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[Yoshihiko Atsumi <1658629@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

Resource tracker in nova-compute checks the resource usage every minute.
If the latest resource usage is different from the previous of that,
nova-compute request nova-scheduler to update compute_nodes table in DB.
https://github.com/openstack/nova/blob/master/nova/compute/resource_tracker.py#L712-L728
_update() calls _resource_change(). And in _resource_change(), resource usages are compared by obj_equal_prims().

In obj_equal_prims(), the resource usage lists are created.
https://github.com/openstack/nova/blob/master/nova/objects/base.py#L328-L360
And I found that the lists contained "updated_at" in their keys.

 prim_1 ={'nova_object.version': u'1.16',
'nova_object.name': 'ComputeNode', 
'nova_object.data': {'pci_device_pools': {'nova_object.version': '1.1',
'nova_object.name': 'PciDevicePoolList', 
'nova_object.data': {'objects': []}, 'nova_object.namespace': 'nova'}, 
'updated_at': '2017-01-20T01:07:43Z',　★here
(omission)

prim_2 ={'nova_object.version': '1.16', 
'nova_object.name': 'ComputeNode', 
'nova_object.data': {'pci_device_pools': {'nova_object.version': '1.1',
'nova_object.name': 'PciDevicePoolList', 
'nova_object.data': {'objects': []}, 'nova_object.namespace': 'nova'}, 
'updated_at': '2017-01-20T01:06:42Z',　★here
(omission)

These difference in "updated_at" values makes unequal resource usage in recent 2 times checks,
and causes update of compute_nodes table every minute.
I noticed this problem in Mitaka. According to the code, I think this happens in master.

** Affects: nova
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1658629

Title:
  Resource tracker causes update of compute_nodes table every minute

Status in OpenStack Compute (nova):
  New

Bug description:
  Resource tracker in nova-compute checks the resource usage every minute.
  If the latest resource usage is different from the previous of that,
  nova-compute request nova-scheduler to update compute_nodes table in DB.
  https://github.com/openstack/nova/blob/master/nova/compute/resource_tracker.py#L712-L728
  _update() calls _resource_change(). And in _resource_change(), resource usages are compared by obj_equal_prims().

  In obj_equal_prims(), the resource usage lists are created.
  https://github.com/openstack/nova/blob/master/nova/objects/base.py#L328-L360
  And I found that the lists contained "updated_at" in their keys.

   prim_1 ={'nova_object.version': u'1.16',
  'nova_object.name': 'ComputeNode', 
  'nova_object.data': {'pci_device_pools': {'nova_object.version': '1.1',
  'nova_object.name': 'PciDevicePoolList', 
  'nova_object.data': {'objects': []}, 'nova_object.namespace': 'nova'}, 
  'updated_at': '2017-01-20T01:07:43Z',　★here
  (omission)

  prim_2 ={'nova_object.version': '1.16', 
  'nova_object.name': 'ComputeNode', 
  'nova_object.data': {'pci_device_pools': {'nova_object.version': '1.1',
  'nova_object.name': 'PciDevicePoolList', 
  'nova_object.data': {'objects': []}, 'nova_object.namespace': 'nova'}, 
  'updated_at': '2017-01-20T01:06:42Z',　★here
  (omission)

  These difference in "updated_at" values makes unequal resource usage in recent 2 times checks,
  and causes update of compute_nodes table every minute.
  I noticed this problem in Mitaka. According to the code, I think this happens in master.

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