EC2 memory hog

Introduction

EC2 memory hog disrupts the state of infrastructure resources. This fault:

• Induces stress on AWS EC2 instance using Amazon SSM Run command. The SSM Run command is executed using SSM documentation that is built into the fault.
• Causes memory exhaustion on the EC2 instance for a specific duration.

Use cases

EC2 memory hog:

• Causes memory stress on the target AWS EC2 instance(s).
• Simulates the situation of memory leaks in the deployment of microservices.
• Simulates application slowness due to memory starvation, and noisy neighbour problems due to hogging.

note

• Kubernetes version 1.17 or later is required to execute the fault.
• The EC2 instance should be in a healthy state.
• SSM agent should be installed and running on the target EC2 instance.
• The Kubernetes secret should have the AWS Access Key ID and Secret Access Key credentials 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 = XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
• We recommend 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.
• Go to AWS named profile for chaos to use a different profile for AWS faults, and the superset permission/policy to execute all AWS faults.

Below is an example AWS policy to execute the fault.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "ssm:GetDocument",
                "ssm:DescribeDocument",
                "ssm:GetParameter",
                "ssm:GetParameters",
                "ssm:SendCommand",
                "ssm:CancelCommand",
                "ssm:CreateDocument",
                "ssm:DeleteDocument",
                "ssm:GetCommandInvocation",          
                "ssm:UpdateInstanceInformation",
                "ssm:DescribeInstanceInformation"
            ],
            "Resource": "*"
        },
        {
            "Effect": "Allow",
            "Action": [
                "ec2messages:AcknowledgeMessage",
                "ec2messages:DeleteMessage",
                "ec2messages:FailMessage",
                "ec2messages:GetEndpoint",
                "ec2messages:GetMessages",
                "ec2messages:SendReply"
            ],
            "Resource": "*"
        },
        {
            "Effect": "Allow",
            "Action": [
                "ec2:DescribeInstanceStatus",
                "ec2:DescribeInstances"
            ],
            "Resource": [
                "*"
            ]
        }
    ]
}

Fault tunables

Mandatory tunables

Tunable	Description	Notes
EC2_INSTANCE_ID	ID of the target EC2 instance.	For example, i-044d3cb4b03b8af1f.
REGION	AWS region ID where the EC2 instance has been created.	For example, us-east-1.

Optional tunables

Tunable	Description	Notes
TOTAL_CHAOS_DURATION	Duration to insert chaos (in seconds).	Defaults to 30s.
CHAOS_INTERVAL	Time interval between two successive instance terminations (in seconds).	Defaults to 60s.
AWS_SHARED_CREDENTIALS_FILE	Path to the AWS secret credentials.	Defaults to /tmp/cloud_config.yml.
INSTALL_DEPENDENCIES	Install dependencies to run network chaos. It can be 'True' or 'False'.	If the dependency already exists, you can turn it off. Defaults to True.
MEMORY_CONSUMPTION	Amount of memory to be consumed by the EC2 instance (in megabytes).	Defaults to 500MB.
MEMORY_PERCENTAGE	Amount of memory to be consumed by the EC2 instance (in percentage).	Defaults to 0.
NUMBER_OF_WORKERS	Number of workers used to run the stress process.	Defaults to 1.
SEQUENCE	Sequence of chaos execution for multiple instances.	Defaults to parallel. Supports serial and parallel.
RAMP_TIME	Period to wait before and after injecting chaos (in seconds).	For example, 30s.

Memory consumption in megabytes

It specifies the amount of memory to be utilized (in megabytes) on the EC2 instance. Tune it by using the MEMORY_CONSUMPTION environment variable.

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

# memory in mb to utilize
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ec2-memory-hog
    spec:
      components:
        env:
        - name: MEMORY_CONSUMPTION
          VALUE: '1024'
        # ID of the EC2 instance
        - name: EC2_INSTANCE_ID
          value: 'instance-1'
        # region for the EC2 instance
        - name: REGION
          value: 'us-east-1'

Memory consumption by percentage

It specifies the amount of memory (in percentage) to be utilized on the EC2 instance. Tune it by using the MEMORY_PERCENTAGE environment variable.

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

# memory percentage to utilize
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ec2-memory-hog
    spec:
      components:
        env:
        - name: MEMORY_PERCENTAGE
          value: '50'
        # ID of the EC2 instance
        - name: EC2_INSTANCE_ID
          value: 'instance-1'
        # region for the EC2 instance
        - name: REGION
          value: 'us-east-1'

Multiple EC2 instances

It specifies multiple EC2 instances as comma-separated IDs that are targeted in one chaos run. Tune it by using the EC2_INSTANCE_ID environment variable.

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

# multiple instance targets
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ec2-memory-hog
    spec:
      components:
        env:
        # ids of the EC2 instances
        - name: EC2_INSTANCE_ID
          value: 'instance-1,instance-2,instance-3'
        # region for the EC2 instance
        - name: REGION
          value: 'us-east-1'

Multiple workers

It specifies the CPU threads that need to be run to increase the file system utilization. This increases the amount of file system consumed. Tune it using the NUMBER_OF_WORKERS environment variable.

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

# multiple workers to utilize resources
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ec2-memory-hog
    spec:
      components:
        env:
        - name: NUMBER_OF_WORKERS
          value: '3'
        # ID of the EC2 instance
        - name: EC2_INSTANCE_ID
          value: 'instance-1'
        # region for the EC2 instance
        - name: REGION
          value: 'us-east-1'