litmus-docs/node-restart.md at cccf7c6a7635737bf2fe2cc4fe937a2b3c84673b

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id	title	sidebar_label	original_id
node-restart	Node Restart Experiment Details	Node Restart	node-restart

Experiment Metadata

Type	Description	Tested K8s Platform
Generic	Restart the target node	Kubevirt VMs

Prerequisites

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-restart experiment resource is available in the cluster by executing kubectl get chaosexperiments in the desired namespace. If not, install from here
Create a Kubernetes secret having the private SSH key for SSH_USER used to connect to TARGET_NODE. The name of secret should be id-rsa along with private SSH key data, named ssh-privatekey. A sample secret example is given below:

apiVersion: v1
kind: Secret
metadata:
  name: id-rsa
type: Opaque
stringData:
  ssh-privatekey: |-
    # Add the private key for ssh here

Entry-Criteria

Application pods should be healthy before chaos injection.
Target Nodes should be in Ready state before chaos injection.

Exit-Criteria

Application pods should be healthy after chaos injection.
Target Nodes should be in Ready state after chaos injection.

Details

Causes chaos to disrupt state of node by restarting it.
Tests deployment sanity (replica availability & uninterrupted service) and recovery workflows of the application pod

Integrations

Node Restart can be effected using the chaos library: litmus.

Steps to Execute the Chaos Experiment

This Chaos Experiment can be triggered by creating a ChaosEngine resource on the cluster. To understand the values to provide in a ChaosEngine specification, refer Getting Started
Follow the steps in the sections below to create the chaosServiceAccount, prepare the ChaosEngine & execute the experiment.

Prepare chaosServiceAccount

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.

Sample Rbac Manifest

---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: node-restart-sa
  namespace: default
  labels:
    name: node-restart-sa
    app.kubernetes.io/part-of: litmus
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: node-restart-sa
  labels:
    name: node-restart-sa
    app.kubernetes.io/part-of: litmus
rules:
  - apiGroups: ["", "litmuschaos.io", "batch", "apps"]
    resources:
      [
        "pods",
        "jobs",
        "secrets",
        "events",
        "chaosengines",
        "pods/log",
        "pods/exec",
        "chaosexperiments",
        "chaosresults",
      ]
    verbs:
      ["create", "list", "get", "patch", "update", "delete", "deletecollection"]
  - apiGroups: [""]
    resources: ["nodes"]
    verbs: ["get", "list"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: node-restart-sa
  labels:
    name: node-restart-sa
    app.kubernetes.io/part-of: litmus
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: node-restart-sa
subjects:
  - kind: ServiceAccount
    name: node-restart-sa
    namespace: default

Note: In case of restricted systems/setup, create a PodSecurityPolicy(psp) with the required permissions. The chaosServiceAccount can subscribe to work around the respective limitations. An example of a standard psp that can be used for litmus chaos experiments can be found here.

Prepare ChaosEngine

Provide the application info in spec.appinfo
Provide the auxiliary applications info (ns & labels) in spec.auxiliaryAppInfo
Override the experiment tunables if desired in experiments.spec.components.env
To understand the values to provided in a ChaosEngine specification, refer ChaosEngine Concepts

Supported Experiment Tunables

Variables	Description	Specify In ChaosEngine	Notes
LIB_IMAGE	The image used to restart the node	Optional	Defaults to `litmuschaos/go-runner:1.11.0`
SSH_USER	name of ssh user	Mandatory	Defaults to `root`
TARGET_NODE	name of target node, subjected to chaos	Mandatory
TARGET_NODE_IP	ip of the target node, subjected to chaos	Mandatory
REBOOT_COMMAND	Command used for reboot	Mandatory	Defaults to `sudo systemctl reboot`
TOTAL_CHAOS_DURATION	The time duration for chaos insertion (sec)	Optional	Defaults to 30s
RAMP_TIME	Period to wait before injection of chaos in sec	Optional
LIB	The chaos lib used to inject the chaos	Optional	Defaults to `litmus` supported litmus only
LIB_IMAGE	The image used to restart the node	Optional	Defaults to `litmuschaos/go-runner:1.11.0`
INSTANCE_ID	A user-defined string that holds metadata/info about current run/instance of chaos. Ex: 04-05-2020-9-00. This string is appended as suffix in the chaosresult CR name.	Optional	Ensure that the overall length of the chaosresult CR is still < 64 characters

Sample ChaosEngine Manifest

apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: nginx-chaos
  namespace: default
spec:
  # It can be true/false
  annotationCheck: "false"
  # It can be active/stop
  engineState: "active"
  #ex. values: ns1:name=percona,ns2:run=nginx
  auxiliaryAppInfo: ""
  appinfo:
    appns: "default"
    applabel: "app=nginx"
    appkind: "deployment"
  chaosServiceAccount: node-restart-sa
  monitoring: false
  # It can be delete/retain
  jobCleanUpPolicy: "delete"
  experiments:
    - name: node-restart
      spec:
        components:
          nodeSelector:
            # provide the node labels
            kubernetes.io/hostname: "node02"
          env:
            # ENTER THE TARGET NODE NAME
            - name: TARGET_NODE
              value: "node01"

            # ENTER THE TARGET NODE IP
            - name: TARGET_NODE_IP
              value: ""

              # ENTER THE USER TO BE USED FOR SSH AUTH
            - name: SSH_USER
              value: ""

Create the ChaosEngine Resource

Create the ChaosEngine manifest prepared in the previous step to trigger the Chaos.

kubectl apply -f chaosengine.yml
If the chaos experiment is not executed, refer to the troubleshooting section to identify the root cause and fix the issues.

Watch Chaos progress

View the status of the nodes as they are subjected to node restart.

watch -n 1 kubectl get nodes

Check Chaos Experiment Result

Check whether the application is resilient to the node restart, once the experiment (job) is completed. The ChaosResult resource name is derived like this: <ChaosEngine-Name>-<ChaosExperiment-Name>.

kubectl describe chaosresult nginx-chaos-node-restart -n <application-namespace>

Node Restart Experiment Demo

A sample recording of this experiment execution will be added soon.

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