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devguide Developer Guide for ChaosCharts Developer Guide devguide

This page serves as a guide to develop either a new ChaosChart or a new experiment in a ChaosChart which are published at ChaosHub.

Below are some key points to remember before understanding how to write a new chart or an experiment.

ChaosCharts repository : https://github.com/litmuschaos/chaos-charts

Litmusbooks repository : https://github.com/litmuschaos/litmus-ansible/tree/master/experiments

Website rendering code repository: https://github.com/litmuschaos/charthub.litmuschaos.io

The experiments & chaos libraries are typically written in Ansible, though not mandatory. Ensure that the experiments can be executed in a container & can read/update the litmuschaos custom resources. For example, if you are writing an experiment in Go, use this clientset

Glossary

ChaosChart

A group of ChaosExperiments put together in a YAML file. Each group or chart has a metadata manifest called ChartServiceVersion that holds data such as ChartVersion, Contributors, Description, links etc.., This metadata is rendered on the ChartHub. A ChaosChart also consists of a package manifest that is an index of available experiments in the chart.

Here is an example of the ChartServiceVersion & package manifests of the generic ChaosChart.

ChaosExperiment

ChaosExperiment is a CRD that specifies the nature of a ChaosExperiment. The YAML file that constitutes a ChaosExperiment CR is stored under a ChaosChart of ChaosHub and typically consists of low-level chaos parameters specific to that experiment, set to their default values.

Here is an example chaos experiment CR for a pod-delete experiment

Litmus Book

Litmus book is an ansible playbook that encompasses the logic of pre-checks, chaos-injection, post-checks, and result-updates. Typically, these are accompanied by a Kubernetes job that can execute the respective playbook.

Here is an example of the litmus book for the pod-delete experiment.

Chaos functions

The ansible business logic inside Litmus books can make use of readily available chaos functions. The chaos functions are available as task-files which are wrapped in one of the chaos libraries. See plugins for more details.

Developing a ChaosExperiment

A detailed how-to guide on developing chaos experiments is available here