Add support for cgroup v2 in Pulsar Loadbalancer

[lhotari]

Is your feature request related to a problem? Please describe.

The Pulsar loadbalancer detects CPU limits using cgroup v1 API.
Newer Kubernetes runtimes support cgroup v2 and popular Linux distributions are migrating to use cgroup v2 as the default option.

https://kubernetes.io/docs/setup/production-environment/container-runtimes/#cgroup-v2

https://kubernetes.io/docs/concepts/architecture/cgroups/

"Cgroup v2 is the next version of the cgroup Linux API. Differently than cgroup v1, there is a single hierarchy instead of a different one for each controller."

Describe the solution you'd like

The Pulsar loadbalancer should also support cgroup v2.

Additional context

LinuxInfoUtils class currently supports only cgroup v1

[lhotari]

Java 11 is getting cgroup v2 support in 11.0.16 with https://bugs.openjdk.org/browse/JDK-8230305 changes. It seems that Java 17 already supports cgroup v2.

[github-actions]

The issue had no activity for 30 days, mark with Stale label.

[lhotari]

It looks like Kubernetes 1.25.2+ defaults to cgroups v2 based on https://twitter.com/brunoborges/status/1644413308571721750?t=YLdUH-DamtbgA43dLCBbdw&s=19 and Azure/AKS#3443 . See https://kubernetes.io/blog/2022/08/31/cgroupv2-ga-1-25/ .
Pulsar load balancer doesn't balance memory consumption in that case since it doesn't support cgroups V2.
/Cc @nicoloboschi @michaeljmarshall

[lhotari]

" AKS Kubernetes 1.25+ uses cgroups v2."
https://github.com/Azure/AKS/releases/tag/2023-03-05

[lhotari]

GKE seems to have a way to select between cgroup v1 & cgroup v2:
https://cloud.google.com/kubernetes-engine/docs/how-to/node-system-config#cgroup-mode-options

GKE will default to cgroup v2 in new Kubernetes 1.26 clusters or node pools. Based on the doc, I would assume that upgraded clusters / node pools would continue to use cgroup v1 in GKE. However this is something that needs verification.

[lhotari]

AWS EKS v1.26 nodes will default to cgroup v2 based on this comment: awslabs/amazon-eks-ami#824 (comment)

[lhotari]

Resolved by #16832

[lhotari]

there's a backport to branch-2.10 in #20659