Deprecate aggregated disk.* metrics on instance

disk.* are just aggregates of disk.device.*. We
basically build the same think twice.

It's up to the backend (ie: Gnocchi) to aggregate them
if someone want the aggregate.

Change-Id: I612b575004f65665f8630f19f56c2fb3637448fd

ceilometer/compute/pollsters/disk.py

@@ -23,6 +23,8 @@ from ceilometer import sample
 
 LOG = log.getLogger(__name__)
 
+AGGREGATED_DEPRECATION_DONE = set()
+
 
 class AggregateDiskPollster(pollsters.GenericComputePollster):
     inspector_method = "inspect_disks"
@@ -44,6 +46,14 @@ class AggregateDiskPollster(pollsters.GenericComputePollster):
     def get_additional_metadata(instance, stats):
         return {'device': stats.device}
 
+    def get_samples(self, *args, **kwargs):
+        if self.sample_name not in AGGREGATED_DEPRECATION_DONE:
+            AGGREGATED_DEPRECATION_DONE.add(self.sample_name)
+            LOG.warning("The %s metric is deprecated, instead use %s" %
+                        (self.sample_name,
+                         self.sample_name.replace("disk.", "disk.device.")))
+        return super(AggregateDiskPollster, self).get_samples(*args, **kwargs)
+
 
 class PerDeviceDiskPollster(pollsters.GenericComputePollster):
     inspector_method = "inspect_disks"

etc/ceilometer/polling.yaml

@@ -10,10 +10,10 @@ sources:
         - network.incoming.packets
         - network.outgoing.bytes
         - network.outgoing.packets
-        - disk.read.bytes
-        - disk.read.requests
-        - disk.write.bytes
-        - disk.write.requests
+        - disk.device.read.bytes
+        - disk.device.read.requests
+        - disk.device.write.bytes
+        - disk.device.write.requests
         - hardware.cpu.util
         - hardware.memory.used
         - hardware.memory.total

releasenotes/notes/deprecate-aggregated-disk-metrics-54a395c05e74d685.yaml

@@ -0,0 +1,6 @@
+---
+deprecations:
+  - |
+    disk.* aggregated metrics for instance are deprecated, in favor of the
+    per disk metrics (disk.device.*). Now, it's up to the backend to provide
+    such aggregation feature. Gnocchi already provides this.