Docker Service Kill

Introduction

• This experiment Causes the application to become unreachable on account of node turning unschedulable (NotReady) due to docker service kill
• The docker service has been stopped/killed on a node to make it unschedulable for a certain duration i.e TOTAL_CHAOS_DURATION. The application node should be healthy after the chaos injection and the services should be reaccessable.
• The application implies services. Can be reframed as: Test application resiliency upon replica getting unreachable caused due to docker service down.

Scenario: Kill the docker service of the node

Uses

View the uses of the experiment

coming soon

Prerequisites

Verify the 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 docker-service-kill experiment resource is available in the cluster by executing kubectl get chaosexperiments in the desired namespace. If not, install from here
• Ensure that the node specified in the experiment ENV variable TARGET_NODE (the node for which docker service need to be killed) should be cordoned before execution of the chaos experiment (before applying the chaosengine manifest) to ensure that the litmus experiment runner pods are not scheduled on it / subjected to eviction. This can be achieved with the following steps:
  • Get node names against the applications pods: kubectl get pods -o wide
  • Cordon the node kubectl cordon <nodename>

Default Validations

View the default validations

The target nodes should be in ready state before and after chaos injection.

Minimal RBAC configuration example (optional)

NOTE

If you are using this experiment as part of a litmus workflow scheduled constructed & executed from chaos-center, then you may be making use of the litmus-admin RBAC, which is pre installed in the cluster as part of the agent setup.

View the Minimal RBAC permissions

---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: docker-service-kill-sa
  namespace: default
  labels:
    name: docker-service-kill-sa
    app.kubernetes.io/part-of: litmus
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: docker-service-kill-sa
  labels:
    name: docker-service-kill-sa
    app.kubernetes.io/part-of: litmus
rules:
  # Create and monitor the experiment & helper pods
  - apiGroups: [""]
    resources: ["pods"]
    verbs: ["create","delete","get","list","patch","update", "deletecollection"]
  # Performs CRUD operations on the events inside chaosengine and chaosresult
  - apiGroups: [""]
    resources: ["events"]
    verbs: ["create","get","list","patch","update"]
  # Fetch configmaps details and mount it to the experiment pod (if specified)
  - apiGroups: [""]
    resources: ["configmaps"]
    verbs: ["get","list",]
  # Track and get the runner, experiment, and helper pods log 
  - apiGroups: [""]
    resources: ["pods/log"]
    verbs: ["get","list","watch"]  
  # for creating and managing to execute comands inside target container
  - apiGroups: [""]
    resources: ["pods/exec"]
    verbs: ["get","list","create"]
  # for configuring and monitor the experiment job by the chaos-runner pod
  - apiGroups: ["batch"]
    resources: ["jobs"]
    verbs: ["create","list","get","delete","deletecollection"]
  # for creation, status polling and deletion of litmus chaos resources used within a chaos workflow
  - apiGroups: ["litmuschaos.io"]
    resources: ["chaosengines","chaosexperiments","chaosresults"]
    verbs: ["create","list","get","patch","update","delete"]
  # for experiment to perform node status checks
  - apiGroups: [""]
    resources: ["nodes"]
    verbs: ["get","list"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: docker-service-kill-sa
  labels:
    name: docker-service-kill-sa
    app.kubernetes.io/part-of: litmus
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: docker-service-kill-sa
subjects:
- kind: ServiceAccount
  name: docker-service-kill-sa
  namespace: default

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.

Experiment tunables

check the experiment tunables

Mandatory Fields

Variables	Description	Notes
TARGET_NODE	Name of the target node
NODE_LABEL	It contains node label, which will be used to filter the target node if TARGET_NODE ENV is not set	It is mutually exclusive with the TARGET_NODE ENV. If both are provided then it will use the TARGET_NODE

Optional Fields

Variables	Description	Notes
TOTAL_CHAOS_DURATION	The time duration for chaos insertion (seconds)	Defaults to 60s
LIB	The chaos lib used to inject the chaos	Defaults to litmus
RAMP_TIME	Period to wait before injection of chaos in sec

Experiment Examples

Common and Node specific tunables

Refer the common attributes and Node specific tunable to tune the common tunables for all experiments and node specific tunables.

Kill Docker Service

It contains name of target node subjected to the chaos. It can be tuned via TARGET_NODE ENV.

Use the following example to tune this:

# kill the docker service of the target node
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  chaosServiceAccount: docker-service-kill-sa
  experiments:
  - name: docker-service-kill
    spec:
      components:
        env:
        # name of the target node
        - name: TARGET_NODE
          value: 'node01'
        - name: TOTAL_CHAOS_DURATION
          value: '60'