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Pod Delete Experiment Details

Experiment Metadata

Type Description Tested K8s Platform
Generic Fail the application pod GKE, Konvoy(AWS), Packet(Kubeadm), Minikube, EKS, AKS, TKGi(VMware)

Prerequisites

  • Ensure that Kubernetes Version > 1.16
  • Ensure that the Litmus Chaos Operator is running by executing kubectl get pods in operator namespace (typically, litmus).If not, install from here
  • Ensure that the pod-delete 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

  • Causes (forced/graceful) pod failure of specific/random replicas of an application resources
  • Tests deployment sanity (replica availability & uninterrupted service) and recovery workflow of the application

Integrations

  • The desired chaos library can be selected by setting one of the above options as value for the env variable LIB

Steps to Execute the Chaos Experiment

  • This Chaos Experiment 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: pod-delete-sa
  namespace: default
  labels:
    name: pod-delete-sa
    app.kubernetes.io/part-of: litmus
---
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: pod-delete-sa
  namespace: default
  labels:
    name: pod-delete-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: ["create","list","get"]
- 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: pod-delete-sa
  namespace: default
  labels:
    name: pod-delete-sa
    app.kubernetes.io/part-of: litmus
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: pod-delete-sa
subjects:
- kind: ServiceAccount
  name: pod-delete-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

Supported Experiment Tunables

Variables Description Specify In ChaosEngine Notes
TOTAL_CHAOS_DURATION The time duration for chaos insertion (in sec) Optional Defaults to 15s, NOTE: Overall run duration of the experiment may exceed the TOTAL_CHAOS_DURATION by a few min
CHAOS_INTERVAL Time interval b/w two successive pod failures (in sec) Optional Defaults to 5s
RANDOMNESS Introduces randomness to pod deletions with a minimum period defined by CHAOS_INTERVAL Optional It supports true or false. Default value: false
FORCE Application Pod deletion mode. `False` indicates graceful deletion with default termination period of 30s. 'True' indicates an immediate forceful deletion with 0s grace period Optional Default to `true`, With `terminationGracePeriodSeconds=0`
TARGET_PODS Comma separated list of application pod name subjected to pod delete chaos Optional If not provided, it will select target pods randomly based on provided appLabels
PODS_AFFECTED_PERC The Percentage of total pods to target Optional Defaults to 0 (corresponds to 1 replica), provide numeric value only
RAMP_TIME Period to wait before and after injection of chaos in sec Optional
SEQUENCE It defines sequence of chaos execution for multiple target pods Optional Default value: parallel. Supported: serial, parallel
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:
  appinfo:
    appns: 'default'
    applabel: 'app=nginx'
    appkind: 'deployment'
  # It can be active/stop
  engineState: 'active'
  chaosServiceAccount: pod-delete-sa
  experiments:
    - name: pod-delete
      spec:
        components:
          env:
            # set chaos duration (in sec) as desired
            - name: TOTAL_CHAOS_DURATION
              value: '30'

            # set chaos interval (in sec) as desired
            - name: CHAOS_INTERVAL
              value: '10'
              
            # pod failures without '--force' & default terminationGracePeriodSeconds
            - name: FORCE
              value: 'false'

             ## percentage of total pods to target
            - name: PODS_AFFECTED_PERC
              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 terminations & recovery by setting up a watch on the pods in the application namespace

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

Abort/Restart the Chaos Experiment

  • 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 Chaos Experiment Result

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

    kubectl describe chaosresult nginx-chaos-pod-delete -n <application-namespace>

Application Pod Failure Demo

  • A sample recording of this experiment execution is provided here
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