Document using multiple scheduler profiles (#19172)
* Add instructions for using multiple scheduling profiles. Signed-off-by: Aldo Culquicondor <acondor@google.com> * Move scheduling policies and profiles to Reference Signed-off-by: Aldo Culquicondor <acondor@google.com> * Renames and nits Signed-off-by: Aldo Culquicondor <acondor@google.com> * Fix links and grammar Signed-off-by: Aldo Culquicondor <acondor@google.com> * Fix link and flag usage Signed-off-by: Aldo Culquicondor <acondor@google.com>pull/19551/head
Aldo Culquicondor
GitHub
parent
615c7f619f
commit
d1056364e2
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@ -54,14 +54,12 @@ individual and collective resource requirements, hardware / software /
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policy constraints, affinity and anti-affinity specifications, data
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locality, inter-workload interference, and so on.
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## Scheduling with kube-scheduler {#kube-scheduler-implementation}
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### Node selection in kube-scheduler {#kube-scheduler-implementation}
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kube-scheduler selects a node for the pod in a 2-step operation:
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1. Filtering
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2. Scoring
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1. Scoring
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The _filtering_ step finds the set of Nodes where it's feasible to
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schedule the Pod. For example, the PodFitsResources filter checks whether a
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@ -78,105 +76,15 @@ Finally, kube-scheduler assigns the Pod to the Node with the highest ranking.
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If there is more than one node with equal scores, kube-scheduler selects
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one of these at random.
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There are two supported ways to configure the filtering and scoring behavior
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of the scheduler:
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### Default policies
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kube-scheduler has a default set of scheduling policies.
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### Filtering
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- `PodFitsHostPorts`: Checks if a Node has free ports (the network protocol kind)
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for the Pod ports the Pod is requesting.
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- `PodFitsHost`: Checks if a Pod specifies a specific Node by its hostname.
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- `PodFitsResources`: Checks if the Node has free resources (eg, CPU and Memory)
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to meet the requirement of the Pod.
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- `PodMatchNodeSelector`: Checks if a Pod's Node {{< glossary_tooltip term_id="selector" >}}
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matches the Node's {{< glossary_tooltip text="label(s)" term_id="label" >}}.
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- `NoVolumeZoneConflict`: Evaluate if the {{< glossary_tooltip text="Volumes" term_id="volume" >}}
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that a Pod requests are available on the Node, given the failure zone restrictions for
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that storage.
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- `NoDiskConflict`: Evaluates if a Pod can fit on a Node due to the volumes it requests,
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and those that are already mounted.
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- `MaxCSIVolumeCount`: Decides how many {{< glossary_tooltip text="CSI" term_id="csi" >}}
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volumes should be attached, and whether that's over a configured limit.
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- `CheckNodeMemoryPressure`: If a Node is reporting memory pressure, and there's no
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configured exception, the Pod won't be scheduled there.
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- `CheckNodePIDPressure`: If a Node is reporting that process IDs are scarce, and
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there's no configured exception, the Pod won't be scheduled there.
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- `CheckNodeDiskPressure`: If a Node is reporting storage pressure (a filesystem that
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is full or nearly full), and there's no configured exception, the Pod won't be
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scheduled there.
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- `CheckNodeCondition`: Nodes can report that they have a completely full filesystem,
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that networking isn't available or that kubelet is otherwise not ready to run Pods.
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If such a condition is set for a Node, and there's no configured exception, the Pod
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won't be scheduled there.
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- `PodToleratesNodeTaints`: checks if a Pod's {{< glossary_tooltip text="tolerations" term_id="toleration" >}}
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can tolerate the Node's {{< glossary_tooltip text="taints" term_id="taint" >}}.
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- `CheckVolumeBinding`: Evaluates if a Pod can fit due to the volumes it requests.
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This applies for both bound and unbound
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{{< glossary_tooltip text="PVCs" term_id="persistent-volume-claim" >}}.
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### Scoring
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- `SelectorSpreadPriority`: Spreads Pods across hosts, considering Pods that
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belong to the same {{< glossary_tooltip text="Service" term_id="service" >}},
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{{< glossary_tooltip term_id="statefulset" >}} or
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{{< glossary_tooltip term_id="replica-set" >}}.
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- `InterPodAffinityPriority`: Computes a sum by iterating through the elements
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of weightedPodAffinityTerm and adding “weight” to the sum if the corresponding
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PodAffinityTerm is satisfied for that node; the node(s) with the highest sum
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are the most preferred.
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- `LeastRequestedPriority`: Favors nodes with fewer requested resources. In other
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words, the more Pods that are placed on a Node, and the more resources those
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Pods use, the lower the ranking this policy will give.
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- `MostRequestedPriority`: Favors nodes with most requested resources. This policy
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will fit the scheduled Pods onto the smallest number of Nodes needed to run your
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overall set of workloads.
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- `RequestedToCapacityRatioPriority`: Creates a requestedToCapacity based ResourceAllocationPriority using default resource scoring function shape.
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- `BalancedResourceAllocation`: Favors nodes with balanced resource usage.
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- `NodePreferAvoidPodsPriority`: Prioritizes nodes according to the node annotation
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`scheduler.alpha.kubernetes.io/preferAvoidPods`. You can use this to hint that
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two different Pods shouldn't run on the same Node.
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- `NodeAffinityPriority`: Prioritizes nodes according to node affinity scheduling
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preferences indicated in PreferredDuringSchedulingIgnoredDuringExecution.
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You can read more about this in [Assigning Pods to Nodes](https://kubernetes.io/docs/concepts/configuration/assign-pod-node/).
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- `TaintTolerationPriority`: Prepares the priority list for all the nodes, based on
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the number of intolerable taints on the node. This policy adjusts a node's rank
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taking that list into account.
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- `ImageLocalityPriority`: Favors nodes that already have the
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{{< glossary_tooltip text="container images" term_id="image" >}} for that
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Pod cached locally.
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- `ServiceSpreadingPriority`: For a given Service, this policy aims to make sure that
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the Pods for the Service run on different nodes. It favours scheduling onto nodes
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that don't have Pods for the service already assigned there. The overall outcome is
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that the Service becomes more resilient to a single Node failure.
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- `CalculateAntiAffinityPriorityMap`: This policy helps implement
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[pod anti-affinity](/docs/concepts/configuration/assign-pod-node/#affinity-and-anti-affinity).
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- `EqualPriorityMap`: Gives an equal weight of one to all nodes.
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1. [Scheduling Policies](/docs/reference/scheduling/policies) allow you to
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configure _Predicates_ for filtering and _Priorities_ for scoring.
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1. [Scheduling Profiles](/docs/reference/scheduling/profiles) allow you to
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configure Plugins that implement different scheduling stages, including:
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`QueueSort`, `Filter`, `Score`, `Bind`, `Reserve`, `Permit`, and others. You
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can also configure the kube-scheduler to run different profiles.
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{{% /capture %}}
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{{% capture whatsnext %}}
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@ -38,13 +38,15 @@ client libraries:
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* [JSONPath](/docs/reference/kubectl/jsonpath/) - Syntax guide for using [JSONPath expressions](http://goessner.net/articles/JsonPath/) with kubectl.
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* [kubeadm](/docs/reference/setup-tools/kubeadm/kubeadm/) - CLI tool to easily provision a secure Kubernetes cluster.
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## Config Reference
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## Components Reference
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* [kubelet](/docs/reference/command-line-tools-reference/kubelet/) - The primary *node agent* that runs on each node. The kubelet takes a set of PodSpecs and ensures that the described containers are running and healthy.
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* [kube-apiserver](/docs/reference/command-line-tools-reference/kube-apiserver/) - REST API that validates and configures data for API objects such as pods, services, replication controllers.
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* [kube-controller-manager](/docs/reference/command-line-tools-reference/kube-controller-manager/) - Daemon that embeds the core control loops shipped with Kubernetes.
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* [kube-proxy](/docs/reference/command-line-tools-reference/kube-proxy/) - Can do simple TCP/UDP stream forwarding or round-robin TCP/UDP forwarding across a set of back-ends.
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* [kube-scheduler](/docs/reference/command-line-tools-reference/kube-scheduler/) - Scheduler that manages availability, performance, and capacity.
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* [kube-scheduler Policies](/docs/reference/scheduling/policies)
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* [kube-scheduler Profiles](/docs/reference/scheduling/profiles)
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## Design Docs
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@ -0,0 +1,5 @@
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---
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title: Scheduling
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weight: 70
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toc-hide: true
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---
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@ -0,0 +1,125 @@
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---
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title: Scheduling Policies
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content_template: templates/concept
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weight: 10
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---
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{{% capture overview %}}
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A scheduling Policy can be used to specify the *predicates* and *priorities*
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that the {{< glossary_tooltip text="kube-scheduler" term_id="kube-scheduler" >}}
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runs to [filter and score nodes](/docs/concepts/scheduling/kube-scheduler/#kube-scheduler-implementation),
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respectively.
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You can set a scheduling policy by running
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`kube-scheduler --policy-config-file <filename>` or
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`kube-scheduler --policy-configmap <ConfigMap>`
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and using the [Policy type](https://pkg.go.dev/k8s.io/kube-scheduler@v0.18.0/config/v1?tab=doc#Policy).
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{{% /capture %}}
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{{% capture body %}}
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## Predicates
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The following *predicates* implement filtering:
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- `PodFitsHostPorts`: Checks if a Node has free ports (the network protocol kind)
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for the Pod ports the Pod is requesting.
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- `PodFitsHost`: Checks if a Pod specifies a specific Node by its hostname.
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- `PodFitsResources`: Checks if the Node has free resources (eg, CPU and Memory)
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to meet the requirement of the Pod.
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- `PodMatchNodeSelector`: Checks if a Pod's Node {{< glossary_tooltip term_id="selector" >}}
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matches the Node's {{< glossary_tooltip text="label(s)" term_id="label" >}}.
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- `NoVolumeZoneConflict`: Evaluate if the {{< glossary_tooltip text="Volumes" term_id="volume" >}}
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that a Pod requests are available on the Node, given the failure zone restrictions for
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that storage.
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- `NoDiskConflict`: Evaluates if a Pod can fit on a Node due to the volumes it requests,
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and those that are already mounted.
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- `MaxCSIVolumeCount`: Decides how many {{< glossary_tooltip text="CSI" term_id="csi" >}}
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volumes should be attached, and whether that's over a configured limit.
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- `CheckNodeMemoryPressure`: If a Node is reporting memory pressure, and there's no
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configured exception, the Pod won't be scheduled there.
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- `CheckNodePIDPressure`: If a Node is reporting that process IDs are scarce, and
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there's no configured exception, the Pod won't be scheduled there.
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|
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- `CheckNodeDiskPressure`: If a Node is reporting storage pressure (a filesystem that
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is full or nearly full), and there's no configured exception, the Pod won't be
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scheduled there.
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- `CheckNodeCondition`: Nodes can report that they have a completely full filesystem,
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that networking isn't available or that kubelet is otherwise not ready to run Pods.
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If such a condition is set for a Node, and there's no configured exception, the Pod
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won't be scheduled there.
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- `PodToleratesNodeTaints`: checks if a Pod's {{< glossary_tooltip text="tolerations" term_id="toleration" >}}
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can tolerate the Node's {{< glossary_tooltip text="taints" term_id="taint" >}}.
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- `CheckVolumeBinding`: Evaluates if a Pod can fit due to the volumes it requests.
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This applies for both bound and unbound
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{{< glossary_tooltip text="PVCs" term_id="persistent-volume-claim" >}}.
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## Priorities
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The following *priorities* implement scoring:
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- `SelectorSpreadPriority`: Spreads Pods across hosts, considering Pods that
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belong to the same {{< glossary_tooltip text="Service" term_id="service" >}},
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{{< glossary_tooltip term_id="statefulset" >}} or
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{{< glossary_tooltip term_id="replica-set" >}}.
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- `InterPodAffinityPriority`: Implements preferred
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[inter pod affininity and antiaffinity](/docs/concepts/configuration/assign-pod-node/#inter-pod-affinity-and-anti-affinity).
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- `LeastRequestedPriority`: Favors nodes with fewer requested resources. In other
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words, the more Pods that are placed on a Node, and the more resources those
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Pods use, the lower the ranking this policy will give.
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- `MostRequestedPriority`: Favors nodes with most requested resources. This policy
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will fit the scheduled Pods onto the smallest number of Nodes needed to run your
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overall set of workloads.
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- `RequestedToCapacityRatioPriority`: Creates a requestedToCapacity based ResourceAllocationPriority using default resource scoring function shape.
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- `BalancedResourceAllocation`: Favors nodes with balanced resource usage.
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- `NodePreferAvoidPodsPriority`: Prioritizes nodes according to the node annotation
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`scheduler.alpha.kubernetes.io/preferAvoidPods`. You can use this to hint that
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two different Pods shouldn't run on the same Node.
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|
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- `NodeAffinityPriority`: Prioritizes nodes according to node affinity scheduling
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preferences indicated in PreferredDuringSchedulingIgnoredDuringExecution.
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You can read more about this in [Assigning Pods to Nodes](/docs/concepts/configuration/assign-pod-node/).
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|
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- `TaintTolerationPriority`: Prepares the priority list for all the nodes, based on
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the number of intolerable taints on the node. This policy adjusts a node's rank
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taking that list into account.
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|
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- `ImageLocalityPriority`: Favors nodes that already have the
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{{< glossary_tooltip text="container images" term_id="image" >}} for that
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Pod cached locally.
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- `ServiceSpreadingPriority`: For a given Service, this policy aims to make sure that
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the Pods for the Service run on different nodes. It favours scheduling onto nodes
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that don't have Pods for the service already assigned there. The overall outcome is
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that the Service becomes more resilient to a single Node failure.
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- `EqualPriority`: Gives an equal weight of one to all nodes.
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- `EvenPodsSpreadPriority`: Implements preferred
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[pod topology spread constraints](/docs/concepts/workloads/pods/pod-topology-spread-constraints/).
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{{% /capture %}}
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{{% capture whatsnext %}}
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* Learn about [scheduling](/docs/concepts/scheduling/kube-scheduler/)
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* Learn about [kube-scheduler profiles](/docs/reference/scheduling/profiles/)
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{{% /capture %}}
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@ -0,0 +1,181 @@
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---
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title: Scheduling Profiles
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content_template: templates/concept
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weight: 20
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---
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{{% capture overview %}}
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{{< feature-state for_k8s_version="v1.18" state="alpha" >}}
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A scheduling Profile allows you to configure the different stages of scheduling
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in the {{< glossary_tooltip text="kube-scheduler" term_id="kube-scheduler" >}}.
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Each stage is exposed in a extension point. Plugins provide scheduling behaviors
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by implementing one or more of these extension points.
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You can specify scheduling profiles by running `kube-scheduler --config <filename>`,
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using the component config APIs
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([`v1alpha1`](https://pkg.go.dev/k8s.io/kube-scheduler@{{< param "fullversion" >}}/config/v1alpha1?tab=doc#KubeSchedulerConfiguration)
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or [`v1alpha2`](https://pkg.go.dev/k8s.io/kube-scheduler@{{< param "fullversion" >}}/config/v1alpha2?tab=doc#KubeSchedulerConfiguration)).
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The `v1alpha2` API allows you to configure kube-scheduler to run
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[multiple profiles](#multiple-profiles).
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{{% /capture %}}
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{{% capture body %}}
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## Extension points
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Scheduling happens in a series of stages that are exposed through the following
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extension points:
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1. `QueueSort`: These plugins provide an ordering function that is used to
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sort pending Pods in the scheduling queue. Exactly one queue sort plugin
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may be enabled at a time.
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1. `PreFilter`: These plugins are used to pre-process or check information
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about a Pod or the cluster before filtering.
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1. `Filter`: These plugins are the equivalent of Predicates in a scheduling
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Policy and are used to filter out nodes that can not run the Pod. Filters
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are called in the configured order.
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1. `PreScore`: This is an informational extension point that can be used
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for doing pre-scoring work.
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1. `Score`: These plugins provide a score to each node that has passed the
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filtering phase. The scheduler will then select the node with the highest
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weighted scores sum.
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1. `Reserve`: This is an informational extension point that notifies plugins
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when resources have being reserved for a given Pod.
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1. `Permit`: These plugins can prevent or delay the binding of a Pod.
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1. `PreBind`: These plugins perform any work required before a Pod is bound.
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1. `Bind`: The plugins bind a Pod to a Node. Bind plugins are called in order
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and once one has done the binding, the remaining plugins are skipped. At
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least one bind plugin is required.
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1. `PostBind`: This is an informational extension point that is called after
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a Pod has been bound.
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1. `UnReserve`: This is an informational extension point that is called if
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a Pod is rejected after being reserved and put on hold by a `Permit` plugin.
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## Scheduling plugins
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The following plugins, enabled by default, implement one or more of these
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extension points:
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- `DefaultTopologySpread`: Favors spreading across nodes for Pods that belong to
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{{< glossary_tooltip text="Services" term_id="service" >}},
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{{< glossary_tooltip text="ReplicaSets" term_id="replica-set" >}} and
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{{< glossary_tooltip text="StatefulSets" term_id="statefulset" >}}
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Extension points: `PreScore`, `Score`.
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- `ImageLocality`: Favors nodes that already have the container images that the
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Pod runs.
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Extension points: `Score`.
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- `TaintToleration`: Implements
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[taints and tolerations](/docs/concepts/configuration/taint-and-toleration/).
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Implements extension points: `Filter`, `Prescore`, `Score`.
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- `NodeName`: Checks if a Pod spec node name matches the current node.
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Extension points: `Filter`.
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- `NodePorts`: Checks if a node has free ports for the requested Pod ports.
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Extension points: `PreFilter`, `Filter`.
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- `NodePreferAvoidPods`: Scores nodes according to the node
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{{< glossary_tooltip text="annotation" term_id="annotation" >}}
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`scheduler.alpha.kubernetes.io/preferAvoidPods`.
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Extension points: `Score`.
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- `NodeAffinity`: Implements
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[node selectors](/docs/concepts/configuration/assign-pod-node/#nodeselector)
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and [node affinity](/docs/concepts/configuration/assign-pod-node/#node-affinity).
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Extension points: `Filter`, `Score`.
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- `PodTopologySpread`: Implements
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[Pod topology spread](/docs/concepts/workloads/pods/pod-topology-spread-constraints/).
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Extension points: `PreFilter`, `Filter`, `PreScore`, `Score`.
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- `NodeUnschedulable`: Filters out nodes that have `.spec.unschedulable` set to
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true.
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Extension points: `Filter`.
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- `NodeResourcesFit`: Checks if the node has all the resources that the Pod is
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requesting.
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Extension points: `PreFilter`, `Filter`.
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- `NodeResourcesBallancedAllocation`: Favors nodes that would obtain a more
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balanced resource usage if the Pod is scheduled there.
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Extension points: `Score`.
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- `NodeResourcesLeastAllocated`: Favors nodes that have a low allocation of
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resources.
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Extension points: `Score`.
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- `VolumeBinding`: Checks if the node has or if it can bind the requested
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{{< glossary_tooltip text="volumes" term_id="volume" >}}.
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Extension points: `Filter`.
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- `VolumeRestrictions`: Checks that volumes mounted in the node satisfy
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restrictions that are specific to the volume provider.
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Extension points: `Filter`.
|
||||
- `VolumeZone`: Checks that volumes requested satisfy any zone requirements they
|
||||
might have.
|
||||
Extension points: `Filter`.
|
||||
- `NodeVolumeLimits`: Checks that CSI volume limits can be satisfied for the
|
||||
node.
|
||||
Extension points: `Filter`.
|
||||
- `EBSLimits`: Checks that AWS EBS volume limits can be satisfied for the node.
|
||||
Extension points: `Filter`.
|
||||
- `GCEPDLimits`: Checks that GCP-PD volume limits can be satisfied for the node.
|
||||
Extension points: `Filter`.
|
||||
- `AzureDiskLimits`: Checks that Azure disk volume limits can be satisfied for
|
||||
the node.
|
||||
Extension points: `Filter`.
|
||||
- `InterPodAffinity`: Implements
|
||||
[inter-Pod affinity and anti-affinity](/docs/concepts/configuration/assign-pod-node/#inter-pod-affinity-and-anti-affinity).
|
||||
Extension points: `PreFilter`, `Filter`, `PreScore`, `Score`.
|
||||
- `PrioritySort`: Provides the default priority based sorting.
|
||||
Extension points: `QueueSort`.
|
||||
- `DefaultBinder`: Provides the default binding mechanism.
|
||||
Extension points: `Bind`.
|
||||
|
||||
You can also enable the following plugins, through the component config APIs,
|
||||
that are not enabled by default:
|
||||
|
||||
- `NodeResourcesMostAllocated`: Favors nodes that have a high allocation of
|
||||
resources.
|
||||
Extension points: `Score`.
|
||||
- `RequestedToCapacityRatio`: Favor nodes according to a configured function of
|
||||
the allocated resources.
|
||||
Extension points: `Score`.
|
||||
- `NodeResourceLimits`: Favors nodes that satisfy the Pod resource limits.
|
||||
Extension points: `PreScore`, `Score`.
|
||||
- `CinderVolume`: Checks that OpenStack Cinder volume limits can be satisfied
|
||||
for the node.
|
||||
Extension points: `Filter`.
|
||||
- `NodeLabel`: Filters and / or scores a node according to configured
|
||||
{{< glossary_tooltip text="label(s)" term_id="label" >}}.
|
||||
Extension points: `Filter`, `Score`.
|
||||
- `ServiceAffinity`: Checks that Pods that belong to a
|
||||
{{< glossary_tooltip term_id="service" >}} fit in a set of nodes defined by
|
||||
configured labels. This plugin also favors spreading the Pods belonging to a
|
||||
Service across nodes.
|
||||
Extension points: `PreFilter`, `Filter`, `Score`.
|
||||
|
||||
## Multiple profiles
|
||||
|
||||
When using the component config API v1alpha2, a scheduler can be configured to
|
||||
run more than one profile. Each profile has an associated scheduler name.
|
||||
Pods that want to be scheduled according to a specific profile can include
|
||||
the corresponding scheduler name in its `.spec.schedulerName`.
|
||||
|
||||
By default, one profile with the scheduler name `default-scheduler` is created.
|
||||
This profile includes the default plugins described above. When declaring more
|
||||
than one profile, a unique scheduler name for each of them is required.
|
||||
|
||||
If a Pod doesn't specify a scheduler name, kube-apiserver will set it to
|
||||
`default-scheduler`. Therefore, a profile with this scheduler name should exist
|
||||
to get those pods scheduled.
|
||||
|
||||
{{< note >}}
|
||||
Pod's scheduling events have `.spec.schedulerName` as the ReportingController.
|
||||
Events for leader election use the scheduler name of the first profile in the
|
||||
list.
|
||||
{{< /note >}}
|
||||
|
||||
{{< note >}}
|
||||
All profiles must use the same plugin in the QueueSort extension point and have
|
||||
the same configuration parameters (if applicable). This is because the scheduler
|
||||
only has one pending pods queue.
|
||||
{{< /note >}}
|
||||
|
||||
{{% /capture %}}
|
||||
|
||||
{{% capture whatsnext %}}
|
||||
* Learn about [scheduling](/docs/concepts/scheduling/kube-scheduler/)
|
||||
{{% /capture %}}
|
||||
Loading…
Reference in New Issue