Fix tag attribute disappearing
In the context of virtual device role tagging at instance boot time, a bug has caused the tag attribute to no longer be accepted starting with version 2.33 for block_device_mapping_v2 and starting with version 2.37 for networks. In other words, block devices can only be tagged in 2.32 and network interfaces between 2.32 and 2.36 inclusively. This spec introduces a new API microversion that re-adds the tag attribute to both block_device_mapping_v2 and networks. APIImpact Change-Id: I37cec158c6f998143842ad44f739fe2031d75eef Implements: blueprint fix-tag-attribute-disappearing
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Artom Lifshitz
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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==============================
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Fix tag attribute disappearing
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==============================
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https://blueprints.launchpad.net/nova/+spec/fix-tag-attribute-disappearing
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In the context of virtual device role tagging at instance boot time, a bug [1]_
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has caused the tag attribute to no longer be accepted starting with version
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2.33 for block_device_mapping_v2 and starting with version 2.37 for networks.
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In other words, block devices can only be tagged in 2.32 and network interfaces
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between 2.32 and 2.36 inclusively. This spec introduces a new API microversion
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that re-adds the tag attribute to both block_device_mapping_v2 and networks.
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Problem description
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===================
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For block_device_mapping_v2, the problem stems from the use of the equality
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comparison in [2]_. It causes the Nova API to accept the tag attribute only in
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microversion 2.32. The intent was of course to support tags in all versions
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greater than or equal to 2.32, but the implementation mistake was missed by the
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author, the reviewers, and tests.
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In the case of networks, microversion 2.37 introduced a new choice for the
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network item in the instance boot request body [3]_. In addition to the
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previously allowed dictionary containing one of port, uuid or fixed_ip, a new
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string item - either 'auto' or 'none' - became accepted. When writing the
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schema for this change, the previous schema had to be copied and included as
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one of the two choices. It is this copying that introduced the error: the tag
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item was not copied along with the rest of the schema.
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Use Cases
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---------
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As an end user, I want block device role tagging to continue working beyond
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microversion 2.32.
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As an end user, I want network interface role tagging to continue working
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beyond microversion 2.37.
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Proposed change
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===============
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This spec proposes to document the bug in api-ref and reno while at the same
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time reintroducing the tag attribute to both block_device_mapping_v2 and
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networks in a new API microversion.
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In order to prevent future bugs of the same kind, the microversion will be
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passed to extensions as an APIVersionRequest object and APIVersionRequest's
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__eq__ operator will be removed. This will dissuade future code from doing
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version equality comparisons.
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One of the reasons the original bug was missed is that functional tests are
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only run on the specific microversion they are concerned with. That is, the
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tests for 2.32 are only run against 2.32. While having every test class for a
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new microversion inherit from the test class for the previous microversion (for
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example, ServersSampleJson232Test inheriting from ServersSampleJson231Test) is
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wasteful, this spec proposes to run all of the API samples tests against
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2.latest. This will ensure no accidental breakage at any single point in the
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microversion timeline.
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Alternatives
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------------
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Because the tag attribute needs to be reintroduced to the API, a new
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microversion is necessary, as per Nova project policy. There are therefore no
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alternatives.
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Data model impact
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-----------------
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None.
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REST API impact
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---------------
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This spec impacts only the body of the POST /servers method. The tag attribute
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is re-added to the networks and block_device_mapping_v2 items.
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Networks example::
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{
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"server": {
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"name": "nic-tagging",
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"imageRef": "70a599e0-31e7-49b7-b260-868f441e862b",
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"flavorRef": "http://openstack.example.com/flavors/1",
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"networks": {
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"uuid": "a0ef4e02-9150-418c-b4cf-cf4a86e92bf1",
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"tag": "nic1"
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}
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}
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}
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Block device mapping example::
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{
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"server": {
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"name": "nic-tagging",
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"imageRef": "70a599e0-31e7-49b7-b260-868f441e862b",
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"flavorRef": "http://openstack.example.com/flavors/1",
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"block_device_mapping_v2": [{
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"boot_index": "0",
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"uuid": "ac408821-c95a-448f-9292-73986c790911",
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"source_type": "image",
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"volume_size": "25",
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"destination_type": "volume",
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"delete_on_termination": true,
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"tag": "disk1"
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}]
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}
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}
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Security impact
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---------------
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None.
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Notifications impact
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--------------------
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None.
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Other end user impact
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---------------------
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Python-novaclient will be updated to work with the disappearance of the tag
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attribute in 2.33 and 2.37. It will also be updated to use the new microversion
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that reintroduces the tag attribute.
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Performance Impact
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------------------
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None.
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Other deployer impact
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---------------------
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None.
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Developer impact
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----------------
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None.
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Implementation
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==============
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Assignee(s)
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-----------
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Primary assignee:
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Artom Lifshitz (notartom)
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Other contributors:
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None
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Work Items
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----------
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* Implement a new API microversion that reintroduces the tag attribute to
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networks and block_device_mapping_v2.
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* When calling extensions, pass the version as an APIVersionRequest object
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instead of a string.
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* Run all API samples tests against 2.latest, except where an API feature has
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been removed.
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Dependencies
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============
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None.
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Testing
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=======
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A functional test will be added for the new API microversion. The existing
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Tempest test [4]_ will be modified to test 2.32 and the new microversion that
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reintroduces the tag attribute.
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Documentation Impact
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====================
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The API reference will be updated to document the bug as well as the new API
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microversion. Release notes will do the same.
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References
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==========
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.. [1] https://bugs.launchpad.net/nova/+bug/1658571
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.. [2] https://review.openstack.org/#/c/304510/64/nova/api/openstack/compute/block_device_mapping.py@77
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.. [3] https://review.openstack.org/#/c/316398/37/nova/api/openstack/compute/schemas/servers.py
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.. [4] https://review.openstack.org/#/c/305120/
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History
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=======
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.. list-table:: Revisions
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:header-rows: 1
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* - Release Name
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- Description
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* - Ocata
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- Introduced
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