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Pod Network Duplication Experiment Details

Experiment Metadata

Type Description Tested K8s Platform
Generic Inject Packet Duplication Into Application Pod GKE, Packet(Kubeadm), EKS, Minikube > v1.6.0, AKS

Prerequisites

  • Ensure that Kubernetes Version > 1.16
  • Ensure that the Litmus Chaos Operator is running by executing kubectl get pods in operator namespace (typically, litmus). If not, install from here
  • Ensure that the pod-network-duplication experiment resource is available in the cluster by executing kubectl get chaosexperiments in the desired namespace. If not, install from here

Entry Criteria

  • Application pods are healthy before chaos injection

Exit Criteria

  • Application pods are healthy post chaos injection

Details

  • pod-network-duplication injects chaos to disrupt network connectivity to kubernetes pods.
  • The application pod should be healthy once chaos is stopped. Service-requests should be served despite chaos.
  • Causes Injection of network duplication on the specified container by starting a traffic control (tc) process with netem rules to add egress delays. It Can test the application's resilience to duplicate network.

Steps to Execute the Chaos Experiment

  • This Chaos Experiment can be triggered by creating a ChaosEngine resource on the cluster. To understand the values to provide in a ChaosEngine specification, refer Getting Started

  • Follow the steps in the sections below to create the chaosServiceAccount, prepare the ChaosEngine & execute the experiment.

Prepare chaosServiceAccount

  • Use this sample RBAC manifest to create a chaosServiceAccount in the desired (app) namespace. This example consists of the minimum necessary role permissions to execute the experiment.

Sample Rbac Manifest

apiVersion: v1
kind: ServiceAccount
metadata:
  name: pod-network-duplication-sa
  namespace: default
  labels:
    name: pod-network-duplication-sa
    app.kubernetes.io/part-of: litmus
---
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: pod-network-duplication-sa
  namespace: default
  labels:
    name: pod-network-duplication-sa
    app.kubernetes.io/part-of: litmus
rules:
- apiGroups: [""]
  resources: ["pods","events"]
  verbs: ["create","list","get","patch","update","delete","deletecollection"]
- apiGroups: [""]
  resources: ["pods/exec","pods/log","replicationcontrollers"]
  verbs: ["create","list","get"]
- apiGroups: ["batch"]
  resources: ["jobs"]
  verbs: ["create","list","get","delete","deletecollection"]
- apiGroups: ["apps"]
  resources: ["deployments","statefulsets","daemonsets","replicasets"]
  verbs: ["list","get"]
- apiGroups: ["apps.openshift.io"]
  resources: ["deploymentconfigs"]
  verbs: ["list","get"]
- apiGroups: ["argoproj.io"]
  resources: ["rollouts"]
  verbs: ["list","get"]
- apiGroups: ["litmuschaos.io"]
  resources: ["chaosengines","chaosexperiments","chaosresults"]
  verbs: ["create","list","get","patch","update"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: pod-network-duplication-sa
  namespace: default
  labels:
    name: pod-network-duplication-sa
    app.kubernetes.io/part-of: litmus
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: pod-network-duplication-sa
subjects:
- kind: ServiceAccount
  name: pod-network-duplication-sa
  namespace: default

Note: In case of restricted systems/setup, create a PodSecurityPolicy(psp) with the required permissions. The chaosServiceAccount can subscribe to work around the respective limitations. An example of a standard psp that can be used for litmus chaos experiments can be found here.

Prepare ChaosEngine

  • Provide the application info in spec.appinfo
  • Override the experiment tunables if desired in experiments.spec.components.env
  • To understand the values to provided in a ChaosEngine specification, refer ChaosEngine Concepts

Supported Experiment Tunables

Variables Description Specify In ChaosEngine Notes
NETWORK_INTERFACE Name of ethernet interface considered for shaping traffic Mandatory
TARGET_CONTAINER Name of container which is subjected to network latency Optional Applicable for containerd & CRI-O runtime only. Even with these runtimes, if the value is not provided, it injects chaos on the first container of the pod
NETWORK_PACKET_DUPLICATION_PERCENTAGE The packet duplication in percentage Optional Default to 100 percentage
TOTAL_CHAOS_DURATION The time duration for chaos insertion (seconds) Optional Default (60s)
PODS_AFFECTED_PERC The Percentage of total pods to target Optional Defaults to 0 (corresponds to 1 replica), provide numeric value only
CONTAINER_RUNTIME container runtime interface for the cluster Optional Defaults to docker, supported values: docker, containerd and crio for litmus and only docker for pumba LIB
SOCKET_PATH Path of the containerd/crio/docker socket file Optional Defaults to `/var/run/docker.sock`
TARGET_PODS Comma separated list of application pod name subjected to pod network duplication chaos Optional If not provided, it will select target pods randomly based on provided appLabels
DESTINATION_IPS IP addresses of the services or pods or the CIDR blocks(range of IPs), the accessibility to which is impacted Optional 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/FQDN names of the services, the accessibility to which, is impacted Optional if not provided, it will induce network chaos for all ips/destinations or DESTINATION_IPS if already defined
LIB The chaos lib used to inject the chaos Optional Default value: litmus, supported values: pumba and litmus
TC_IMAGE Image used for traffic control in linux Optional default value is `gaiadocker/iproute2`
LIB_IMAGE Image used to run the netem command Optional Defaults to `litmuschaos/go-runner:latest`
RAMP_TIME Period to wait before and after injection of chaos in sec Optional
SEQUENCE It defines sequence of chaos execution for multiple target pods Optional Default value: parallel. Supported: serial, parallel
INSTANCE_ID A user-defined string that holds metadata/info about current run/instance of chaos. Ex: 04-05-2020-9-00. This string is appended as suffix in the chaosresult CR name. Optional Ensure that the overall length of the chaosresult CR is still < 64 characters

Sample ChaosEngine Manifest

# chaosengine.yaml
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: nginx-network-chaos
  namespace: default
spec:
  # It can be active/stop
  engineState: 'active'
  appinfo: 
    appns: 'default'
    # FYI, To see app label, apply kubectl get pods --show-labels
    applabel: 'app=nginx'
    appkind: 'deployment'
  chaosServiceAccount: pod-network-duplication-sa 
  experiments:
    - name: pod-network-duplication
      spec:
        components:
          env:
            - name: TOTAL_CHAOS_DURATION
              value: '60' # in seconds

            - name: NETWORK_PACKET_DUPLICATION_PERCENTAGE
              value: '100'
  
            # provide the name of container runtime
            # for litmus LIB, it supports docker, containerd, crio
            # for pumba LIB, it supports docker only
            - name: CONTAINER_RUNTIME
              value: 'docker'

            # provide the socket file path
            - name: SOCKET_PATH
              value: '/var/run/docker.sock'
              
            ## percentage of total pods to target
            - name: PODS_AFFECTED_PERC
              value: ''

Create the ChaosEngine Resource

  • Create the ChaosEngine manifest prepared in the previous step to trigger the Chaos.

    kubectl apply -f chaosengine.yml

  • If the chaos experiment is not executed, refer to the troubleshooting section to identify the root cause and fix the issues.

Watch Chaos progress

  • View network latency by setting up a ping on the affected pod from the cluster nodes

    ping <pod_ip_address>

Abort/Restart the Chaos Experiment

  • To stop the pod-network-duplication experiment immediately, either delete the ChaosEngine resource or execute the following command:

    kubectl patch chaosengine <chaosengine-name> -n <namespace> --type merge --patch '{"spec":{"engineState":"stop"}}'

  • To restart the experiment, either re-apply the ChaosEngine YAML or execute the following command:

    kubectl patch chaosengine <chaosengine-name> -n <namespace> --type merge --patch '{"spec":{"engineState":"active"}}'

Check Chaos Experiment Result

  • Check whether the application is resilient to the Pod Network Duplication, once the experiment (job) is completed. The ChaosResult resource name is derived like this: <ChaosEngine-Name>-<ChaosExperiment-Name>.

    kubectl describe chaosresult <ChaosEngine-Name>-<ChaosExperiment-Name> -n <application-namespace>

Application Pod Network Duplication Demo

  • A sample recording of this experiment execution will be provided very soon.
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