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Janet Kuo
2016-03-29 16:45:37 -07:00
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docs/admin/limitrange/index.md
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the cluster operator may want to set limits that a pod must consume at least 20% of the memory and cpu of their
average node size in order to provide for more uniform scheduling and to limit waste.
This example demonstrates how limits can be applied to a Kubernetes [namespace](/docs/admin/namespaces) to control
This example demonstrates how limits can be applied to a Kubernetes [namespace](/docs/admin/namespaces/walkthrough/) to control
min/max resource limits per pod. In addition, this example demonstrates how you can
apply default resource limits to pods in the absence of an end-user specified value.
docs/admin/namespaces/index.md
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---
---
Kubernetes _namespaces_ help different projects, teams, or customers to share a Kubernetes cluster.
A Namespace is a mechanism to partition resources created by users into
a logically named group.
It does this by providing the following:
## Motivation
1. A scope for [Names](/docs/user-guide/identifiers).
2. A mechanism to attach authorization and policy to a subsection of the cluster.
A single cluster should be able to satisfy the needs of multiple users or groups of users (henceforth a 'user community').
Use of multiple namespaces is optional.
Each user community wants to be able to work in isolation from other communities.
This example demonstrates how to use Kubernetes namespaces to subdivide your cluster.
Each user community has its own:
### Step Zero: Prerequisites
1. resources (pods, services, replication controllers, etc.)
2. policies (who can or cannot perform actions in their community)
3. constraints (this community is allowed this much quota, etc.)
This example assumes the following:
A cluster operator may create a Namespace for each unique user community.
1. You have an [existing Kubernetes cluster](/docs/getting-started-guides/).
2. You have a basic understanding of Kubernetes _[Pods](/docs/user-guide/pods)_, _[Services](/docs/user-guide/services)_, and _[Deployments](/docs/user-guide/deployments)_.
The Namespace provides a unique scope for:
### Step One: Understand the default namespace
1. named resources (to avoid basic naming collisions)
2. delegated management authority to trusted users
3. ability to limit community resource consumption
By default, a Kubernetes cluster will instantiate a default namespace when provisioning the cluster to hold the default set of Pods,
Services, and Deployments used by the cluster.
## Use cases
Assuming you have a fresh cluster, you can introspect the available namespace's by doing the following:
1. As a cluster operator, I want to support multiple user communities on a single cluster.
2. As a cluster operator, I want to delegate authority to partitions of the cluster to trusted users
in those communities.
3. As a cluster operator, I want to limit the amount of resources each community can consume in order
to limit the impact to other communities using the cluster.
4. As a cluster user, I want to interact with resources that are pertinent to my user community in
isolation of what other user communities are doing on the cluster.
## Usage
Look [here](/docs/admin/namespaces/) for an in depth example of namespaces.
### Viewing namespaces
You can list the current namespaces in a cluster using:
```shell
$ kubectl get namespaces
NAME STATUS AGE
default Active 13m
NAME LABELS STATUS
default <none> Active
kube-system <none> Active
```
### Step Two: Create new namespaces
Kubernetes starts with two initial namespaces:
* `default` The default namespace for objects with no other namespace
* `kube-system` The namespace for objects created by the Kubernetes system
For this exercise, we will create two additional Kubernetes namespaces to hold our content.
Let's imagine a scenario where an organization is using a shared Kubernetes cluster for development and production use cases.
The development team would like to maintain a space in the cluster where they can get a view on the list of Pods, Services, and Deployments
they use to build and run their application. In this space, Kubernetes resources come and go, and the restrictions on who can or cannot modify resources
are relaxed to enable agile development.
The operations team would like to maintain a space in the cluster where they can enforce strict procedures on who can or cannot manipulate the set of
Pods, Services, and Deployments that run the production site.
One pattern this organization could follow is to partition the Kubernetes cluster into two namespaces: development and production.
Let's create two new namespaces to hold our work.
Use the file [`namespace-dev.json`](/docs/admin/namespaces/namespace-dev.json) which describes a development namespace:
{% include code.html language="json" file="namespace-dev.json" ghlink="/docs/admin/namespaces/namespace-dev.json" %}
Create the development namespace using kubectl.
You can also get the summary of a specific namespace using:
```shell
$ kubectl create -f docs/admin/namespaces/namespace-dev.json
$ kubectl get namespaces <name>
```
And then lets create the production namespace using kubectl.
Or you can get detailed information with:
```shell
$ kubectl create -f docs/admin/namespaces/namespace-prod.json
$ kubectl describe namespaces <name>
Name: default
Labels: <none>
Status: Active
No resource quota.
Resource Limits
Type Resource Min Max Default
---- -------- --- --- ---
Container cpu - - 100m
```
To be sure things are right, let's list all of the namespaces in our cluster.
Note that these details show both resource quota (if present) as well as resource limit ranges.
```shell
$ kubectl get namespaces --show-labels
NAME STATUS AGE LABELS
default Active 32m <none>
development Active 29s name=development
production Active 23s name=production
```
Resource quota tracks aggregate usage of resources in the *Namespace* and allows cluster operators
to define *Hard* resource usage limits that a *Namespace* may consume.
### Step Three: Create pods in each namespace
A limit range defines min/max constraints on the amount of resources a single entity can consume in
a *Namespace*.
A Kubernetes namespace provides the scope for Pods, Services, and Deployments in the cluster.
See [Admission control: Limit Range](https://github.com/kubernetes/kubernetes/blob/{{page.githubbranch}}/docs/design/admission_control_limit_range.md)
Users interacting with one namespace do not see the content in another namespace.
A namespace can be in one of two phases:
* `Active` the namespace is in use
* `Terminating` the namespace is being deleted, and can not be used for new objects
To demonstrate this, let's spin up a simple Deployment and Pods in the development namespace.
See the [design doc](https://github.com/kubernetes/kubernetes/blob/{{page.githubbranch}}/docs/design/namespaces.md#phases) for more details.
We first check what is the current context:
### Creating a new namespace
```shell
$ kubectl config view
To create a new namespace, first create a new YAML file called `my-namespace.yaml` with the contents:
```yaml
apiVersion: v1
clusters:
- cluster:
certificate-authority-data: REDACTED
server: https://130.211.122.180
name: lithe-cocoa-92103_kubernetes
contexts:
- context:
cluster: lithe-cocoa-92103_kubernetes
user: lithe-cocoa-92103_kubernetes
name: lithe-cocoa-92103_kubernetes
current-context: lithe-cocoa-92103_kubernetes
kind: Config
preferences: {}
users:
- name: lithe-cocoa-92103_kubernetes
user:
client-certificate-data: REDACTED
client-key-data: REDACTED
token: 65rZW78y8HbwXXtSXuUw9DbP4FLjHi4b
- name: lithe-cocoa-92103_kubernetes-basic-auth
user:
password: h5M0FtUUIflBSdI7
username: admin
$ kubectl config current-context
lithe-cocoa-92103_kubernetes
kind: Namespace
metadata:
name: <insert-namespace-name-here>
```
The next step is to define a context for the kubectl client to work in each namespace. The value of "cluster" and "user" fields are copied from the current context.
Note that the name of your namespace must be a DNS compatible label.
More information on the `finalizers` field can be found in the namespace [design doc](https://github.com/kubernetes/kubernetes/blob/{{page.githubbranch}}/docs/design/namespaces.md#finalizers).
Then run:
```shell
$ kubectl config set-context dev --namespace=development --cluster=lithe-cocoa-92103_kubernetes --user=lithe-cocoa-92103_kubernetes
$ kubectl config set-context prod --namespace=production --cluster=lithe-cocoa-92103_kubernetes --user=lithe-cocoa-92103_kubernetes
$ kubectl create -f ./my-namespace.yaml
```
The above commands provided two request contexts you can alternate against depending on what namespace you
wish to work against.
### Working in namespaces
Let's switch to operate in the development namespace.
See [Setting the namespace for a request](/docs/user-guide/namespaces/#setting-the-namespace-for-a-request)
and [Setting the namespace preference](/docs/user-guide/namespaces/#setting-the-namespace-preference).
### Deleting a namespace
You can delete a namespace with
```shell
$ kubectl config use-context dev
$ kubectl delete namespaces <insert-some-namespace-name>
```
You can verify your current context by doing the following:
**WARNING, this deletes _everything_ under the namespace!**
```shell
$ kubectl config current-context
dev
```
This delete is asynchronous, so for a time you will see the namespace in the `Terminating` state.
At this point, all requests we make to the Kubernetes cluster from the command line are scoped to the development namespace.
## Namespaces and DNS
Let's create some content.
When you create a [Service](/docs/user-guide/services), it creates a corresponding [DNS entry](/docs/admin/dns).
This entry is of the form `<service-name>.<namespace-name>.svc.cluster.local`, which means
that if a container just uses `<service-name>` it will resolve to the service which
is local to a namespace. This is useful for using the same configuration across
multiple namespaces such as Development, Staging and Production. If you want to reach
across namespaces, you need to use the fully qualified domain name (FQDN).
```shell
$ kubectl run snowflake --image=kubernetes/serve_hostname --replicas=2
```
We have just created a deployment whose replica size is 2 that is running the pod called snowflake with a basic container that just serves the hostname.
Note that `kubectl run` creates deployments only on kubernetes cluster >= v1.2. If you are running older versions, it creates replication controllers instead.
If you want to obtain the old behavior, use `--generator=run/v1` to create replication controllers. See [`kubectl run`](/docs/user-guide/kubectl/kubectl_run/) for more details.
## Design
```shell
$ kubectl get deployment
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
snowflake 2 2 2 2 2m
$ kubectl get pods -l run=snowflake
NAME READY STATUS RESTARTS AGE
snowflake-3968820950-9dgr8 1/1 Running 0 2m
snowflake-3968820950-vgc4n 1/1 Running 0 2m
```
And this is great, developers are able to do what they want, and they do not have to worry about affecting content in the production namespace.
Let's switch to the production namespace and show how resources in one namespace are hidden from the other.
```shell
$ kubectl config use-context prod
```
The production namespace should be empty, and the following commands should return nothing.
```shell
$ kubectl get deployment
$ kubectl get pods
```
Production likes to run cattle, so let's create some cattle pods.
```shell
$ kubectl run cattle --image=kubernetes/serve_hostname --replicas=5
$ kubectl get deployment
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
cattle 5 5 5 5 10s
kubectl get pods -l run=cattle
NAME READY STATUS RESTARTS AGE
cattle-2263376956-41xy6 1/1 Running 0 34s
cattle-2263376956-kw466 1/1 Running 0 34s
cattle-2263376956-n4v97 1/1 Running 0 34s
cattle-2263376956-p5p3i 1/1 Running 0 34s
cattle-2263376956-sxpth 1/1 Running 0 34s
```
At this point, it should be clear that the resources users create in one namespace are hidden from the other namespace.
As the policy support in Kubernetes evolves, we will extend this scenario to show how you can provide different
authorization rules for each namespace.
Details of the design of namespaces in Kubernetes, including a [detailed example](https://github.com/kubernetes/kubernetes/blob/{{page.githubbranch}}/docs/design/namespaces.md#example-openshift-origin-managing-a-kubernetes-namespace)
can be found in the [namespaces design doc](https://github.com/kubernetes/kubernetes/blob/{{page.githubbranch}}/docs/design/namespaces.md)
docs/admin/namespaces/walkthrough.md
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It does this by providing the following:
1. A scope for [Names](/docs/user-guide/identifiers).
1. A scope for [Names](/docs/user-guide/identifiers/).
2. A mechanism to attach authorization and policy to a subsection of the cluster.
Use of multiple namespaces is optional.
@@ -17,7 +17,7 @@ This example demonstrates how to use Kubernetes namespaces to subdivide your clu
This example assumes the following:
1. You have an [existing Kubernetes cluster](/docs/getting-started-guides/).
2. You have a basic understanding of Kubernetes _[Pods](/docs/user-guide/pods)_, _[Services](/docs/user-guide/services)_, and _[Deployments](/docs/user-guide/deployments)_.
2. You have a basic understanding of Kubernetes _[Pods](/docs/user-guide/pods/)_, _[Services](/docs/user-guide/services/)_, and _[Deployments](/docs/user-guide/deployments/)_.
### Step One: Understand the default namespace
docs/admin/resourcequota/index.md
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---
---
This example demonstrates how [resource quota](/docs/admin/admission-controllers/#resourcequota) and
[limitsranger](/docs/admin/admission-controllers/#limitranger) can be applied to a Kubernetes namespace.
When several users or teams share a cluster with a fixed number of nodes,
there is a concern that one team could use more than its fair share of resources.
Resource quotas are a tool for administrators to address this concern. Resource quotas
work like this:
- Different teams work in different namespaces. Currently this is voluntary, but
support for making this mandatory via ACLs is planned.
- 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](/docs/user-guide/compute-resources).
- 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 *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* (then resource *requests* would be equal to *limits* by default, see
[admission controller](/docs/admin/admission-controllers)) 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,
let B use 10GiB and 4 cores, and hold 2GiB and 2 cores in reserve for future allocation.
- Limit the "testing" namespace to using 1 core and 1GiB RAM. Let the "production" namespace
use any amount.
In the case where the total capacity of the cluster is less than the sum of the quotas of the namespaces,
there may be contention for resources. This is handled on a first-come-first-served basis.
Neither contention nor changes to quota will affect already-running pods.
## Enabling Resource Quota
Resource Quota support is enabled by default for many Kubernetes distributions. It is
enabled when the apiserver `--admission-control=` flag has `ResourceQuota` as
one of its arguments.
Resource Quota is enforced in a particular namespace when there is a
`ResourceQuota` object in that namespace. There should be at most one
`ResourceQuota` object in a namespace.
## Compute Resource Quota
The total sum of [compute resources](/docs/user-guide/compute-resources) requested by pods
in a namespace can be limited. The following compute resource types are supported:
| ResourceName | Description |
| ------------ | ----------- |
| cpu | Total cpu requests of containers |
| memory | Total memory requests of containers
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
The number of objects of a given type can be restricted. The following types
are supported:
| ResourceName | Description |
| ------------ | ----------- |
| pods | Total number of pods |
| services | Total number of services |
| replicationcontrollers | Total number of replication controllers |
| resourcequotas | Total number of [resource quotas](/docs/admin/admission-controllers/#resourcequota) |
| secrets | Total number of secrets |
| persistentvolumeclaims | Total number of [persistent volume claims](/docs/user-guide/persistent-volumes/#persistentvolumeclaims) |
For example, `pods` quota counts and enforces a maximum on the number of `pods`
created in a single namespace.
You might want to set a pods quota on a namespace
to avoid the case where a user creates many small pods and exhausts the cluster's
supply of Pod IPs.
## Viewing and Setting Quotas
Kubectl supports creating, updating, and viewing quotas:
```shell
$ kubectl namespace myspace
$ cat <<EOF > quota.json
{
"apiVersion": "v1",
"kind": "ResourceQuota",
"metadata": {
"name": "quota"
},
"spec": {
"hard": {
"memory": "1Gi",
"cpu": "20",
"pods": "10",
"services": "5",
"replicationcontrollers":"20",
"resourcequotas":"1"
}
}
}
EOF
$ kubectl create -f ./quota.json
$ kubectl get quota
NAME
quota
$ kubectl describe quota quota
Name: quota
Resource Used Hard
-------- ---- ----
cpu 0m 20
memory 0 1Gi
pods 5 10
replicationcontrollers 5 20
resourcequotas 1 1
services 3 5
```
## Quota and Cluster Capacity
Resource Quota objects are independent of the Cluster Capacity. They are
expressed in absolute units. So, if you add nodes to your cluster, this does *not*
automatically give each namespace the ability to consume more resources.
Sometimes more complex policies may be desired, such as:
- proportionally divide total cluster resources among several teams.
- allow each tenant to grow resource usage as needed, but have a generous
limit to prevent accidental resource exhaustion.
- detect demand from one namespace, add nodes, and increase quota.
Such policies could be implemented using ResourceQuota as a building-block, by
writing a 'controller' which watches the quota usage and adjusts the quota
hard limits of each namespace according to other signals.
Note that resource quota divides up aggregate cluster resources, but it creates no
restrictions around nodes: pods from several namespaces may run on the same node.
## Example
See a [detailed example for how to use resource quota](/docs/admin/resourcequota/).
## Read More
See [ResourceQuota design doc](https://github.com/kubernetes/kubernetes/blob/{{page.githubbranch}}/docs/design/admission_control_resource_quota.md) for more information.
This example assumes you have a functional Kubernetes setup.
## Step 1: Create a namespace
This example will work in a custom namespace to demonstrate the concepts involved.
Let's create a new namespace called quota-example:
```shell
$ kubectl create namespace quota-example
namespace "quota-example" created
```
Note that `kubectl` commands will print the type and name of the resource created or mutated, which can then be used in subsequent commands:
```shell
$ kubectl get namespaces
NAME STATUS AGE
default Active 50m
quota-example Active 2s
```
## Step 2: Apply a quota to the namespace
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. 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:
```shell
$ 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
in the namespace until the quota usage has been calculated. This should happen quickly.
You can describe your current quota usage to see what resources are being consumed in your
namespace.
```shell
$ 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
```
## Step 3: Applying default resource requests and limits
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.
To demonstrate, lets create a Deployment that runs nginx:
```shell
$ kubectl run nginx --image=nginx --replicas=1 --namespace=quota-example
deployment "nginx" created
```
This creates a Deployment "nginx" with its underlying resource, a ReplicaSet, which handles the creation and deletion of Pod replicas. Now let's look at the pods that were created.
```shell
$ kubectl get pods --namespace=quota-example
NAME READY STATUS RESTARTS AGE
```
What happened? I have no pods! Let's describe the ReplicaSet managed by the nginx Deployment to get a view of what is happening.
Note that `kubectl describe rs` works only on kubernetes cluster >= v1.2. If you are running older versions, use `kubectl describe rc` instead.
If you want to obtain the old behavior, use `--generator=run/v1` to create replication controllers. See [`kubectl run`](/docs/user-guide/kubectl/kubectl_run/) for more details.
```shell
$ kubectl describe rs -l run=nginx --namespace=quota-example
Name: nginx-2040093540
Namespace: quota-example
Image(s): nginx
Selector: pod-template-hash=2040093540,run=nginx
Labels: pod-template-hash=2040093540,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 Type Reason Message
--------- -------- ----- ---- ------------- -------- ------ -------
48s 26s 4 {replicaset-controller } Warning FailedCreate Error creating: pods "nginx-2040093540-" is forbidden: Failed quota: quota: must specify cpu,memory
```
The Kubernetes API server is rejecting the ReplicaSet requests to create a pod because our pods
do not specify any memory usage *request*.
So let's set some default values for the amount of cpu and memory a pod can consume:
```shell
$ kubectl create -f docs/admin/resourcequota/limits.yaml --namespace=quota-example
limitrange "limits" created
$ kubectl describe limits limits --namespace=quota-example
Name: limits
Namespace: quota-example
Type Resource Min Max Default Request Default Limit Max Limit/Request Ratio
---- -------- --- --- --------------- ------------- -----------------------
Container cpu - - 100m 200m -
Container memory - - 256Mi 512Mi -
```
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 resource *request* for our namespace, our Deployment should be able to
create its pods.
```shell
$ kubectl get pods --namespace=quota-example
NAME READY STATUS RESTARTS AGE
nginx-2040093540-miohp 1/1 Running 0 5s
```
And if we print out our quota usage in the namespace:
```shell
$ kubectl describe quota quota --namespace=quota-example
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 (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. 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.