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 Memory 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 memory requests and limits for a namespace.
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If a Container is created in a namespace that has a default memory limit, and the Container
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does not specify its own memory limit, then the Container is assigned the default memory limit.
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Kubernetes assigns a default memory request 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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Each node in your cluster must have at least 300 GiB of memory.
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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-mem-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 memory request and a default memory limit.
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{% include code.html language="yaml" file="memory-defaults.yaml" ghlink="/docs/tasks/administer-cluster/memory-defaults.yaml" %}
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Create the LimitRange in the default-mem-example namespace:
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```shell
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kubectl create -f https://k8s.io/docs/tasks/administer-cluster/memory-defaults.yaml --namespace=default-mem-example
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```
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Now if a Container is created in the default-mem-example namespace, and the
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Container does not specify its own values for memory request and memory limit,
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the Container is given a default memory request of 256 MiB and a default
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memory limit of 512 MiB.
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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 memory request and limit.
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{% include code.html language="yaml" file="memory-defaults-pod.yaml" ghlink="/docs/tasks/administer-cluster/memory-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/memory-defaults-pod.yaml --namespace=default-mem-example
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```
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View detailed information about the Pod:
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```shell
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kubectl get pod default-mem-demo --output=yaml --namespace=default-mem-example
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```
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The output shows that the Pod's Container has a memory request of 256 MiB and
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a memory limit of 512 MiB. 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-mem-demo-ctr
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resources:
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limits:
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memory: 512Mi
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requests:
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memory: 256Mi
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```
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Delete your Pod:
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```shell
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kubectl delete pod default-mem-demo --namespace=default-mem-example
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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 memory limit, but not a request:
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{% include code.html language="yaml" file="memory-defaults-pod-2.yaml" ghlink="/docs/tasks/administer-cluster/memory-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/memory-defaults-pod-2.yaml --namespace=default-mem-example
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```
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View detailed information about the Pod:
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```shell
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kubectl get pod mem-limit-no-request --output=yaml --namespace=default-mem-example
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```
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The output shows that the Container's memory request is set to match its memory limit.
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Notice that the Container was not assigned the default memory request value of 256Mi.
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```
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resources:
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limits:
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memory: 1Gi
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requests:
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memory: 1Gi
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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 memory request, but not a limit:
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{% include code.html language="yaml" file="memory-defaults-pod-3.yaml" ghlink="/docs/tasks/administer-cluster/memory-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/memory-defaults-pod-3.yaml --namespace=default-mem-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-mem-request-no-limit --output=yaml --namespace=default-mem-example
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```
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The output shows that the Container's memory request is set to the value specified in the
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Container's configuration file. The Container's memory limit is set to 512Mi, which is the
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default memory limit for the namespace.
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```
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resources:
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limits:
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memory: 512Mi
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requests:
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memory: 128Mi
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```
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## Motivation for default memory limits and requests
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If your namespace has a resource quota,
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it is helpful to have a default value in place for memory 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 memory limit.
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* The total amount of memory 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 memory 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 CPU Requests and Limits for a Namespace](docs/tasks/administer-cluster/default-cpu-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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