Configure Quality of Service(QoS) for Pods

Kubernetes uses Quality of Service classes (QoS) to make decisions about scheduling and evicting pods.

QoS classes:

When Kubernetes creates a Pod it assigns one of these QoS classes to the Pod:

• Guaranteed
• Burstable
• BestEffort

Guaranteed:

A pod gets assigned a QoS class of Guaranteed when it satisfies the following,

• Every Container in the Pod must have a memory limit and a memory request.
• For every Container in the Pod, the memory limit must equal the memory request.
• Every Container in the Pod must have a CPU limit and a CPU request.
• For every Container in the Pod, the CPU limit must equal the CPU request.

These restrictions apply to init containers and app containers equally.

apiVersion: v1

kind: Pod

metadata:

  name: qos-demo

  namespace: qos-example

spec:

  containers:

  - name: qos-demo-ctr

    image: nginx

    resources:

      limits:

        memory: "200Mi"

        cpu: "700m"

      requests:

        memory: "200Mi"

        cpu: "700m"

Above is the configuration file for a Pod that has one Container. The Container has a memory limit and a memory request, both equal to 200 MiB. The Container has a CPU limit and a CPU request, both equal to 700 milliCPU.

Now create the pod.

kubectl apply -f qos-pod.yaml

Check the QoS class assigned to Pod,

Burstable:

A Pod is given a QoS class of Burstable if:

• The Pod does not meet the criteria for QoS class Guaranteed.
• At least one Container in the Pod has a memory or CPU request or limit.

apiVersion: v1

kind: Pod

metadata:

  name: qos-demo-2

  namespace: qos-example

spec:

  containers:

  - name: qos-demo-2-ctr

    image: nginx

    resources:

      limits:

        memory: "200Mi"

      requests:

        memory: "100Mi"

Above is the configuration file for a Pod that has one Container. The Container has a memory limit of 200 MiB and a memory request of 100 MiB.

Create the Pod:

kubectl apply -f qos-pod-2.yaml

Check the QoS class assigned to Pod:

kubectl get pod qos-demo-2 --namespace=qos-example --output=yaml | grep "qosClass:"

BestEffort:

For a Pod to be given a QoS class of BestEffort, the Containers in the Pod must not have any memory or CPU limits or requests.

apiVersion: v1

kind: Pod

metadata:

  name: qos-demo-3

  namespace: qos-example

spec:

  containers:

  - name: qos-demo-3-ctr

    image: nginx

Above is the configuration file for a Pod that has one Container. The Container has no memory or CPU limits or requests.

Create the Pod:

kubectl apply -f qos-pod-3.yaml

Check the QoS class assigned to Pod:

kubectl describe -n qos-example pod qos-demo-3 | grep "QoS Class"