This page shows how to configure Pods so that they will be assigned particular Quality of Service (QoS) classes. Kubernetes uses QoS classes to make decisions about scheduling and evicting Pods.
You need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. 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 kubectl version
.
When Kubernetes creates a Pod it assigns one of these QoS classes to the Pod:
Create a namespace so that the resources you create in this exercise are isolated from the rest of your cluster.
kubectl create namespace qos-example
For a Pod to be given a QoS class of Guaranteed:
Here 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:
pods/qos/qos-pod.yaml
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Create the Pod:
kubectl create -f https://k8s.io/examples/pods/qos/qos-pod.yaml --namespace=qos-example
View detailed information about the Pod:
kubectl get pod qos-demo --namespace=qos-example --output=yaml
The output shows that Kubernetes gave the Pod a QoS class of Guaranteed. The output also verifies that the Pod Container has a memory request that matches its memory limit, and it has a CPU request that matches its CPU limit.
spec:
containers:
...
resources:
limits:
cpu: 700m
memory: 200Mi
requests:
cpu: 700m
memory: 200Mi
...
qosClass: Guaranteed
Note: If a Container specifies its own memory limit, but does not specify a memory request, Kubernetes automatically assigns a memory request that matches the limit. Similarly, if a Container specifies its own CPU limit, but does not specify a CPU request, Kubernetes automatically assigns a CPU request that matches the limit.
Delete your Pod:
kubectl delete pod qos-demo --namespace=qos-example
A Pod is given a QoS class of Burstable if:
Here 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.
pods/qos/qos-pod-2.yaml
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Create the Pod:
kubectl create -f https://k8s.io/examples/pods/qos/qos-pod-2.yaml --namespace=qos-example
View detailed information about the Pod:
kubectl get pod qos-demo-2 --namespace=qos-example --output=yaml
The output shows that Kubernetes gave the Pod a QoS class of Burstable.
spec:
containers:
- image: nginx
imagePullPolicy: Always
name: qos-demo-2-ctr
resources:
limits:
memory: 200Mi
requests:
memory: 100Mi
...
qosClass: Burstable
Delete your Pod:
kubectl delete pod qos-demo-2 --namespace=qos-example
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.
Here is the configuration file for a Pod that has one Container. The Container has no memory or CPU limits or requests:
pods/qos/qos-pod-3.yaml
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Create the Pod:
kubectl create -f https://k8s.io/examples/pods/qos/qos-pod-3.yaml --namespace=qos-example
View detailed information about the Pod:
kubectl get pod qos-demo-3 --namespace=qos-example --output=yaml
The output shows that Kubernetes gave the Pod a QoS class of BestEffort.
spec:
containers:
...
resources: {}
...
qosClass: BestEffort
Delete your Pod:
kubectl delete pod qos-demo-3 --namespace=qos-example
Here is the configuration file for a Pod that has two Containers. One container specifies a memory request of 200 MiB. The other Container does not specify any requests or limits.
pods/qos/qos-pod-4.yaml
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Notice that this Pod meets the criteria for QoS class Burstable. That is, it does not meet the criteria for QoS class Guaranteed, and one of its Containers has a memory request.
Create the Pod:
kubectl create -f https://k8s.io/examples/pods/qos/qos-pod-4.yaml --namespace=qos-example
View detailed information about the Pod:
kubectl get pod qos-demo-4 --namespace=qos-example --output=yaml
The output shows that Kubernetes gave the Pod a QoS class of Burstable:
spec:
containers:
...
name: qos-demo-4-ctr-1
resources:
requests:
memory: 200Mi
...
name: qos-demo-4-ctr-2
resources: {}
...
qosClass: Burstable
Delete your Pod:
kubectl delete pod qos-demo-4 --namespace=qos-example
Delete your namespace:
kubectl delete namespace qos-example
Configure Default Memory Requests and Limits for a Namespace
Configure Minimum and Maximum Memory Constraints for a Namespace
Configure Minimum and Maximum CPU Constraints for a Namespace
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