Merge pull request #13725 from HaiyangDING/update_resource-quota_doc

docs/admin/resource-quota.md

@@ -40,15 +40,24 @@ Resource quotas are a tool for administrators to address this concern. Resource
 work like this:
 - Different teams work in different namespaces.  Currently this is voluntary, but
   support for making this mandatory via ACLs is planned.
-- Users put [compute resource limits](../user-guide/compute-resources.md) on their pods.
 - The administrator creates a Resource Quota for each namespace.
+- Users put compute resource requests on their pods. The sum of all resource requests across
+  all pods in the same namespace must not exceed any hard resource limit in any Resource Quota
+  document for the namespace. Note that we used to verify Resource Quota by taking the sum of
+  resource limits of the pods, but this was altered to use resource requests. Backwards compatibility
+  for those pods previously created is preserved because pods that only specify a resource limit have
+  their resource requests defaulted to match their defined limits. The user is only charged for the
+  resources they request in the Resource Quota versus their limits because the request is the minimum
+  amount of resource guaranteed by the cluster during scheduling. For more information on over commit,
+  see [compute-resources](../user-guide/compute-resources.md).
 - If creating a pod would cause the namespace to exceed any of the limits specified in the
   the Resource Quota for that namespace, then the request will fail with HTTP status
   code `403 FORBIDDEN`.
-- If quota is enabled in a namespace and the user does not specify limits on the pod for each
+- If quota is enabled in a namespace and the user does not specify *requests* on the pod for each
   of the resources for which quota is enabled, then the POST of the pod will fail with HTTP
   status code `403 FORBIDDEN`.  Hint: Use the LimitRange admission controller to force default
-  values of limits before the quota is checked to avoid this problem.
+  values of *limits* (then resource *requests* would be equal to *limits* by default, see
+  [admission controller](admission-controllers.md)) before the quota is checked to avoid this problem.
 
 Examples of policies that could be created using namespaces and quotas are:
 - In a cluster with a capacity of 32 GiB RAM, and 16 cores, let team A use 20 Gib and 10 cores,
@@ -78,10 +87,10 @@ in a namespace can be limited.  The following compute resource types are support
 
 | ResourceName | Description |
 | ------------ | ----------- |
-| cpu | Total cpu limits of containers |
-| memory | Total memory limits of containers
+| cpu | Total cpu requests of containers |
+| memory | Total memory requests of containers
 
-For example, `cpu` quota sums up the `resources.limits.cpu` fields of every
+For example, `cpu` quota sums up the `resources.requests.cpu` fields of every
 container of every pod in the namespace, and enforces a maximum on that sum.
 
 ## Object Count Quota
@@ -107,7 +116,7 @@ supply of Pod IPs.
 
 ## Viewing and Setting Quotas
 
-Kubectl supports creating, updating, and viewing quotas
+Kubectl supports creating, updating, and viewing quotas:
 
 ```console
 $ kubectl namespace myspace

docs/admin/resourcequota/README.md

@@ -32,7 +32,9 @@ Documentation for other releases can be found at
 <!-- END MUNGE: UNVERSIONED_WARNING -->
 Resource Quota
 ========================================
-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.
+This example demonstrates how [resource quota](../../admin/admission-controllers.md#resourcequota) and
+[limitsranger](../../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.
 
 This example assumes you have a functional Kubernetes setup.
 
@@ -44,26 +46,29 @@ Let's create a new namespace called quota-example:
 
 ```console
 $ kubectl create -f docs/admin/resourcequota/namespace.yaml
+namespace "quota-example" created
 $ kubectl get namespaces
-NAME            LABELS             STATUS
-default         <none>             Active
-quota-example   <none>             Active
+NAME            LABELS    STATUS    AGE
+default         <none>    Active    2m
+quota-example   <none>    Active    39s
 ```
 
 Step 2: Apply a quota to the namespace
 -----------------------------------------
-By default, a pod will run with unbounded CPU and memory limits.  This means that any pod in the
+By default, a pod will run with unbounded CPU and memory requests/limits.  This means that any pod in the
 system will be able to consume as much CPU and memory on the node that executes the pod.
 
 Users may want to restrict how much of the cluster resources a given namespace may consume
 across all of its pods in order to manage cluster usage.  To do this, a user applies a quota to
 a namespace.  A quota lets the user set hard limits on the total amount of node resources (cpu, memory)
-and API resources (pods, services, etc.) that a namespace may consume.
+and API resources (pods, services, etc.) that a namespace may consume. In term of resources, Kubernetes
+checks the total resource *requests*, not resource *limits* of all containers/pods in the namespace.
 
 Let's create a simple quota in our namespace:
 
 ```console
 $ kubectl create -f docs/admin/resourcequota/quota.yaml --namespace=quota-example
+resourcequota "quota" created
 ```
 
 Once your quota is applied to a namespace, the system will restrict any creation of content
@@ -74,23 +79,23 @@ namespace.
 
 ```console
 $ kubectl describe quota quota --namespace=quota-example
-Name:                   quota
-Namespace:              quota-example
-Resource                Used    Hard
---------                ----    ----
-cpu                     0       20
-memory                  0       1Gi
-persistentvolumeclaims  0       10
-pods                    0       10
-replicationcontrollers  0       20
-resourcequotas          1       1
-secrets                 1       10
-services                0       5
+Name:			quota
+Namespace:		quota-example
+Resource		Used	Hard
+--------		----	----
+cpu			0	20
+memory			0	1Gi
+persistentvolumeclaims	0	10
+pods			0	10
+replicationcontrollers	0	20
+resourcequotas		1	1
+secrets			1	10
+services		0	5
 ```
 
-Step 3: Applying default resource limits
+Step 3: Applying default resource requests and limits
 -----------------------------------------
-Pod authors rarely specify resource limits for their pods.
+Pod authors rarely specify resource requests and limits for their pods.
 
 Since we applied a quota to our project, let's see what happens when an end-user creates a pod that has unbounded
 cpu and memory by creating an nginx container.
@@ -99,8 +104,7 @@ To demonstrate, lets create a replication controller that runs nginx:
 
 ```console
 $ kubectl run nginx --image=nginx --replicas=1 --namespace=quota-example
-CONTROLLER   CONTAINER(S)   IMAGE(S)   SELECTOR    REPLICAS
-nginx        nginx          nginx      run=nginx   1
+replicationcontroller "nginx" created
 ```
 
 Now let's look at the pods that were created.
@@ -114,78 +118,78 @@ What happened?  I have no pods!  Let's describe the replication controller to ge
 
 ```console
 kubectl describe rc nginx --namespace=quota-example
-Name:   nginx
-Image(s): nginx
-Selector: run=nginx
-Labels:   run=nginx
-Replicas: 0 current / 1 desired
-Pods Status:  0 Running / 0 Waiting / 0 Succeeded / 0 Failed
+Name:		nginx
+Namespace:	quota-example
+Image(s):	nginx
+Selector:	run=nginx
+Labels:		run=nginx
+Replicas:	0 current / 1 desired
+Pods Status:	0 Running / 0 Waiting / 0 Succeeded / 0 Failed
+No volumes.
 Events:
-  FirstSeen       LastSeen      Count From        SubobjectPath Reason    Message
-  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
+  FirstSeen	LastSeen	Count	From				SubobjectPath	Reason		Message
+  42s		11s		3	{replication-controller }			FailedCreate	Error creating: Pod "nginx-" is forbidden: Must make a non-zero request for memory since it is tracked by quota.
 ```
 
 The Kubernetes API server is rejecting the replication controllers requests to create a pod because our pods
-do not specify any memory usage.
+do not specify any memory usage *request*.
 
-So let's set some default limits for the amount of cpu and memory a pod can consume:
+So let's set some default values for the amount of cpu and memory a pod can consume:
 
 ```console
 $ kubectl create -f docs/admin/resourcequota/limits.yaml --namespace=quota-example
-limitranges/limits
+limitrange "limits" created
 $ kubectl describe limits limits --namespace=quota-example
-Name:           limits
-Namespace:      quota-example
-Type            Resource        Min     Max     Default
-----            --------        ---     ---     ---
-Container       memory          -       -       512Mi
-Container       cpu             -       -       100m
+Name:		limits
+Namespace:	quota-example
+Type		Resource	Min	Max	Request	Limit	Limit/Request
+----		--------	---	---	-------	-----	-------------
+Container	memory		-	-	256Mi	512Mi	-
+Container	cpu		-	-	100m	200m	-
 ```
 
-Now any time a pod is created in this namespace, if it has not specified any resource limits, the default
-amount of cpu and memory per container will be applied as part of admission control.
+Now any time a pod is created in this namespace, if it has not specified any resource request/limit, the default
+amount of cpu and memory per container will be applied, and the request will be used as part of admission control.
 
-Now that we have applied default limits for our namespace, our replication controller should be able to
+Now that we have applied default resource *request* for our namespace, our replication controller should be able to
 create its pods.
 
 ```console
 $ kubectl get pods --namespace=quota-example
 NAME          READY     STATUS    RESTARTS   AGE
-nginx-t9cap   1/1       Running   0          49s
+nginx-fca65   1/1       Running   0          1m
 ```
 
 And if we print out our quota usage in the namespace:
 
 ```console
 $ kubectl describe quota quota --namespace=quota-example
-Name:                   quota
-Namespace:              default
-Resource                Used            Hard
---------                ----            ----
-cpu                     100m            20
-memory                  536870912       1Gi
-persistentvolumeclaims  0               10
-pods                    1               10
-replicationcontrollers  1               20
-resourcequotas          1               1
-secrets                 1               10
-services                0               5
+Name:			quota
+Namespace:		quota-example
+Resource		Used	Hard
+--------		----	----
+cpu			100m	20
+memory			256Mi	1Gi
+persistentvolumeclaims	0	10
+pods			1	10
+replicationcontrollers	1	20
+resourcequotas		1	1
+secrets			1	10
+services		0	5
 ```
 
-You can now see the pod that was created is consuming explicit amounts of resources, and the usage is being
-tracked by the Kubernetes system properly.
+You can now see the pod that was created is consuming explicit amounts of resources (specified by resource *request*),
+and the usage is being tracked by the Kubernetes system properly.
 
 Summary
 ----------------------------
 Actions that consume node resources for cpu and memory can be subject to hard quota limits defined
-by the namespace quota.
+by the namespace quota. The resource consumption is measured by resource *request* in pod specification.
 
 Any action that consumes those resources can be tweaked, or can pick up namespace level defaults to
 meet your end goal.
 
 
-
-
 <!-- BEGIN MUNGE: GENERATED_ANALYTICS -->
 [![Analytics](https://kubernetes-site.appspot.com/UA-36037335-10/GitHub/docs/admin/resourcequota/README.md?pixel)]()
 <!-- END MUNGE: GENERATED_ANALYTICS -->

docs/admin/resourcequota/limits.yaml

@@ -5,6 +5,9 @@ metadata:
 spec:
   limits:
   - default:
-      cpu: 100m
+      cpu: 200m
       memory: 512Mi
+    defaultRequest:
+      cpu: 100m
+      memory: 256Mi
     type: Container