Update Task topics on resource management. (#4158)
This commit is contained in:
Steve Perry
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---
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title: Configure Default CPU Requests and Limits for a Namespace
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---
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{% capture overview %}
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This page shows how to configure default CPU requests and limits for a namespace.
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A Kubernetes cluster can be divided into namespaces. If a Container is created in a namespace
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that has a default CPU limit, and the Container does not specify its own CPU limit, then
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the Container is assigned the default CPU limit. Kubernetes assigns a default CPU request
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under certain conditions that are explained later in this topic.
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{% endcapture %}
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{% capture prerequisites %}
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{% include task-tutorial-prereqs.md %}
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{% endcapture %}
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{% capture 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 the configuration file for a LimitRange object. The configuration specifies
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a default CPU request and a default CPU limit.
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{% include code.html language="yaml" file="cpu-defaults.yaml" ghlink="/docs/tasks/administer-cluster/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 create -f https://k8s.io/docs/tasks/administer-cluster/cpu-defaults.yaml --namespace=default-cpu-example
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```
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Now if a Container is created in the default-cpu-example namespace, and the
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Container does not specify its own values for CPU request and CPU limit,
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the Container is given a default CPU request of 0.5 and a default
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CPU limit of 1.
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Here's the configuration file 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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{% include code.html language="yaml" file="cpu-defaults-pod.yaml" ghlink="/docs/tasks/administer-cluster/cpu-defaults-pod.yaml" %}
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Create the Pod.
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```shell
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kubectl create -f https://k8s.io/docs/tasks/administer-cluster/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 Container has a CPU request of 500 millicpus and
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a CPU limit of 1 cpu. These are the default values specified by the LimitRange.
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```shel
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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 the configuration file 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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{% include code.html language="yaml" file="cpu-defaults-pod-2.yaml" ghlink="/docs/tasks/administer-cluster/cpu-defaults-pod-2.yaml" %}
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Create the Pod:
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```shell
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kubectl create -f https://k8s.io/docs/tasks/administer-cluster/cpu-defaults-pod-2.yaml --namespace=default-cpu-example
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```
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View the Pod specification:
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```
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kubectl get pod cpu-limit-no-request --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 the configuration file 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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{% include code.html language="yaml" file="cpu-defaults-pod-3.yaml" ghlink="/docs/tasks/administer-cluster/cpu-defaults-pod-3.yaml" %}
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Create the Pod:
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```shell
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kubectl create -f https://k8s.io/docs/tasks/administer-cluster/cpu-defaults-pod-3.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 specified in the
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Container's configuration file. The Container's CPU limit is set to 1 cpu, wh70cb02113b7c7cc1604d1951ef82e1c82850eef2ich is the
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default CPU limit for the 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
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[resource quota](),
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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 resource quota imposes on a namespace:
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* Every Container that runs in the namespace must have its own CPU limit.
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* The total amount of CPU used by all Containers in the namespace must not exceed a specified limit.
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If a Container does not specify its own CPU limit, it is given the default limit, and then
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it can be allowed to run in a namespace that is restricted by a quota.
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{% endcapture %}
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{% capture 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/default-memory-request-limit/)
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* [Configure Minimum and Maximum Memory Constraints for a Namespace](/docs/tasks/administer-cluster/memory-constraint-namespace/)
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* [Configure Minimum and Maximum CPU Constraints for a Namespace](/docs/tasks/administer-cluster/cpu-constraint-namespace/)
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* [Configure Memory and CPU Quotas for a Namespace](/docs/tasks/administer-cluster/quota-memory-cpu-namespace/)
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* [Configure a Pod Quota for a Namespace](/docs/tasks/administer-cluster/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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{% endcapture %}
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{% include templates/task.md %}
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