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EC2 stop by tag

EC2 stop by tag stops an EC2 instance using the provided tag and brings back the instance after a specific duration. When the MANAGED_NODEGROUP environment variable is enabled, the fault will not try to start the instance after chaos. Instead, it checks for the addition of a new node instance to the cluster.

EC2 Stop By Tag

Use cases​

EC2 stop by tag:

  • Determines the performance of the application (or process) running on the EC2 instance.
  • Determines the resilience of an application to unexpected halts in the EC2 instance by validating its failover capabilities.

Prerequisites​

  • Kubernetes >= 1.17
  • Appropriate AWS access to stop and start an EC2 instance.
  • The EC2 instances should be in a healthy state.
  • The Kubernetes secret should have the AWS access configuration(key) in the CHAOS_NAMESPACE. Below is the 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
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 with the new secret name 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:StartInstances",
                "ec2:StopInstances",
                "ec2:DescribeInstanceStatus",
                "ec2:DescribeInstances"
            ],
            "Resource": "*"
        },
        {
            "Effect": "Allow",
            "Action": [
                "autoscaling:DescribeAutoScalingInstances"
            ],
            "Resource": "*"
        }
    ]
}
note

Mandatory tunables​

Tunable Description Notes
EC2_INSTANCE_TAG Instance Tag to filter the target EC2 instance. Provided as key:value ex: team:devops. For more information, go to instance tag.
REGION The region name of the target instance. For more information, go to region.

Optional tunables​

Tunable Description Notes
INSTANCE_AFFECTED_PERC Percentage of total EC2 instances to target. Provide numeric values only. Defaults to 0 (corresponds to 1 instance). For more information, go to instance affected percentage.
TOTAL_CHAOS_DURATION Duration that you specify, through which chaos is injected into the target resource (in seconds). Default: 30 s. For more information, go to duration of the chaos.
CHAOS_INTERVAL The interval (in sec) between successive instance termination. Default: 30 s. For more information, go to chaos interval.
MANAGED_NODEGROUP Set to enable if the target instance is the part of self-managed nodegroups. Defaults to disable.
AWS_SHARED_CREDENTIALS_FILE Path to the AWS secret credentials. Default: /tmp/cloud_config.yml.
SEQUENCE It defines sequence of chaos execution for multiple instance. Defaults to parallel. Supports serial and parallel. For more information, go to sequence of chaos execution.
RAMP_TIME Period to wait before and after injecting chaos (in seconds). For example, 30 s. For more information, go to ramp time.
warning

If the target EC2 instance is a part of a self-managed nodegroup, ensure that you drain the target node if any application is running on it. Cordon the target node before running the fault so that the fault pods do not schedule on it.

Target single instance​

Random EC2 instance that is stopped. Tune it by using the EC2_INSTANCE_TAG tag and REGION region.

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

# target the EC2 instances with matching tag
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ec2-terminate-by-tag
    spec:
      components:
        env:
        # tag of the EC2 instance
        - name: EC2_INSTANCE_TAG
          value: 'key:value'
        # region for the EC2 instance
        - name: REGION
          value: 'us-east-1'

Target percent of instances​

Percentage of EC2 instances to stop, based on the EC2_INSTANCE_TAG tag and REGION region. Tune it by using the INSTANCE_AFFECTED_PERC environment variable.

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

# percentage of EC2 instances, needs to terminate with provided tags
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ec2-terminate-by-tag
    spec:
      components:
        env:
        # percentage of EC2 instance filtered by tags
        - name: INSTANCE_AFFECTED_PERC
          value: '100'
        # tag of the EC2 instance
        - name: EC2_INSTANCE_TAG
          value: 'key:value'
        # region for the EC2 instance
        - name: REGION
          value: 'us-east-1'