Node Drain Experiment Details
Experiment Metadata
Type | Description | Tested K8s Platform |
---|---|---|
Generic | Drain the node where application pod is scheduled. | GKE, AWS, Packet(Kubeadm), Konvoy(AWS) |
Prerequisites
Ensure that the Litmus Chaos Operator is running by executing
kubectl get pods
in operator namespace (typically,litmus
). If not, install from hereEnsure that the
node-drain
experiment resource is available in the cluster by executingkubectl get chaosexperiments
in the desired namespace. If not, install from hereEnsure that the node specified in the experiment ENV variable
APP_NODE
(the node which will be drained) 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>
- Get node names against the applications pods:
Entry Criteria
- Application pods are healthy on the respective Nodes before chaos injection
Exit Criteria
- Target nodes are in Ready state post chaos injection
Details
- This experiment drains the node where application pod is running and verifies if it is scheduled on another available node.
- In the end of experiment it uncordons the specified node so that it can be utilised in future.
Integrations
- Drain node 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 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: nginx-sa
namespace: default
labels:
name: nginx-sa
---
# Source: openebs/templates/clusterrole.yaml
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
name: nginx-sa
labels:
name: nginx-sa
rules:
- apiGroups: ["","litmuschaos.io","batch","extensions"]
resources: ["pods","jobs","chaosengines","daemonsets","pods/eviction","chaosexperiments","chaosresults"]
verbs: ["create","list","get","patch","update","delete"]
- apiGroups: [""]
resources: ["nodes"]
verbs: ["patch","get","list"]
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
name: nginx-sa
labels:
name: nginx-sa
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: ClusterRole
name: nginx-sa
subjects:
- kind: ServiceAccount
name: nginx-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
Supported Experiment Tunables
Variables | Description | Type | Notes |
---|---|---|---|
APP_NODE | Name of the node to drain | Mandatory | |
TOTAL_CHAOS_DURATION | The time duration for chaos insertion (seconds) | Optional | Defaults to 60s |
Sample ChaosEngine Manifest
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
name: nginx-chaos
namespace: default
spec:
# It can be app/infra
chaosType: 'infra'
#ex. values: ns1:name=percona,ns2:run=nginx
auxiliaryAppInfo: ""
appinfo:
appns: default
applabel: 'app=nginx'
appkind: deployment
chaosServiceAccount: nginx-sa
monitoring: false
components:
runner:
image: "litmuschaos/chaos-executor:1.0.0"
type: "go"
# It can be delete/infra
jobCleanUpPolicy: delete
experiments:
- name: node-drain
spec:
components:
# set node name
- name: APP_NODE
value: 'node-1'
Create the ChaosEngine Resource
Create the ChaosEngine manifest prepared in the previous step to trigger the Chaos.
kubectl apply -f chaosengine.yml
Watch Chaos progress
Set up a watch on the applications originally scheduled on the affected node and verify whether they are rescheduled on the other nodes in the Kubernetes Cluster.
watch kubectl get pods,nodes --all-namespaces
Check Chaos Experiment Result
Check whether the application is resilient to the node drain, once the experiment (job) is completed. The ChaosResult resource name is derived like this:
<ChaosEngine-Name>-<ChaosExperiment-Name>
.kubectl describe chaosresult nginx-chaos-node-drain -n <application-namespace>
Node Drain Experiment Demo [TODO]
- A sample recording of this experiment execution is provided here.