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a6cd9bac16
K8s 1.6 has affinity/antiaffinity funtionalities as a beta feature. This means we don't need to declare them using annotations. This commit switches usages of affinity to 1.6 syntax. Change-Id: Ia68f4ab28a018617bd44b1295fea58cd30eb4a39
103 lines
3.6 KiB
ReStructuredText
103 lines
3.6 KiB
ReStructuredText
Labels
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------
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This project uses ``nodeSelectors`` as well as ``podAntiAffinity`` rules
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to ensure resources land in the proper place within Kubernetes. Today,
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OpenStack-Helm employs four labels:
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- ceph-storage: enabled
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- openstack-control-plane: enabled
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- openstack-compute-node: enabled
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- openvswitch: enabled
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NOTE: The ``openvswitch`` label is an element that is applicable to both
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``openstack-control-plane`` as well as ``openstack-compute-node`` nodes.
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Ideally, you would eliminate the ``openvswitch`` label if you could
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simply do an OR of (``openstack-control-plane`` and
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``openstack-compute-node``). However, Kubernetes ``nodeSelectors``
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prohibits this specific logic. As a result of this, a third label that
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spans all hosts is required, which in this case is ``openvswitch``. The
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Open vSwitch service must run on both control plane and tenant nodes
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with both labels to provide connectivity for DHCP, L3, and Metadata
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services. These Open vSwitch services run as part of the control plane
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as well as tenant connectivity, which runs as part of the compute node
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infrastructure.
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Labels are of course definable and overridable by the chart operators.
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Labels are defined in charts by using a ``labels:`` section, which is a
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common convention that defines both a selector and a value:
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::
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labels:
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node_selector_key: openstack-control-plane
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node_selector_value: enabled
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In some cases, such as with the Neutron chart, a chart may need to
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define more then one label. In cases such as this, each element should
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be articulated under the ``labels:`` section, nesting where appropriate:
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::
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labels:
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# ovs is a special case, requiring a special
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# label that can apply to both control hosts
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# and compute hosts, until we get more sophisticated
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# with our daemonset scheduling
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ovs:
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node_selector_key: openvswitch
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node_selector_value: enabled
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agent:
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dhcp:
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node_selector_key: openstack-control-plane
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node_selector_value: enabled
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l3:
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node_selector_key: openstack-control-plane
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node_selector_value: enabled
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metadata:
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node_selector_key: openstack-control-plane
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node_selector_value: enabled
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server:
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node_selector_key: openstack-control-plane
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node_selector_value: enabled
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These labels should be leveraged by ``nodeSelector`` definitions in
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charts for all resources, including jobs:
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::
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...
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spec:
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nodeSelector:
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{{ .Values.labels.node_selector_key }}: {{ .Values.labels.node_selector_value }}
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containers:
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...
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In some cases, especially with infrastructure components, it is
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necessary for the chart developer to provide scheduling instruction to
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Kubernetes to help ensure proper resiliency. The most common examples
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employed today are podAntiAffinity rules, such as those used in the
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``mariadb`` chart. These should be placed on all foundational elements
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so that Kubernetes will not only disperse resources for resiliency, but
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also allow multi-replica installations to deploy successfully into a
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single host environment:
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::
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# alanmeadows: this soft requirement allows single
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# host deployments to spawn several mariadb containers
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# but in a larger environment, would attempt to spread
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# them out
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affinity:
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podAntiAffinity:
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preferredDuringSchedulingIgnoredDuringExecution:
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- podAffinityTerm:
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labelSelector:
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matchExpressions:
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- key: app
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operator: In
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values: ["mariadb"]
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topologyKey: kubernetes.io/hostname
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weight: 10
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