Pod CPU hog

Pod CPU hog is a Kubernetes pod-level chaos fault that excessively consumes CPU resources, resulting in a significant increase in the CPU resource usage of a pod.

• Simulates a situation where an application's CPU resource usage unexpectedly spikes.

Usage

View fault usage

Disk pressure or CPU hog affects Kubernetes applications which result in the eviction of the application replica and impacts its delivery. These issues are referred to as "noisy neighbour" problems. The fault causes CPU stress on the target pod(s). It simulates the situation of lack of CPU for processes running on the application, which degrades their performance. It also helps verify metrics-based horizontal pod autoscaling as well as vertical autoscale, i.e. demand based CPU addition. It helps scalability of nodes based on growth beyond budgeted pods. It verifies the autopilot functionality of (cloud) managed clusters. Injecting a rogue process into a target container starves the main microservice (typically pid 1) of the resources allocated to it (where limits are defined). This slows down the application traffic or exhausts the resources leading to eviction of all pods. These faults helps build immunity to such stress cases. It benefits include verifying multi-tenant load issues (when the load increases on one container, it does not cause downtime in other containers).

Prerequisites

• Kubernetes> 1.16.

Default validations

The application pods should be in running state before and after chaos injection.

Fault tunables

Fault tunables

Optional fields

Variables	Description	Notes
CPU_CORES	Number of the CPU cores subjected to CPU stress	Default to 1
TOTAL_CHAOS_DURATION	The time duration for chaos insertion (seconds)	Default to 60s
LIB_IMAGE	Image used to run the helper pod.	Defaults to litmuschaos/go-runner:1.13.8
STRESS_IMAGE	Container run on the node at runtime by the pumba lib to inject stressors. Only used in LIB pumba	Default to alexeiled/stress-ng:latest-ubuntu
TARGET_PODS	Comma separated list of application pod name subjected to pod CPU hog chaos	If not provided, it will select target pods randomly based on provided appLabels
TARGET_CONTAINER	Name of the target container under chaos	If not provided, it will select the first container of the target pod
PODS_AFFECTED_PERC	The Percentage of total pods to target	Defaults to 0 (corresponds to 1 replica), provide numeric value only
CONTAINER_RUNTIME	container runtime interface for the cluster	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	Defaults to /var/run/docker.sock
RAMP_TIME	Period to wait before injection of chaos in sec	For example, 30
SEQUENCE	It defines sequence of chaos execution for multiple target pods	Default value: parallel. Supported: serial, parallel

Fault examples

Common and pod-specific tunables

Refer to the common attributes and pod-specific tunables to tune the common tunables for all fault and pod specific tunables.

CPU Cores

It specifies the number of CPU cores to target for a duration specified by TOTAL_CHAOS_DURATION environment variable. You can tune it using the CPU_CORE environment variable.

Use the following example to tune tithis:

# CPU cores for the stress
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  appinfo:
    appns: "default"
    applabel: "app=nginx"
    appkind: "deployment"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: pod-cpu-hog
    spec:
      components:
        env:
        # CPU cores for stress
        - name: CPU_CORES
          value: '1'
        - name: TOTAL_CHAOS_DURATION
          value: '60'

CPU load

It contains percentage of pod CPU to be consumed. You can tune it using the CPU_LOAD ENV.

Use the following example to tune it:

# CPU load for the stress
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  appinfo:
    appns: "default"
    applabel: "app=nginx"
    appkind: "deployment"
  chaosServiceAccount: litmus-admin
  experiments:
    - name: pod-cpu-hog
      spec:
        components:
          env:
            # CPU load in percentage for the stress
            - name: CPU_LOAD
              value: "100"
            # CPU core should be provided as 0 for CPU load
            # to work, otherwise it will take CPU core as priority
            - name: CPU_CORES
              value: "0"
            - name: TOTAL_CHAOS_DURATION
              value: "60"

Container runtime and socket path

It defines the CONTAINER_RUNTIME and SOCKET_PATH ENV to set the container runtime and socket file path.

• CONTAINER_RUNTIME: It supports docker, containerd, and crio runtimes. The default value is docker.
• SOCKET_PATH: It contains path of docker socket file by default(/var/run/docker.sock). For containerd, specify path as /var/containerd/containerd.sock. For crio, speecify path as /var/run/crio/crio.sock.

Use the following example to tune it:

## provide the container runtime and socket file path
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  appinfo:
    appns: "default"
    applabel: "app=nginx"
    appkind: "deployment"
  chaosServiceAccount: litmus-admin
  experiments:
    - name: pod-cpu-hog
      spec:
        components:
          env:
            # runtime for the container
            # supports docker, containerd, crio
            - name: CONTAINER_RUNTIME
              value: "docker"
            # path of the socket file
            - name: SOCKET_PATH
              value: "/var/run/docker.sock"
            - name: TOTAL_CHAOS_DURATION
              VALUE: "60"