Pod Network Loss Experiment Details
Experiment Metadata
Type | Description | Tested K8s Platform |
---|---|---|
Generic | Inject Packet Loss 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-loss
experiment resource is available in the cluster by executingkubectl 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-loss 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 loss of access to application replica by injecting packet loss using pumba
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-loss-sa
namespace: default
labels:
name: pod-network-loss-sa
app.kubernetes.io/part-of: litmus
---
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
name: pod-network-loss-sa
namespace: default
labels:
name: pod-network-loss-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-loss-sa
namespace: default
labels:
name: pod-network-loss-sa
app.kubernetes.io/part-of: litmus
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: Role
name: pod-network-loss-sa
subjects:
- kind: ServiceAccount
name: pod-network-loss-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 loss | 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_LOSS_PERCENTAGE | The packet loss in percentage | Optional | Default to 100 percentage |
TOTAL_CHAOS_DURATION | The time duration for chaos insertion (seconds) | Optional | Default (60s) |
TARGET_PODS | Comma separated list of application pod name subjected to pod network loss 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 |
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` |
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-loss-sa
experiments:
- name: pod-network-loss
spec:
components:
env:
- name: TOTAL_CHAOS_DURATION
value: '60' # in seconds
- name: NETWORK_PACKET_LOSS_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-loss 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 Loss, 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 Loss Demo
- A sample recording of this experiment execution is provided here.