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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/cpu-default-namespace.md
+51 -32
View File
@@ -6,19 +6,29 @@ weight: 20
<!-- overview -->
This page shows how to configure default CPU requests and limits for a namespace.
A Kubernetes cluster can be divided into namespaces. If a Container is created in a namespace
that has a default CPU limit, and the Container does not specify its own CPU limit, then
the Container is assigned the default CPU limit. Kubernetes assigns a default CPU request
under certain conditions that are explained later in this topic.
This page shows how to configure default CPU requests and limits for a
{{< glossary_tooltip text="namespace" term_id="namespace" >}}.
A Kubernetes cluster can be divided into namespaces. If you create a Pod within a
namespace that has a default CPU
[limit](/docs/concepts/configuration/manage-resources-containers/#requests-and-limits), and any container in that Pod does not specify
its own CPU limit, then the
{{< glossary_tooltip text="control plane" term_id="control-plane" >}} assigns the default
CPU limit to that container.
Kubernetes assigns a default CPU
[request](/docs/concepts/configuration/manage-resources-containers/#requests-and-limits),
but only under certain conditions that are explained later in this page.
## {{% heading "prerequisites" %}}
{{< include "task-tutorial-prereqs.md" >}} {{< version-check >}}
{{< include "task-tutorial-prereqs.md" >}}
You must have access to create namespaces in your cluster.
If you're not already familiar with what Kubernetes means by 1.0 CPU,
read [meaning of CPU](/docs/concepts/configuration/manage-resources-containers/#meaning-of-cpu).
<!-- steps -->
@@ -33,8 +43,8 @@ kubectl create namespace default-cpu-example
## Create a LimitRange and a Pod
Here's the configuration file for a LimitRange object. The configuration specifies
a default CPU request and a default CPU limit.
Here's a manifest for an example {{< glossary_tooltip text="LimitRange" term_id="limitrange" >}}.
The manifest specifies a default CPU request and a default CPU limit.
{{< codenew file="admin/resource/cpu-defaults.yaml" >}}
@@ -44,12 +54,12 @@ Create the LimitRange in the default-cpu-example namespace:
kubectl apply -f https://k8s.io/examples/admin/resource/cpu-defaults.yaml --namespace=default-cpu-example
```
Now if a Container is created in the default-cpu-example namespace, and the
Container does not specify its own values for CPU request and CPU limit,
the Container is given a default CPU request of 0.5 and a default
Now if you create a Pod in the default-cpu-example namespace, and any container
in that Pod does not specify its own values for CPU request and CPU limit,
then the control plane applies default values: a CPU request of 0.5 and a default
CPU limit of 1.
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
does not specify a CPU request and limit.
{{< codenew file="admin/resource/cpu-defaults-pod.yaml" >}}
@@ -66,8 +76,9 @@ View the Pod's specification:
kubectl get pod default-cpu-demo --output=yaml --namespace=default-cpu-example
```
The output shows that the Pod's Container has a CPU request of 500 millicpus and
a CPU limit of 1 cpu. These are the default values specified by the LimitRange.
The output shows that the Pod's only container has a CPU request of 500m `cpu`
(which you can read as “500 millicpu”), and a CPU limit of 1 `cpu`.
These are the default values specified by the LimitRange.
```shell
containers:
@@ -81,9 +92,9 @@ containers:
cpu: 500m
```
## 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 CPU limit, but not a request:
{{< codenew file="admin/resource/cpu-defaults-pod-2.yaml" >}}
@@ -95,14 +106,15 @@ Create the Pod:
kubectl apply -f https://k8s.io/examples/admin/resource/cpu-defaults-pod-2.yaml --namespace=default-cpu-example
```
View the Pod specification:
View the [specification](/docs/concepts/overview/working-with-objects/kubernetes-objects/#object-spec-and-status)
of the Pod that you created:
```
kubectl get pod default-cpu-demo-2 --output=yaml --namespace=default-cpu-example
```
The output shows that the Container's CPU request is set to match its CPU limit.
Notice that the Container was not assigned the default CPU request value of 0.5 cpu.
The output shows that the container's CPU request is set to match its CPU limit.
Notice that the container was not assigned the default CPU request value of 0.5 `cpu`:
```
resources:
@@ -112,9 +124,9 @@ resources:
cpu: "1"
```
## 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 an example manifest for a Pod that has one container. The container
specifies a CPU request, but not a limit:
{{< codenew file="admin/resource/cpu-defaults-pod-3.yaml" >}}
@@ -125,15 +137,16 @@ Create the Pod:
kubectl apply -f https://k8s.io/examples/admin/resource/cpu-defaults-pod-3.yaml --namespace=default-cpu-example
```
View the Pod specification:
View the specification of the Pod that you created:
```
kubectl get pod default-cpu-demo-3 --output=yaml --namespace=default-cpu-example
```
The output shows that the Container's CPU request is set to the value specified in the
Container's configuration file. The Container's CPU limit is set to 1 cpu, which is the
default CPU limit for the namespace.
The output shows that the container's CPU request is set to the value you specified at
the time you created the Pod (in other words: it matches the manifest).
However, the same container's CPU limit is set to 1 `cpu`, which is the default CPU limit
for that namespace.
```
resources:
@@ -145,16 +158,22 @@ resources:
## Motivation for default CPU limits and requests
If your namespace has a
[resource quota](/docs/tasks/administer-cluster/manage-resources/quota-memory-cpu-namespace/),
If your namespace has a CPU {{< glossary_tooltip text="resource quota" term_id="resource-quota" >}}
configured,
it is helpful to have a default value in place for CPU limit.
Here are two of the restrictions that a resource quota imposes on a namespace:
Here are two of the restrictions that a CPU resource quota imposes on a namespace:
* Every Container that runs in the namespace must have its own CPU limit.
* The total amount of CPU used by all Containers in the namespace must not exceed a specified limit.
* For every Pod that runs in the namespace, each of its containers must have a CPU limit.
* CPU limits apply a resource reservation on the node where the Pod in question is scheduled.
The total amount of CPU that is reserved for use by all Pods in the namespace must not
exceed a specified limit.
When you add a LimitRange:
If any Pod in that namespace that includes a container does not specify its own CPU limit,
the control plane applies the default CPU limit to that container, and the Pod can be
allowed to run in a namespace that is restricted by a CPU ResourceQuota.
If a Container does not specify its own CPU limit, it is given the default limit, and then
it can be allowed to run in a namespace that is restricted by a quota.
## Clean up