litmus-docs/website/versioned_docs/version-1.0.0/openebs-pool-container-failure.md

id	title	sidebar_label	original_id
openebs-pool-container-failure	OpenEBS Pool Container Failure Experiment Details	Pool Container Failure	openebs-pool-container-failure

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Experiment Metadata

Type	Description	Tested K8s Platform
OpenEBS	Kill the cstor pool pod container and check if gets created again	GKE, Konvoy(AWS), Packet(Kubeadm), Minikube, OpenShift(Baremetal)

Prerequisites

• Ensure that the Litmus Chaos Operator is running in the cluster. If not, install from here

• Ensure that the openebs-pool-container-failure experiment resource is available in the cluster. If not, install from here

• If DATA_PERSISTENCE is 'enabled', provide the application info in a configmap volume so that the experiment can perform necessary checks. Currently, LitmusChaos supports data consistency checks only on MySQL databases. Create a configmap as shown below in the application namespace (replace with actual credentials):

  ---
  apiVersion: v1
  kind: ConfigMap
  metadata:
    name: openebs-pool-container-failure
  data:
    parameters.yml: |
      dbuser: root
      dbpassword: k8sDem0
      dbname: test
  

• Ensure that the chaosServiceAccount used for the experiment has cluster-scope permissions as the experiment may involve carrying out the chaos in the openebs namespace while performing application health checks in its respective namespace.

Entry Criteria

• Application pods are healthy before chaos injection
• Application writes are successful on OpenEBS PVs

Exit Criteria

• Stateful application pods are healthy post chaos injection
• OpenEBS Storage target pods are healthy

If the experiment tunable DATA_PERSISTENCE is set to 'enabled':

• Application data written prior to chaos is successfully retrieved/read
• Database consistency is maintained as per db integrity check utils

Details

• This scenario validates the behaviour of stateful applications and OpenEBS data plane upon forced termination of the targeted pool pod container
• Containers are killed using the kill command provided by pumba
• Pumba is run as a daemonset on all nodes in dry-run mode to begin with; the kill command is issued during experiment execution via kubectl exec
• Can test the stateful application's resilience to momentary iSCSI connection loss

Integrations

• Container kill is achieved using the pumba chaos library for docker runtime.
• The desired lib image can be configured in the env variable LIB_IMAGE.

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 be provided in a ChaosEngine specification, refer Getting Started

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

Prepare ChaosEngine

• Provide the application info in spec.appinfo
• Override the experiment tunables if desired

Supported Experiment Tunables

Variables	Description	Type	Notes
APP_PVC	The PersistentVolumeClaim used by the stateful application	Mandatory	PVC must use OpenEBS cStor storage class
DEPLOY_TYPE	Type of Kubernetes resource used by the stateful application	Optional	Defaults to deployment. Supported: deployment, statefulset
LIB_IMAGE	The chaos library image used to inject the latency	Optional	Defaults to gaiaadm/pumba:0.4.8. Supported: gaiaadm/pumba:0.4.8
TOTAL_CHAOS_DURATION	Amount of soak time for I/O post pod kill	Optional	Defaults to 600 seconds
DATA_PERSISTENCE	Flag to perform data consistency checks on the application	Optional	Default value is disabled (empty/unset). Set to enabled to perform data checks. Ensure configmap with app details are created

Sample ChaosEngine Manifest

apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: target-chaos
  namespace: default
spec:
  appinfo:
    appns: default
    applabel: "app=percona"
    appkind: deployment
  chaosServiceAccount: percona-sa
  monitoring: false
  jobCleanUpPolicy: delete
  experiments:
    - name: openebs-pool-container-failure
      spec:
        components:
          - name: APP_PVC
            value: "pvc-c466262a-a5f2-4f0f-b594-5daddfc2e29d"
          - name: DEPLOY_TYPE
            value: deployment

Create the ChaosEngine Resource

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

  kubectl apply -f chaosengine.yml

Watch Chaos progress

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

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

Check Chaos Experiment Result

• Check whether the application is resilient to the pool pod container failure, once the experiment (job) is completed. The ChaosResult resource naming convention is: <ChaosEngine-Name>-<ChaosExperiment-Name>.

  kubectl describe chaosresult target-chaos-openebs-pool-container-failure -n <application-namespace>

OpenEBS Pool Container Failure Demo [TODO]

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