nri/plugins/ulimit-adjuster

ulimit Adjuster Plugin

This sample plugin can adjust ulimits for containers using pod annotations.

Annotations

ulimits are annotated using the key ulimits.noderesource.dev/container.$CONTAINER_NAME, which adjusts ulimits for $CONTAINER_NAME. For compatibility, this plugin also accepts annotations named ulimits.nri.containerd.io/container.$CONTAINER_NAME. The ulimit names are the valid names of Linux resource limits, which can be seen on the setrlimit(2) manual page.

The annotation syntax for ulimit adjustment is

- type: RLIMIT_NOFILE
  soft: 1024
  hard: 4096
- path: RLIMIT_MEMLOCK
  soft: 1073741824
  hard: 1073741824
  ...

All fields are mandatory (soft and hard will be interpreted as 0 if missing). The type field accepts names in uppercase letters ("RLIMIT_NOFILE"), lowercase letters ("rlimit_memlock"), and omitting the "RLIMIT_" prefix ("nproc").

Deployment

The NRI repository contains minimal kustomize overlays for this plugin at contrib/kustomize/ulimit-adjuster.

Deploy the latest release with:

kubectl apply -k https://github.com/containerd/nri/contrib/kustomize/ulimit-adjuster

Deploy a specific release with:

RELEASE_TAG=v0.10.0
kubectl apply -k "github.com/containerd/nri/contrib/kustomize/ulimit-adjuster?ref=${RELEASE_TAG}"

Deploy the latest development build from tip of the main branch with:

kubectl apply -k https://github.com/containerd/nri/contrib/kustomize/ulimit-adjuster/unstable

Testing

You can test this plugin using a kubernetes cluster/node with a container runtime that has NRI support enabled. Start the plugin on the target node (ulimit-adjuster -idx 10), create a pod with some annotated ulimits, then verify that those get adjusted in the container. See the sample pod spec for an example.