The experiment aims to check the ability of nodes to accommodate the number of replicas a given application pod.
This experiment can be used for other scenarios as well, such as for checking the Node auto-scaling feature. For example, check if the pods are successfully rescheduled within a specified period in cases where the existing nodes are already running at the specified limits.
Scenario: Scale the replicas
View the uses of the experiment
Verify the prerequisites
- Ensure that Kubernetes Version > 1.16
- Ensure that the Litmus Chaos Operator is running by executing
kubectl get podsin operator namespace (typically,
litmus).If not, install from here
- Ensure that the
pod-autoscalerexperiment resource is available in the cluster by executing
kubectl get chaosexperimentsin the desired namespace. If not, install from here
View the default validations
The application pods should be in running state before and after chaos injection.
Minimal RBAC configuration example (optional)¶
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: pod-autoscaler-sa namespace: default labels: name: pod-autoscaler-sa app.kubernetes.io/part-of: litmus --- apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRole metadata: name: pod-autoscaler-sa labels: name: pod-autoscaler-sa app.kubernetes.io/part-of: litmus rules: # Create and monitor the experiment & helper pods - apiGroups: [""] resources: ["pods"] verbs: ["create","delete","get","list","patch","update", "deletecollection"] # Performs CRUD operations on the events inside chaosengine and chaosresult - apiGroups: [""] resources: ["events"] verbs: ["create","get","list","patch","update"] # Fetch configmaps details and mount it to the experiment pod (if specified) - apiGroups: [""] resources: ["configmaps"] verbs: ["get","list",] # Track and get the runner, experiment, and helper pods log - apiGroups: [""] resources: ["pods/log"] verbs: ["get","list","watch"] # for creating and managing to execute comands inside target container - apiGroups: [""] resources: ["pods/exec"] verbs: ["get","list","create"] # performs CRUD operations on the deployments and statefulsets - apiGroups: ["apps"] resources: ["deployments","statefulsets"] verbs: ["list","get","patch","update"] # for configuring and monitor the experiment job by the chaos-runner pod - apiGroups: ["batch"] resources: ["jobs"] verbs: ["create","list","get","delete","deletecollection"] # for creation, status polling and deletion of litmus chaos resources used within a chaos workflow - apiGroups: ["litmuschaos.io"] resources: ["chaosengines","chaosexperiments","chaosresults"] verbs: ["create","list","get","patch","update","delete"] --- apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRoleBinding metadata: name: pod-autoscaler-sa labels: name: pod-autoscaler-sa app.kubernetes.io/part-of: litmus roleRef: apiGroup: rbac.authorization.k8s.io kind: ClusterRole name: pod-autoscaler-sa subjects: - kind: ServiceAccount name: pod-autoscaler-sa namespace: default
check the experiment tunables
|REPLICA_COUNT||Number of replicas upto which we want to scale||
|TOTAL_CHAOS_DURATION||The timeout for the chaos experiment (in seconds)||Defaults to 60|
|LIB||The chaos lib used to inject the chaos|| Defaults to
||RAMP_TIME||Period to wait before and after injection of chaos in sec|
Common and Pod specific tunables¶
It defines the number of replicas, which should be present in the targeted application during the chaos. It can be tuned via
Use the following example to tune this:
# provide the number of replicas apiVersion: litmuschaos.io/v1alpha1 kind: ChaosEngine metadata: name: engine-nginx spec: engineState: "active" annotationCheck: "false" appinfo: appns: "default" applabel: "app=nginx" appkind: "deployment" chaosServiceAccount: pod-autoscaler-sa experiments: - name: pod-autoscaler spec: components: env: # number of replica, needs to scale - name: REPLICA_COUNT value: '3' - name: TOTAL_CHAOS_DURATION VALUE: '60'