Allow selection of which metrics to send to Librato metrics

lib/metriks/reporter/librato_metrics.rb

@@ -12,6 +12,12 @@ def initialize(email, token, options = {})
       @registry  = options[:registry] || Metriks::Registry.default
       @interval  = options[:interval] || 60
       @on_error  = options[:on_error] || proc { |ex| }
+
+      if options[:only] and options[:except]
+        raise 'Can only specify one of :only or :except'
+      end
+      @only     = options[:only] || []
+      @except   = options[:except] || []
     end
 
     def start
@@ -121,6 +127,15 @@ def prepare_metric(base_name, metric, keys, snapshot_keys = [])
         base_name = "#{@prefix}.#{base_name}"
       end
 
+      if @only
+        keys = keys & @only
+        snapshot_keys = snapshot_keys & @only
+      end
+      if @except
+        keys = keys - @except
+        snapshot_keys = snapshot_keys - @except
+      end
+
       keys.flatten.each do |key|
         name = key.to_s.gsub(/^get_/, '')
         value = metric.send(key)