Merge "Narrow the list of ResourceProviders"
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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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Resource Providers - Filtered Resource Providers by Request
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===========================================================
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https://blueprints.launchpad.net/nova/+spec/resource-providers-get-by-request
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This blueprint aims to modify the POST method of the resource_providers REST
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resource so that it returns a list of resource providers that can support
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the list of requested resource classes.
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Problem description
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===================
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There is currently no way to get a list of resource providers that can fulfill
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a set of requested resources by verifying that the respective inventories can
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support the existing allocation plus the requested overhead.
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That work is a necessary prerequisite for the scheduler being able to call the
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placement API in order to narrow the list of acceptable hosts before calling
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the filters.
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Use Cases
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----------
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None.
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Proposed change
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===============
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We propose to change the existing /resource_providers REST resource to
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support a method providing a request body that would describe a list of
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requested amounts of resource classes and would return a list of resource
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providers supporting those amounts.
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To be clear, the math for knowing whether a resource provider is acceptable
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would be, for each resource class, take the related inventory, lookup the
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allocations against that inventory and make sure that the amount of free
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resource for the inventory is more or equal than the requested amount, with
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respect to the defined allocation ratio and the reserved size.
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Alternatives
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------------
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There can be many ways to provide a solution for getting a list of resource
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providers but given we prefer to review the implementation rather than
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nitpicking which HTTP method or which REST resource could be the best, I
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prefer to add a disclaimer below.
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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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.. warning ::
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The following REST API proposal is a possible solution that will be reviewed
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during the implementation. That means that the REST resource or the HTTP
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method could be eventually different in the Nova tree, implying that this
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spec would be amended in a later change.
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The following new REST API call will be modified:
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`POST /resource_providers`
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*************************
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The POST method for that /resource_providers REST resource will now accept
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a new query string in the URI called 'request' that will return a list of
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all the resource providers accepted a list of resource requirements.
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Example::
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POST /resource_providers?request
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The body of the request must match the following JSONSchema document::
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{
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"type": "object",
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"properties": {
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"resources": {
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"type": "object",
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"patternProperties": {
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"^[0-9a-fA-F-]+$": {
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"type": "object",
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"patternProperties": {
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"^[A-Z_]+$": {"type": "integer"}
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}
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},
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"additionalProperties": false
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}
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},
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"required": [
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"resources"
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]
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"additionalProperties": False
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}
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For example, a request body asking for VCPUs and RAM would look like::
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POST /resource_providers?request
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{
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"resources": {
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"VCPU": 2,
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"MEMORY_MB": 1024
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}
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}
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The response would be::
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200 OK
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Content-Type: application/json
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{
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"resource_providers": [
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{
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"uuid": "b6b065cc-fcd9-4342-a7b0-2aed2d146518",
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"name": "RBD volume group",
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"generation": 12,
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"links": [
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{
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"rel": "self",
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"href": "/resource_providers/b6b065cc-fcd9-4342-a7b0-2aed2d146518"
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},
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{
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"rel": "inventories",
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"href": "/resource_providers/b6b065cc-fcd9-4342-a7b0-2aed2d146518/inventories"
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},
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{
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"rel": "aggregates",
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"href": "resource_providers/b6b065cc-fcd9-4342-a7b0-2aed2d146518/aggregates"
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},
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{
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"rel": "usages",
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"href": "resource_providers/b6b065cc-fcd9-4342-a7b0-2aed2d146518/usages"
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}
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]
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},
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{
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"uuid": "eaaf1c04-ced2-40e4-89a2-87edded06d64",
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"name": "Global NFS share",
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"generation": 4,
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"links": [
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{
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"rel": "self",
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"href": "/resource_providers/eaaf1c04-ced2-40e4-89a2-87edded06d64"
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},
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{
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"rel": "inventories",
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"href": "/resource_providers/eaaf1c04-ced2-40e4-89a2-87edded06d64/inventories"
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},
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{
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"rel": "aggregates",
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"href": "resource_providers/eaaf1c04-ced2-40e4-89a2-87edded06d64/aggregates"
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},
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{
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"rel": "usages",
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"href": "resource_providers/eaaf1c04-ced2-40e4-89a2-87edded06d64/usages"
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}
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]
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}
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]
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}
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In case a requested resource class doesn't exist, a HTTP400 will be returned.
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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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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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bauzas
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Other contributors:
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cdent
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jaypipes
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Work Items
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----------
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* Write the math
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* Expose the API change
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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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Gabbi functional tests will cover that.
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Documentation Impact
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====================
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Of course, we should amend the docs that we need to write anyway.
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References
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==========
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None.
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