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EBS loss by tag

EBS (Elastic Block Store) loss by tag disrupts the state of EBS volume by detaching it from the node (or EC2) instance using volume ID for a certain duration. In case of EBS persistent volumes, the volumes can self-attach, and the re-attachment step can be skipped.

EBS Loss By Tag

Use cases​

EBS loss by tag tests the deployment sanity (replica availability and uninterrupted service) and recovery workflows of the application pod.

Prerequisites​

  • Kubernetes >= 1.17
  • EBS volume is attached to the instance.
  • Appropriate AWS access to attach or detach an EBS volume for the instance.
  • The Kubernetes secret should have 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
tip

HCE recommends that you use the same secret name, that is, cloud-secret. Otherwise, you will need to update the AWS_SHARED_CREDENTIALS_FILE environment variable in the fault template and you won't be able to use the default health check probes.

Below is an example AWS policy to execute the fault.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "ec2:AttachVolume",
                "ec2:DetachVolume"
            ],
            "Resource": "*"
        },
        {
            "Effect": "Allow",
            "Action": "ec2:DescribeVolumes",
            "Resource": "*"
        },
        {
            "Effect": "Allow",
            "Action": [
                "ec2:DescribeInstanceStatus",
                "ec2:DescribeInstances"
            ],
            "Resource": "*"
        }
    ]
}
note

Mandatory tunables​

Tunable Description Notes
EBS_VOLUME_TAG Common tag for target volumes. It is in the format key=value (for example, 'team=devops'). For more information, go to target single volume.
REGION Region name for the target volumes For example, us-east-1.

Optional tunables​

Tunable Description Notes
VOLUME_AFFECTED_PERC Percentage of total EBS volumes to target Default: 0 (corresponds to 1 volume), provide numeric value only. For more information, go to target percentage of volumes.
AWS_SHARED_CREDENTIALS_FILE Path to the AWS secret credentials. Default: /tmp/cloud_config.yml.
TOTAL_CHAOS_DURATION Time duration for chaos insertion (sec) Default: 30 s . For more information, go to duration of the chaos.
CHAOS_INTERVAL The time duration between the attachment and detachment of the volumes (sec) Default: 30 s. For more information, go to chaos interval.
SEQUENCE Sequence of chaos execution for multiple volumes Default value: parallel. Supports serial and parallel. For more information, go to sequence of chaos execution.
RAMP_TIME Period to wait before and after injection of chaos in sec For example, 30 s. For more information, go to ramp time.

Target single volume​

Random EBS volume that is detached from the node, based on the given EBS_VOLUME_TAG tag and REGION region.

The following YAML snippet illustrates the use of this environment variable:

# contains the tags for the EBS volumes 
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ebs-loss-by-tag
    spec:
      components:
        env:
        # tag of the EBS volume
        - name: EBS_VOLUME_TAG
          value: 'key=value'
        # region for the EBS volume
        - name: REGION
          value: 'us-east-1'
        - name: TOTAL_CHAOS_DURATION
          VALUE: '60'

Target percent of volumes​

Percentage of EBS volumes that are detached from the node, based on EBS_VOLUME_TAG tag and REGION region. Tune it by using the VOLUME_AFFECTED_PERC environment variable.

The following YAML snippet illustrates the use of this environment variable:

# target percentage of the EBS volumes with the provided tag
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ebs-loss-by-tag
    spec:
      components:
        env:
        # percentage of EBS volumes filter by tag
        - name: VOLUME_AFFECTED_PERC
          value: '100'
        # tag of the EBS volume
        - name: EBS_VOLUME_TAG
          value: 'key=value'
        # region for the EBS volume
        - name: REGION
          value: 'us-east-1'
        - name: TOTAL_CHAOS_DURATION
          VALUE: '60'