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ECS container network latency

ECS container network latency disrupts the state of infrastructure resources. It brings delay on the AWS ECS container using Amazon SSM Run command, which is carried out using SSM docs which is in-built into the fault.

  • It causes network stress on the containers of the ECS task using the given CLUSTER_NAME environment variable for a specific duration.
  • To select the Task Under Chaos (TUC), use the service name associated with the task. If you provide the service name along with the cluster name, all the tasks associated with the given service will be selected as chaos targets.
  • It tests the ECS task sanity (service availability) and recovery of the task containers subject to network stress.
  • This experiment induces chaos within a container and depends on an EC2 instance. Typically, these are prefixed with "ECS container" and involve direct interaction with the EC2 instances hosting the ECS containers.

ECS Container Network Latency

Use cases​

This fault degrades the network of the task container without the container being marked as unhealthy/ (or unworthy) of traffic. It simulates issues within the ECS task network or communication across services in different availability zones (or regions). This can be resolved using middleware that switches traffic based on certain SLOs (or performance parameters). This can also be resolved by highlighting the degradation using notifications (or alerts). It also determines the impact of the fault on the microservice. The task may stall or get corrupted while waiting endlessly for a packet. The fault limits the impact (blast radius) to only the traffic you wish to test by specifying the service to find TUC (Task Under Chaos). This fault helps improve the resilience of the services over time.

Prerequisites​

  • Kubernetes >= 1.17
  • Adequate AWS access to stop and start an EC2 instance.
  • Create a Kubernetes secret that has the AWS access configuration(key) 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 = 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": [
        {
            "Sid": "VisualEditor0",
            "Effect": "Allow",
            "Action": [
                "ecs:UpdateContainerInstancesState",
                "ecs:RegisterContainerInstance",
                "ecs:ListContainerInstances",
                "ecs:DeregisterContainerInstance",
                "ecs:DescribeContainerInstances",
                "ecs:ListTasks",
                "ecs:DescribeClusters"

            ],
            "Resource": "*"
        },
        {
            "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:DescribeInstances"
            ],
            "Resource": [
                "*"
            ]
        }
    ]
}
note

Mandatory tunables​

Variables Description Notes
CLUSTER_NAME Name of the target ECS cluster. For example, cluster-1.
REGION Region name of the target ECS cluster. For example, us-east-1.

Optional tunables​

Variables Description Notes
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 Interval between successive instance terminations (in seconds). Default: 30 s. For more information, go to chaos interval.
AWS_SHARED_CREDENTIALS_FILE Path to the AWS secret credentials. Defaults to /tmp/cloud_config.yml.
SERVICE_NAME Target ECS service name. For example, app-svc. For more information, go to ECS service name.
NETWORK_LATENCY Latency you wish to induce within the service (in milliseconds). Default: 2000 ms. For more information, go to latency.
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. For more information, go to destination IPs.
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. For more information, go to destination hosts.
NETWORK_INTERFACE Name of ethernet interface considered for shaping traffic Default: eth0. For more information, go to network interface.
JITTER Specify the value of jitter. Default: 0. For more information, go to jitter.
SEQUENCE It defines sequence of chaos execution for multiple instance Default: 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.

Network latency​

Delay (in ms) to be injected in the target container. Tune it by using the NETWORK_LATENCY environment variable.

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

# injects network latency for a certain chaos duration
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ecs-container-network-latency
    spec:
      components:
        env:
        # network latency to be injected
        - name: NETWORK_LATENCY
          value: '2000' #in ms
        - name: TOTAL_CHAOS_DURATION
          value: '60'

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:

# provide the network interface
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ecs-container-network-latency
    spec:
      components:
        env:
        # name of the network interface
        - name: NETWORK_INTERFACE
          value: 'eth0'
        - name: TOTAL_CHAOS_DURATION
          value: '60'

Jitter​

Jitter (in ms), a parameter that allows introducing a network delay variation. Tune it by using the JITTER environment variable. Its default value is 0.

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

# provide the network latency jitter
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ecs-container-network-latency
    spec:
      components:
        env:
        # value of the network latency jitter (in ms)
        - name: JITTER
          value: '200'

Destination IPs and destination hosts​

The network faults interrupt traffic for all the IPs/hosts by default. Tune the interruption of specific IPs/Hosts using DESTINATION_IPS and DESTINATION_HOSTS environment variables.

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

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

# it inject the chaos for the ingress/egress traffic for specific ips/hosts
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ecs-container-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: 'nginx.default.svc.cluster.local,google.com'
        - name: TOTAL_CHAOS_DURATION
          value: '60'

ECS service name​

Service name whose tasks are stopped. Tune it by using the SERVICE_NAME environment variable.

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

# stop the tasks of an ECS cluster
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ecs-task-stop
    spec:
      components:
        env:
        # provide the name of ECS cluster
        - name: CLUSTER_NAME
          value: 'demo'
        - name: SERVICE_NAME
          vale: 'test-svc'
        - name: REGION
          value: 'us-east-1'
        - name: TOTAL_CHAOS_DURATION
          VALUE: '60'