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Version: 2.4.0

Construct Workflow YAML without ChaosCenter

Chaos Workflow is a set of different operations coupled together to achieve desired chaos imapact on a Kubernetes Cluster.
A basic chaos workflow consists of these steps:

  1. Install ChaosExperiment
  2. Install ChaosEngine
  3. Revert Chaos

Before we begin#

To construct a Chaos Workflow without ChaosCenter, make sure you are aware of Chaos Workflow, ChaosEngine CR and the different steps present in it.

Steps to Construct a Chaos Workflow#

LitmusChaos leverages the popular workflow and GitOps tool Argo to achieve this goal. Argo enables the orchestration of different chaos scenarios together in the form of workflow which is extremly simple and efficient to use.

The structure of a chaos workflow is similar to that of a Kubernetes Object. It consists of the mandatory fields like apiVersion, kind, metadata, spec.

Few additional terms in an Argo workflows are:

  1. Template : It consists of different steps with their specific operations.
      templates:    - name: custom-chaos      steps:        - - name: install-chaos-experiments            template: install-chaos-experiments        - - name: pod-delete            template: pod-delete        - - name: revert-chaos            template: revert-chaos
  1. Steps : It is a single step inside a workflow which runs a container based on the input parameters. These can also be sequenced parallely.
steps:  - - name: install-chaos-experiments      template: install-chaos-experiments  - - name: pod-delete      template: pod-delete    - name: pod-cpu-hog      template: pod-cpu-hog  - - name: revert-chaos      template: revert-chaos
  1. Entrypoint : The first step that executes in a workflow is called its entrypoint.
entrypoint: custom-chaos

Here, the template with the name custom-chaos will be executed first.

  1. Artifacts : Artifacts are defined as the files saved by the containers in each step.
- name: install-chaos-experiments      inputs:        artifacts:          - name: pod-delete            path: /tmp/pod-delete.yaml            raw:              data: >                apiVersion: litmuschaos.io/v1alpha1
                description:                  message: |...

Once the workflow is constructed, it should look like this:

apiVersion: argoproj.io/v1alpha1kind: Workflowmetadata:  name: pod-delete-experiment  namespace: litmusspec:  arguments:    parameters:      - name: adminModeNamespace        value: litmus  entrypoint: custom-chaos  securityContext:    runAsNonRoot: true    runAsUser: 1000  serviceAccountName: argo-chaos  templates:    - name: custom-chaos      steps:        - - name: install-chaos-experiments            template: install-chaos-experiments        - - name: pod-delete            template: pod-delete        - - name: revert-chaos            template: revert-chaos    - name: install-chaos-experiments      inputs:        artifacts:          - name: pod-delete            path: /tmp/pod-delete.yaml            raw:              data: >                apiVersion: litmuschaos.io/v1alpha1
                description:                  message: |                    Deletes a pod belonging to a deployment/statefulset/daemonset                kind: ChaosExperiment
                metadata:                  name: pod-delete                  labels:                    name: pod-delete                    app.kubernetes.io/part-of: litmus                    app.kubernetes.io/component: chaosexperiment                    app.kubernetes.io/version: 1.13.8                spec:                  definition:                    scope: Namespaced                    permissions:                      - apiGroups:                          - ""                          - apps                          - apps.openshift.io                          - argoproj.io                          - batch                          - litmuschaos.io                        resources:                          - deployments                          - jobs                          - pods                          - pods/log                          - replicationcontrollers                          - deployments                          - statefulsets                          - daemonsets                          - replicasets                          - deploymentconfigs                          - rollouts                          - pods/exec                          - events                          - chaosengines                          - chaosexperiments                          - chaosresults                        verbs:                          - create                          - list                          - get                          - patch                          - update                          - delete                          - deletecollection                    image: litmuschaos/go-runner:1.13.8                    imagePullPolicy: Always                    args:                      - -c                      - ./experiments -name pod-delete                    command:                      - /bin/bash                    env:                      - name: TOTAL_CHAOS_DURATION                        value: "15"                      - name: RAMP_TIME                        value: ""                      - name: FORCE                        value: "true"                      - name: CHAOS_INTERVAL                        value: "5"                      - name: PODS_AFFECTED_PERC                        value: ""                      - name: LIB                        value: litmus                      - name: TARGET_PODS                        value: ""                      - name: SEQUENCE                        value: parallel                    labels:                      name: pod-delete                      app.kubernetes.io/part-of: litmus                      app.kubernetes.io/component: experiment-job                      app.kubernetes.io/version: 1.13.8      container:        args:          - kubectl apply -f /tmp/pod-delete.yaml -n            {{workflow.parameters.adminModeNamespace}} |  sleep 30        command:          - sh          - -c        image: litmuschaos/k8s:latest    - name: pod-delete      inputs:        artifacts:          - name: pod-delete            path: /tmp/chaosengine-pod-delete.yaml            raw:              data: |                apiVersion: litmuschaos.io/v1alpha1                kind: ChaosEngine                metadata:                  namespace: "{{workflow.parameters.adminModeNamespace}}"                  generateName: pod-delete                  labels:                    instance_id: 86a4f130-d99b-4e91-b34b-8f9eee22cb63                spec:                  appinfo:                    appns: default                    applabel: app=nginx                    appkind: deployment                  jobCleanUpPolicy: retain                  engineState: active                  chaosServiceAccount: litmus-admin                  experiments:                    - name: pod-delete                      spec:                        components:                          env:                            - name: TOTAL_CHAOS_DURATION                              value: "30"                            - name: CHAOS_INTERVAL                              value: "10"                            - name: FORCE                              value: "false"                            - name: PODS_AFFECTED_PERC                              value: ""      container:        args:          - -file=/tmp/chaosengine-pod-delete.yaml          - -saveName=/tmp/engine-name        image: litmuschaos/litmus-checker:latest    - name: revert-chaos      container:        image: litmuschaos/k8s:latest        command:          - sh          - -c        args:          - "kubectl delete chaosengine -l 'instance_id in            (86a4f130-d99b-4e91-b34b-8f9eee22cb63, )' -n            {{workflow.parameters.adminModeNamespace}} "

Install Experiment#

  1. ChaosExperiment CR:#

    The install-experiment step consists of ChaosExperiment CR in its artifact. ChaosExperiment CR is the heart of LitmusChaos and contains the low-level execution information. They serve as off-the-shelf templates that one needs to "pull" (install on the cluster) before including them as part of chaos run against any target applications (the binding being defined in the ChaosEngine). The experiments are installed on the cluster as Kubernetes custom resources and are designed to hold granular details of the experiment such as image, library, necessary permissions, chaos parameters (set to their default values). Most of the ChaosExperiment parameters are essentially tunables that can be overridden from the ChaosEngine resource.

  2. ChaosEngine CR:#

    The ChaosEngine is the main user-facing chaos custom resource with a namespace scope and is designed to hold information around how the chaos experiments are executed. It connects an application instance with one or more chaos experiments while allowing the users to specify run level details (override experiment defaults, provide new environment variables and volumes, options to delete or retain experiment pods, etc.,). This CR is also updated/patched with the status of the chaos experiments, making it the single source of truth with respect to the chaos.

Resources#

  • The ChaosExperiment CR and ChaosEngine CR of different experiments are available at ChaosHub.

Learn More#