219 lines
6.8 KiB
Markdown
219 lines
6.8 KiB
Markdown
---
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title: Configure Default CPU Requests and Limits for a Namespace
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content_type: task
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weight: 20
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description: >-
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Define a default CPU resource limits for a namespace, so that every new Pod
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in that namespace has a CPU resource limit configured.
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---
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<!-- overview -->
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This page shows how to configure default CPU requests and limits for a
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{{< glossary_tooltip text="namespace" term_id="namespace" >}}.
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A Kubernetes cluster can be divided into namespaces. If you create a Pod within a
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namespace that has a default CPU
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[limit](/docs/concepts/configuration/manage-resources-containers/#requests-and-limits), and any container in that Pod does not specify
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its own CPU limit, then the
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{{< glossary_tooltip text="control plane" term_id="control-plane" >}} assigns the default
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CPU limit to that container.
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Kubernetes assigns a default CPU
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[request](/docs/concepts/configuration/manage-resources-containers/#requests-and-limits),
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but only under certain conditions that are explained later in this page.
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## {{% heading "prerequisites" %}}
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{{< include "task-tutorial-prereqs.md" >}}
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You must have access to create namespaces in your cluster.
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If you're not already familiar with what Kubernetes means by 1.0 CPU,
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read [meaning of CPU](/docs/concepts/configuration/manage-resources-containers/#meaning-of-cpu).
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<!-- steps -->
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## Create a namespace
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Create a namespace so that the resources you create in this exercise are
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isolated from the rest of your cluster.
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```shell
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kubectl create namespace default-cpu-example
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```
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## Create a LimitRange and a Pod
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Here's a manifest for an example {{< glossary_tooltip text="LimitRange" term_id="limitrange" >}}.
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The manifest specifies a default CPU request and a default CPU limit.
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{{< codenew file="admin/resource/cpu-defaults.yaml" >}}
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Create the LimitRange in the default-cpu-example namespace:
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```shell
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kubectl apply -f https://k8s.io/examples/admin/resource/cpu-defaults.yaml --namespace=default-cpu-example
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```
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Now if you create a Pod in the default-cpu-example namespace, and any container
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in that Pod does not specify its own values for CPU request and CPU limit,
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then the control plane applies default values: a CPU request of 0.5 and a default
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CPU limit of 1.
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Here's a manifest for a Pod that has one container. The container
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does not specify a CPU request and limit.
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{{< codenew file="admin/resource/cpu-defaults-pod.yaml" >}}
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Create the Pod.
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```shell
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kubectl apply -f https://k8s.io/examples/admin/resource/cpu-defaults-pod.yaml --namespace=default-cpu-example
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```
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View the Pod's specification:
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```shell
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kubectl get pod default-cpu-demo --output=yaml --namespace=default-cpu-example
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```
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The output shows that the Pod's only container has a CPU request of 500m `cpu`
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(which you can read as “500 millicpu”), and a CPU limit of 1 `cpu`.
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These are the default values specified by the LimitRange.
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```shell
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containers:
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- image: nginx
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imagePullPolicy: Always
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name: default-cpu-demo-ctr
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resources:
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limits:
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cpu: "1"
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requests:
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cpu: 500m
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```
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## What if you specify a container's limit, but not its request?
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Here's a manifest for a Pod that has one container. The container
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specifies a CPU limit, but not a request:
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{{< codenew file="admin/resource/cpu-defaults-pod-2.yaml" >}}
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Create the Pod:
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```shell
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kubectl apply -f https://k8s.io/examples/admin/resource/cpu-defaults-pod-2.yaml --namespace=default-cpu-example
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```
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View the [specification](/docs/concepts/overview/working-with-objects/kubernetes-objects/#object-spec-and-status)
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of the Pod that you created:
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```
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kubectl get pod default-cpu-demo-2 --output=yaml --namespace=default-cpu-example
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```
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The output shows that the container's CPU request is set to match its CPU limit.
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Notice that the container was not assigned the default CPU request value of 0.5 `cpu`:
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```
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resources:
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limits:
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cpu: "1"
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requests:
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cpu: "1"
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```
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## What if you specify a container's request, but not its limit?
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Here's an example manifest for a Pod that has one container. The container
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specifies a CPU request, but not a limit:
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{{< codenew file="admin/resource/cpu-defaults-pod-3.yaml" >}}
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Create the Pod:
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```shell
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kubectl apply -f https://k8s.io/examples/admin/resource/cpu-defaults-pod-3.yaml --namespace=default-cpu-example
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```
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View the specification of the Pod that you created:
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```
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kubectl get pod default-cpu-demo-3 --output=yaml --namespace=default-cpu-example
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```
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The output shows that the container's CPU request is set to the value you specified at
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the time you created the Pod (in other words: it matches the manifest).
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However, the same container's CPU limit is set to 1 `cpu`, which is the default CPU limit
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for that namespace.
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```
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resources:
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limits:
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cpu: "1"
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requests:
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cpu: 750m
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```
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## Motivation for default CPU limits and requests
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If your namespace has a CPU {{< glossary_tooltip text="resource quota" term_id="resource-quota" >}}
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configured,
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it is helpful to have a default value in place for CPU limit.
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Here are two of the restrictions that a CPU resource quota imposes on a namespace:
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* For every Pod that runs in the namespace, each of its containers must have a CPU limit.
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* CPU limits apply a resource reservation on the node where the Pod in question is scheduled.
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The total amount of CPU that is reserved for use by all Pods in the namespace must not
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exceed a specified limit.
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When you add a LimitRange:
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If any Pod in that namespace that includes a container does not specify its own CPU limit,
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the control plane applies the default CPU limit to that container, and the Pod can be
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allowed to run in a namespace that is restricted by a CPU ResourceQuota.
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## Clean up
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Delete your namespace:
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```shell
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kubectl delete namespace default-cpu-example
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```
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## {{% heading "whatsnext" %}}
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### For cluster administrators
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* [Configure Default Memory Requests and Limits for a Namespace](/docs/tasks/administer-cluster/manage-resources/memory-default-namespace/)
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* [Configure Minimum and Maximum Memory Constraints for a Namespace](/docs/tasks/administer-cluster/manage-resources/memory-constraint-namespace/)
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* [Configure Minimum and Maximum CPU Constraints for a Namespace](/docs/tasks/administer-cluster/manage-resources/cpu-constraint-namespace/)
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* [Configure Memory and CPU Quotas for a Namespace](/docs/tasks/administer-cluster/manage-resources/quota-memory-cpu-namespace/)
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* [Configure a Pod Quota for a Namespace](/docs/tasks/administer-cluster/manage-resources/quota-pod-namespace/)
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* [Configure Quotas for API Objects](/docs/tasks/administer-cluster/quota-api-object/)
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### For app developers
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* [Assign Memory Resources to Containers and Pods](/docs/tasks/configure-pod-container/assign-memory-resource/)
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* [Assign CPU Resources to Containers and Pods](/docs/tasks/configure-pod-container/assign-cpu-resource/)
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* [Configure Quality of Service for Pods](/docs/tasks/configure-pod-container/quality-service-pod/)
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