container-kill.md

id	title	sidebar_label
container-kill	Container Kill Experiment Details	Container Kill

---

Experiment Metadata

Type	Description	Tested K8s Platform
Generic	Kill one container in the application pod	GKE, Packet(Kubeadm), Minikube, EKS, AKS

Prerequisites

• Ensure that the Litmus ChaosOperator is running by executing kubectl get pods in operator namespace (typically, litmus). If not, install from here
• Ensure that the container-kill experiment resource is available in the cluster by executing kubectl get chaosexperiments in the desired namespace. If not, install from here

Entry Criteria

• Application pods are healthy before chaos injection

Exit Criteria

• Application pods are healthy post chaos injection

Details

• litmus LIB Details:
  • It supports docker, containerd and crio container runtime.
  • It can kill the container of multiple pods in parallel (can be tuned by PODS_AFFECTED_PERC env).
  • Containers are killed using the docker kill in docker runtime and crictl stop command in containerd or crio runtime.
  • container-kill is run as a pod on the application node. It have ability to kill the application containers multiple times. Which can be varied by TOTAL_CHAOS_DURATION and CHAOS_INTERVAL.
• pumba LIB Details:
  • It support only docker container runtime.
  • It can kill the container of multiple pods in parallel (can be tuned by PODS_AFFECTED_PERC env). It kill the container by sending SIGKILL termination signal to its docker socket (hence docker runtime is required).
  • Containers are killed using the kill command provided by pumba
  • Pumba is run as a pod on the application node. It have ability to kill the application containers multiple times. Which can be varied by TOTAL_CHAOS_DURATION and CHAOS_INTERVAL.
• Tests deployment sanity (replica availability & uninterrupted service) and recovery workflow of the application
• Good for testing recovery of pods having side-car containers

Integrations

• Container kill supports litmus and pumba LIB.
• The container runtime can be choose via setting CONTAINER_RUNTIME env. supported values: docker, containerd, crio
• The desired pumba and litmus image can be configured in the env variable LIB_IMAGE.

Steps to Execute the ChaosExperiment

• This ChaosExperiment can be triggered by creating a ChaosEngine resource on the cluster. To understand the values to provide in a ChaosEngine specification, refer Getting Started

• Follow the steps in the sections below to create the chaosServiceAccount, prepare the ChaosEngine & execute the experiment.

Prepare chaosServiceAccount

• Use this sample RBAC manifest to create a chaosServiceAccount in the desired (app) namespace. This example consists of the minimum necessary role permissions to execute the experiment.

Sample RBAC Manifest

---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: container-kill-sa
  namespace: default
  labels:
    name: container-kill-sa
    app.kubernetes.io/part-of: litmus
---
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: container-kill-sa
  namespace: default
  labels:
    name: container-kill-sa
    app.kubernetes.io/part-of: litmus
rules:
- apiGroups: [""]
  resources: ["pods","events"]
  verbs: ["create","list","get","patch","update","delete","deletecollection"]
- apiGroups: [""]
  resources: ["pods/exec","pods/log","replicationcontrollers"]
  verbs: ["list","get","create"]
- 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: container-kill-sa
  namespace: default
  labels:
    name: container-kill-sa
    app.kubernetes.io/part-of: litmus
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: container-kill-sa
subjects:
- kind: ServiceAccount
  name: container-kill-sa
  namespace: default

Note: In case of restricted systems/setup, create a PodSecurityPolicy(psp) with the required permissions. The chaosServiceAccount can subscribe to work around the respective limitations. An example of a standard psp that can be used for litmus chaos experiments can be found here.

Prepare ChaosEngine

• Provide the application info in spec.appinfo
• Override the experiment tunables if desired in experiments.spec.components.env
• To understand the values to provided in a ChaosEngine specification, refer ChaosEngine Concepts

Note: Ensure that the CHAOS_INTERVAL used in the experiment is fairly high (i.e., enough time is provided for app recovery). Else, it can cause an exponential increase in the backOff delay, causing the app to stay in CrashLoopBackOff state for much longer

Supported Experiment Tunables

Variables	Description	Specify In ChaosEngine	Notes
TARGET_CONTAINER	The name of container to be killed inside the pod	Optional	If the TARGET_CONTAINER is not provided it will delete the first container
CHAOS_INTERVAL	Time interval b/w two successive container kill (in sec)	Optional	If the CHAOS_INTERVAL is not provided it will take the default value of 10s
TOTAL_CHAOS_DURATION	The time duration for chaos injection (seconds)	Optional	Defaults to 20s
PODS_AFFECTED_PERC	The Percentage of total pods to target	Optional	Defaults to 0 (corresponds to 1 replica), provide numeric value only
TARGET_PODS	Comma separated list of application pod name subjected to container kill chaos	Optional	If not provided, it will select target pods randomly based on provided appLabels
LIB_IMAGE	LIB Image used to kill the container	Optional	Defaults to `litmuschaos/go-runner:latest`
LIB	The category of lib use to inject chaos	Optional	Default value: litmus, supported values: pumba and litmus
RAMP_TIME	Period to wait before injection of chaos in sec	Optional
SEQUENCE	It defines sequence of chaos execution for multiple target pods	Optional	Default value: parallel. Supported: serial, parallel
SIGNAL	It contains termination signal used for container kill	Optional	Default value: SIGKILL
SOCKET_PATH	Path of the containerd/crio/docker socket file	Optional	Defaults to `/var/run/docker.sock`
CONTAINER_RUNTIME	container runtime interface for the cluster	Optional	Defaults to docker, supported values: docker, containerd and crio for litmus and only docker for pumba LIB
INSTANCE_ID	A user-defined string that holds metadata/info about current run/instance of chaos. Ex: 04-05-2020-9-00. This string is appended as suffix in the chaosresult CR name.	Optional	Ensure that the overall length of the chaosresult CR is still < 64 characters

Sample ChaosEngine Manifest

apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: nginx-chaos
  namespace: default
spec:
  # It can be active/stop
  engineState: 'active'
  appinfo:
    appns: 'default'
    applabel: 'app=nginx'
    appkind: 'deployment'
  chaosServiceAccount: container-kill-sa
  experiments:
    - name: container-kill
      spec:
        components:
          env:
            # provide the total chaos duration
            - name: TOTAL_CHAOS_DURATION
              value: '20'

            # provide the chaos interval
            - name: CHAOS_INTERVAL
              value: '10'

            # provide the name of container runtime
            # for litmus LIB, it supports docker, containerd, crio
            # for pumba LIB, it supports docker only
            - name: CONTAINER_RUNTIME
              value: 'docker'

            # provide the socket file path
            - name: SOCKET_PATH
              value: '/var/run/docker.sock'

            - name: PODS_AFFECTED_PERC
              value: ''

            - name: TARGET_CONTAINER
              value: ''
              

Create the ChaosEngine Resource

• Create the ChaosEngine manifest prepared in the previous step to trigger the Chaos.

  kubectl apply -f chaosengine.yml

• If the chaos experiment is not executed, refer to the troubleshooting section to identify the root cause and fix the issues.

Watch Chaos progress

• View pod restart count by setting up a watch on the pods in the application namespace

  watch -n 1 kubectl get pods -n <application-namespace>

Abort/Restart the ChaosExperiment

• To stop the pod-delete experiment immediately, either delete the ChaosEngine resource or execute the following command:

  kubectl patch chaosengine <chaosengine-name> -n <namespace> --type merge --patch '{"spec":{"engineState":"stop"}}'

• To restart the experiment, either re-apply the ChaosEngine YAML or execute the following command:

  kubectl patch chaosengine <chaosengine-name> -n <namespace> --type merge --patch '{"spec":{"engineState":"active"}}'

Check ChaosExperiment Result

• Check whether the application is resilient to the container kill, once the experiment (job) is completed. The ChaosResult resource name is derived like this: <ChaosEngine-Name>-<ChaosExperiment-Name>.

  kubectl describe chaosresult nginx-chaos-container-kill -n <application-namespace>

Application Container Kill Demo

• A sample recording of this experiment execution is provided here.