Node Taint

Introduction¶

It taints the node to apply the desired effect. The resources which contains the correspoing tolerations can only bypass the taints.

Scenario: Taint the node

Node Taint

Uses¶

View the uses of the experiment

coming soon

Prerequisites¶

Verify the prerequisites

Ensure that Kubernetes Version > 1.16
Ensure that the Litmus Chaos Operator is running by executing kubectl get pods in operator namespace (typically, litmus).If not, install from here
Ensure that the node-taint experiment resource is available in the cluster by executing kubectl get chaosexperiments in the desired namespace. If not, install from here
Ensure that the node specified in the experiment ENV variable TARGET_NODE (the node which will be tainted) should be cordoned before execution of the chaos experiment (before applying the chaosengine manifest) to ensure that the litmus experiment runner pods are not scheduled on it / subjected to eviction. This can be achieved with the following steps:
- Get node names against the applications pods: kubectl get pods -o wide
- Cordon the node kubectl cordon <nodename>

Default Validations¶

View the default validations

The target nodes should be in ready state before and after chaos injection.

Minimal RBAC configuration example (optional)¶

NOTE

If you are using this experiment as part of a litmus workflow scheduled constructed & executed from chaos-center, then you may be making use of the litmus-admin RBAC, which is pre installed in the cluster as part of the agent setup.

View the Minimal RBAC permissions

---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: node-taint-sa
  namespace: default
  labels:
    name: node-taint-sa
    app.kubernetes.io/part-of: litmus
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: node-taint-sa
  labels:
    name: node-taint-sa
    app.kubernetes.io/part-of: litmus
rules:
# Create and monitor the experiment & helper pods
  - apiGroups: [""]
    resources: ["pods"]
    verbs: ["create","delete","get","list","patch","update", "deletecollection"]
  # Performs CRUD operations on the events inside chaosengine and chaosresult
  - apiGroups: [""]
    resources: ["events"]
    verbs: ["create","get","list","patch","update"]
  # Fetch configmaps details and mount it to the experiment pod (if specified)
  - apiGroups: [""]
    resources: ["configmaps"]
    verbs: ["get","list",]
  # Track and get the runner, experiment, and helper pods log 
  - apiGroups: [""]
    resources: ["pods/log"]
    verbs: ["get","list","watch"]  
  # for creating and managing to execute comands inside target container
  - apiGroups: [""]
    resources: ["pods/exec","pods/eviction"]
    verbs: ["get","list","create"]
  # ignore daemonsets while draining the node
  - apiGroups: ["apps"]
    resources: ["daemonsets"]
    verbs: ["list","get","delete"]
  # for configuring and monitor the experiment job by the chaos-runner pod
  - apiGroups: ["batch"]
    resources: ["jobs"]
    verbs: ["create","list","get","delete","deletecollection"]
  # for creation, status polling and deletion of litmus chaos resources used within a chaos workflow
  - apiGroups: ["litmuschaos.io"]
    resources: ["chaosengines","chaosexperiments","chaosresults"]
    verbs: ["create","list","get","patch","update","delete"]
  # for experiment to perform node status checks
  - apiGroups: [""]
    resources: ["nodes"]
    verbs: ["get","list","patch","update"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: node-taint-sa
  labels:
    name: node-taint-sa
    app.kubernetes.io/part-of: litmus
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: node-taint-sa
subjects:
- kind: ServiceAccount
  name: node-taint-sa
  namespace: default

Use this sample RBAC manifest to create a chaosServiceAccount in the desired (app) namespace. This example consists of the minimum necessary role permissions to execute the experiment.

Experiment tunables¶

check the experiment tunables

Mandatory Fields

Variables	Description	Notes
TARGET_NODE	Name of the node to be tainted
NODE_LABEL	It contains node label, which will be used to filter the target node if TARGET_NODE ENV is not set	It is mutually exclusive with the TARGET_NODE ENV. If both are provided then it will use the TARGET_NODE
TAINT_LABEL	Label and effect to be tainted on application node

Optional Fields

Variables	Description	Notes
TOTAL_CHAOS_DURATION	The time duration for chaos insertion (seconds)	Defaults to 60s
LIB	The chaos lib used to inject the chaos	Defaults to `litmus`
RAMP_TIME	Period to wait before injection of chaos in sec

Experiment Examples¶

Common and Node specific tunables¶

Refer the common attributes and Node specific tunable to tune the common tunables for all experiments and node specific tunables.

Taint Label¶

It contains label and effect to be tainted on application node. It can be tuned via TAINT_LABEL ENV.

Use the following example to tune this:

# node tainted with provided key and effect
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  chaosServiceAccount: node-taint-sa
  experiments:
  - name: node-taint
    spec:
      components:
        env:
        # label and effect to be tainted on the targeted node
        - name: TAINT_LABEL
          value: 'key=value:effect'
        - name: TOTAL_CHAOS_DURATION
          value: '60'