chaosexperiment-concepts.md

id	title	sidebar_label
chaosexperiment	Constructing the ChaosExperiment	ChaosExperiment

---

ChaosExperiment CR is the heart of litmus 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 a 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. The ChaosExperiment CRs are the primary artifacts hosted on the ChaosHub

This section describes the fields in the ChaosExperiment spec and the possible values that can be set against the same.

Scope Specification

Field	.spec.definition.scope
Description	Flag to specify the scope of the ChaosExperiment
Type	Optional
Range	Namespaced, Cluster
Default	n/a (depends on experiment type)
Notes	The .spec.definition.scope specifies the scope of the experiment. It can be Namespaced scope for pod level experiments and Cluster for the experiments having a cluster wide impact.

Field	.spec.definition.permissions
Description	Flag to specify the minimum permission to run the ChaosExperiment
Type	Optional
Range	user-defined (type: list)
Default	n/a
Notes	The .spec.definition.permissions specify the minimum permission that is required to run the ChaosExperiment. It also helps to estimate the blast radius for the ChaosExperiment.

Component Specification

Field	.spec.definition.image
Description	Flag to specify the image to run the ChaosExperiment
Type	Mandatory
Range	user-defined (type: string)
Default	n/a (refer Notes)
Notes	The .spec.definition.image allows the developers to specify their experiment images. Typically set to the Litmus go-runner or the ansible-runner. This feature of the experiment enables BYOC (BringYourOwnChaos), where developers can implement their own variants of a standard chaos experiment

Field	.spec.definition.imagePullPolicy
Description	Flag that helps the developers to specify imagePullPolicy for the ChaosExperiment
Type	Mandatory
Range	IfNotPresent, Always (type: string)
Default	Always
Notes	The .spec.definition.imagePullPolicy allows developers to specify the pull policy for ChaosExperiment image. Set to Always during debug/test

Field	.spec.definition.args
Description	Flag to specify the entrypoint for the ChaosExperiment
Type	Mandatory
Range	user-defined (type:list of string)
Default	n/a
Notes	The .spec.definition.args specifies the entrypoint for the ChaosExperiment. It depends on the language used in the experiment. For litmus-go the .spec.definition.args contains a single binary of all experiments and managed via -name flag to indicate experiment to run(-name (exp-name)).

Field	.spec.definition.command
Description	Flag to specify the shell on which the ChaosExperiment will execute
Type	Mandatory
Range	user-defined (type: list of string).
Default	/bin/bash
Notes	The .spec.definition.command specifies the shell used to run the experiment /bin/bash is the most common shell to be used.

Experiment Tunables Specification

Field	.spec.definition.env
Description	Flag to specify env used for ChaosExperiment
Type	Mandatory
Range	user-defined (type: {name: string, value: string})
Default	n/a
Notes	The .spec.definition.env specifies the array of tunables passed to the experiment pods as environment variables. It is used to manage the experiment execution. We can set the default values for all the variables (tunable) here which can be overridden by ChaosEngine from .spec.experiments[].spec.components.env if required. To know about the variables that need to be overridden check the list of "mandatory" & "optional" env for an experiment as provided within the respective experiment documentation.

Configuration Specification

Field	.spec.definition.securityContext.containerSecurityContext.privileged
Description	Flag to specify the security context for the ChaosExperiment pod
Type	Optional
Range	true, false (type:bool)
Default	n/a
Notes	The .spec.definition.securityContext.containerSecurityContext.privileged specify the securityContext params to the experiment container.

Field	.spec.definition.labels
Description	Flag to specify the label for the ChaosPod
Type	Optional
Range	user-defined (type:map[string]string)
Default	n/a
Notes	The .spec.definition.labels allow developers to specify the ChaosPod label for an experiment.

Field	.spec.definition.securityContext.podSecurityContext
Description	Flag to specify security context for ChaosPod
Type	Optional
Range	user-defined (type:corev1.PodSecurityContext)
Default	n/a
Notes	The .spec.definition.securityContext.podSecurityContext allows the developers to specify the security context for the ChaosPod which applies to all containers inside the Pod.

Field	.spec.definition.configMaps
Description	Flag to specify the configmap for ChaosPod
Type	Optional
Range	user-defined
Default	n/a
Notes	The .spec.definition.configMaps allows the developers to mount the ConfigMap volume into the experiment pod.

Field	.spec.definition.secrets
Description	Flag to specify the secrets for ChaosPod
Type	Optional
Range	user-defined
Default	n/a
Notes	The .spec.definition.secrets specify the secret data to be passed for the ChaosPod. The secrets typically contains confidential information like credentials.

Field	.spec.definition.experimentAnnotations
Description	Flag to specify the custom annotation to the ChaosPod
Type	Optional
Range	user-defined (type:map[string]string)
Default	n/a
Notes	The .spec.definition.experimentAnnotations allows the developer to specify the Custom annotation for the chaos pod.

Field	.spec.definition.hostFileVolumes
Description	Flag to specify the host file volumes to the ChaosPod
Type	Optional
Range	user-defined (type:map[string]string)
Default	n/a
Notes	The .spec.definition.hostFileVolumes allows the developer to specify the host file volumes to the ChaosPod.

Field	.spec.definition.hostPID
Description	Flag to specify the host PID for the ChaosPod
Type	Optional
Range	true, false (type:bool)
Default	n/a
Notes	The .spec.definition.hostPID allows the developer to specify the host PID for the ChaosPod.