XenAPI: add common os-xenapi libary
xenapi is currenly involved in several OpenStack projects(e.g. nova, neutron, ceilometer) and may be involved in other projects in the future. By creating a new common project to hold the common xenapi modules, it will help to reduce the code duplication between these projects; and also making it easier to maintain, review and propose new changes to current and future projects. Change-Id: Ib9b06465ff2162d1f56196b1b2f1ce7a5bd45cfc Blueprint: add-os-xenapi-library
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Jianghua Wang
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specs/ocata/approved/add-os-xenapi-library.rst
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specs/ocata/approved/add-os-xenapi-library.rst
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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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Add os-xenapi library
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=====================
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https://blueprints.launchpad.net/nova/+spec/add-os-xenapi-library
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XenAPI is currenly involved in several OpenStack projects (e.g. Nova,
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Neutron, Ceilometer[1]) and may be involved in other projects in the future.
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By creating a new common project to hold the common XenAPI code, it will
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help to reduce the duplication between these projects; and also making
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it easier to maintain, review and propose new changes to current and future
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projects.
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Problem description
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===================
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There are serveral almost identical XenAPI classes existing in different
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projects.
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We can refactor these classes to the common project os-xenapi. So it
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will reduce the code duplication and make it easier to maintain.
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Specially there is currently duplication among session management and
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XAPI plugins.
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Further, these XAPI plugins cannot conform to new Python standards as they
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run in XenServer's dom0 where there is only Python2.4 (XenServer 6.5 and
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older releases). It makes things tricky when modify plugins and also bring
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trouble to add unit tests for these plugins in a way compatible with the
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rest of Nova.
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Use Cases
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---------
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This blueprint impacts Developers and Reviewers.
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Developers will be able to submit xenapi related commits directly to
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os-xenapi.
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Nova reviewers will not have to review low level xenapi related code.
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Proposed change
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===============
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The primary changes that needs to be done on nova are as follows:
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* Copy the classes from nova/virt/xenapi/client/ to os-xenapi.
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* Copy the plugins from ``plugins/xenserver/xenapi/etc/xapi.d/plugins``
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to os-xenapi.
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* Add os-xenapi in requirements.txt
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* Replace all ``nova.virt.xenapi.client`` imports used by the XenAPI
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driver with "os_xenapi.client".
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* Improve interface between Nova and os-xenapi so dom0 plugins are
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invoked through python calls to os-xenapi so version consistency is
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provided using os-xenapi rather than an explicit API check against
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the plugins in dom0.
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Alternatives
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------------
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Continue to duplicate session handling and XenServer plugins between
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OpenStack projects.
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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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None
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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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None
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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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os-xenapi dependency will have to be installed in order for the XenAPI
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driver to be used.
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Developer impact
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----------------
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In a typical scenario, a blueprint implementation for the Nova XenAPI
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driver may require 2 parts:
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* os-xenapi release, adding xenapi related utils required in order to
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implement the blueprint.
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* nova commit, implementing the blueprint and using the changes made in
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os-xenapi.
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If a Nova commit needs changes in os-xenapi, we must release a new version
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of os-xenapi. The Nova change needs to bump Nova's requirements file so
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we pull in the required changes and it must depends-on the global
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requirements change that bumps the global minimal version for os-xenapi.
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If we need to backport a Nova fix to a pre-os-xenapi world and this fix
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depends on changes which are merged in os-xenapi, the Nova backport commit
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should also cover the needed changes which are equivalent of the os-xenapi
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changes.
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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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Huan Xie <huan.xie@citrix.com>
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Other contributors:
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Jianghua Wang <jianghua.wang@citrix.com>
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Bob Ball <bob.ball@citrix.com>
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Work Items
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----------
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As described in the 'Proposed change' section.
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Dependencies
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============
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The os-xenapi library must be implemented.
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Testing
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=======
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* os-xenapi will contain unit tests for all moved functionality
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* Citrix's Xenserver CI will continue to test XenAPI changes when
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os-xenapi is in use.
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Documentation Impact
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====================
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None
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References
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==========
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[1] XenAPI support in Ceilometer: https://specs.openstack.org/openstack/ceilometer-specs/specs/juno/xenapi-support.html
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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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* - Ocata
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- Introduced
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