4c1f16b020
This adds the meta-data caching to the compute-agent as discussed in the Operators feedback session. Change-Id: I3e72e3acb84a545853d144dffa73da9707603bee
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2.7 KiB
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139 lines
2.7 KiB
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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 Meta-data Caching
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==========================
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This was discussed at the YVR summit as follow up to issues raised during the
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Operators feedback session.
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Problem description
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===================
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Ceilometer polls regularly via the compute-agent to get resource meta-data'
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for all instances. This polling adds load to Nova, Neutron, and Keystone
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APIs, which at scale causes a significant performance impact. This meta-data
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does not change very often, and the load is likewise often unnecessary.
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Proposed change
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===============
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Lets take advantage of the changes-since parameter in the nova api call.
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We'll start by creating an in-memory cache to store the resource meta-data
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on the initial polling and the time of that polling. Then the compute agent
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will use the changes-since parameter in all subsequent pollings. This will
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reduce the amount of data queried and returned by the Nova API. The results
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of this call will update the cache, and the cache will be used to return
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the data. Also, we should populate the instance flavor and image data in
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the cache as well.
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Alternatives
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------------
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Do nothing
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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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Pipeline 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/Scalability Impacts
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-------------------------------
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Should provide greater overall scalability due to the reduction in API load
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and reduced traffic flows.
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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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jasonamyers
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Other contributors:
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None
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Ongoing maintainer:
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jasonamyers
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Work Items
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----------
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- Implement an in-memory cache in the compute agent.
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- Change compute-agent to populate an in-memory cache.
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- Change compute-agent to use the changes-since parameter in the Nova API call .
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- Change compute-agent to record the polling timestamp in the cache.
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- Change compute-agent to cache the flavor and image metadata as well.
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Future lifecycle
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================
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None
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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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We will need to add tests for meta-data cache flag, API changed-since
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queries, compute-agent cache control, and image/flavor caching.
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Documentation Impact
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====================
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We will need to document the changes to the polling process, the new meta-data
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cache config option, and create new documentation that describes the caching
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work-flow.
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References
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==========
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https://etherpad.openstack.org/p/YVR-ops-ceilometer
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