Tasks

Tasks
Administer a Cluster
Access Clusters Using the Kubernetes API
Access Services Running on Clusters
Advertise Extended Resources for a Node
Autoscale the DNS Service in a Cluster
Change the Reclaim Policy of a PersistentVolume
Change the default StorageClass
Cluster Management
Configure Multiple Schedulers
Configure Out Of Resource Handling
Configure Quotas for API Objects
Control CPU Management Policies on the Node
Customizing DNS Service
Debugging DNS Resolution
Declare Network Policy
Developing Cloud Controller Manager
Encrypting Secret Data at Rest
Guaranteed Scheduling For Critical Add-On Pods
IP Masquerade Agent User Guide
Kubernetes Cloud Controller Manager
Limit Storage Consumption
Namespaces Walkthrough
Operating etcd clusters for Kubernetes
Reconfigure a Node's Kubelet in a Live Cluster
Reserve Compute Resources for System Daemons
Safely Drain a Node while Respecting Application SLOs
Securing a Cluster
Set Kubelet parameters via a config file
Set up High-Availability Kubernetes Masters
Share a Cluster with Namespaces
Static Pods
Storage Object in Use Protection
Using CoreDNS for Service Discovery
Using a KMS provider for data encryption
Using sysctls in a Kubernetes Cluster
Extend kubectl with plugins
Manage HugePages
Schedule GPUs

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Advertise Extended Resources for a Node

This page shows how to specify extended resources for a Node. Extended resources allow cluster administrators to advertise node-level resources that would otherwise be unknown to Kubernetes.

FEATURE STATE: Kubernetes v1.13 stable

Before you begin

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.

Get the names of your Nodes

kubectl get nodes

Choose one of your Nodes to use for this exercise.

To advertise a new extended resource on a Node, send an HTTP PATCH request to the Kubernetes API server. For example, suppose one of your Nodes has four dongles attached. Here’s an example of a PATCH request that advertises four dongle resources for your Node.

PATCH /api/v1/nodes/<your-node-name>/status HTTP/1.1
Accept: application/json
Content-Type: application/json-patch+json
Host: k8s-master:8080

[
  {
    "op": "add",
    "path": "/status/capacity/example.com~1dongle",
    "value": "4"
  }
]

Note that Kubernetes does not need to know what a dongle is or what a dongle is for. The preceding PATCH request just tells Kubernetes that your Node has four things that you call dongles.

Start a proxy, so that you can easily send requests to the Kubernetes API server:

kubectl proxy

In another command window, send the HTTP PATCH request. Replace <your-node-name> with the name of your Node:

curl --header "Content-Type: application/json-patch+json" \
--request PATCH \
--data '[{"op": "add", "path": "/status/capacity/example.com~1dongle", "value": "4"}]' \
http://localhost:8001/api/v1/nodes/<your-node-name>/status
Note: In the preceding request, ~1 is the encoding for the character / in the patch path. The operation path value in JSON-Patch is interpreted as a JSON-Pointer. For more details, see IETF RFC 6901, section 3.

The output shows that the Node has a capacity of 4 dongles:

"capacity": {
  "cpu": "2",
  "memory": "2049008Ki",
  "example.com/dongle": "4",

Describe your Node:

kubectl describe node <your-node-name>

Once again, the output shows the dongle resource:

Capacity:
 cpu:  2
 memory:  2049008Ki
 example.com/dongle:  4

Now, application developers can create Pods that request a certain number of dongles. See Assign Extended Resources to a Container.

Discussion

Extended resources are similar to memory and CPU resources. For example, just as a Node has a certain amount of memory and CPU to be shared by all components running on the Node, it can have a certain number of dongles to be shared by all components running on the Node. And just as application developers can create Pods that request a certain amount of memory and CPU, they can create Pods that request a certain number of dongles.

Extended resources are opaque to Kubernetes; Kubernetes does not know anything about what they are. Kubernetes knows only that a Node has a certain number of them. Extended resources must be advertised in integer amounts. For example, a Node can advertise four dongles, but not 4.5 dongles.

Storage example

Suppose a Node has 800 GiB of a special kind of disk storage. You could create a name for the special storage, say example.com/special-storage. Then you could advertise it in chunks of a certain size, say 100 GiB. In that case, your Node would advertise that it has eight resources of type example.com/special-storage.

Capacity:
 ...
 example.com/special-storage: 8

If you want to allow arbitrary requests for special storage, you could advertise special storage in chunks of size 1 byte. In that case, you would advertise 800Gi resources of type example.com/special-storage.

Capacity:
 ...
 example.com/special-storage:  800Gi

Then a Container could request any number of bytes of special storage, up to 800Gi.

Clean up

Here is a PATCH request that removes the dongle advertisement from a Node.

PATCH /api/v1/nodes/<your-node-name>/status HTTP/1.1
Accept: application/json
Content-Type: application/json-patch+json
Host: k8s-master:8080

[
  {
    "op": "remove",
    "path": "/status/capacity/example.com~1dongle",
  }
]

Start a proxy, so that you can easily send requests to the Kubernetes API server:

kubectl proxy

In another command window, send the HTTP PATCH request. Replace <your-node-name> with the name of your Node:

curl --header "Content-Type: application/json-patch+json" \
--request PATCH \
--data '[{"op": "remove", "path": "/status/capacity/example.com~1dongle"}]' \
http://localhost:8001/api/v1/nodes/<your-node-name>/status

Verify that the dongle advertisement has been removed:

kubectl describe node <your-node-name> | grep dongle

What's next

For application developers

For cluster administrators

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