ALB AZ down

ALB AZ down takes down the AZ (Availability Zones) on a target application load balancer for a specific duration. This fault:

• Restricts access to certain availability zones for a specific duration.
• Tests the application sanity, availability, and recovery workflows of the application pod attached to the load balancer.

Use cases

• ALB AZ down fault breaks the connectivity of an ALB with the given zones and impacts their delivery.
• Detaching the AZ from the application load balancer disrupts the application's performance.

note

• Kubernetes > 1.17 is required to execute this fault.
• Appropriate AWS access to attach or detach subnet from the target ALB.
• There needs to be a minimum of two AZs attached to the target ALB after injecting chaos; otherwise, the fault will fail to detach the given AZ.
• The ALB should be attached to the given availability zones.
• Kubernetes secret that has the AWS access configuration(key) in the CHAOS_NAMESPACE. Below is a sample secret file.

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

• It is recommended to 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 with the new secret name and you may be unable to use the default health check probes.
• Refer to AWS named profile for chaos to know how to use a different profile for AWS faults.

Below is an example AWS policy to execute the fault.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "ec2:DescribeInstanceStatus",
                "ec2:DescribeInstances",
                "ec2:DescribeSubnets",
                "elasticloadbalancing:DetachLoadBalancerFromSubnets",
                "elasticloadbalancing:AttachLoadBalancerToSubnets",
                "elasticloadbalancing:DescribeLoadBalancers"
            ],
            "Resource": "*"
        }
    ]
}

Refer to the superset permission or policy to execute all AWS faults.

Fault tunables

Mandatory fields

Variables	Description	Notes
LOAD_BALANCER_ARN	Target load balancer ARN whose AZ should be detached.	For example, arn:aws:elasticloadbalancing:us-east-2:100054111296:loadbalancer/app/test-alb/09121290906ffab7.
ZONES	Target zones that should be detached from ALB.	For example, us-east-1a.
REGION	Region name for the target volumes.	For example, us-east-1.

Optional fields

Variables	Description	Notes
TOTAL_CHAOS_DURATION	Duration to insert chaos (in seconds).	Defaults to 30s. For more information, go to duration of the chaos.
CHAOS_INTERVAL	Duration between the attachment and detachment of the volumes (in seconds).	Defaults to 30s. For more information, go to chaos interval.
SEQUENCE	Sequence of chaos execution for multiple volumes.	Default value is parallel. Supports serial and parallel. For more information, go to sequence of chaos execution.
RAMP_TIME	Duration to wait before and after injecting chaos (in seconds).	For example, 30s. For more information, go to ramp time.

Target zones

It contains the comma-separated list of target zones. Tune it by using the ZONES environment variable.

Use the following example to tune the target zones:

# contains alb az down for given zones
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: alb-az-down
    spec:
      components:
        env:
        # load balancer arn for chaos
        - name: LOAD_BALANCER_ARN
          value: 'arn:aws:elasticloadbalancing:us-east-2:100054111296:loadbalancer/app/test-alb/09121290906ffab7'
        # target zones for the chaos
        - name: ZONES
          value: 'us-east-1a,us-east-1b'
        # region for chaos
        - name: REGION
          value: 'us-east-1'