Node CPU Hog

Introduction¶

This experiment causes CPU resource exhaustion on the Kubernetes node. The experiment aims to verify resiliency of applications whose replicas may be evicted on account on nodes turning unschedulable (Not Ready) due to lack of CPU resources.
The CPU chaos is injected using a helper pod running the linux stress tool (a workload generator). The chaos is effected for a period equalling the TOTAL_CHAOS_DURATION Application implies services. Can be reframed as: Tests application resiliency upon replica evictions caused due to lack of CPU resources

Scenario: Stress the CPU of node

Node CPU Hog

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 node-cpu-hog experiment resource is available in the cluster by executing kubectl get chaosexperiments in the desired namespace. If not, install from here

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: node-cpu-hog-sa
  namespace: default
  labels:
    name: node-cpu-hog-sa
    app.kubernetes.io/part-of: litmus
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: node-cpu-hog-sa
  labels:
    name: node-cpu-hog-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: node-cpu-hog-sa
  labels:
    name: node-cpu-hog-sa
    app.kubernetes.io/part-of: litmus
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: node-cpu-hog-sa
subjects:
- kind: ServiceAccount
  name: node-cpu-hog-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_NODES	Comma separated list of nodes, subjected to node cpu hog chaos
NODE_LABEL	It contains node label, which will be used to filter the target nodes if TARGET_NODES ENV is not set	It is mutually exclusive with the TARGET_NODES ENV. If both are provided then it will use the TARGET_NODES

Optional Fields

Variables	Description	Notes
TOTAL_CHAOS_DURATION	The time duration for chaos insertion (seconds)	Defaults to 60
LIB	The chaos lib used to inject the chaos	Defaults to `litmus`
LIB_IMAGE	Image used to run the stress command	Defaults to `litmuschaos/go-runner:latest`
RAMP_TIME	Period to wait before & after injection of chaos in sec	Optional
NODE_CPU_CORE	Number of cores of node CPU to be consumed	Defaults to `2`
NODES_AFFECTED_PERC	The Percentage of total nodes to target	Defaults to 0 (corresponds to 1 node), provide numeric value only
SEQUENCE	It defines sequence of chaos execution for multiple target pods	Default value: parallel. Supported: serial, parallel

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.

Node CPU Cores¶

It contains number of cores of node CPU to be consumed. It can be tuned via NODE_CPU_CORE ENV.

Use the following example to tune this:

# stress the cpu of the targeted nodes
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  chaosServiceAccount: node-cpu-hog-sa
  experiments:
  - name: node-cpu-hog
    spec:
      components:
        env:
        # number of cpu cores to be stressed
        - name: NODE_CPU_CORE
          value: '2'
        - name: TOTAL_CHAOS_DURATION
          value: '60'

Node CPU Load¶

It contains percentage of node CPU to be consumed. It can be tuned via CPU_LOAD ENV.

Use the following example to tune this:

# stress the cpu of the targeted nodes by load percentage
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  chaosServiceAccount: node-cpu-hog-sa
  experiments:
  - name: node-cpu-hog
    spec:
      components:
        env:
        # percentage of cpu to be stressed
        - name: CPU_LOAD
          value: "100"
        # node cpu core should be provided as 0 for cpu load
        # to work otherwise it will take cpu core as priority
        - name: NODE_CPU_CORE
          value: '0'
        - name: TOTAL_CHAOS_DURATION
          value: '60'