k6 Load Generator

Introduction¶

k6 loadgen fault simulates load generation on the target hosts for a specific chaos duration. This fault: - Slows down or makes the target host unavailable due to heavy load. - Checks the performance of the application or process running on the instance. Support various types of load testing (ex. spike, smoke, stress)

Scenario: Load generating with k6

k6-loadgen

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 to create a Kubernetes secret having the JS script file in the Chaos Infrastructure's namespace (litmus by default). The simplest way to create a secret object looks like this:
```
kubectl create secret generic k6-script \
    --from-file=script.js=<<script-path>> -n <<chaos_infrastructure_namespace>>
```

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: k6-loadgen-sa
namespace: default
labels:
name: k6-loadgen-sa
---
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
name: k6-loadgen-sa
namespace: default
labels:
name: k6-loadgen-sa
rules:
- apiGroups: ["","litmuschaos.io","batch","apps"]
  resources: ["pods","configmaps","jobs","pods/exec","pods/log","events","chaosengines","chaosexperiments","chaosresults"]
  verbs: ["create","list","get","patch","update","delete","deletecollection"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
name: k6-loadgen-sa
namespace: default
labels:
name: k6-loadgen-sa
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: Role
name: k6-loadgen-sa
subjects:
- kind: ServiceAccount
  name: k6-loadgen-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

Optional Fields

Variables	Description	Notes
TOTAL_CHAOS_DURATION	The time duration for chaos injection (seconds)	Defaults to 20s
CHAOS_INTERVAL	Time interval b/w two successive k6-loadgen (in sec)	If the CHAOS_INTERVAL is not provided it will take the default value of 10s
RAMP_TIME	Period to wait before injection of chaos in sec
LIB_IMAGE	LIB Image used to excute k6 engine	Defaults to `ghcr.io/grafana/k6-operator:latest-runner`
LIB_IMAGE_PULL_POLICY	LIB Image pull policy	Defaults to `Always`
SCRIPT_SECRET_NAME	Provide the k8s secret name of the JS script to run k6.	Default value: k6-script
SCRIPT_SECRET_KEY	Provide the key of the k8s secret named SCRIPT_SECRET_NAME	Default value: script.js

Experiment Examples¶

Common and Pod specific tunables¶

Refer the common attributes and Pod specific tunable to tune the common tunables for all experiments and pod specific tunables.

Custom k6 configuration¶

You can add k6 options(ex hosts, thresholds) in the script options object. More details can be found here

Custom Secret Name and Secret Key¶

You can provide the secret name and secret key of the JS script to be used for k6-loadgen. The secret should be created in the same namespace where the chaos infrastructure is created. For example, if the chaos infrastructure is created in the litmus namespace, then the secret should also be created in the litmus namespace.

You can write a JS script like below. If you want to know more about the script, checkout this documentation.

import http from 'k6/http';
import { sleep } from 'k6';
export const options = {
    vus: 100,
    duration: '30s',
};
export default function () {
    http.get('http://<<target_domain_name>>/');
    sleep(1);
}

Then create a secret with the above script.

kubectl create secret generic custom-k6-script \
  --from-file=script.js=custom-script.js -n <<chaos_infrastructure_namespace>>

And If we want to use custom-k6-script secret and custom-script.js as the secret key, then the experiment tunable will look like this:

---
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: nginx-chaos
  namespace: default
spec:
  engineState: 'active'
  chaosServiceAccount: litmus-admin
  experiments:
    - name: k6-loadgen
      spec:
        components:
          env:
            # set chaos duration (in sec) as desired
            - name: TOTAL_CHAOS_DURATION
              value: "30"

            # Interval between chaos injection in sec
            - name: CHAOS_INTERVAL
              value: "30"

            # Period to wait before and after injection of chaos in sec
            - name: RAMP_TIME
              value: "0"

            # Provide the secret name of the JS script
            - name: SCRIPT_SECRET_NAME
              value: "custom-k6-script"

            # Provide the secret key of the JS script
            - name: SCRIPT_SECRET_KEY
              value: "custom-script.js"

            # Provide the image name of the helper pod
            - name: LIB_IMAGE
              value: "ghcr.io/grafana/k6-operator:latest-runner"

            # Provide the image pull policy of the helper pod
            - name: LIB_IMAGE_PULL_POLICY
              value: "Always"