|Type||Description||Tested K8s Platform|
|Generic||Restart the target node||Kubevirt VMs, AWS(kubeadm), EKS|
- Ensure that Kubernetes Version > 1.16
- 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
node-restartexperiment resource is available in the cluster by executing
kubectl get chaosexperimentsin the desired namespace. If not, install from here
- Create a Kubernetes secret named
id-rsawhere the experiment will run, where its contents will be the private SSH key for
SSH_USERused to connect to the node that hosts the target pod in the secret field
ssh-privatekey. A sample secret is shown below:
apiVersion: v1 kind: Secret metadata: name: id-rsa type: kubernetes.io/ssh-auth stringData: ssh-privatekey: |- # SSH private key for ssh contained here
Creating the RSA key pair for remote SSH access should be a trivial exercise for those who are already familiar with an ssh client, which entails the following actions:
- Create a new key pair and store the keys in a file named
my-id-rsa-key.pubfor the private and public keys respectively:
ssh-keygen -f ~/my-id-rsa-key -t rsa -b 4096
- For each node available, run this following command to copy the public key of
ssh-copy-id -i my-id-rsa-key user@node
For further details, please check this documentation. Once you have copied the public key to all nodes and created the secret described earlier, you are ready to start your experiment.
- Application pods should be healthy before chaos injection.
- Target Nodes should be in Ready state before chaos injection.
- Application pods should be healthy after chaos injection.
- Target Nodes should be in Ready state after chaos injection.
- Causes chaos to disrupt state of node by restarting it.
- Tests deployment sanity (replica availability & uninterrupted service) and recovery workflows of the application pod
- Node Restart can be effected using the chaos library:
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: 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","events","secrets"] verbs: ["create","list","get","patch","update","delete","deletecollection"] - apiGroups: [""] resources: ["pods/exec","pods/log"] verbs: ["create","list","get"] - 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.
- Provide the application info in
spec.appinfo. It is an optional parameter for infra level experiment.
- Populate the
experiments.spec.components.envsection. Note that the environment values take precedence over the
- Provide the auxiliary applications info (ns & labels) in
- Override the extra 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|
|LIB_IMAGE||The image used to restart the node||Optional||Defaults to `litmuschaos/go-runner:1.13.8`|
|SSH_USER||name of ssh user||Mandatory||Defaults to `root`|
|TARGET_NODE||Name of target node, subjected to chaos. If not provided, the experiment will lookup the node that hosts the pod running based on the `appInfo` details section in the `ChaosEngine`. If provided, it also requires the `TARGET_NODE_IP` to be populated.||Optional||Defaults to empty|
|NODE_LABEL||It contains node label, which will be used to filter the target nodes if TARGET_NODE ENV is not set||Optional|
|TARGET_NODE_IP||Internal IP of the target node, subjected to chaos. If not provided, the experiment will lookup the node IP that hosts the pod running based on the `appInfo` details section in the `ChaosEngine`. If provided, it also requires `TARGET_NODE` to be populated.||Optional||Defaults to empty|
|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 and after injection of chaos in sec||Optional|
|LIB||The chaos lib used to inject the chaos||Optional||Defaults to `litmus` supported litmus only|
|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 active/stop engineState: 'active' #ex. values: ns1:name=percona,ns2:run=nginx auxiliaryAppInfo: '' chaosServiceAccount: node-restart-sa experiments: - name: node-restart spec: components: # nodeSelector: # # provide the node labels # kubernetes.io/hostname: 'node02' env: - name: TOTAL_CHAOS_DURATION value: '60' # ENTER THE TARGET NODE NAME - name: TARGET_NODE value: '' # ENTER THE TARGET NODE IP - name: TARGET_NODE_IP value: '' # ENTER THE USER TO BE USED FOR SSH AUTH - name: SSH_USER value: 'root'
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
SSH into the targeted node and verify the
uptime. The uptime should be reinitialized to
0minsafter the node restart.
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:
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.