Kubelet Service Kill Experiment Details
Experiment Metadata
Type | Description | Tested K8s Platform |
---|---|---|
Generic | Kills the kubelet service on the application node to check the resiliency. | GKE, EKS, Packet(Kubeadm), Minikube |
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
kubelet-service-kill
experiment resource is available in the cluster by executingkubectl get chaosexperiments
in the desired namespace. If not, install from here
Entry Criteria
- Application pods should be healthy before chaos injection.
Exit Criteria
- Application pods and the node should be healthy post chaos injection.
Details
- This experiment Causes the application to become unreachable on account of node turning unschedulable (NotReady) due to kubelet service kill.
- The kubelet service has been stopped/killed on a node to make it unschedulable for a certain duration i.e
TOTAL_CHAOS_DURATION
. The application node should be healthy after the chaos injection and the services should be reaccessable. - The application implies services. Can be reframed as: Test application resiliency upon replica getting unreachable caused due to kubelet service down.
Integrations
- Kubelet Service Kill can be effected using the chaos library:
litmus
- The desired chaos library can be selected by setting
litmus
as value for the env variableLIB
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: kubelet-service-kill
namespace: default
labels:
name: kubelet-service-kill
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
name: kubelet-service-kill
labels:
name: kubelet-service-kill
rules:
- apiGroups: ["","litmuschaos.io","batch","apps"]
resources: ["pods","jobs","pods/log","events","chaosengines","chaosexperiments","chaosresults"]
verbs: ["create","list","get","patch","update","delete"]
- apiGroups: [""]
resources: ["nodes"]
verbs: ["get","list"]
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
name: kubelet-service-kill
labels:
name: kubelet-service-kill
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: ClusterRole
name: kubelet-service-kill
subjects:
- kind: ServiceAccount
name: kubelet-service-kill
namespace: default
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 |
---|---|---|---|
TOTAL_CHAOS_DURATION | The time duration for chaos insertion (seconds) | Optional | Defaults to 90 |
LIB | The chaos lib used to inject the chaos | Optional | Defaults to `litmus` |
RAMP_TIME | Period to wait before & after injection of chaos in sec | Optional | |
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: kubelet-service-kill-sa
monitoring: false
# It can be delete/retain
jobCleanUpPolicy: 'delete'
experiments:
- name: kubelet-service-kill
spec:
components:
env:
- name: TOTAL_CHAOS_DURATION
value: '90' # in seconds
Create the ChaosEngine Resource
Create the ChaosEngine manifest prepared in the previous step to trigger the Chaos.
kubectl apply -f chaosengine.yml
Watch Chaos progress
- Setting up a watch over the nodes getting not schedulable in the Kubernetes Cluster
watch kubectl nodes
Check Chaos Experiment Result
Check whether the application is resilient after the kubelet service kill, once the experiment (job) is completed. The ChaosResult resource name is derived like this:
<ChaosEngine-Name>-<ChaosExperiment-Name>
.kubectl describe chaosresult nginx-chaos-kubelet-service-kill -n <application-namespace>
Kubelet Service Kill Demo [TODO]
- A sample recording of this experiment execution is provided here.