100644
--- a/templates/postgresql.12.conf.j2
+++ b/templates/postgresql.12.conf.j2
@@ -260,20 +260,18 @@ archive_command = ''
 
 # These are only used in recovery mode.
 
-{% if postgres_primary %}
 {# In PG < 12 versions all the recovery settings were in a separate recovery.conf file #}
-restore_command = '/usr/bin/barman-wal-restore --user barman --parallel 8 {{ postgres_barman_server }} {{ postgres_primary.restore_directory }} %f %p'          # command to use to restore an archived logfile segment
-                                # placeholders: %p = path of file to restore
-                                #               %f = file name only
-                                # e.g. 'cp /mnt/server/archivedir/%f %p'
-                                # (change requires restart)
+{% if postgres_primary and postgres_primary.restore_command is defined %}
+restore_command = '{{ postgres_primary.restore_command }}'              # command to use to restore an archived logfile segment
+{% elif postgres_primary and postgres_primary.restore_barman_directory is defined %}
+restore_command = '/usr/bin/barman-wal-restore --user barman --parallel 8 {{ postgres_barman_server }} {{ postgres_primary.restore_barman_directory }} %f %p'           # command to use to restore an archived logfile segment
 {% else %}
 #restore_command = ''           # command to use to restore an archived logfile segment
+{% endif %}
                                 # placeholders: %p = path of file to restore
                                 #               %f = file name only
                                 # e.g. 'cp /mnt/server/archivedir/%f %p'
                                 # (change requires restart)
-{% endif %}
 #archive_cleanup_command = ''   # command to execute at every restartpoint
 #recovery_end_command = ''      # command to execute at completion of recovery