Node Restart Experiment Details
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 executingkubectl 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 toTARGET_NODE
. The name of secret should beid-rsa
along with private SSH key data, namedssh-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: [""]
resources: ["pods","pods/exec","pods/log","events","secrets"]
verbs: ["create","list","get","patch","update","delete","deletecollection"]
- apiGroups: ["batch"]
resources: ["jobs"]
verbs: ["create","list","get","delete","deletecollection"]
- apiGroups: ["litmuschaos.io"]
resources: ["chaosengines","chaosexperiments","chaosresults"]
verbs: ["create","list","get","patch","update"]
- 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.