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AWS SSM Chaos By Tag Experiment Details

Experiment Metadata

Type Description Tested K8s Platform
AWS SSM Perform chaos on AWS EC2 instance using SSM docs and instance ID 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 aws-ssm-chaos-by-tag 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 the required AWS access and your target EC2 instances have attached an IAM instance profile. To know more checkout Systems Manager Docs.
  • 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

  • EC2 instance is healthy before chaos injection.

Exit-Criteria

  • EC2 instance is healthy post chaos injection.

Details

  • AWS SSM Chaos By Tag contains chaos to disrupt the state of infra resources. The experiment can induce chaos on AWS EC2 instance using Amazon SSM Run Command This is carried out by using SSM Docs that defines the actions performed by Systems Manager on your managed instances (having SSM agent installed) which let you perform chaos experiments on the instances.

  • Causes chaos (like stress, network, disk or IO) on AWS EC2 instances with given instance Tag using SSM docs for a certain chaos duration.

  • For the default execution the experiment uses SSM docs for stress-chaos while you can add your own SSM docs using configMap (.spec.definition.configMaps) in ChaosExperiment CR.

  • Tests deployment sanity (replica availability & uninterrupted service) and recovery workflows of the target application pod(if provided).

Integrations

  • AWS SSM Chaos can be effected using the chaos library: litmus, which makes use of aws sdk to run ssm command on an EC2 instance using instance Tag.
  • 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: aws-ssm-chaos-by-tag-sa
  namespace: default
  labels:
    name: aws-ssm-chaos-by-tag-sa
    app.kubernetes.io/part-of: litmus
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: aws-ssm-chaos-by-tag-sa
  labels:
    name: aws-ssm-chaos-by-tag-sa
    app.kubernetes.io/part-of: litmus
rules:
- apiGroups: [""]
  resources: ["pods","events","secrets","configmaps"]
  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: aws-ssm-chaos-by-tag-sa
  labels:
    name: aws-ssm-chaos-by-tag-sa
    app.kubernetes.io/part-of: litmus
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: aws-ssm-chaos-by-tag-sa
subjects:
- kind: ServiceAccount
  name: aws-ssm-chaos-by-tag-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
EC2_INSTANCE_TAG Instance Tag to filter the target ec2 instance. Mandatory The EC2_INSTANCE_TAG should be provided as key:value ex: chaos:ssm
TOTAL_CHAOS_DURATION The total time duration for chaos insertion (sec) Optional Defaults to 60s
CHAOS_INTERVAL The interval (in sec) between successive instance termination. Optional Defaults to 60s
AWS_SHARED_CREDENTIALS_FILE Provide the path for aws secret credentials Optional Defaults to /tmp/cloud_config.yml
DOCUMENT_NAME Provide the name of addded ssm docs (if not using the default docs) Optional Default to LitmusChaos-AWS-SSM-Doc
DOCUMENT_FORMAT Provide the format of the ssm docs. It can be YAML or JSON Optional Defaults to YAML
DOCUMENT_TYPE Provide the document type of added ssm docs (if not using the default docs) Optional Defaults to Command
DOCUMENT_PATH Provide the document path if added using configmaps Optional Defaults to the litmus ssm docs path
INSTALL_DEPENDENCIES Select to install dependencies used to run stress-ng with default docs. It can be either True or False Optional Defaults to True
NUMBER_OF_WORKERS Provide the number of workers to run stress-chaos with default ssm docs Optional Defaults to 1
MEMORY_PERCENTAGE Provide the memory consumption in percentage on the instance for default ssm docs Optional Defaults to 80
CPU_CORE Provide the number of cpu cores to run stress-chaos on EC2 with default ssm docs Optional Defaults to 0. It means it'll consume all the available cpu cores on the instance
RAMP_TIME Period to wait before and after injection of chaos in sec Optional
SEQUENCE It defines sequence of chaos execution for multiple instance Optional Default value: parallel. Supported: serial, parallel
INSTANCE_AFFECTED_PERC The Percentage of total ec2 instance to target Optional Defaults to 0 (corresponds to 1 instance), provide numeric value only
REGION The region name of the target instace 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: aws-ssm-chaos-by-tag-sa
  experiments:
    - name: aws-ssm-chaos-by-tag
      spec:
        components:
          env: 
            # set chaos duration (in sec) as desired
            - name: TOTAL_CHAOS_DURATION
              value: '60'

            # set chaos duration (in sec) as desired
            - name: CHAOS_INTERVAL
              value: '60'              

             # provide tag of the target ec2 instances
             # ex: team:devops (key:value)
            - name: EC2_INSTANCE_TAG
              value: ''

            # provide the region name of the target instances
            - name: REGION
              value: ''

             # provide the percentage of available memory to stress
            - name: MEMORY_PERCENTAGE
              value: '80'

            # provide the CPU chores to comsumed
            # 0 will consume all the available cpu cores
            - name: CPU_CORE
              value: '0'

             # Provide the name of ssm doc 
            # if not using the default stress docs  
            - name: DOCUMENT_NAME
              value: ''

            # Provide the type of ssm doc 
            # if not using the default stress docs  
            - name: DOCUMENT_TYPE
              value: ''

            # Provide the format of ssm doc
            # if not using the default stress docs  
            - name: DOCUMENT_FORMAT
              value: ''

            # Provide the path of ssm doc 
            # if not using the default stress docs  
            - name: DOCUMENT_PATH
              value: ''

             # if you want to install dependencies to run default ssm docs
            - name: INSTALL_DEPENDENCIES
              value: 'True'

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

  • Monitor the command status

aws ssm list-commands --command-id "command-ID"

Note: To list down the ssm docs and command to get the command id check out the AWS SSM userguide

  • Monitor the ec2 state from AWS CLI.

    aws ec2 describe-instance-status --instance-ids <instance-id>

  • You can also use aws console to keep a watch over the instance state and the ssm command state.

Abort/Restart the Chaos Experiment

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

    kubectl describe chaosresult nginx-chaos-aws-ssm-chaos-by-tag -n <application-namespace>

AWS SSM Chaos Experiment Demo

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