This page shows how to configure default memory requests and limits for a namespace. If a Container is created in a namespace that has a default memory limit, and the Container does not specify its own memory limit, then the Container is assigned the default memory limit. Kubernetes assigns a default memory request under certain conditions that are explained later in this topic.
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
.
Each node in your cluster must have at least 2 GiB of memory.
Create a namespace so that the resources you create in this exercise are isolated from the rest of your cluster.
kubectl create namespace default-mem-example
Here’s the configuration file for a LimitRange object. The configuration specifies a default memory request and a default memory limit.
admin/resource/memory-defaults.yaml
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Create the LimitRange in the default-mem-example namespace:
kubectl create -f https://k8s.io/examples/admin/resource/memory-defaults.yaml --namespace=default-mem-example
Now if a Container is created in the default-mem-example namespace, and the Container does not specify its own values for memory request and memory limit, the Container is given a default memory request of 256 MiB and a default memory limit of 512 MiB.
Here’s the configuration file for a Pod that has one Container. The Container does not specify a memory request and limit.
admin/resource/memory-defaults-pod.yaml
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Create the Pod.
kubectl create -f https://k8s.io/examples/admin/resource/memory-defaults-pod.yaml --namespace=default-mem-example
View detailed information about the Pod:
kubectl get pod default-mem-demo --output=yaml --namespace=default-mem-example
The output shows that the Pod’s Container has a memory request of 256 MiB and a memory limit of 512 MiB. These are the default values specified by the LimitRange.
containers:
- image: nginx
imagePullPolicy: Always
name: default-mem-demo-ctr
resources:
limits:
memory: 512Mi
requests:
memory: 256Mi
Delete your Pod:
kubectl delete pod default-mem-demo --namespace=default-mem-example
Here’s the configuration file for a Pod that has one Container. The Container specifies a memory limit, but not a request:
admin/resource/memory-defaults-pod-2.yaml
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Create the Pod:
kubectl create -f https://k8s.io/examples/admin/resource/memory-defaults-pod-2.yaml --namespace=default-mem-example
View detailed information about the Pod:
kubectl get pod default-mem-demo-2 --output=yaml --namespace=default-mem-example
The output shows that the Container’s memory request is set to match its memory limit. Notice that the Container was not assigned the default memory request value of 256Mi.
resources:
limits:
memory: 1Gi
requests:
memory: 1Gi
Here’s the configuration file for a Pod that has one Container. The Container specifies a memory request, but not a limit:
admin/resource/memory-defaults-pod-3.yaml
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Create the Pod:
kubectl create -f https://k8s.io/examples/admin/resource/memory-defaults-pod-3.yaml --namespace=default-mem-example
View the Pod’s specification:
kubectl get pod default-mem-demo-3 --output=yaml --namespace=default-mem-example
The output shows that the Container’s memory request is set to the value specified in the Container’s configuration file. The Container’s memory limit is set to 512Mi, which is the default memory limit for the namespace.
resources:
limits:
memory: 512Mi
requests:
memory: 128Mi
If your namespace has a resource quota, it is helpful to have a default value in place for memory limit. Here are two of the restrictions that a resource quota imposes on a namespace:
If a Container does not specify its own memory limit, it is given the default limit, and then it can be allowed to run in a namespace that is restricted by a quota.
Configure Minimum and Maximum Memory Constraints for a Namespace
Configure Minimum and Maximum CPU Constraints for a Namespace
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