ECS container HTTP modify body

ECS container HTTP modify body injects HTTP chaos which affects the request or response by modifying the status code, body, or headers. This is achieved by starting a proxy server and redirecting the traffic through the proxy server.

Use cases

ECS container HTTP modify body:

• Tests the application's resilience to erroneous (or incorrect) HTTP response body.
• Tests the resilience of the ECS application container to erroneous or incorrect HTTP response body.

Prerequisites

• Kubernetes >= 1.17
• ECS container metadata is enabled (disabled by default). To enable it, go to container metadata. If your task is currently running, you may need to restart it to get the metadata directory.
• ECS cluster running with the desired tasks and containers and familiarity with ECS service update and deployment concepts.
• Access to the ECS cluster instances with the necessary permissions to update the start and stop timeouts for containers. Refer to systems manager docs.
• Backup and recovery mechanisms in place to handle potential failures during the testing process.
• You and the ECS cluster instances have a role with the required AWS access to perform the SSM and ECS operations.
• Kubernetes secret with AWS Access Key ID and secret access key credentials 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 = XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

• 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 and you may be unable to use the default health check probes.

note

• You can pass the VM credentials as secrets or as a ChaosEngine environment variable.
• The ECS container instance should be in a healthy state before and after introducing chaos.
• Refer to the superset permission or policy to execute all AWS faults.
• Refer to the common attributes to tune the common tunables for all the faults.
• Refer to AWS named profile for chaos to use a different profile for AWS faults.

Permissions required

Here 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": [
                "*"
            ]
        }
    ]
}

Mandatory tunables

Tunable	Description	Notes
REGION	The AWS region ID where the ECS container has been created.	For example, us-east-1.
TARGET_SERVICE_PORT	Port of the service to the target.	Defaults to port 80.
RESPONSE_BODY	Body string to overwrite the http response body.	If no value is provided, the response will be an empty body (defaults to empty body).

Optional tunables

Tunable	Description	Notes
TOTAL_CHAOS_DURATION	Duration that you specify, through which chaos is injected into the target resource (in seconds).	Defaults to 30s.
CHAOS_INTERVAL	Time interval between two successive instance terminations (in seconds).	Defaults to 30s.
AWS_SHARED_CREDENTIALS_FILE	Provide the path for AWS secret credentials.	Defaults to /tmp/cloud_config.yml.
SEQUENCE	Defines the sequence of chaos execution for multiple instances.	Defaults to parallel. Supports serial sequence as well.
RAMP_TIME	Period to wait before and after injection of chaos (in seconds).	For example, 30.
INSTALL_DEPENDENCY	Select to install dependencies used to run the network chaos. It can be either True or False.	If the dependency already exists, you can turn it off. Defaults to True.
PROXY_PORT	Port where the proxy listens to requests.	Defaults to 20000.
NETWORK_INTERFACE	Network interface used for the proxy.	Defaults to `eth0`.

Target service port

Service port that is targeted. Tune it by using the TARGET_SERVICE_PORT environment variable.

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

## provide the port of the targeted service
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ecs-container-http-modify-body
    spec:
      components:
        env:
        # provide the port of the targeted service
        - name: TARGET_SERVICE_PORT
          value: "80"

Modifying the response body

Response body that is modified. Tune it by using the RESPONSE_BODY environment variable.

note

HTTP_CHAOS_TYPE should be provided as the body.

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

## provide the headers as a map
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ecs-container-http-modify-body
    spec:
      components:
        env:
        # provide the body string to overwrite the response body
        - name: RESPONSE_BODY
          value: '2000'
        # provide the port of the targeted service
        - name: TARGET_SERVICE_PORT
          value: "80"

Proxy port

Port where the proxy server listens for requests. Tune it by using the PROXY_PORT environment variable.

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

# provide the port for proxy server
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ecs-container-http-modify-body
    spec:
      components:
        env:
        # provide the port for proxy server
        - name: PROXY_PORT
          value: '8080'
        # provide the port of the targeted service
        - name: TARGET_SERVICE_PORT
          value: "80"

Network interface

Network interface used for the proxy. Tune it by using the NETWORK_INTERFACE environment variable.

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

## provide the network interface for proxy
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ecs-container-http-modify-body
    spec:
      components:
        env:
        # provide the network interface for proxy
        - name: NETWORK_INTERFACE
          value: "eth0"
        # provide the port of the targeted service
        - name: TARGET_SERVICE_PORT
          value: '80'