lib/ganymed/sampler/derive.rb in ganymed-0.2.3 vs lib/ganymed/sampler/derive.rb in ganymed-0.3.0

@@ -8,29 +8,20 @@
     # going from the last to the current value of the data source. Derive is
     # similar to a {Counter} {DataSource data source} in that it produces a
     # rate/s gauge, but only accepts absolute values and produces the
     # derivative instead of summation of all samples.
     #
-    # In order to get (meaningful) realtime events from a Derive {DataSource}
-    # samples must be sent multiple times per second. Derive does not store the
-    # previously flushed value for performance reasons and therefore cannot
-    # infer a rate/s gauge with only one event per flush.
-    #
     class Derive < DataSource
-      def flush(tick, &block)
-        each(tick) do |ns, origin, events|
-          values = events.sort_by do |event| # sort by timestamp
-            event[0]
-          end.each_cons(2).map do |a, b| # derive each consective sample
-            (b[1] - a[1])/(b[0] - a[0]) # ∆value / ∆ts
+      def flush
+        each do |ns, origin, ts|
+          values = ts.each_cons(2).map do |a, b|
+            (b[1].last - a[1].last)/(b[0] - a[0]) # ∆value / ∆ts
+          end.reject do |value|
+            value < 0 # ignore overflow/counter wrap
           end
 
           yield ns, origin, values
         end
-      end
-
-      def feed(ns, origin, ts, value)
-        add(ns, origin, [ts, value])
       end
     end
   end
 end