Leverage PodDefaults

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This guide explains how to apply some common configurations to Pods with the use of PodDefaults.

PodDefaults in Charmed Kubeflow (CKF) automate the modification of PodSpecs requested by Kubeflow components at creation time. The PodDefault API resource is defined by a CustomResourceDefinition (CRD) created by the admission-webhook charm.

Inject environment variables

Create a PodDefault to inject environment variables into a Pod as follows:

apiVersion: kubeflow.org/v1alpha1
kind: PodDefault
metadata:
  name: env-poddefault
spec:
  desc: short description of the PodDefault
  env:
  - name: ENV1
    value: value1
  - name: ENV2
    value: value2
  selector:
    matchLabels:
      env-poddefault: "true"

This PodDefault adds ENV1 and ENV2 with values value1 and value2 respectively to all containers of the Pod with the label env-poddefault.

For example, the PodDefault for integrating MinIO adds the environment variables with S3 credentials.

Add tolerations

Create a PodDefault to add tolerations to a Pod as follows:

apiVersion: kubeflow.org/v1alpha1
kind: PodDefault
metadata:
  name: tolerations-poddefault
spec:
  desc: short description of the PodDefault
  tolerations:
  - key: "myToleration"
    operator: "Equal"
    value: "true"
    effect: "NoSchedule"
  selector:
    matchLabels:
      tolerations-poddefault: "true"

This PodDefault adds to the Pod tolerations, where the toleration allows Pods with the label toleration-poddefault to be scheduled on nodes that have a taint with the same key and value as mentioned in the toleration.

See Taints and Tolerations for more details.

Set command and arguments

Create a PodDefault to set the commands and/or arguments of containers in the Pod as follows:

apiVersion: kubeflow.org/v1alpha1
kind: PodDefault
metadata:
  name: command-poddefault
spec:
  desc: short description of the PodDefault
  command: ["printenv"]
  args: ["HOSTNAME", "KUBERNETES_PORT"]
  selector:
    matchLabels:
      command-poddefault: "true"

This PodDefaults sets the command and arguments to print the values of environment variables HOSTNAME and KUBERNETES_PORT.

For example, the allow-ngc-notebook PodDefault in the ngc-integrator charm sets the command and args to start an NGC notebook.

Disable Istio sidecar

By default, Istio sidecar injection for Pods in Kubeflow namespaces is enabled. To disable it, you can leverage the following PodDefault:

apiVersion: kubeflow.org/v1alpha1
kind: PodDefault
metadata:
  name: disable-istio-poddefault
spec:
  desc: Disable Istio sidecar injection
  annotations:
    "sidecar.istio.io/inject": "false"
  selector:
    matchLabels:
      disable-istio-sidecar: "true"

For example, to create a KServe InferenceService as shown in Build your first ML model, you need to disable Istio sidecar injection for the InferenceService Pod.

In the tutorial, it is done by adding the annotation "sidecar.istio.io/inject": "false". Instead, you can create the PodDefault above and apply the disable-istio-sidecar label to the InferenceService definition.