Previously "repmgr standby switchover" would abort if any node was unreachable,
as that means it was unable to check if repmgrd is running.
However if the node has been marked as inactive in the repmgr metadata, it's
reasonable to assume the node is no longer part of the replication cluster
and does not need to be checked.
If the sibling node has already been promoted (for whatever
reason, e.g. "repmgr standby promote" was executed manually)
and has exited recovery, the upstream node ID will normally
be reported as "-1", which is correct, but looks confusing in
the logs.
We now only report the upstream node ID if the sibling node
is still in recovery, *or* if it has exited recovery but is
still reporting an extant node ID.
This functionality enables repmgrd (when running on the primary) to
monitor connected child nodes. It will log connections and disconnections
and generate events.
Additionally, repmgrd can execute a custom script if the number of connected
child nodes falls below a configurable threshold. This script can be used
e.g. to "fence" the primary following a failover situation where a new primary
has been promoted and all standbys are now child nodes of that primary.
In Barman mode, if there is an existing, populated data directory, and
the "--force" option is provided, the entire directory was being deleted,
and later recreated as part of the rsync process, but with the default
permissions.
Fix this by recreating the data directory with the correct permissions
after deleting it.
If --siblings-follow is not supplied, list all nodes which repmgr considers
to be siblings (this will include the witness server, if in use), and
which will remain attached to the old primary.
Improve sample PostgreSQL replication configuration, including
links to the PostgreSQL documentation for each configuration item.
Also set "max_replication_slots" to the same value as "max_wal_senders"
to ensure the sample configuration will work regardless of whether
replication slots are in use, though we do still encourage careful
reading of the comments in the sample configuration and the documentation
in general.
