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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-default-namespace.md
+47 -26
View File
@@ -6,17 +6,28 @@ weight: 10
<!-- overview -->
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.
This page shows how to configure default memory requests and limits for a
{{< glossary_tooltip text="namespace" term_id="namespace" >}}.
A Kubernetes cluster can be divided into namespaces. Once you have a namespace that
that has a default memory
[limit](/docs/concepts/configuration/manage-resources-containers/#requests-and-limits),
and you then try to create a Pod with a container that does not specify its own memory
limit its own memory limit, then the
{{< glossary_tooltip text="control plane" term_id="control-plane" >}} assigns the default
memory limit to that container.
Kubernetes assigns a default memory request under certain conditions that are explained later in this topic.
## {{% heading "prerequisites" %}}
{{< include "task-tutorial-prereqs.md" >}} {{< version-check >}}
{{< include "task-tutorial-prereqs.md" >}}
You must have access to create namespaces in your cluster.
Each node in your cluster must have at least 2 GiB of memory.
@@ -35,8 +46,9 @@ kubectl create namespace default-mem-example
## Create a LimitRange and a Pod
Here's the configuration file for a LimitRange object. The configuration specifies
a default memory request and a default memory limit.
Here's a manifest for an example {{< glossary_tooltip text="LimitRange" term_id="limitrange" >}}.
The manifest specifies a default memory
request and a default memory limit.
{{< codenew file="admin/resource/memory-defaults.yaml" >}}
@@ -46,12 +58,13 @@ Create the LimitRange in the default-mem-example namespace:
kubectl apply -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.
Now if you create a Pod in the default-mem-example namespace, and any container
within that Pod does not specify its own values for memory request and memory limit,
then the {{< glossary_tooltip text="control plane" term_id="control-plane" >}}
applies default values: a memory request of 256MiB and a memory limit of 512MiB.
Here's the configuration file for a Pod that has one Container. The Container
Here's an example manifest for a Pod that has one container. The container
does not specify a memory request and limit.
{{< codenew file="admin/resource/memory-defaults-pod.yaml" >}}
@@ -68,7 +81,7 @@ 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
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.
```shell
@@ -89,9 +102,9 @@ Delete your Pod:
kubectl delete pod default-mem-demo --namespace=default-mem-example
```
## What if you specify a Container's limit, but not its request?
## What if you specify a container's limit, but not its request?
Here's the configuration file for a Pod that has one Container. The Container
Here's a manifest for a Pod that has one container. The container
specifies a memory limit, but not a request:
{{< codenew file="admin/resource/memory-defaults-pod-2.yaml" >}}
@@ -109,8 +122,8 @@ 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.
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:
@@ -120,9 +133,9 @@ resources:
memory: 1Gi
```
## What if you specify a Container's request, but not its limit?
## What if you specify a container's request, but not its limit?
Here's the configuration file for a Pod that has one Container. The Container
Here's a manifest for a Pod that has one container. The container
specifies a memory request, but not a limit:
{{< codenew file="admin/resource/memory-defaults-pod-3.yaml" >}}
@@ -139,9 +152,9 @@ 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.
The output shows that the container's memory request is set to the value specified in the
container's manifest. The container is limited to use no more than 512MiB of
memory, which matches the default memory limit for the namespace.
```
resources:
@@ -153,15 +166,23 @@ resources:
## Motivation for default memory limits and requests
If your namespace has a resource quota,
If your namespace has a memory {{< glossary_tooltip text="resource quota" term_id="resource-quota" >}}
configured,
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:
* Every Container that runs in the namespace must have its own memory limit.
* The total amount of memory used by all Containers in the namespace must not exceed a specified limit.
* For every Pod that runs in the namespace, the Pod and each of its containers must have a memory limit.
(If you specify a memory limit for every container in a Pod, Kubernetes can infer the Pod-level memory
limit by adding up the limits for its containers).
* CPU limits apply a resource reservation on the node where the Pod in question is scheduled.
The total amount of memory reserved for all Pods in the namespace must not exceed a specified limit.
* The total amount of memory actually used by all Pods in the namespace must also not exceed a specified limit.
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.
When you add a LimitRange:
If any Pod in that namespace that includes a container does not specify its own memory limit,
the control plane applies the default memory limit to that container, and the Pod can be
allowed to run in a namespace that is restricted by a memory ResourceQuota.
## Clean up