mirror of https://github.com/k3s-io/k3s
190 lines
7.1 KiB
Markdown
190 lines
7.1 KiB
Markdown
<!-- BEGIN MUNGE: UNVERSIONED_WARNING -->
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<!-- BEGIN STRIP_FOR_RELEASE -->
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<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
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width="25" height="25">
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<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
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width="25" height="25">
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<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
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width="25" height="25">
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<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
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width="25" height="25">
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<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
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width="25" height="25">
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<h2>PLEASE NOTE: This document applies to the HEAD of the source tree</h2>
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If you are using a released version of Kubernetes, you should
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refer to the docs that go with that version.
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<strong>
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The latest 1.0.x release of this document can be found
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[here](http://releases.k8s.io/release-1.0/docs/user-guide/resourcequota/README.md).
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Documentation for other releases can be found at
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[releases.k8s.io](http://releases.k8s.io).
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</strong>
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--
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<!-- END STRIP_FOR_RELEASE -->
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<!-- END MUNGE: UNVERSIONED_WARNING -->
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Resource Quota
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========================================
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This example demonstrates how [resource quota](../../admin/admission-controllers.md#resourcequota) and [limits](../../admin/admission-controllers.md#limitranger) can be applied to a Kubernetes namespace. See [ResourceQuota design doc](../../design/admission_control_resource_quota.md) for more information.
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This example assumes you have a functional Kubernetes setup.
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Step 1: Create a namespace
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-----------------------------------------
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This example will work in a custom namespace to demonstrate the concepts involved.
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Let's create a new namespace called quota-example:
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```console
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$ kubectl create -f docs/user-guide/resourcequota/namespace.yaml
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$ kubectl get namespaces
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NAME LABELS STATUS
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default <none> Active
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quota-example <none> Active
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```
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Step 2: Apply a quota to the namespace
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-----------------------------------------
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By default, a pod will run with unbounded CPU and memory limits. This means that any pod in the
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system will be able to consume as much CPU and memory on the node that executes the pod.
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Users may want to restrict how much of the cluster resources a given namespace may consume
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across all of its pods in order to manage cluster usage. To do this, a user applies a quota to
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a namespace. A quota lets the user set hard limits on the total amount of node resources (cpu, memory)
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and API resources (pods, services, etc.) that a namespace may consume.
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Let's create a simple quota in our namespace:
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```console
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$ kubectl create -f docs/user-guide/resourcequota/quota.yaml --namespace=quota-example
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```
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Once your quota is applied to a namespace, the system will restrict any creation of content
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in the namespace until the quota usage has been calculated. This should happen quickly.
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You can describe your current quota usage to see what resources are being consumed in your
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namespace.
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```console
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$ kubectl describe quota quota --namespace=quota-example
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Name: quota
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Namespace: quota-example
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Resource Used Hard
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-------- ---- ----
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cpu 0 20
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memory 0 1Gi
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persistentvolumeclaims 0 10
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pods 0 10
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replicationcontrollers 0 20
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resourcequotas 1 1
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secrets 1 10
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services 0 5
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```
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Step 3: Applying default resource limits
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-----------------------------------------
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Pod authors rarely specify resource limits for their pods.
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Since we applied a quota to our project, let's see what happens when an end-user creates a pod that has unbounded
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cpu and memory by creating an nginx container.
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To demonstrate, lets create a replication controller that runs nginx:
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```console
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$ kubectl run nginx --image=nginx --replicas=1 --namespace=quota-example
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CONTROLLER CONTAINER(S) IMAGE(S) SELECTOR REPLICAS
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nginx nginx nginx run=nginx 1
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```
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Now let's look at the pods that were created.
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```console
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$ kubectl get pods --namespace=quota-example
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NAME READY STATUS RESTARTS AGE
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```
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What happened? I have no pods! Let's describe the replication controller to get a view of what is happening.
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```console
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kubectl describe rc nginx --namespace=quota-example
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Name: nginx
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Image(s): nginx
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Selector: run=nginx
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Labels: run=nginx
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Replicas: 0 current / 1 desired
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Pods Status: 0 Running / 0 Waiting / 0 Succeeded / 0 Failed
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Events:
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FirstSeen LastSeen Count From SubobjectPath Reason Message
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Mon, 01 Jun 2015 22:49:31 -0400 Mon, 01 Jun 2015 22:52:22 -0400 7 {replication-controller } failedCreate Error creating: Pod "nginx-" is forbidden: Limited to 1Gi memory, but pod has no specified memory limit
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```
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The Kubernetes API server is rejecting the replication controllers requests to create a pod because our pods
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do not specify any memory usage.
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So let's set some default limits for the amount of cpu and memory a pod can consume:
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```console
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$ kubectl create -f docs/user-guide/resourcequota/limits.yaml --namespace=quota-example
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limitranges/limits
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$ kubectl describe limits limits --namespace=quota-example
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Name: limits
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Namespace: quota-example
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Type Resource Min Max Default
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---- -------- --- --- ---
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Container memory - - 512Mi
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Container cpu - - 100m
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```
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Now any time a pod is created in this namespace, if it has not specified any resource limits, the default
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amount of cpu and memory per container will be applied as part of admission control.
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Now that we have applied default limits for our namespace, our replication controller should be able to
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create its pods.
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```console
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$ kubectl get pods --namespace=quota-example
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NAME READY STATUS RESTARTS AGE
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nginx-t9cap 1/1 Running 0 49s
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```
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And if we print out our quota usage in the namespace:
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```console
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$ kubectl describe quota quota --namespace=quota-example
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Name: quota
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Namespace: default
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Resource Used Hard
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-------- ---- ----
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cpu 100m 20
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memory 536870912 1Gi
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persistentvolumeclaims 0 10
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pods 1 10
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replicationcontrollers 1 20
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resourcequotas 1 1
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secrets 1 10
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services 0 5
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```
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You can now see the pod that was created is consuming explicit amounts of resources, and the usage is being
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tracked by the Kubernetes system properly.
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Summary
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----------------------------
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Actions that consume node resources for cpu and memory can be subject to hard quota limits defined
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by the namespace quota.
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Any action that consumes those resources can be tweaked, or can pick up namespace level defaults to
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meet your end goal.
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<!-- BEGIN MUNGE: GENERATED_ANALYTICS -->
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[]()
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<!-- END MUNGE: GENERATED_ANALYTICS -->
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