EC2 network loss

EC2 network loss causes flaky access to the application (or services) by injecting network packet loss to EC2 instance(s).

• It checks the performance of the application (or process) running on the EC2 instances.

Usage

View fault usage

This fault degrades the network without the EC2 instance being marked as unhealthy (or unworthy) of traffic. This can be resolved by using a middleware that switches traffic based on some SLOs (performance parameters). The EC2 instance may stall or get corrupted while waiting endlessly for a packet. This fault limits the impact (blast radius) to only the traffic that you wish to test, by specifying the IP addresses.

It simulates degraded network with varied percentages of dropped packets between microservices, loss of access to specific third party (or dependent) services (or components), blackhole against traffic to a given AZ (failure simulation of availability zones), and network partitions (split-brain) between peer replicas for a stateful application.

This fault helps improve the resilience of your services over time.

Prerequisites

• Kubernetes > 1.16
• SSM agent is installed and running on the target EC2 instance.
• Ensure to create a Kubernetes secret having the 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

• If you change the secret name then please also update the experiment.yml environment variable for deriving the respective data from the secret. Also account for the path at which this secret is mounted as a file in the manifest environment variable AWS_SHARED_CREDENTIALS_FILE.

Note

You can pass the VM credentials as secrets or as a ChaosEngine environment variable.

Permissions required

Here is an example AWS policy to execute the fault.

View policy for 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": [
                "*"
            ]
        }
    ]
}

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

Default validations

The EC2 instance should be in healthy state.

Fault tunables

Fault tunables

Mandatory fields

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

Optional fields

Variables	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.
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.
NETWORK_PACKET_LOSS_PERCENTAGE	The packet loss in percentage.	Default to 100 percentage.
DESTINATION_IPS	IP addresses of the services or the CIDR blocks(range of IPs), the accessibility to which is impacted.	comma-separated IP(S) or CIDR(S) can be provided. If not provided, it will induce network chaos for all ips/destinations.
DESTINATION_HOSTS	DNS Names of the services, the accessibility to which, is impacted.	if not provided, it will induce network chaos for all ips/destinations or DESTINATION_IPS if already defined.
NETWORK_INTERFACE	Name of ethernet interface considered for shaping traffic.	Defaults to `eth0`.
SEQUENCE	It defines sequence of chaos execution for multiple instance.	Defaults to parallel. Supports serial sequence as well.
RAMP_TIME	Period to wait before and after injecting chaos (in seconds).	For example, 30s

Fault examples

Fault tunables

Refer to the common attributes to tune the common tunables for all the faults.

Network packet loss

It defines the network packet loss percentage to be injected on the EC2 instances. You can tune it using the NETWORK_PACKET_LOSS_PERCENTAGE environment variable.

You can tune it using the following example:

# it injects the chaos into the egress traffic
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ec2-network-loss
    spec:
      components:
        env:
        # network packet loss percentage
        - name: NETWORK_PACKET_LOSS_PERCENTAGE
          value: '100'
        - name: EC2_INSTANCE_ID
          value: 'instance-1'
        - name: REGION
          value: 'us-west-2'

Run with destination IPs and destination hosts

The network faults interrupt traffic for all the IPs/hosts by default. The interruption of specific IPs/Hosts can be tuned via DESTINATION_IPS and DESTINATION_HOSTS environment variable.

DESTINATION_IPS: It contains the IP addresses of the services or the CIDR blocks(range of IPs), the accessibility to which is impacted. DESTINATION_HOSTS: It contains the DNS Names of the services, the accessibility to which, is impacted

You can tune it using the following example:

# it injects the chaos into the egress traffic for specific IPs/hosts
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ec2-network-loss
    spec:
      components:
        env:
        # supports comma-separated destination ips
        - name: DESTINATION_IPS
          value: '8.8.8.8,192.168.5.6'
        # supports comma-separated destination hosts
        - name: DESTINATION_HOSTS
          value: 'google.com'
        - name: EC2_INSTANCE_ID
          value: 'instance-1'
        - name: REGION
          value: 'us-west-2'

Network interface

The defined name of the ethernet interface, which is considered for shaping traffic. You can tune it using the NETWORK_INTERFACE environment variable. Its default value is eth0.

You can tune it using the following example:

# it injects the chaos into the egress traffic for specific network interface
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ec2-network-loss
    spec:
      components:
        env:
        # name of the network interface
        - name: NETWORK_INTERFACE
          value: 'eth0'
        - name: EC2_INSTANCE_ID
          value: 'instance-1'
        - name: REGION
          value: 'us-west-2'