Merge "Support multiple store of Glance"
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Zuul
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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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Support multiple stores of Glance
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=================================
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https://blueprints.launchpad.net/nova/+spec/support-glance-multiple-backend
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This blueprint proposed to support the multiple backend of glance.
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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 case of Nova snapshot or backup, if no changes are made to Nova, even if
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multiple stores are configured then the snapshot or backup image will be
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uploaded to default store. This will not cause any issue unless Nova is using
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ceph as a backend and glance has configured ceph store as well and default
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store in glance is not ceph. This will affect nova's ability to use ceph
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backend for uploading snapshots or backup images in more efficient way.
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Use Cases
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---------
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1. Operator wants to upload all the snapshot or backup images to one
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specific/dedicated store in Glance.
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2. Fast snapshot using ceph even ceph is not a default store in glance.
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Proposed change
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===============
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In case if instance is created using image then it stores the image uuid as
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'image_ref'. When instance snapshot or backup is requested nova should
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pass the 'image_ref' as a header 'X-OpenStack-Base-Image-Ref' to glance, so
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that glance will identify in which store the base image is stored and use that
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same store to upload the instance snapshot or instance backup.
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In case if instance is created using volume then the snapshot or backup image
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should be uploaded to default store configured in Glance.
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Alternatives
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------------
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* Add a new microversion to snapshot and backup API to support configuring to
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upload the snapshot/backup image to specific store. I am proposing to add
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new --store option to snapshot and backup API where user can specify to
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which store snapshot/backend image will be uploaded. If --store option
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is not specified then the image will be uploaded to default store.
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If user chooses the 'store' which is not configured in
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glance then glance will return with 404 NotFound error and the image which
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is created in 'queued' state while 'snapshot' or 'backup' operation will
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be deleted during the cleanup operation. The alternate way is, In the
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beginning before creating queued image, validate the 'store' specified by
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end user using '/v2/info/stores' discovery call of glance. If specified
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'store' is not present in the discovery response then whole operation will
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be skipped with 404 response to end user.
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End user can identify available 'stores' in glance using
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'GET $IMAGE_API_URL/v2/info/stores' discovery call. It will return the
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list of stores configured at glance side. The "id" field from the
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discovery response represents the configured store. Following is the
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example of discover '/v2/stores/info' response call::
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GET $IMAGE_API_URL/v2/info/stores
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{
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"stores": [
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{
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"id":"reliable",
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"description": "Reliable filesystem store"
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},
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{
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"id":"fast",
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"description": "Fast access to rbd store",
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"default": true
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},
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{
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"id":"cheap",
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"description": "Less expensive rbd store"
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}
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]
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}
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For example glance has two file stores configured as 'file_1', 'file_2' and
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'file_1' is set as default store then at present scenario all images of
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'snapshot'or 'backup' operation will always be uploaded to 'file_1' store of
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glance.
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* Add a new configuration option 'store' under 'glance' section to
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upload all the snapshot/backup images to specified/dedicated store. If this
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option is not defined then all the snapshot/backup images will be uploaded to
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default store. This solution will be efficient if operator doesn't want to
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expose the use of uploading snapshot image to specific store to end user.
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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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None
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Developer impact
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----------------
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None
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Upgrade 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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abhishek-kekane
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Feature Liaison
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---------------
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Feature liaison:
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Liaison Needed
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Work Items
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----------
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* Change glanceclient in nova to pass 'X-OpenStack-Base-Image-Ref' header
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to upload call.
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* Add related tests
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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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* 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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None
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References
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==========
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.. [1] https://docs.openstack.org/glance/train/admin/multistores.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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* - Release Name
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- Description
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* - Ussuri
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- Introduced
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