Scale Undercloud with a Minion
During the Train PTG, we identified that scaling the heat-engine and ironic-conductor may be beneficial to improving scale. This spec proposes to create a new undercloud minion node so that an operator can provide additional systems for heat and ironic usages. Change-Id: Ic5a5a785b4102383d7369b3a825fe5d615d381c0 Related-Blueprint: undercloud-minion
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Alex Schultz
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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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Scale Undercloud with a Minion
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==============================
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https://blueprints.launchpad.net/tripleo/undercloud-minion
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In order to improve our scale, we have identified heat-engine and possibly
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ironic-conductor as services that we can add on to an existing undercloud
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deployment. Adding heat-engine allows for additional processing capacity
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when creating and updating stacks for deployment. By adding a new light
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weight minion node, we can scale the Heat capacity horizontally.
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Additionally since these nodes could be more remote, we could add an
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ironic-conductor instance to be able to manage hosts in a remote region
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while still having a central undercloud for the main management.
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Problem Description
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===================
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Currently we use a single heat-engine on the undercloud for the deployment.
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According to the Heat folks, it can be beneficial for processing to have
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additional heat-engine instances for scale. The recommended scaling is out
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rather than up. Additionally by being able to deploy a secondary host, we
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can increase our capacity for the undercloud when additional scale capacity
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is required.
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Proposed Change
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===============
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Overview
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--------
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We are proposing to add a new undercloud "minion" configuration that can be
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used by operators to configure additional instances of heat-engine and
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ironic-conductor when they need more processing capacity. We would also
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allow the operator to disable heat-engine from the main undercloud to reduce
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the resource usage of the undercloud. By removing the heat-engine from the
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regular undercloud, the operator could possibly avoid timeouts on other services
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like keystone and neutron that can occur when the system is under load.
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Alternatives
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------------
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An alternative would be to make the undercloud deployable in a traditional
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HA capacity where we share the services across multiple nodes. This would
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increase the overall capacity but adds additional complexity to the undercloud.
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Additionally this does not let us target specific services that are resource
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heavy.
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Security Impact
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---------------
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The new node would need to have access to the the main undercloud's keystone,
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database and messaging services.
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Upgrade Impact
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--------------
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The new minion role would need to be able to be upgraded by the user.
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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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* This additional minion role may improve heat processing due to the additional
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resource capacity being provided.
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* Locating an ironic-conductor closer to the nodes being managed can improve
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performance by being closer to the systems (less latency, etc).
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Other Deployer Impact
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---------------------
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Additional undercloud role and a new undercloud-minion.conf configuration file
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will be created. Additionally a new option may be added to the undercloud.conf
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to manage heat-engine instalation.
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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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mwhahaha
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Other contributors:
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slagle
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EmilienM
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Work Items
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----------
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Work items or tasks -- break the feature up into the things that need to be
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done to implement it. Those parts might end up being done by different people,
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but we're mostly trying to understand the timeline for implementation.
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python-tripleoclient
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~~~~~~~~~~~~~~~~~~~~
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* New 'openstack undercloud minion deploy' command for installation
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* New 'openstack undercloud minion upgrade' command for upgrades
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* New configuration file 'undercloud-minion.conf' to drive the installation
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and upgrades.
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* New configuration option in 'undercloud.conf' to provide ability to disable
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the heat-engine on the undercloud.
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tripleo-heat-templates
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~~~~~~~~~~~~~~~~~~~~~~
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* New 'UndercloudMinion' role file
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* New environment file for the undercloud minion deployment
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* Additional environment files to enable or disable heat-engine and
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ironic-conductor.
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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 would add a new CI job to test the deployment of the minion node. This job
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will likely be a new multinode job.
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Documentation Impact
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====================
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We will need to document the usage of the undercloud minion installation and
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the specific use cases where this can be beneficial.
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References
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==========
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See the notes from the Train PTG around Scaling.
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* https://etherpad.openstack.org/p/tripleo-ptg-train
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* https://etherpad.openstack.org/p/DEN-tripleo-forum-scale
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