Copy volume to image in multiple stores of glance
Change-Id: Ic7f259c3af6bd691e6d24ed180430e760d28eba8 Implements: copy-image-in-multiple-stores
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Abhishek Kekane
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specs/ussuri/copy-image-in-multiple-stores.rst
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specs/ussuri/copy-image-in-multiple-stores.rst
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..
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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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Copy volume to image in multiple stores of glance
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=================================================
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https://blueprints.launchpad.net/cinder/+spec/copy-image-in-multiple-stores
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This specs propose to send base image reference to glance on volume
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upload to image API.
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Problem description
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===================
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In Train, Glance has added the ability to configure multiple stores
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[1]_. This way an operator can configure more than one of similar or
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different kind of stores and use one as a default store. If a store
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is not specified at the time of uploading an image then the image
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will be stored in default store.
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In Train, I have proposed a spec [2]_ where cinder can specify the glance
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store via the volume-type. The store specified in volume-type will be
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passed to glance using `x-image-meta-store` header. Even operator
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specifies the glance store identifier in volume-type it will only allow
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volume image to be uploaded to single specified store and does not allow
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for co-location of the image. Also, it depends on the operator configuring
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the volume-type extra-specs to define a preferred Glance store; if the
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operator doesn't take this step, all uploads go to the default Glance store.
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Use Cases
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=========
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1. At the moment, if cloud provider decided to upgrade their cloud to Train
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release to use the ability of glance of configuring multiple store and the
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base image from which volume is created resides in multiple stores
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of glance, then if the operator has not defined a glance store in the
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volume-type extra specs, the image created from volume will always
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be uploaded to default store and there is no way to replicate/copy these
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image bits to all the stores where base image is uploaded. As a result,
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operators today need to perform a number of manual steps in order
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to replicate/copy image bits on glance stores despite using the
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'enabled_backends' configuration option. For this purpose, he/she need
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to manually copy the newly created image from volume in all stores and
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register these others locations URL with the image using the glance API.
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Proposed change
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===============
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When a volume is created from an image, Cinder currently stores the
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image_uuid in the volume_image_metadata. When Cinder upload volume to
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image is requested cinder should pass the 'image_uuid' as a header
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'x-openstack-base-image-ref' to glance, so that glance can identify the
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store(s) in which the original image is located. Cinder is also storing
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this glance store information in volume types [2]_, where the store
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identifier associated with volume-type will be passed as a header
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'x-image-meta-store' to glance to upload the image created from volume to
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that specific store.
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If a volume is created from an image and Cinder passes both the
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'x-image-meta-store' and 'x-openstack-base-image-ref' headers, Glance will
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ignore the 'x-openstack-base-image-ref' header and will use the store_id
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specified in the 'x-image-meta-store' header.
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If volume is not bootable and store information is available in
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volume type then glance will use store associated with volume type to upload
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the image created from volume.
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If volume is not bootable and store information is not available in
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volume type then glance will use 'default store' to upload the image
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created from volume.
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Alternatives
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------------
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Continue with passing store information using volume types [2]_.
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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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Active/Active HA 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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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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whoami-rajat
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Other contributors:
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abhishek-kekane
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Work Items
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----------
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* Pass image uuid stored in 'volume_image_metadata' as header to glance
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* Add related tests
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Dependencies
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============
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* Depends on implementation of 'Support Glance multiple stores' [2]_.
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Testing
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=======
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* Add related unittest
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* Add related functional test
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* Add tempest tests
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Documentation Impact
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====================
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Operators documentation should be updated according to spec implementation.
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References
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==========
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.. [1] https://docs.openstack.org/glance/rocky/admin/multistores.html
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.. [2] http://specs.openstack.org/openstack/cinder-specs/specs/train/support-glance-multiple-backend.html
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