Pod Memory Hog Details
Experiment Metadata
Type | Description | Tested K8s Platform |
---|---|---|
Generic | Consume memory resources on the application container | GKE, Packet(Kubeadm), Minikube, EKS, AKS |
Prerequisites
- 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-memory-hog
experiment resource is available in the cluster by executingkubectl get chaosexperiments
in the desired namespace. If not, install from here - Cluster must run docker container runtime
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 Memory resources on the application container on specified memory in megabytes.
- It simulates conditions where app pods experience Memory spikes either due to expected/undesired processes thereby testing how the overall application stack behaves when this occurs.
Integrations
- Pod Memory 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-memory-hog-sa
namespace: default
labels:
name: pod-memory-hog-sa
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: Role
metadata:
name: pod-memory-hog-sa
namespace: default
labels:
name: pod-memory-hog-sa
rules:
- apiGroups: ["","litmuschaos.io","batch"]
resources: ["pods","jobs","events","pods/log","pods/exec","chaosengines","chaosexperiments","chaosresults"]
verbs: ["create","list","get","patch","update","delete","deletecollection"]
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: RoleBinding
metadata:
name: pod-memory-hog-sa
namespace: default
labels:
name: pod-memory-hog-sa
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: Role
name: pod-memory-hog-sa
subjects:
- kind: ServiceAccount
name: pod-memory-hog-sa
namespace: default
Prepare ChaosEngine
- Provide the application info in
spec.appinfo
- Provide the auxiliary applications info (ns & labels) in
spec.auxiliaryAppInfo
- 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 | |
---|---|---|---|---|
TARGET_CONTAINER | Name of the container subjected to Memory stress | Mandatory | ||
MEMORY_CONSUMPTION | The amount of memory used of hogging a Kubernetes pod (megabytes) | Optional | Defaults to 500MB (Up to 2000MB) | |
TOTAL_CHAOS_DURATION | The time duration for chaos insertion (seconds) | Optional | Defaults to 60s | LIB | The chaos lib used to inject the chaos. Available libs are litmus and pumba |
Optional | Defaults to litmus |
LIB_IMAGE | Image used to run the stress command. Only used in LIB pumba |
Optional | Defaults to gaiaadm/pumba |
|
PODS_AFFECTED_PERC | The Percentage of total pods to target | Optional | Defaults to 0% (corresponds to 1 replica) | |
TARGET_POD | Name of the application pod subjected to pod memory hog chaos | Optional | If not provided it will select from the app label provided | |
CHAOS_KILL_COMMAND | The command to kill the chaos process | Optional | Default to kill $(find /proc -name exe -lname '*/dd' 2>&1 | grep -v 'Permission denied' | awk -F/ '{print $(NF-1)}' | head -n 1 |
|
RAMP_TIME | Period to wait before and after injection of chaos in sec | Optional | ||
LIB | The chaos lib used to inject the chaos | Optional | Defaults to litmus, only litmus supported | |
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 true/false
annotationCheck: 'true'
# It can be active/stop
engineState: 'active'
#ex. values: ns1:name=percona,ns2:run=nginx
auxiliaryAppInfo: ''
appinfo:
appns: 'default'
applabel: 'app=nginx'
appkind: 'deployment'
chaosServiceAccount: pod-memory-hog-sa
monitoring: false
# It can be delete/retain
jobCleanUpPolicy: 'delete'
experiments:
- name: pod-memory-hog
spec:
components:
env:
# Provide name of target container
# where chaos has to be injected
- name: TARGET_CONTAINER
value: 'nginx'
# Enter the amount of memory in megabytes to be consumed by the application pod
- name: MEMORY_CONSUMPTION
value: '500'
- name: TOTAL_CHAOS_DURATION
value: '60' # in seconds
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>
Check Chaos Experiment Result
Check whether the application stack is resilient to Memory 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-memory-hog -n <application-namespace>
Pod Memory Hog Experiment Demo
- A sample recording of this experiment execution is provided here