Decommission of specific node
When facing issues with a cluster it can be useful to remove an specific instance. The way that Sahara is constructed today allows the user to scale a cluster down but it will choose a random instance from the selected node group to be removed. We want to give the users the opportunity to choose which instance(s) he/she would like to remove from the cluster. Change-Id: I885f0583b97c29abb71888114597a7da8deaf4b3
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Telles Nobrega
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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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Decommission of specific instance
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=================================
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https://blueprints.launchpad.net/sahara/+spec/decommission-specific-instance
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When facing issues with a cluster it can be useful to remove an specific
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instance. The way that Sahara is constructed today allows the user to scale a
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cluster down but it will choose a random instance from the selected node group
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to be removed. We want to give the users the opportunity to choose which
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instance(s) he/she would like to remove from the cluster.
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Problem description
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===================
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Users may need to remove specific node to make cluster healthier. This is not
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possible today.
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Proposed change
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===============
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We will add the possibility for the user to choose the specific instance to
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remove from the cluster.
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After selecting the node group from which the instance will be removed the user
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will be allowed to choose the instance or instances to be removed.
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We will also allow wildcard removal, if the user wants to randomly select the
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instance he can just leave it blank as well as if more than one instance is
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being deleted the user will be able to choose each instance to be deleted or
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just a subset and Sahara will choose the rest.
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Alternatives
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------------
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Keep randomly selecting instance to be scaled down.
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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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We will change the body request for scale cluster.
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Currently the body should be like this:
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{
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"add_node_groups": [
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{
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"count": 1,
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"name": "b-worker",
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"node_group_template_id": "bc270ffe-a086-4eeb-9baa-2f5a73504622"
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}
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],
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"resize_node_groups": [
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{
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"count": 4,
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"name": "worker"
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}
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]
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}
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We will change the second part to support an extra parameter:
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{
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"add_node_groups": [
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{
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"count": 1,
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"name": "b-worker",
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"node_group_template_id": "bc270ffe-a086-4eeb-9baa-2f5a73504622"
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}
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],
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"resize_node_groups": [
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{
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"count": 4,
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"name": "worker",
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"instances": ["instance_id1", "instance_id2"]
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}
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]
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}
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In case the user does not specify instances to be removed the parameter will
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not be passed and we will act on removing with the current approach.
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Other end user impact
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---------------------
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CLI command will have a new option to select instances.
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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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Sahara-image-elements impact
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----------------------------
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None
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Sahara-dashboard / Horizon impact
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---------------------------------
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We will need to add a place for user to select the instances to be removed. It
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can be after the NG selection and we add the number of selector of instances to
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be removed with the option to leave it blank.
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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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Telles Nobrega
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Other contributors:
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None
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Work Items
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----------
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* Add the possibility to select an instance when scaling down
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* Add CLI option to select instances to be removed
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* Add UI option to select instances to be removed
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* Unit tests
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* Documentation
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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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Unit tests will be needed.
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Documentation Impact
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====================
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Nothing out of the ordinary, but important to keep in mind both user and
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developer perspective.
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References
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==========
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None
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