Configure Minimum and Maximum CPU Constraints for a Namespace

    You need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. It is recommended to run this tutorial on a cluster with at least two nodes that are not acting as control plane hosts. If you do not already have a cluster, you can create one by using minikube or you can use one of these Kubernetes playgrounds:

    To check the version, enter .

    Your cluster must have at least 1 CPU available for use to run the task examples.

    Create a namespace

    Create a namespace so that the resources you create in this exercise are isolated from the rest of your cluster.

    Create a LimitRange and a Pod

    Here’s the configuration file for a LimitRange:

    1. apiVersion: v1
    2. kind: LimitRange
    3. metadata:
    4.   name: cpu-min-max-demo-lr
    5. spec:
    6.   limits:
    7.   - max:
    8.       cpu: "800m"
    9.     min:
    10.       cpu: "200m"
    11.     type: Container

    Create the LimitRange:

    1. kubectl apply -f https://k8s.io/examples/admin/resource/cpu-constraints.yaml --namespace=constraints-cpu-example

    View detailed information about the LimitRange:

    1. kubectl get limitrange cpu-min-max-demo-lr --output=yaml --namespace=constraints-cpu-example

    The output shows the minimum and maximum CPU constraints as expected. But notice that even though you didn’t specify default values in the configuration file for the LimitRange, they were created automatically.

    1. limits:
    2. - default:
    3.     cpu: 800m
    4.   defaultRequest:
    5.     cpu: 800m
    6.   max:
    7.     cpu: 800m
    8.     cpu: 200m
    9.   type: Container

    Now whenever a Container is created in the constraints-cpu-example namespace, Kubernetes performs these steps:

    • If the Container does not specify its own CPU request and limit, assign the default CPU request and limit to the Container.

    • Verify that the Container specifies a CPU request that is greater than or equal to 200 millicpu.

    • Verify that the Container specifies a CPU limit that is less than or equal to 800 millicpu.

    Note: When creating a LimitRange object, you can specify limits on huge-pages or GPUs as well. However, when both default and defaultRequest are specified on these resources, the two values must be the same.

    Here’s the configuration file for a Pod that has one Container. The Container manifest specifies a CPU request of 500 millicpu and a CPU limit of 800 millicpu. These satisfy the minimum and maximum CPU constraints imposed by the LimitRange.

    admin/resource/cpu-constraints-pod.yaml Configure Minimum and Maximum CPU Constraints for a Namespace - 图2

    2. kind: Pod
    3. metadata:
    4.   name: constraints-cpu-demo
    5. spec:
    6.   containers:
    7.   - name: constraints-cpu-demo-ctr
    8.     image: nginx
    9.     resources:
    10.       limits:
    11.         cpu: "800m"
    12.       requests:
    13.         cpu: "500m"
    1. kubectl apply -f https://k8s.io/examples/admin/resource/cpu-constraints-pod.yaml --namespace=constraints-cpu-example

    Verify that the Pod’s Container is running:

    View detailed information about the Pod:

    1. kubectl get pod constraints-cpu-demo --output=yaml --namespace=constraints-cpu-example

    The output shows that the Container has a CPU request of 500 millicpu and CPU limit of 800 millicpu. These satisfy the constraints imposed by the LimitRange.

    1. resources:
    2.   limits:
    3.     cpu: 800m
    4.   requests:
    5.     cpu: 500m
    1. kubectl delete pod constraints-cpu-demo --namespace=constraints-cpu-example

    Attempt to create a Pod that exceeds the maximum CPU constraint

    Here’s the configuration file for a Pod that has one Container. The Container specifies a CPU request of 500 millicpu and a cpu limit of 1.5 cpu.

    admin/resource/cpu-constraints-pod-2.yaml 

    1. apiVersion: v1
    2. kind: Pod
    3. metadata:
    4.   name: constraints-cpu-demo-2
    5. spec:
    6.   containers:
    8.     image: nginx
    9.     resources:
    10.         cpu: "1.5"
    11.       requests:
    12.         cpu: "500m"

    Attempt to create the Pod:

    1. kubectl apply -f https://k8s.io/examples/admin/resource/cpu-constraints-pod-2.yaml --namespace=constraints-cpu-example

    The output shows that the Pod does not get created, because the Container specifies a CPU limit that is too large:

    1. Error from server (Forbidden): error when creating "examples/admin/resource/cpu-constraints-pod-2.yaml":
    2. pods "constraints-cpu-demo-2" is forbidden: maximum cpu usage per Container is 800m, but limit is 1500m.

    Attempt to create a Pod that does not meet the minimum CPU request

    Here’s the configuration file for a Pod that has one Container. The Container specifies a CPU request of 100 millicpu and a CPU limit of 800 millicpu.

    admin/resource/cpu-constraints-pod-3.yaml Configure Minimum and Maximum CPU Constraints for a Namespace - 图4

    Attempt to create the Pod:

    1. kubectl apply -f https://k8s.io/examples/admin/resource/cpu-constraints-pod-3.yaml --namespace=constraints-cpu-example

    The output shows that the Pod does not get created, because the Container specifies a CPU request that is too small:

    1. Error from server (Forbidden): error when creating "examples/admin/resource/cpu-constraints-pod-3.yaml":
    2. pods "constraints-cpu-demo-3" is forbidden: minimum cpu usage per Container is 200m, but request is 100m.

    Here’s the configuration file for a Pod that has one Container. The Container does not specify a CPU request, and it does not specify a CPU limit.

    1. apiVersion: v1
    2. kind: Pod
    3. metadata:
    4.   name: constraints-cpu-demo-4
    5. spec:
    6.   containers:
    7.   - name: constraints-cpu-demo-4-ctr
    8.     image: vish/stress

    Create the Pod:

    1. kubectl apply -f https://k8s.io/examples/admin/resource/cpu-constraints-pod-4.yaml --namespace=constraints-cpu-example

    View detailed information about the Pod:

    1. kubectl get pod constraints-cpu-demo-4 --namespace=constraints-cpu-example --output=yaml

    The output shows that the Pod’s Container has a CPU request of 800 millicpu and a CPU limit of 800 millicpu. How did the Container get those values?

    1. resources:
    2.   limits:
    3.     cpu: 800m
    4.   requests:

    At this point, your Container might be running or it might not be running. Recall that a prerequisite for this task is that your cluster must have at least 1 CPU available for use. If each of your Nodes has only 1 CPU, then there might not be enough allocatable CPU on any Node to accommodate a request of 800 millicpu. If you happen to be using Nodes with 2 CPU, then you probably have enough CPU to accommodate the 800 millicpu request.

    Delete your Pod:

    Enforcement of minimum and maximum CPU constraints

    The maximum and minimum CPU constraints imposed on a namespace by a LimitRange are enforced only when a Pod is created or updated. If you change the LimitRange, it does not affect Pods that were created previously.

    Motivation for minimum and maximum CPU constraints

    As a cluster administrator, you might want to impose restrictions on the CPU resources that Pods can use. For example:

    • Each Node in a cluster has 2 CPU. You do not want to accept any Pod that requests more than 2 CPU, because no Node in the cluster can support the request.

    • A cluster is shared by your production and development departments. You want to allow production workloads to consume up to 3 CPU, but you want development workloads to be limited to 1 CPU. You create separate namespaces for production and development, and you apply CPU constraints to each namespace.

    Delete your namespace:

    1. kubectl delete namespace constraints-cpu-example

    What’s next

    For app developers