Pod CPU Hog Details
Experiment Metadata
Type | Description | Tested K8s Platform |
---|---|---|
Generic | Consume CPU resources on the application container | GKE, Packet(Kubeadm), Minikube, EKS, 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-cpu-hog
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 on the respective nodes before chaos injection
Exit Criteria
- Application pods are healthy on the respective nodes post chaos injection
Details
- This experiment consumes the CPU resources on the application container on specified number of cores
- It simulates conditions where app pods experience CPU spikes either due to expected/undesired processes thereby testing how the overall application stack behaves when this occurs.
- Causes CPU resource consumption on specified application containers using cgroups and litmus nsutil which consume CPU resources of the given target containers.
- It can test the application's resilience to potential slowness/unavailability of some replicas due to high CPU load
Integrations
- Pod CPU Hog can be effected using the chaos library:
litmus
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-cpu-hog-sa
namespace: default
labels:
name: pod-cpu-hog-sa
app.kubernetes.io/part-of: litmus
---
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
name: pod-cpu-hog-sa
namespace: default
labels:
name: pod-cpu-hog-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-cpu-hog-sa
namespace: default
labels:
name: pod-cpu-hog-sa
app.kubernetes.io/part-of: litmus
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: Role
name: pod-cpu-hog-sa
subjects:
- kind: ServiceAccount
name: pod-cpu-hog-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 | Type | Notes |
---|---|---|---|
CPU_CORES | Number of the cpu cores subjected to CPU stress | Optional | Default to 1 |
TOTAL_CHAOS_DURATION | The time duration for chaos insertion (seconds) | Optional | Default to 60s |
LIB | The chaos lib used to inject the chaos. Available libs are litmus and pumba |
Optional | Default to litmus |
LIB_IMAGE | Image used to run the helper pod. | Optional | 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 |
Optional | Default to alexeiled/stress-ng:latest-ubuntu |
TARGET_PODS | Comma separated list of application pod name subjected to pod cpu hog chaos | Optional | If not provided, it will select target pods randomly based on provided appLabels |
TARGET_CONTAINER | Name of the target container under chaos. | Optional | If not provided, it will select the first container of the target pod |
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` |
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
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
name: nginx-chaos
namespace: default
spec:
# It can be active/stop
engineState: 'active'
appinfo:
appns: 'default'
applabel: 'app=nginx'
appkind: 'deployment'
chaosServiceAccount: pod-cpu-hog-sa
experiments:
- name: pod-cpu-hog
spec:
components:
env:
- name: TOTAL_CHAOS_DURATION
value: '60' # in seconds
- name: CPU_CORES
value: '1'
## Percentage of total pods to target
- name: PODS_AFFECTED_PERC
value: ''
## provide the cluster runtime
- name: CONTAINER_RUNTIME
value: 'docker'
# provide the socket file path
- name: SOCKET_PATH
value: '/var/run/docker.sock'
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
Set up a watch on the applications interacting/dependent on the affected pods and verify whether they are running
watch kubectl get pods -n <application-namespace>
Verify the resource consumption
kubectl top pod <target-pod-name> -n <application-namespace>
Abort/Restart the Chaos Experiment
To stop the pod-cpu-hog 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 stack is resilient to CPU spikes on the app replica, once the experiment (job) is completed. The ChaosResult resource name is derived like this:
<ChaosEngine-Name>-<ChaosExperiment-Name>
.kubectl describe chaosresult nginx-chaos-pod-cpu-hog -n <application-namespace>
Pod CPU Hog Experiment Demo
- A sample recording of this experiment execution is provided here.