Proper delta reporting of metrics

Author: pglombardo

instana/meter.py

@@ -5,6 +5,7 @@
 import gc as gc_
 import sys
 import instana.agent_const as a
+import copy
 
 
 class Snapshot(object):
@@ -63,6 +64,17 @@ class Metrics(object):
     def __init__(self, **kwds):
         self.__dict__.update(kwds)
 
+    def delta_data(self, delta):
+        data = self.__dict__
+        if delta is None:
+            return data
+
+        unchanged_items = set(data.items()) & set(delta.items())
+        for x in unchanged_items:
+            data.pop(x[0])
+
+        return data
+
 
 class EntityData(object):
     pid = 0
@@ -80,6 +92,7 @@ class Meter(object):
     last_usage = None
     last_collect = None
     timer = None
+    last_metrics = None
 
     def __init__(self, sensor):
         self.sensor = sensor
@@ -95,17 +108,18 @@ def process(self):
         if self.sensor.agent.can_send():
             self.snapshot_countdown = self.snapshot_countdown - 1
             s = None
+            cm = self.collect_metrics()
             if self.snapshot_countdown == 0:
                 self.snapshot_countdown = self.SNAPSHOT_PERIOD
                 s = self.collect_snapshot()
-
-            m = self.collect_metrics()
-            d = EntityData(pid=os.getpid(), snapshot=s, metrics=m)
-
-            t.Thread(target=self.sensor.agent.request,
-                     args=(self.sensor.agent.make_url(a.AGENT_DATA_URL),
-                           "POST", d),
-                     name="Metrics POST").start()
+                md = cm.delta_data(None)
+            else:
+                md = copy.deepcopy(cm).delta_data(self.last_metrics)
+
+            d = EntityData(pid=os.getpid(), snapshot=s, metrics=md)
+            self.sensor.agent.request(
+                self.sensor.agent.make_url(a.AGENT_DATA_URL), "POST", d)
+            self.last_metrics = cm.__dict__
 
         self.tick()