This Ruby example lists the clusters.

# Get the reference to the root of the services tree:
system_service = connection.system_service

# Get the reference to the service that manages the
# collection of clusters:
cls_service = system_service.clusters_service

# Retrieve the list of clusters and for each one
# print its name:
cls = cls_service.list
cls.each do |cl|
  puts cl.name
end

In an environment with only the Default cluster, the example outputs:

Default