Litmus chaos-scheduler for injecting chaos experiments on Kubernetes
Litmus chaos scheduler is used by Kubernetes application developers and SREs to inject chaos into the applications
and Kubernetes infrastructure periodically based on the specified schedule. Perform the following steps to use the chaos scheduler:
- Install the Litmus infrastructure components (RBAC, CRDs), the scheduler, the operator & Experiment custom resource bundles via helm charts
- Create a ChaosSchedule custom resource, which describes the ChaosEngine template to be scheduled
What is a chaos scheduler and how is it built?
The Chaos scheduler is a custom-controllers with direct access to Kubernetes API that can manage the lifecycle of certain resources or applications,
while always trying to ensure the resource is in the "desired state". The logic that ensures this is commonly called "reconcile" function.
The Chaos scheduler is built using Operator-SDK framework,
which provides bootstrap support for new scheduler projects, allowing teams to focus on business/operational logic.
What is a chaos schedule?
Currently, it defines the following:
- Execution Schedule for the batch run of the experiments
- Template Spec of ChaosEngine according to which chaos is to be exceuted
The ChaosSchedule is referenced as the owner of the secondary (reconcile) resource with Kubernetes deletePropagation
ensuring these also are removed upon deletion of the ChaosSchedule CR.
Sample ChaosSchedule for reference:
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosSchedule
metadata:
name: schedule-nginx
spec:
schedule:
repeat:
timeRange:
startTime: "2020-05-12T05:47:00Z" #should be modified according to current UTC Time, for type=repeat
endTime: "2020-09-13T02:58:00Z" #should be modified according to current UTC Time, for type=repeat
properties:
minChaosInterval: "2m" #format should be like "10m" or "2h" accordingly for minutes and hours, for type=repeat
workHours:
includedHours: 0-12
workDays:
includedDays: "Mon,Tue,Wed,Sat,Sun" #should be set for type=repeat
engineTemplateSpec:
appinfo:
appns: 'default'
applabel: 'app=nginx'
appkind: 'deployment'
# It can be true/false
annotationCheck: 'false'
# It can be active/stop
engineState: 'active'
#ex. values: ns1:name=percona,ns2:run=nginx
auxiliaryAppInfo: ''
chaosServiceAccount: pod-delete-sa
# It can be delete/retain
jobCleanUpPolicy: 'delete'
experiments:
- name: pod-delete
spec:
components:
env:
# set chaos duration (in sec) as desired
- name: TOTAL_CHAOS_DURATION
value: '30'
# set chaos interval (in sec) as desired
- name: CHAOS_INTERVAL
value: '10'
# pod failures without '--force' & default terminationGracePeriodSeconds
- name: FORCE
value: 'false'
What is a chaos engine?
The ChaosEngine is the main user-facing chaos custom resource with a namespace scope and is designed to hold information around how the chaos experiments are executed. It connects an application instance with one or more chaos experiments,
For more details refer
What is a litmus chaos chart and how can I use it?
Litmus chaos chart is the heart of litmus and contains the low-level execution information. They serve as off-the-shelf templates that one needs to "pull" (install on the cluster) before including them as part of a chaos run against any target applications (the binding being defined in the ChaosEngine).
For more details refer litmus docs and hub.
What are the steps to get started?
-
Install Operator Components and RBAC and CRDs
kubectl apply -f https://litmuschaos.github.io/litmus/litmus-operator-latest.yaml
-
Install Scheduler and it's CRDs
kubectl apply -f https://raw.githubusercontent.com/litmuschaos/chaos-scheduler/master/deploy/crds/chaosschedule_crd.yaml
kubectl apply -f https://raw.githubusercontent.com/litmuschaos/chaos-scheduler/master/deploy/chaos-scheduler.yaml
-
Create the pod delete Chaos Experiment in default namespace
kubectl apply -f https://raw.githubusercontent.com/litmuschaos/chaos-charts/master/charts/generic/pod-delete/experiment.yaml
-
Create the RBAC for execute the pod-delete chaos
kubectl apply -f https://raw.githubusercontent.com/litmuschaos/chaos-charts/master/charts/generic/pod-delete/rbac.yaml
-
Annotate your application to enable chaos. For ex:
kubectl annotate deploy/nginx-deployment litmuschaos.io/chaos="true"
-
Create a ChaosSchedule yaml with the application information and chaos experiment with their scheduling logic, For example: Click Here
-
Create a ChaosSchedule customer resource in the desired cluster, For example
kubectl apply -f chaos-schedule.yaml
-
Watch the injection of chaos at the scheduled time, For example
watch kubectl get pod,chaosschedule,chaosengine -n litmus
-
Describe the ChaosSchedule for see the detail of chaos injection.
kubectl describe chaosschedule schedule-nginx
Refer the ChaosSchedule Status. While any ChaosEngine is active or yet to be formed according to the schedule time. The .status.schedule.status
is set to running
eventually changed to completed
Name: schedule-nginx
Namespace: default
Labels: <none>
Annotations: API Version: litmuschaos.io/v1alpha1
Kind: ChaosSchedule
Metadata:
Creation Timestamp: 2020-05-14T08:44:32Z
Generation: 3
Resource Version: 899464
Self Link: /apis/litmuschaos.io/v1alpha1/namespaces/default/chaosschedules/ schedule-nginx
UID: 347fb7e6-2c9d-428e-9ce1-42bdcfdab37d
Spec:
Chaos Service Account:
Engine Template Spec:
Appinfo:
Appkind: deployment
Applabel: app=nginx
Appns: default
Chaos Service Account: litmus
Components:
Runner:
Experiments:
Name: pod-delete
Spec:
Components:
Rank: 0
Job Clean Up Policy: retain
Schedule:
Repeat:
End Time: 2020-05-12T05:52:00Z
Included Days: Mon,Tue,Wed
Instance Count: 2
Min Chaos Interval: 2m
Start Time: 2020-05-12T05:47:00Z
Schedule State: active
Status:
Active:
API Version: litmuschaos.io/v1alpha1
Kind: ChaosEngine
Name: schedule-nginx
Namespace: default
Resource Version: 899463
UID: 14f49857-8879-4129-a5b9-a3a592149725
Last Schedule Time: 2020-05-14T08:44:32Z
Schedule:
Start Time: 2020-05-14T08:44:32Z
Status: running
Total Instances: 1
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal SuccessfulCreate 39s chaos-scheduler Created engine schedule-nginx
How to halt the chaosschedule?
-
Edit the applied chaosschedule
kubectl edit chaosschedule schedule-nginx
-
Change the state to halt
spec:
scheduleState: halt
How to resume the chaosschedule?
-
Edit the applied chaosschedule
kubectl edit chaosschedule schedule-nginx
-
Change the state to active
spec:
scheduleState: active
-
If you face any probelem check the Troubleshooting Guide
Where are the docs?
They are available at litmus docs and experiment docs
How do I contribute?
You can contribute by raising issues, improving the documentation, contributing to the core framework and tooling, etc.
Head over to the Contribution guide