Improve Compute Data Model

The fields(vcpus, memory and disk_capacity) in the Watcher ComputeNode
do not take allocation ratios used for overcommit into account so there
may be disparity between this and the used count. We need to add some
fields to solve this problem.

Change-Id: If2a6bbcd1faa735e93eabbbdb4cc99ae324fd85f
Implements: blueprint improve-compute-data-model

specs/train/approved/improve-compute-data-model.rst

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+..
+ This work is licensed under a Creative Commons Attribution 3.0 Unported
+ License.
+
+ http://creativecommons.org/licenses/by/3.0/legalcode
+
+==========================
+Improve Compute Data Model
+==========================
+
+https://blueprints.launchpad.net/watcher/+spec/improve-compute-data-model
+
+
+Problem description
+===================
+
+The fields(vcpus, memory and disk_capacity) in the Watcher ComputeNode
+correspond to the fields(vcpus, memory_mb and local_gb) in Nova API
+`list-hypervisors-details`_. Unfortunately, these fields do not take
+allocation ratios used for overcommit into account so there may be
+disparity between this and the used count.
+
+.. _list-hypervisors-details: https://developer.openstack.org/api-ref/compute/?expanded=list-hypervisors-details-detail#list-hypervisors-details
+
+Use Cases
+----------
+
+As a Watcher user, I wish Watcher can work correctly in the case of
+overcommit resources(cpu, memory and disk).
+
+
+Proposed change
+===============
+
+Now Watcher had added `Placement helper`_. Watcher can get resource
+information such as total, allocation ratio and reserved information
+from API `list resource provider inventories`_,
+and resource usage from API `list resource provider usages`_.
+
+Watcher ComputeNode
+-------------------
+
+We need to add some fields to the Watcher ComputeNode:
+
+* vcpus_used: the number of vcpu used in this node.
+* cpu_reserved: The amount of cpu a node has reserved for its own use.
+* cpu_ratio: CPU allocation ratio.
+* memory_mb_used: The memory used in this node(in MiB).
+* memory_mb_reserved: The amount of memory a node has reserved for
+  its own use.
+* ram_ratio: Memory allocation ratio.
+* disk_gb_used: The disk used in this node(in GiB).
+* disk_gb_reserved: The amount of disk a node has reserved for its own use.
+* disk_ratio: Disk allocation ratio.
+
+We can calculate the free resource through the total, reserved, used and
+allocation ratio.
+
+The formula:
+free = (vcpus-cpu_reserved)*cpu_ratio-vcpus_used
+
+For example, for vcpu resource with:
+
+::
+
+  vcpus = 8
+  vcpus_used = 16
+  cpu_reserved = 2
+  cpu_ratio = 5.0
+
+The free vcpus is (8 - 2) * 5 - 16 = 14.
+
+.. _Placement helper: http://specs.openstack.org/openstack/watcher-specs/specs/train/approved/support-placement-api.html
+.. _list resource provider inventories: https://developer.openstack.org/api-ref/placement/?expanded=list-resource-provider-inventories-detail#list-resource-provider-inventories
+.. _list resource provider usages: https://developer.openstack.org/api-ref/placement/?expanded=list-resource-provider-usages-detail
+
+Compute Data Model
+------------------
+
+CDM(Compute Data Model) will be built when creating audit and updated
+when receiving Nova notifications. So when building and updating CDM
+we need to get resource information from Placement API.
+
+Alternatives
+------------
+
+None
+
+Data model impact
+-----------------
+
+None
+
+REST API impact
+---------------
+
+None
+
+Security impact
+---------------
+
+None
+
+Notifications impact
+--------------------
+
+None
+
+Other end user impact
+---------------------
+
+None
+
+Performance Impact
+------------------
+
+None
+
+Other deployer impact
+---------------------
+
+None
+
+Developer impact
+----------------
+
+None
+
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  licanwei
+
+Work Items
+----------
+
+* Add new fields to Watcher ComputeNode
+* Update compute collector
+* Update the processing about Nova notifications
+
+
+Dependencies
+============
+
+None
+
+
+Testing
+=======
+
+Add unit test
+
+
+Documentation Impact
+====================
+
+None
+
+
+References
+==========
+
+https://developer.openstack.org/api-ref/compute/
+
+https://developer.openstack.org/api-ref/placement/
+
+
+History
+=======
+
+
+.. list-table:: Revisions
+   :header-rows: 1
+
+   * - Release Name
+     - Description
+   * - Train
+     - Introduced
+