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EBS Loss By ID Experiment Details

Experiment Metadata

Type Description Tested K8s Platform
Kube AWS EBS volume loss by ID against specified application EKS

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 ebs-loss-by-id experiment resource is available in the cluster by executing kubectl get chaosexperiments in the desired namespace If not, install from here
  • Ensure that you have sufficient AWS access to attach or detach an ebs volume for the instance.
  • Ensure the target volume to detach should not be the root volume for the instance.
  • Ensure to create a Kubernetes secret having the AWS access configuration(key) in the CHAOS_NAMESPACE. A sample secret file looks like:
apiVersion: v1
kind: Secret
metadata:
  name: cloud-secret
type: Opaque
stringData:
  cloud_config.yml: |-
    # Add the cloud AWS credentials respectively
    [default]
    aws_access_key_id = XXXXXXXXXXXXXXXXXXX
    aws_secret_access_key = XXXXXXXXXXXXXXX
  • If you change the secret key name (from cloud_config.yml) please also update the AWS_SHARED_CREDENTIALS_FILE ENV value on experiment.yamlwith the same name.

Entry-Criteria

  • Application pods are healthy before chaos injection
  • EBS volume is attached to the instance.

Exit-Criteria

  • Application pods are healthy post chaos injection
  • EBS volume is attached to the instance.

Details

  • Causes chaos to disrupt state of ebs volume by detaching it from the node/ec2 instance for a certain chaos duration using volume id.
  • In case of EBS persistent volumes, the volumes can get self-attached and experiment skips the re-attachment step.
  • Tests deployment sanity (replica availability & uninterrupted service) and recovery workflows of the application pod.

Integrations

  • EBS Loss by id can be effected using the chaos library: litmus, which makes use of aws sdk to attach/detach an ebs volume from the target instance. specified capacity on the node.
  • The desired chaoslib can be selected by setting 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: ebs-loss-by-id-sa
  namespace: default
  labels:
    name: ebs-loss-by-id-sa
    app.kubernetes.io/part-of: litmus
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: ebs-loss-by-id-sa
  labels:
    name: ebs-loss-by-id-sa
    app.kubernetes.io/part-of: litmus
rules:
- apiGroups: [""]
  resources: ["pods","events","secrets"]
  verbs: ["create","list","get","patch","update","delete","deletecollection"]
- apiGroups: [""]
  resources: ["pods/exec","pods/log"]
  verbs: ["create","list","get"]
- apiGroups: ["batch"]
  resources: ["jobs"]
  verbs: ["create","list","get","delete","deletecollection"]
- apiGroups: ["litmuschaos.io"]
  resources: ["chaosengines","chaosexperiments","chaosresults"]
  verbs: ["create","list","get","patch","update"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: ebs-loss-by-id-sa
  labels:
    name: ebs-loss-by-id-sa
    app.kubernetes.io/part-of: litmus
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: ebs-loss-by-id-sa
subjects:
- kind: ServiceAccount
  name: ebs-loss-by-id-sa
  namespace: default

Prepare ChaosEngine

  • Provide the application info in spec.appinfo. It is an optional parameter for infra level experiment.
  • Provide the auxiliary applications info (ns & labels) in spec.auxiliaryAppInfo
  • 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
EBS_VOLUME_ID Comma separated list of volume IDs subjected to ebs detach chaos Mandatory
TOTAL_CHAOS_DURATION The time duration for chaos insertion (sec) Optional Defaults to 30s
CHAOS_INTERVAL The time duration between the attachment and detachment of the volumes (sec) Optional Defaults to 30s
REGION The region name for the target volumes Optional
SEQUENCE It defines sequence of chaos execution for multiple volumes Optional Default value: parallel. Supported: serial, parallel
RAMP_TIME Period to wait before and after injection of chaos in sec Optional
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:
  engineState: 'active'
  chaosServiceAccount: ebs-loss-by-id-sa
  experiments:
    - name: ebs-loss-by-id
      spec:
        components:
          env: 
            # set chaos duration (in sec) as desired
            - name: TOTAL_CHAOS_DURATION
              value: '30'

            # set chaos duration (in sec) as desired
            - name: CHAOS_INTERVAL
              value: '30'              

            # set target ebs volume ID  
            - name: EBS_VOLUME_ID
              value: ''

            # provide the region name of the instance
            - name: REGION
              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 the status of the pods as they are subjected to ebs loss.

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

  • Monitor the attachment status for ebs volume from AWS CLI.

    aws ec2 describe-volumes --volume-ids <vol-id>

  • You can also use aws console to keep a watch over ebs attachment status.

Abort/Restart the Chaos Experiment

  • To stop the ebs-loss-by-id 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 ebs loss, once the experiment (job) is completed. The ChaosResult resource name is derived like this: <ChaosEngine-Name>-<ChaosExperiment-Name>.

    kubectl describe chaosresult nginx-chaos-ebs-loss-by-id -n <application-namespace>

EBS Loss Experiment Demo

  • A sample recording of this experiment execution will be added soon.
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