Add nodes tagging support

This commit proposes to add nodes tagging support in
Ironic.

Change-Id: I399f1afc1c85bf772617e944666088a067060b3f

specs/liberty/nodes-tagging.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
+
+=============
+Nodes tagging
+=============
+
+https://blueprints.launchpad.net/ironic/+spec/nodes-tagging
+
+This blueprint aims to add support for tagging nodes.
+
+Problem description
+===================
+
+Ironic should have tags field for every node, which can be used to
+divide the nodes to some groups. then we can do list by tag to
+get a group of nodes with same properties like hardware specs.
+
+Proposed change
+===============
+
+* Add APIs that allows a user to add, remove, and list tags for a node.
+
+* Add tag filter parameter to node list API to allow searching for nodes
+  based on one or more string tags.
+
+Alternatives
+------------
+
+Current chassis object is kind of an alternative for grouping nodes.
+
+Data model impact
+-----------------
+
+A new `ironic.objects.tags.TagList` object would be added to the
+object model, and will add a `tags` field to the `node` table of
+type `ironic.objects.tags.TagList` that would be populated on-demand
+(i.e. not eager-loaded).
+
+A tag should be defined as a Unicode string no longer than 255 bytes
+in length.
+
+For the database schema, the following table constructs would suffice ::
+
+    CREATE TABLE tags (
+        resource_id INT(11) NOT NULL PRIMARY KEY,
+        tag VARCHAR(255) NOT NULL CHARACTER SET utf8
+        COLLATION utf8_ci PRIMARY KEY
+    );
+
+REST API impact
+---------------
+
+The tag CRUD operations API extension would look like the following:
+
+Return list of tags for a node ::
+
+    GET /v1/nodes/{node_id}/tags
+
+returns ::
+
+    [
+        'tag1',
+        'tag2'
+    ]
+
+Add set of tags on a node ::
+
+    POST /v1/nodes/{node_id}/tags
+
+with request body ::
+
+    [
+        'tag1',
+        'tag2'
+    ]
+
+Add a single tag on a node ::
+
+    PUT /v1/nodes/{node_id}/tags/{tag}
+
+Remove a single tag on a node ::
+
+    DELETE /v1/nodes/{node_id}/tags/{tag}
+
+Get all nodes tags::
+
+    GET /v1/nodes/tags
+
+returns ::
+
+    [
+        'tag1',
+        'tag2',
+        'tag3'
+    ]
+
+The API that would allow searching/filtering of the `GET /v1/nodes`
+REST API call would add a `tag` query parameter:
+
+Get all nodes having a single tag ::
+
+    GET /v1/nodes?tag={tag}
+
+Get all nodes having *both* tag A and tag B::
+
+    GET /v1/nodes?tag={tag_a}&tag={tag_b}
+
+RPC API impact
+--------------
+
+None
+
+State Machine Impact
+--------------------
+
+None
+
+Client (CLI) impact
+-------------------
+
+Add tags CRUD operations commands:
+
+* ironic node-list-tags <node uuid>
+* ironic node-update-tags <node uuid> <op> <tag>
+
+<op> Operation: 'add' or 'remove'
+
+Add tag-list filtering support to node-list command:
+
+* ironic node-list --tag tag1 --tag tag2
+
+multiple --tag will be used to filter results in an
+AND expression.
+
+Driver API impact
+-----------------
+
+None
+
+Nova driver impact
+------------------
+
+The tags information can be used for nova but it's not being
+considered as part of this spec, and may be addressed at a
+later time.
+
+Security impact
+---------------
+
+None
+
+Other end user impact
+---------------------
+
+None
+
+Scalability impact
+------------------
+
+None
+
+Performance Impact
+------------------
+
+None
+
+Other deployer impact
+---------------------
+
+None
+
+Developer impact
+----------------
+
+None
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  niu-zglinux
+
+Work Items
+----------
+
+* Add `tags` table with a migration.
+* Add DB API layer for CRUD operations on node tags.
+* Added DB API layer for node tag-list filtering support.
+* Add Tag, TagList objects and a new tags field to Node object.
+* Add REST API for CRUD operations on node tags.
+* Add REST API for node tag-list filtering support.
+* python-ironicclient additions and modifications.
+
+
+Dependencies
+============
+
+None
+
+
+Testing
+=======
+
+Add unit tests.
+
+
+Upgrades and Backwards Compatibility
+====================================
+
+Add a migration script for DB.
+
+
+Documentation Impact
+====================
+
+Ironic API and python-ironicclient will need to be updated to accompany
+this change.
+
+
+References
+==========
+
+https://blueprints.launchpad.net/nova/+spec/tag-instances