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Getting Started with Litmus

Pre-requisites

Kubernetes 1.16 or later.

Getting Started

Running chaos on your application involves the following steps:

Install Litmus

Install Chaos Experiments

Setup Service Account

Prepare ChaosEngine

Run Chaos

Observe ChaosResults

Install Litmus

Apply the LitmusChaos Operator manifest:

kubectl apply -f https://litmuschaos.github.io/litmus/litmus-operator-v1.13.8.yaml

The above command installs all the CRDs, required service account configuration, and chaos-operator.

Note: Ensure that you have the right privileges to install the CRDs & setup cluster-wide RBAC policies (by default, the ChaosOperator watches for Chaos CRs across namespaces)

Alternatively, you can choose to install it with Helm:

  • Add the LitmusChaos Helm repo
helm repo add litmuschaos https://litmuschaos.github.io/litmus-helm/
  • Create a Litmus namespace in Kubernetes
kubectl create ns litmus
  • Install the Litmus Helm chart
helm install chaos litmuschaos/litmus --namespace=litmus

Note: Litmus uses Kubernetes CRDs to define chaos intent. Helm3 handles CRDs better than Helm2. Before you start running a chaos experiment, verify if Litmus is installed correctly.

Verify your installation

  • Verify if the ChaosOperator is running
kubectl get pods -n litmus

Expected output:

chaos-operator-ce-554d6c8f9f-slc8k 1/1 Running 0 6m41s

  • Verify if chaos CRDs are installed
kubectl get crds | grep chaos

Expected output:

chaosengines.litmuschaos.io 2019-10-02T08:45:25Z

chaosexperiments.litmuschaos.io 2019-10-02T08:45:26Z

chaosresults.litmuschaos.io 2019-10-02T08:45:26Z

  • Verify if the chaos api resources are successfully created in the desired (application) namespace.

    Note: Sometimes, it can take a few seconds for the resources to be available post the CRD installation

kubectl api-resources | grep chaos

Expected output:

chaosengines litmuschaos.io true ChaosEngine

chaosexperiments litmuschaos.io true ChaosExperiment

chaosresults litmuschaos.io true ChaosResult

NOTE:

  • In this guide, we shall describe the steps to inject pod-delete chaos on an nginx application already deployed in the nginx namespace. If you don't have this setup you can easily create one by running these two commands:

    • Create nginx namespace kubectl create ns nginx.
    • Create nginx deployment in nginx namespace kubectl create deployment nginx --image nginx -n nginx.

  • In all subsequent steps, please follow these instructions by replacing the nginx namespace and labels with that of your application.

  • The ChaosOperator collects some usage metrics (operator installation count & experiment run count) via a google analytics hook. This is done in order to gather chaos trends that will help us to improve the project. However, if you would like to prevent the collection of the same or are operating in an airgapped environment, you can disable it using the procedure suggested here.

Install Chaos Experiments

Chaos experiments contain the actual chaos details. These experiments are installed on your cluster as Kubernetes CRs. The Chaos Experiments are grouped as Chaos Charts and are published on Chaos Hub.

The generic chaos experiments such as pod-delete, container-kill,pod-network-latency are available under Generic Chaos Chart. This is the first chart you are recommended to install.

kubectl apply -f https://hub.litmuschaos.io/api/chaos/master?file=charts/generic/experiments.yaml -n nginx

Verify if the chaos experiments are installed.

kubectl get chaosexperiments -n nginx

Setup Service Account

A service account should be created to allow chaosengine to run experiments in your application namespace. Copy the following into a rbac.yaml manifest and run kubectl apply -f rbac.yaml to create one such account on the nginx namespace. This serviceaccount has just enough permissions needed to run the pod-delete chaos experiment.

NOTE:

  • For rbac samples corresponding to other experiments such as, say, container-kill, please refer the respective experiment folder in the chaos-charts repository.
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: pod-delete-sa
  namespace: nginx
  labels:
    name: pod-delete-sa
---
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: pod-delete-sa
  namespace: nginx
  labels:
    name: pod-delete-sa
rules:
- apiGroups: [""]
  resources: ["pods","events"]
  verbs: ["create","list","get","patch","update","delete","deletecollection"]
- apiGroups: [""]
  resources: ["pods/exec","pods/log","replicationcontrollers"]
  verbs: ["create","list","get"]
- apiGroups: ["batch"]
  resources: ["jobs"]
  verbs: ["create","list","get","delete","deletecollection"]
- apiGroups: ["apps"]
  resources: ["deployments","statefulsets","daemonsets","replicasets"]
  verbs: ["list","get"]
- apiGroups: ["apps.openshift.io"]
  resources: ["deploymentconfigs"]
  verbs: ["list","get"]
- apiGroups: ["argoproj.io"]
  resources: ["rollouts"]
  verbs: ["list","get"]
- apiGroups: ["litmuschaos.io"]
  resources: ["chaosengines","chaosexperiments","chaosresults"]
  verbs: ["create","list","get","patch","update"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: pod-delete-sa
  namespace: nginx
  labels:
    name: pod-delete-sa
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: pod-delete-sa
subjects:
- kind: ServiceAccount
  name: pod-delete-sa
  namespace: nginx

Prepare ChaosEngine

ChaosEngine connects the application instance to a Chaos Experiment. Copy the following YAML snippet into a file called chaosengine.yaml and update the values of applabel , appns, appkind and experiments as per your choice. Change the chaosServiceAccount to the name of service account created in above previous steps.

NOTE: To learn more about the various fields in the ChaosEngine spec and their supported values, refer to Constructing ChaosEngine

apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: nginx-chaos
  namespace: nginx
spec:
  appinfo:
    appns: 'nginx'
    applabel: 'app=nginx'
    appkind: 'deployment'
  # It can be active/stop
  engineState: 'active'
  #ex. values: ns1:name=percona,ns2:run=nginx
  auxiliaryAppInfo: ''
  chaosServiceAccount: pod-delete-sa
  # It can be delete/retain
  jobCleanUpPolicy: 'delete'
  experiments:
    - name: pod-delete
      spec:
        components:
          env:
            # set chaos duration (in sec) as desired
            - name: TOTAL_CHAOS_DURATION
              value: '30'

            # set chaos interval (in sec) as desired
            - name: CHAOS_INTERVAL
              value: '10'
              
            # pod failures without '--force' & default terminationGracePeriodSeconds
            - name: FORCE
              value: 'false'

             ## percentage of total pods to target
            - name: PODS_AFFECTED_PERC
              value: ''

Override Default Chaos Experiments Variables

From LitmusChaos v1.1.0, the default environment variable values in chaosexperiments can be overridden by specifying them in the chaosengine under experiments.<experiment_name>.spec.components.env with the desired value. In the example below, the TOTAL_CHAOS_DURATION is being set to a desired value based on use-case.

...
experiments:
    - name: pod-delete
      spec:
        components:
          env:
            - name: TOTAL_CHAOS_DURATION
              value: '30'

Run Chaos

Apply the ChaosEngine manifest to trigger the experiment.

kubectl apply -f chaosengine.yaml

Observe Chaos results

Describe the ChaosResult CR to know the status of each experiment. The status.verdict is set to Awaited when the experiment is in progress, eventually changing to either Pass or Fail.

NOTE: ChaosResult CR name will be <chaos-engine-name>-<chaos-experiment-name>

kubectl describe chaosresult nginx-chaos-pod-delete -n nginx

Uninstallation

Firstly, delete any active ChaosEngines on the cluster, followed by the deletion of the Operator manifest.

kubectl delete chaosengine --all -n <namespace>

kubectl delete -f https://litmuschaos.github.io/litmus/litmus-operator-v1.13.8.yaml

NOTE

  • Ensure that the chaosengine resources are deleted before removal of the chaos-operator deployment via operator manifest. Failure to do so can cause the uninstall operation to be "stuck". Refer to the these steps to resolve this condition and complete the uninstall.

Troubleshooting

For any issues experienced in running through the the aforementioned steps, refer to the Troubleshooting section.

More Chaos Experiments

  • For more details on supported chaos experiments and the steps to run them, refer the respective Experiment docs.

Join our community

If you have not joined our community, do join us here.

ChaosHub →