|Type||Description||Tested K8s Platform|
|Generic||Kills the docker service on the application node to check the resiliency.||GKE, AKS|
Ensure that the Litmus Chaos Operator is running by executing
kubectl get podsin operator namespace (typically,
litmus). If not, install from here
Ensure that the
docker-service-killexperiment resource is available in the cluster by executing
kubectl get chaosexperimentsin the desired namespace. If not, install from here
Ensure that the node on which application pod is running 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>
- Get node names against the applications pods:
- Application pods should be healthy before chaos injection.
- Application pods and the node should be healthy post chaos injection.
- This experiment Causes the application to become unreachable on account of node turning unschedulable (NotReady) due to docker service kill.
- The docker 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 docker service down.
- After experiment ends, you may manually uncordon the specified node so that it can be utilised in future use
kubectl uncordon <node-name>.
- Docker Service Kill can be effected using the chaos library:
- The desired chaos library can be selected by setting
litmusas value for the env variable
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.
- 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: docker-service-kill-sa namespace: default labels: name: docker-service-kill-sa apiVersion: rbac.authorization.k8s.io/v1beta1 kind: ClusterRole metadata: name: docker-service-kill-sa labels: name: docker-service-kill-sa 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: docker-service-kill-sa labels: name: docker-service-kill-sa roleRef: apiGroup: rbac.authorization.k8s.io kind: ClusterRole name: docker-service-kill-sa subjects: - kind: ServiceAccount name: docker-service-kill-sa namespace: default
- Provide the application info in
- Override the experiment tunables if desired in
- 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 injection (seconds)||Optional||Defaults to 90s|
|LIB||The category of lib use to inject chaos||Optional||litmus|
|RAMP_TIME||Period to wait before 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: appinfo: appns: 'default' applabel: 'app=nginx' appkind: 'deployment' # It can be true/false annotationCheck: 'false' # It can be active/stop engineState: 'active' #ex. values: ns1:name=percona,ns2:run=nginx auxiliaryAppInfo: '' chaosServiceAccount: docker-service-kill-sa monitoring: false # It can be delete/retain jobCleanUpPolicy: 'delete' experiments: - name: docker-service-kill spec: components: nodeSelector: # provide the node labels kubernetes.io/hostname: 'node02' env: # set chaos duration (in sec) as desired - name: TOTAL_CHAOS_DURATION value: '90' # provide the actual name of node under test - name: APP_NODE value: 'node-01'
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
- 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 docker service kill, once the experiment (job) is completed. The ChaosResult resource name is derived like this:
kubectl describe chaosresult nginx-chaos-docker-service-kill -n <application-namespace>
Post Chaos Steps
In the beginning of experiment, we cordon the node so that chaos-pod won't schedule on the same node (to which we are going kill the docker service) to ensure that the chaos pod will not scheduled on it / subjected to eviction After experiment ends you can manually uncordon the application node so that it can be utilised in future.
kubectl uncordon <node-name>
Docker Service Kill Demo [TODO]
- A sample recording of this experiment execution is provided here.