How do I check the max pod capacity of a Kubernetes node

I am busy setting up new k8s cluster.

I am using rke with the --max-pods: 200

kubelet: # https://rancher.com/docs/rke/latest/en/config-options/services/services-extras/#extra-args
    extra_args: 
    - max-pods: 200  # https://forums.rancher.com/t/solved-setting-max-pods/11866/5

How do I check if the running node has been created with the correct settings.

Solution 1:

Inside Kubernetes docs regarding Building large clusters we can read that at v1.17 supports:

Kubernetes supports clusters with up to 5000 nodes. More pecifically, we support configurations that meet all of the following criteria:

• No more than 5000 nodes
• No more than 150000 total pods
• No more than 300000 total containers
• No more than 100 pods per node

Inside GKE a hard limit of pods per node is 110 because of available addresses.

With the default maximum of 110 Pods per node, Kubernetes assigns a /24 CIDR block (256 addresses) to each of the nodes. By having approximately twice as many available IP addresses as the number of pods that can be created on a node, Kubernetes is able to mitigate IP address reuse as Pods are added to and removed from a node.

This is described in Optimizing IP address allocation and Quotas and limits.

As or setting max pods for Rancher here is a solution [Solved] Setting Max Pods.

There also is a discussion about Increase maximum pods per node

... using a single number (max pods) can be misleading for the users, given the huge variation in machine specs, workload, and environment. If we have a node benchmark, we can let users profile their nodes and decide what is the best configuration for them. The benchmark can exist as a node e2e test, or in the contrib repository.

I hope this provides a bit more insides to the limits.

Solution 2:

The following command will return the maximum pods value for <node_name>:

kubectl get node <node_name> -ojsonpath='{.status.capacity.pods}{"\n"}'

edit: fixed typo in my command, thanks @Shtlzut.

Solution 3:

I found this is the best way

kubectl get nodes -A
NAME            STATUS   ROLES                      AGE   VERSION
192.168.1.1   Ready    controlplane,etcd,worker   9d    v1.17.2
192.168.1.2   Ready    controlplane,etcd,worker   9d    v1.17.2

kubectl describe nodes 192.168.1.1 | grep -i pods

Capacity:
cpu:                16
ephemeral-storage:  55844040Ki
hugepages-2Mi:      0
memory:             98985412Ki
pods:               110
Allocatable:
cpu:                16
ephemeral-storage:  51465867179
hugepages-2Mi:      0
memory:             98883012Ki
pods:               110