EC2 network latency

Introduction

EC2 network latency causes flaky access to the application (or services) by injecting network packet latency to EC2 instance(s). This fault:

• Degrades the network without marking the EC2 instance as unhealthy (or unworthy) of traffic, which is resolved using a middleware that switches traffic based on SLOs (performance parameters).
• May stall the EC2 instance or get corrupted waiting endlessly for a packet.
• Limits the impact (blast radius) to the traffic that you wish to test, by specifying the IP addresses.

Use cases

EC2 network latency:

• Determines the performance of the application (or process) running on the EC2 instances.
• Simulates a consistently slow network connection between microservices (for example, cross-region connectivity between active-active peers of a given service or across services or poor cni-performance in the inter-pod-communication network).
• Simulates jittery connection with transient latency spikes between microservices.
• Simulates a slow response on specific third party (or dependent) components (or services), and degraded data-plane of service-mesh infrastructure.

note

• Kubernetes version 1.17 or later is required to execute the fault.
• SSM agent is installed and running on the target EC2 instance.
• The EC2 instance should be in healthy state.
• The Kubernetes secret should have the AWS Access Key ID and Secret Access Key credentials in the CHAOS_NAMESPACE. A sample secret file looks like:

  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 the superset permission/policy to execute all AWS faults and AWS named profile for chaos to use a different profile for AWS faults.
• Go to the common tunables to tune the common tunables for all the 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	The AWS region ID where the EC2 instance has been created.	For example, us-east-1.

Optional tunables

Tunable	Description	Notes
TOTAL_CHAOS_DURATION	Duration that you specify, through which chaos is injected into the target resource (in seconds).	Default: 30 s.
CHAOS_INTERVAL	Time interval between two successive instance terminations (in seconds).	Default: 30 s.
AWS_SHARED_CREDENTIALS_FILE	Provide the path for AWS secret credentials.	Default: /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_LATENCY	The latency/delay in milliseconds.	Default: 2000, provide numeric value only.
JITTER	The network jitter value in ms.	Default: 0, provide numeric value only.
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.	Default: `eth0`.
SEQUENCE	It defines the sequence of chaos execution for multiple instances.	Default: parallel. Supports serial sequence.
RAMP_TIME	Period to wait before and after injecting chaos (in seconds).	For example, 30 s.

Network packet latency

Network packet latency (delay) that is injected on the EC2 instances. Tune it by using the NETWORK_LATENCY environment variable.

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

# 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-latency
    spec:
      components:
        env:
        # network packet latency
        - name: NETWORK_LATENCY
          value: '2000'
        - name: EC2_INSTANCE_ID
          value: 'instance-1'
        - name: REGION
          value: 'us-west-2'

Run with jitter

Introduces a network delay variation (in ms). Tune it by using the JITTER environment variable. Its default value is 0.

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

# 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-latency
    spec:
      components:
        env:
        # value of the network latency jitter (in ms)
        - name: JITTER
          value: '200'
        - name: NETWORK_LATENCY
          value: '2000'
        - name: EC2_INSTANCE_ID
          value: 'instance-1'
        - name: REGION
          value: 'us-west-2'

Run with destination IPs and destination hosts

Interruption of IPs/hosts. By default, all IPs/hosts are interrupted. Tune specific IPs/hosts by using the DESTINATION_IPS and DESTINATION_HOSTS environment variables, respectively.

DESTINATION_IPS: It contains the IP addresses of the services or the CIDR blocks (range of IPs) whose accessibility is impacted. DESTINATION_HOSTS: It contains the DNS names of the services whose accessibility is impacted.

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

# 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-latency
    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

Name of the ethernet interface considered for shaping traffic. Tune it by using the NETWORK_INTERFACE environment variable. Its default value is eth0.

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

# 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-latency
    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'