Update compute CPU pollster to use cache

Use the pollster cache to store the CPU statistics
for an instance. Eventually the single pollster will
be broken up into separate pollsters that all use
the cache.

blueprint one-meter-per-plugin

Change-Id: Iada02930867c09d05684ba0acea728d0d1cf06ae
Signed-off-by: Doug Hellmann <doug.hellmann@dreamhost.com>

ceilometer/compute/pollsters.py

@@ -169,7 +169,7 @@ class CPUPollster(plugin.ComputePollster):
 
     utilization_map = {}
 
-    def get_cpu_util(self, instance, cpu_info):
+    def _get_cpu_util(self, instance, cpu_info):
         prev_times = self.utilization_map.get(instance.id)
         self.utilization_map[instance.id] = (cpu_info.time,
                                              datetime.datetime.now())
@@ -186,6 +186,14 @@ class CPUPollster(plugin.ComputePollster):
             cpu_util = 100 * cores_fraction * time_used / elapsed
         return cpu_util
 
+    CACHE_KEY_CPU = 'cpu'
+
+    def _get_cpu_info(self, inspector, instance_name, cache):
+        i_cache = cache.setdefault(self.CACHE_KEY_CPU, {})
+        if instance_name not in i_cache:
+            i_cache[instance_name] = inspector.inspect_cpus(instance_name)
+        return i_cache[instance_name]
+
     @staticmethod
     def get_counter_names():
         return ['cpu', 'cpu_util']
@@ -194,10 +202,14 @@ class CPUPollster(plugin.ComputePollster):
         self.LOG.info('checking instance %s', instance.id)
         instance_name = _instance_name(instance)
         try:
-            cpu_info = manager.inspector.inspect_cpus(instance_name)
+            cpu_info = self._get_cpu_info(
+                manager.inspector,
+                instance_name,
+                cache,
+            )
             self.LOG.info("CPUTIME USAGE: %s %d",
                           instance.__dict__, cpu_info.time)
-            cpu_util = self.get_cpu_util(instance, cpu_info)
+            cpu_util = self._get_cpu_util(instance, cpu_info)
             self.LOG.info("CPU UTILIZATION %%: %s %0.2f",
                           instance.__dict__, cpu_util)
             # FIXME(eglynn): once we have a way of configuring which measures

tests/compute/test_pollsters.py

@@ -240,7 +240,8 @@ class TestCPUPollster(TestPollsterBase):
         pollster = pollsters.CPUPollster()
 
         def _verify_cpu_metering(zero, expected_time):
-            counters = list(pollster.get_counters(mgr, {}, self.instance))
+            cache = {}
+            counters = list(pollster.get_counters(mgr, cache, self.instance))
             self.assertEquals(len(counters), 2)
             self.assertEqual(set([c.name for c in counters]),
                              set(pollster.get_counter_names()))
@@ -249,9 +250,37 @@ class TestCPUPollster(TestPollsterBase):
                     counters[0].volume > 0.0)
             assert counters[1].name == 'cpu'
             assert counters[1].volume == expected_time
+            assert pollster.CACHE_KEY_CPU in cache
+            assert self.instance.name in cache[pollster.CACHE_KEY_CPU]
             # ensure elapsed time between polling cycles is non-zero
             time.sleep(0.001)
 
         _verify_cpu_metering(True, 1 * (10 ** 6))
         _verify_cpu_metering(False, 3 * (10 ** 6))
         _verify_cpu_metering(False, 2 * (10 ** 6))
+
+    @mock.patch('ceilometer.pipeline.setup_pipeline', mock.MagicMock())
+    def test_get_counters_cache(self):
+        # self.inspector.inspect_cpus(self.instance.name).AndReturn(
+        #     virt_inspector.CPUStats(time=1 * (10 ** 6), number=2))
+        # self.inspector.inspect_cpus(self.instance.name).AndReturn(
+        #     virt_inspector.CPUStats(time=3 * (10 ** 6), number=2))
+        # # cpu_time resets on instance restart
+        # self.inspector.inspect_cpus(self.instance.name).AndReturn(
+        #     virt_inspector.CPUStats(time=2 * (10 ** 6), number=2))
+        self.mox.ReplayAll()
+
+        mgr = manager.AgentManager()
+        pollster = pollsters.CPUPollster()
+
+        cache = {
+            pollster.CACHE_KEY_CPU: {
+                self.instance.name: virt_inspector.CPUStats(
+                    time=10 ** 6,
+                    number=2,
+                ),
+            },
+        }
+        counters = list(pollster.get_counters(mgr, cache, self.instance))
+        self.assertEquals(len(counters), 2)
+        self.assertEquals(counters[1].volume, 10 ** 6)