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Steps to Bootstrap a Chaos Experiment

The artefacts associated with a chaos-experiment are summarized below:

  • Submitted in the litmuschaos/litmus-go repository, under the experiments/chaos-category/experiment-name folder

    • Experiment business logic in golang. May involve creating new or reusing an existing chaoslib
    • Experiment test deployment manifest that is used for verification purposes
    • Experiment RBAC (holds experiment-specific ServiceAccount, Role and RoleBinding)

    Example: pod delete experiment in litmus-go

  • Submitted in litmuschaos/chaos-charts repository, under the chaos-category folder

    • Experiment custom resource (CR) (holds experiment-specific chaos parameters & experiment entrypoint)
    • Experiment ChartServiceVersion (holds experiment metadata that will be rendered on charthub)
    • Experiment RBAC (holds experiment-specific ServiceAccount, Role and RoleBinding)
    • Experiment Engine (holds experiment-specific chaosengine)

    Example: pod delete experiment in chaos-charts

The generate_experiment.go script is a simple way to bootstrap your experiment, and helps create the aforementioned artefacts in the appropriate directory (i.e., as per the chaos-category) based on an attributes file provided as input by the chart-developer. The scaffolded files consist of placeholders which can then be filled as desired.

Pre-Requisites

  • go should be is available & the GOPATH env is configured appropriately

Steps to Generate Experiment Manifests

  • Clone the litmus-go repository & navigate to the contribute/developer-guide folder

    $ git clone https://github.com/litmuschaos/litmus-go.git
$ cd litmus/contribute/developer-guide

  • Populate the attributes.yaml with details of the chaos experiment (or chart). Use the attributes.yaml.sample as reference.

    As an example, let us consider an experiment to kill one of the replicas of a nginx deployment. The attributes.yaml can be constructed like this:

    $ cat attributes.yaml 

---
name: "pod-delete"
version: "0.1.0"
category: "sample-category"
repository: "https://github.com/litmuschaos/litmus-go/tree/master/sample-category/pod-delete"
community: "https://kubernetes.slack.com/messages/CNXNB0ZTN"
description: "kills nginx pods in a random manner"
keywords:
  - "pods"
  - "kubernetes"
  - "sample-category"
  - "nginx"
scope: "Namespaced"
auxiliaryappcheck: false
permissions:
  - apigroups:
      - ""
      - "batch"
      - "litmuschaos.io"
    resources:
      - "jobs"
      - "pods"
      - "chaosengines"
      - "chaosexperiments"
      - "chaosresults"
    verbs:
      - "create"
      - "list"
      - "get"
      - "update"
      - "patch"
      - "delete"
maturity: "alpha"
maintainers:
  - name: "ksatchit"
    email: "ksatchit@mayadata.io"
provider:
  name: "Mayadata"
minkubernetesversion: "1.12.0"
references:
  - name: Documentation
    url: "https://docs.litmuschaos.io/docs/getstarted/"

  • Run the following command to generate the necessary artefacts for submitting the sample-category chaos chart with pod-delete experiment.

    $ go run generate_experiment.go -attributes=attributes.yaml -generateType=experiment

    Note: In the -generateType attribute, select the appropriate type of manifests to be generated, where,

    • chart: Just the chaos-chart metadata, i.e., chartserviceversion yaml
    • experiment: Chaos experiment artefacts belonging to a an existing OR new chart.

    View the generated files in /experiments/chaos-category folder.

    $ cd /experiments

$ ls -ltr

total 8
drwxr-xr-x 3 shubham shubham 4096 May 15 12:02 generic/
drwxr-xr-x 3 shubham shubham 4096 May 15 13:26 sample-category/


$ ls -ltr sample-category/

total 12
-rw-r--r-- 1 shubham shubham   41 May 15 13:26 sample-category.package.yaml
-rw-r--r-- 1 shubham shubham  734 May 15 13:26 sample-category.chartserviceversion.yaml
drwxr-xr-x 2 shubham shubham 4096 May 15 13:26 pod-delete/

$ ls -ltr sample-category/pod-delete

total 28
-rw-r--r-- 1 shubham shubham  791 May 15 13:26 rbac.yaml
-rw-r--r-- 1 shubham shubham  734 May 15 13:26 pod-delete.chartserviceversion.yaml
-rw-r--r-- 1 shubham shubham  792 May 15 13:26 experiment.yaml
drwxr-xr-x 2 shubham shubham 4096 May 15 13:26 test
-rw-r--r-- 1 shubham shubham 4533 May 15 13:26 pod-delete.go
-rw-r--r-- 1 shubham shubham  813 May 15 13:26 engine.yaml

$ ls -ltr sample-category/pod-delete/test

total 4
-rw-r--r-- 1 shubham shubham  1039 May 15 13:26 test.yaml

  • Proceed with construction of business logic inside the pod-delete.go file, by making the appropriate modifications listed below to achieve the desired effect:

  • Update the chaoslib/litmus/pod-delete/pod-delete.go chaoslib to achieve the desired effect or reuse the existing chaoslib.

  • Create an experiment README explaining, briefly, the what, why & how of the experiment to aid users of this experiment.

Steps to Test Experiment

We can use Okteto to help us in performing the dev-tests for experiment created. Follow the steps provided below to setup okteto & test the experiment execution.

  • Install the Okteto CLI

    curl https://get.okteto.com -sSfL | sh

  • (Optional) Create a sample nginx deployment that can be used as the application under test (AUT).

    kubectl create deployment nginx --image=nginx

  • Setup the RBAC necessary for execution of this experiment by applying the generated rbac.yaml

    kubectl apply -f rbac.yaml

  • Modify the test/test.yaml with the desired values (app & chaos info) in the ENV and appropriate chaosServiceAccount along with any other dependencies, if applicable (configmaps, volumes etc.,) & create this deployment

    kubectl apply -f test/test.yml

  • Go to the root of this repository (litmuschaos/litmus-go) & launch the Okteto development environment in your workspace. This should take you to the bash prompt on the dev container into which the content of the litmus-go repo is loaded.

    root@test:~/okteto/litmus-go# okteto up 

Deployment litmus-go doesn't exist in namespace litmus. Do you want to create a new one? [y/n]: y
✓  Development container activated
✓  Files synchronized

The value of /proc/sys/fs/inotify/max_user_watches in your cluster nodes is too low.
This can affect file synchronization performance.
Visit https://okteto.com/docs/reference/known-issues/index.html for more information.
    Namespace: default
    Name:      litmus-experiment
    Forward:   2345 -> 2345
               8080 -> 8080

Welcome to your development container. Happy coding!

    This dev container inherits the env, serviceaccount & other properties specified on the test deployment & is now suitable for running the experiment.

  • Execute the experiment against the sample app chosen & verify the steps via logs printed on the console.

    go run experiments/<chaos-category>/<experiment-name>/<experiment-name>.go

  • In parallel, observe the experiment execution via the changes to the pod/node state

    watch -n 1 kubectl get pods,nodes

  • If there are necessary changes to the code based on the run, make them via your favourite IDE. These changes are automatically reflected on the dev container. Re-run the experiment to confirm changes.

  • Once the experiment code is validated, stop/remove the development environment

    root@test:~/okteto/litmus-go# okteto down
✓  Development container deactivated
i  Run 'okteto push' to deploy your code changes to the cluster

  • (Optional) Once the experiment has been validated using the above step, it can also be tested against the standard Litmus chaos flow. This involves:

    • Creating a custom image built with the code validated by the previous steps
    • Launching the Chaos-Operator
    • Modifying the ChaosExperiment manifest (experiment.yaml) with right defaults (env & other attributes, as applicable) & creating this CR on the cluster (pointing the .spec.definition.image to the custom one just built)
    • Modifying the ChaosEngine manifest (engine.yaml) with right app details, run properties & creating this CR to launch the chaos pods
    • Verifying the experiment status via ChaosResult

    Refer litmus docs for more details on performing each step in this procedure.

Steps to Include the Chaos Charts/Experiments into the ChartHub

  • Send a PR to the litmus-go repo with the modified experiment files, rbac, test deployment & README.
  • Send a PR to the chaos-charts repo with the modified experiment CR, experiment chartserviceversion, rbac, (category-level) chaos chart chartserviceversion & package.yaml (if applicable).