Assume you want to configure stuff one host ("monitor node"),
depending on the configuration of other hosts ("cluster nodes").

For instance, the monitor host would like to know,
which hosts are configured with the provider
"apache" and option --start true.

This requires the monitor node to be able to
query all other configured nodes. It can't
ask for all hosts, because cdist does not
know which hosts are configured or may exist.

Example implementation

If cdist keeps ("caches") the configuration of every
node it configures, each new node can query the
cache for existing nodes that acquired the given
configuration.