aea4693153
Implements:blueprint cluster-maintaining Change-Id: I942b793a3182d81981bb817a6e8c970459a16e43
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3.3 KiB
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147 lines
3.3 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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Host maintenance strategy
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==========================
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https://blueprints.launchpad.net/watcher/+spec/cluster-maintaining
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Problem description
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===================
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Sometimes we need to maintain compute nodes, update hardware or software,
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and so on, without interrupting user's applications.
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Use Cases
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---------
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As an openstack operator, sometimes I want to maintain one compute node
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without interrupting user's applications.
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Proposed change
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===============
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There will be a new goal and strategy for cluster-maintenance.
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* Add one new goal - "Cluster Maintenance"
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* Add one new strategy for this goal - "Host Maintenance"
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The new strategy executes as follows
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* First, get the compute node which needs maintenance. This input parameter
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is provided by the administrator. Call change_nova_service_state action
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to set the maintaining node in "maintaining" state (disabled with
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disable_reason 'watcher_maintaining').
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* Then, call migrate action to migrate all instances on the maintaining node
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to other nodes. Migrate active instances use "live-migrate" and
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others use "cold-migrate". Calculate free cpus/memory/disk of a node
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to determine whether one instance or all instances from the maintaining node
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can migrate to.
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This strategy just consider how to migrate all instances of the
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maintaining node, further optimization rely on other strategies.
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There are two methods to migrate the instances of the maintaining node:
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Method No.1, migrate all instances on the maintaining node intensively to
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one unused host.The 'unused' host means disable but not power-off node
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for Watcher. If there are more than one "unused" hosts, choose one from
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them by random.
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(This method won't result in more VMs migration among other hosts.)
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Method No.2, just migrate all instances on the maintaining node dispersedly
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to other nodes.
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Method No.1 is priority. Only if Method No.1 fails, Method No.2 will
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execute. If both methods fail, this audit fails and raise exception with
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no solution produced.
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After the maintenance finished, the administrator needs to activate the
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maintaining node by cli 'nova service-enable' to change the node's state
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from "maintaining" to "enabled" manually, which will make the compute node
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rejoin into compute resource.
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Alternatives
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------------
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None
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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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Implementation
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==============
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Assignee(s)
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-----------
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Primary assignee:sue
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Work Items
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----------
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* Add strategy and goal for cluster_maintenance
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* Update change_nova_service_state action, to make it available to
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maintain one compute node.
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Dependencies
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============
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https://blueprints.launchpad.net/watcher/+spec/extend-node-status
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Testing
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=======
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Unit tests
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Documentation Impact
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====================
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A documentation explaining how to use this new optimization strategy.
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References
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==========
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None
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History
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=======
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None
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