gistfile1.rb

def get_rrd_backend
  Visage::Collectd::RRD.new(        :rrddir        => Visage::Config.rrddir,
                                    :collectdsock  => Visage::Config.collectdsock,
                                    :rrdcachedsock => Visage::Config.rrdcachedsock)
end

def get_foo_backend
  # something else
end

def get_current_backend
  # when the config file options says :backend => :rrd
  get_rrd_backend()
  # When the config file says :backend => :foo
  get_foo_backend()
  # else misconfiguration or unknown backend, raise "unknown backend"
end
      json = get_current_backend.json(
                           :host        => host,
                           :plugin      => plugin,
                           :instances   => instances,
                           :start       => start,
                           :finish      => finish,
                           :percentiles => percentiles,
                           :resolution  => resolution)