assigning_limit_ranges_and_quotas.md

Assigning Limit Ranges and Quotas

In this lab you will learn how to set up limit ranges and quotas. You will also learn how to assign these to project namespaces.

Limit Ranges

Limit Ranges establish the number of compute resource constraints in a given project. These contraints affect the pod, container, image, image stream, and persistent volume claims. It specifies the amount of resources that these can consume.

It also sets the minimum, maximum, and default resources that something can/will take.

Step 1

Limit Ranges can be set on an existing project or a brand new projects. Depending what you do, there might be a caveat.

• Brand New Projects - The Limit Range will be applied immedietly.
• Existing Projects - The Limit Range will be applied immedietly, and will take affect to newly created resources. Current pods will not be affected until restart.

For this exercise we will be going the "brand new project" route. Create this project called limits-quotas

oc new-project limits-quotas
Now using project "limits-quotas" on server "https://master.example.com:8443".

You can add applications to this project with the 'new-app' command. For example, try:

    oc new-app centos/ruby-22-centos7~https://github.com/openshift/ruby-ex.git

to build a new example application in Ruby.

Assign this to user-1

oc policy add-role-to-user admin user-1 -n limits-quotas
role "admin" added: "user-1"

Step 2

In the webui, login as user-1. You should see limits-quotas listed; click on it to go to the overview page.

On the overview page; navigage to Resources ~> Quota

It should show that there is no limits or quotas set.

This means that any application created in this namespace can use as much resource that is available (default behavior). Now on the command-line (as system:admin) create a yaml file called limits.yaml. Populate it with the following

apiVersion: "v1"
kind: "LimitRange"
metadata:
  name: "resource-limits"
spec:
  limits:
    - type: "Pod"
      max:
        cpu: "2"
        memory: "1Gi"
      min:
        cpu: "200m"
        memory: "6Mi"
    - type: "Container"
      max:
        cpu: "2"
        memory: "1Gi"
      min:
        cpu: "100m"
        memory: "4Mi"
      default:
        cpu: "300m"
        memory: "200Mi"
      defaultRequest:
        cpu: "200m"
        memory: "100Mi"
      maxLimitRequestRatio:
        cpu: "10"

The above configurations sets the lower, upper, and default resources that can be consumned by a pod or container.

Apply this to the limits-quotas project you created.

oc create -f limits.yaml -n limits-quotas
limitrange "resource-limits" created

Refresh the page and you should see the limit range is now applied.

Step 3

Now create an application and see how it affects it.

oc new-app redhatworkshops/welcome-php --name=welcome-limits -n limits-quotas
--> Found Docker image 3e73433 (7 months old) from Docker Hub for "redhatworkshops/welcome-php"

    chx/welcome-php-1:b68a2d86 
    -------------------------- 
    Platform for building and running PHP 5.6 applications

    Tags: builder, php, php56, rh-php56

    * An image stream will be created as "welcome-limits:latest" that will track this image
    * This image will be deployed in deployment config "welcome-limits"
    * Port 8080/tcp will be load balanced by service "welcome-limits"
      * Other containers can access this service through the hostname "welcome-limits"

--> Creating resources ...
    imagestream "welcome-limits" created
    deploymentconfig "welcome-limits" created
    service "welcome-limits" created
--> Success
    Run 'oc status' to view your app.

If you naviate to the overview page; you should see the application up and running.

Click on the blue circle (representing the pod), then click on the "Metrics" tab to see what is being consumed.

Quotas

Limit Ranges only defines what is currently being consumed. If you want to set a "hard limit" or a "ceiling" of resources, then quotas is your friend.

Step 1

You set up quotas in a similar fashion. First you create a yaml definition. For this example we are setting a hard limit of 4 pods. Create the yaml file with the name quotas.yaml

apiVersion: v1
kind: ResourceQuota
metadata:
  name: pod-quota
spec:
  hard:
    pods: "4"

Add this to the limits-quotas project

oc create -f quotas.yaml -n limits-quotas
resourcequota "pod-quota" created

If you navigate to the quotas overview page, you should see the quotas have taken effect.

Test this by trying to scale the app in the overview page. Do this by clicking the ▲ button by the blue circle. You should see a message about your quota being reached

Conclusion

In this lab you learned how to assign limits and quotas. You also learned how to assign these to a specific project and saw how it affected the creation of applications.

Setting up limits and quotas can be a complex subject. Please consult the official documents for further information about quotas and limit ranges