Project: Litmus (Observability and Analysis / Chaos Engineering)
File: pod-autoscaler.md

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. !!! tip "Scenario: Scale the replicas" ??? info "View the uses of the experiment" coming soon ??? info "Verify the prerequisites" Ensure that Kubernetes Version > 1.16 Ensure that the Litmus Chaos Operator is running by executing <code>kubectl get pods</code> in operator namespace (typically, <code>litmus</code>).If not, install from <a href="https://v1-docs.litmuschaos.io/docs/getstarted/#install-litmus">here</a> Ensure that the <code>pod-autoscaler</code> experiment resource is available in the cluster by executing <code>kubectl get chaosexperiments</code> in the desired namespace. If not, install from <a href="https://hub.litmuschaos.io/api/chaos/master?file=faults/kubernetes/pod-autoscaler/fault.yaml">here</a> ??? info "View the default validations" The application pods should be in running state before and after chaos injection. !!! tip "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 RBAC, which is pre installed in the cluster as part of the agent setup. ??? note "View the Minimal RBAC permissions" ```yaml 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: apiGroups: [""] resources: ["pods"] verbs: ["create","delete","get","list","patch","update", "deletecollection"] apiGroups: [""] resources: ["events"] verbs: ["create","get","list","patch","update"] apiGroups: [""] resources: ["configmaps"] verbs: ["get","list",] apiGroups: [""] resources: ["pods/log"] verbs: ["get","list","watch"] apiGroups: [""] resources: ["pods/exec"] verbs: ["get","list","create"] apiGroups: ["apps"] resources: ["deployments","statefulsets"] verbs: ["list","get","patch","update"] apiGroups: ["batch"] resources: ["jobs"] verbs: ["create","list","get","delete","deletecollection"] 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 ``` 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. ??? info "check the experiment tunables" <h2>Mandatory Fields</h2> <table> <tr> <th> Variables </th> <th> Description </th> <th> Notes </th> </tr> <tr> <td> REPLICA_COUNT </td> <td> Number of replicas upto which we want to scale </td> <td> <code>nil</code> </td> </tr> </table> <h2>Optional Fields</h2> <table> <tr> <th> Variables </th> <th> Description </th> <th> Notes </th> </tr> <tr> <td> TOTALCHAOSDURATION </td> <td> The timeout for the chaos experiment (in seconds) </td> <td> Defaults to 60 </td> </tr> <tr> <td> LIB </td> <td> The chaos lib used to inject the chaos </td> <td> Defaults to <code>litmus</code> </td> </tr> <td> RAMP_TIME </td> <td> Period to wait before and after injection of chaos in sec </td> <td> </td> </tr> </table> Refer the and to tune the common tunables for all experiments 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 `REPLICA_COUNT` ENV. Use the following example to tune this: ```yaml 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: name: REPLICA_COUNT value: '3' name: TOTALCHAOSDURATION value: '60' ```