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Tidy resource management task pages

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Revise tasks within “Manage Memory, CPU, and API Resources”:

- reword to avoid implying that API clients can create a container
  (you can, but its done by creating a Pod)
- call a manifest a manifest
- use tooltips where relevant
- link to new API reference not the old one
- other improvements
This commit is contained in:
Tim Bannister
2021-10-12 23:21:17 +01:00
parent 239eb65bc2
commit 5ab064ceea
6 changed files with 225 additions and 155 deletions
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content/en/docs/tasks/administer-cluster/manage-resources/memory-constraint-namespace.md
+43 -37
View File
@@ -7,7 +7,7 @@ weight: 30
<!-- overview -->
This page shows how to set minimum and maximum values for memory used by Containers
This page shows how to set minimum and maximum values for memory used by containers
running in a namespace. You specify minimum and maximum memory values in a
[LimitRange](/docs/reference/generated/kubernetes-api/{{< param "version" >}}/#limitrange-v1-core)
object. If a Pod does not meet the constraints imposed by the LimitRange,
@@ -15,16 +15,14 @@ it cannot be created in the namespace.
## {{% heading "prerequisites" %}}
{{< include "task-tutorial-prereqs.md" >}} {{< version-check >}}
Each node in your cluster must have at least 1 GiB of memory.
{{< include "task-tutorial-prereqs.md" >}}
You must have access to create namespaces in your cluster.
Each node in your cluster must have at least 1 GiB of memory available for Pods.
<!-- steps -->
@@ -39,7 +37,7 @@ kubectl create namespace constraints-mem-example
## Create a LimitRange and a Pod
Here's the configuration file for a LimitRange:
Here's an example manifest for a LimitRange:
{{< codenew file="admin/resource/memory-constraints.yaml" >}}
@@ -72,18 +70,19 @@ file for the LimitRange, they were created automatically.
type: Container
```
Now whenever a Container is created in the constraints-mem-example namespace, Kubernetes
Now whenever you define a Pod within the constraints-mem-example namespace, Kubernetes
performs these steps:
* If the Container does not specify its own memory request and limit, assign the default
memory request and limit to the Container.
* If any container in that Pod does not specify its own memory request and limit, assign
the default memory request and limit to that container.
* Verify that the Container has a memory request that is greater than or equal to 500 MiB.
* Verify that every container in that Pod requests at least 500 MiB of memory.
* Verify that the Container has a memory limit that is less than or equal to 1 GiB.
* Verify that every container in that Pod requests no more than 1024 MiB (1 GiB)
of memory.
Here's the configuration file for a Pod that has one Container. The Container manifest
specifies a memory request of 600 MiB and a memory limit of 800 MiB. These satisfy the
Here's a manifest for a Pod that has one container. Within the Pod spec, the sole
container specifies a memory request of 600 MiB and a memory limit of 800 MiB. These satisfy the
minimum and maximum memory constraints imposed by the LimitRange.
{{< codenew file="admin/resource/memory-constraints-pod.yaml" >}}
@@ -94,7 +93,7 @@ Create the Pod:
kubectl apply -f https://k8s.io/examples/admin/resource/memory-constraints-pod.yaml --namespace=constraints-mem-example
```
Verify that the Pod's Container is running:
Verify that the Pod is running and that its container is healthy:
```shell
kubectl get pod constraints-mem-demo --namespace=constraints-mem-example
@@ -106,8 +105,9 @@ View detailed information about the Pod:
kubectl get pod constraints-mem-demo --output=yaml --namespace=constraints-mem-example
```
The output shows that the Container has a memory request of 600 MiB and a memory limit
of 800 MiB. These satisfy the constraints imposed by the LimitRange.
The output shows that the container within that Pod has a memory request of 600 MiB and
a memory limit of 800 MiB. These satisfy the constraints imposed by the LimitRange for
this namespace:
```yaml
resources:
@@ -125,7 +125,7 @@ kubectl delete pod constraints-mem-demo --namespace=constraints-mem-example
## Attempt to create a Pod that exceeds the maximum memory constraint
Here's the configuration file for a Pod that has one Container. The Container specifies a
Here's a manifest for a Pod that has one container. The container specifies a
memory request of 800 MiB and a memory limit of 1.5 GiB.
{{< codenew file="admin/resource/memory-constraints-pod-2.yaml" >}}
@@ -136,8 +136,8 @@ Attempt to create the Pod:
kubectl apply -f https://k8s.io/examples/admin/resource/memory-constraints-pod-2.yaml --namespace=constraints-mem-example
```
The output shows that the Pod does not get created, because the Container specifies a memory limit that is
too large:
The output shows that the Pod does not get created, because it defines a container that
requests more memory than is allowed:
```
Error from server (Forbidden): error when creating "examples/admin/resource/memory-constraints-pod-2.yaml":
@@ -146,7 +146,7 @@ pods "constraints-mem-demo-2" is forbidden: maximum memory usage per Container i
## Attempt to create a Pod that does not meet the minimum memory request
Here's the configuration file for a Pod that has one Container. The Container specifies a
Here's a manifest for a Pod that has one container. That container specifies a
memory request of 100 MiB and a memory limit of 800 MiB.
{{< codenew file="admin/resource/memory-constraints-pod-3.yaml" >}}
@@ -157,8 +157,8 @@ Attempt to create the Pod:
kubectl apply -f https://k8s.io/examples/admin/resource/memory-constraints-pod-3.yaml --namespace=constraints-mem-example
```
The output shows that the Pod does not get created, because the Container specifies a memory
request that is too small:
The output shows that the Pod does not get created, because it defines a container
that requests less memory than the enforced minimum:
```
Error from server (Forbidden): error when creating "examples/admin/resource/memory-constraints-pod-3.yaml":
@@ -167,9 +167,7 @@ pods "constraints-mem-demo-3" is forbidden: minimum memory usage per Container i
## Create a Pod that does not specify any memory request or limit
Here's the configuration file for a Pod that has one Container. The Container does not
Here's a manifest for a Pod that has one container. The container does not
specify a memory request, and it does not specify a memory limit.
{{< codenew file="admin/resource/memory-constraints-pod-4.yaml" >}}
@@ -182,12 +180,12 @@ kubectl apply -f https://k8s.io/examples/admin/resource/memory-constraints-pod-4
View detailed information about the Pod:
```
```shell
kubectl get pod constraints-mem-demo-4 --namespace=constraints-mem-example --output=yaml
```
The output shows that the Pod's Container has a memory request of 1 GiB and a memory limit of 1 GiB.
How did the Container get those values?
The output shows that the Pod's only container has a memory request of 1 GiB and a memory limit of 1 GiB.
How did that container get those values?
```
resources:
@@ -197,11 +195,20 @@ resources:
memory: 1Gi
```
Because your Container did not specify its own memory request and limit, it was given the
Because your Pod did not define any memory request and limit for that container, the cluster
applied a
[default memory request and limit](/docs/tasks/administer-cluster/manage-resources/memory-default-namespace/)
from the LimitRange.
At this point, your Container might be running or it might not be running. Recall that a prerequisite
This means that the definition of that Pod shows those values. You can check it using
`kubectl describe`:
```shell
# Look for the "Requests:" section of the output
kubectl describe pod constraints-mem-demo-4 --namespace=constraints-mem-example
```
At this point, your Pod might be running or it might not be running. Recall that a prerequisite
for this task is that your Nodes have at least 1 GiB of memory. If each of your Nodes has only
1 GiB of memory, then there is not enough allocatable memory on any Node to accommodate a memory
request of 1 GiB. If you happen to be using Nodes with 2 GiB of memory, then you probably have
@@ -209,7 +216,7 @@ enough space to accommodate the 1 GiB request.
Delete your Pod:
```
```shell
kubectl delete pod constraints-mem-demo-4 --namespace=constraints-mem-example
```
@@ -224,12 +231,12 @@ Pods that were created previously.
As a cluster administrator, you might want to impose restrictions on the amount of memory that Pods can use.
For example:
* Each Node in a cluster has 2 GB of memory. You do not want to accept any Pod that requests
more than 2 GB of memory, because no Node in the cluster can support the request.
* Each Node in a cluster has 2 GiB of memory. You do not want to accept any Pod that requests
more than 2 GiB of memory, 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 8 GB of memory, but
you want development workloads to be limited to 512 MB. You create separate namespaces
You want to allow production workloads to consume up to 8 GiB of memory, but
you want development workloads to be limited to 512 MiB. You create separate namespaces
for production and development, and you apply memory constraints to each namespace.
## Clean up
@@ -241,7 +248,6 @@ kubectl delete namespace constraints-mem-example
```
## {{% heading "whatsnext" %}}