Add node groups documentation
Add documentation with examples for the life cycle of creating/resizing/deleting a node group. Change-Id: Ie34ebef6b46fa6223119696671cd1ac23d4ff855
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Thomas Hartland
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@ -36,6 +36,7 @@ created and managed by Magnum to support the COE's.
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#. `Kubernetes External Load Balancer`_
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#. `Rolling Upgrade`_
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#. `Keystone Authentication and Authorization for Kubernetes`_
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#. `Node Groups`_
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Overview
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========
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@ -3411,3 +3412,8 @@ Keystone Authentication and Authorization for Kubernetes
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========================================================
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.. include:: k8s-keystone-authN-authZ.rst
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Node Groups
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===========
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.. include:: node-groups.rst
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@ -0,0 +1,147 @@
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Node groups can be used to create heterogeneous clusters.
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This functionality is only supported for Kubernetes clusters.
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When a cluster is created it already has two node groups,
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``default-master`` and ``default-worker``.
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::
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$ openstack coe cluster list
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+--------------------------------------+------+-----------+------------+--------------+-----------------+---------------+
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| uuid | name | keypair | node_count | master_count | status | health_status |
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+--------------------------------------+------+-----------+------------+--------------+-----------------+---------------+
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| ef7011bb-d404-4198-a145-e8808204cde3 | kube | default | 1 | 1 | CREATE_COMPLETE | HEALTHY |
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+--------------------------------------+------+-----------+------------+--------------+-----------------+---------------+
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$ openstack coe nodegroup list kube
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+--------------------------------------+----------------+-----------+----------------------------------------+------------+-----------------+--------+
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| uuid | name | flavor_id | image_id | node_count | status | role |
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+--------------------------------------+----------------+-----------+----------------------------------------+------------+-----------------+--------+
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| adc3ecfa-d11e-4da7-8c44-4092ea9dddd9 | default-master | m1.small | Fedora-AtomicHost-29-20190820.0.x86_64 | 1 | CREATE_COMPLETE | master |
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| 186e131f-8103-4285-a900-eb0dcf18a670 | default-worker | m1.small | Fedora-AtomicHost-29-20190820.0.x86_64 | 1 | CREATE_COMPLETE | worker |
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+--------------------------------------+----------------+-----------+----------------------------------------+------------+-----------------+--------+
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The ``default-worker`` node group cannot be removed or reconfigured, so
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the initial cluster configuration should take this into account.
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Create a new node group
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-----------------------
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To add a new node group, use ``openstack coe nodegroup create``. The
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only required parameters are the cluster ID and the name for the new
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node group, but several extra options are available.
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Roles
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+++++
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Roles can be used to show the purpose of a node group, and multiple node
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groups can be given the same role if they share a common purpose.
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::
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$ openstack coe nodegroup create kube test-ng --node-count 1 --role test
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When listing node groups, the role may be used as a filter:
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::
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$ openstack coe nodegroup list kube --role test
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+--------------------------------------+---------+-----------+----------------------------------------+------------+--------------------+------+
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| uuid | name | flavor_id | image_id | node_count | status | role |
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+--------------------------------------+---------+-----------+----------------------------------------+------------+--------------------+------+
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| b4ab1fcb-f23a-4d1f-b583-d699a2f1e2d7 | test-ng | m1.small | Fedora-AtomicHost-29-20190820.0.x86_64 | 1 | CREATE_IN_PROGRESS | test |
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+--------------------------------------+---------+-----------+----------------------------------------+------------+--------------------+------+
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The node group role will default to “worker” if unset, and the only
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reserved role is “master”.
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Role information is available within Kubernetes as labels on the nodes.
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::
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$ kubectl get nodes -L magnum.openstack.org/role
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NAME STATUS AGE VERSION ROLE
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kube-r6cyw4bjb4lr-master-0 Ready 5d5h v1.16.0 master
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kube-r6cyw4bjb4lr-node-0 Ready 5d5h v1.16.0 worker
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kube-test-ng-lg7bkvjgus4y-node-0 Ready 61s v1.16.0 test
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This information can be used for scheduling, using a `node
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selector <https://kubernetes.io/docs/concepts/configuration/assign-pod-node/#step-two-add-a-nodeselector-field-to-your-pod-configuration>`__.
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.. code:: yaml
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nodeSelector:
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magnum.openstack.org/role: test
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The label ``magnum.openstack.org/nodegroup`` is also available for
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selecting a specific node group.
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Flavor
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++++++
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The node group flavor will default to the minion flavor given when
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creating the cluster, but can be changed for each new node group.
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::
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$ openstack coe nodegroup create ef7011bb-d404-4198-a145-e8808204cde3 large-ng --flavor m2.large
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This can be used if you require nodes of different sizes in the same
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cluster, or to switch from one flavor to another by creating a new node
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group and deleting the old one.
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Availability zone
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+++++++++++++++++
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To create clusters which span more than one availability zone, multiple
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node groups must be used. The availability zone is passed as a label to
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the node group.
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::
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$ openstack coe nodegroup create kube zone-a --labels availability_zone=zone-a --labels ...
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$ openstack coe nodegroup create kube zone-b --labels availability_zone=zone-b --labels ...
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$ openstack coe nodegroup create kube zone-c --labels availability_zone=zone-c --labels ...
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Where ``--labels ...`` are the rest of the labels that the cluster was
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created with, which can be obtained from the cluster with this script:
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::
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$ openstack coe cluster show -f json <CLUSTER_ID> |
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jq --raw-output '.labels | to_entries |
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map("--labels \(.key)=\"\(.value)\"") | join(" ")'
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Zone information is available within the cluster as the label
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``topology.kubernetes.io/zone`` on each node, or as the now deprecated
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label ``failure-domain.beta.kubernetes.io/zone``.
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From Kubernetes 1.16 and onwards it is possible to `balance the number
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of pods in a deployment across availability
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zones <https://kubernetes.io/docs/concepts/workloads/pods/pod-topology-spread-constraints/>`__
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(or any other label).
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Resize
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------
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Resizing a node group is done with the same API as resizing a cluster,
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but the ``--nodegroup`` parameter must be used.
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::
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$ openstack coe cluster resize kube --nodegroup default-worker 2
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Request to resize cluster ef7011bb-d404-4198-a145-e8808204cde3 has been accepted.
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As usual the ``--nodes-to-remove`` parameter may be used to remove
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specific nodes when decreasing the size of a node group.
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Delete
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------
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Any node group except the default master and worker node groups can be
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deleted, by specifying the cluster and nodegroup name or ID.
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::
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$ openstack coe nodegroup delete ef7011bb-d404-4198-a145-e8808204cde3 test-ng
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