Project: Litmus (Observability and Analysis / Chaos Engineering)
File: node-drain.md

It drain the node. The resources which are running on the target node should be reschedule on the other nodes. !!! tip "Scenario: Drain the node" ??? 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>node-drain</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/node-drain/fault.yaml">here</a> Ensure that the node specified in the experiment ENV variable <code>TARGET_NODE</code> (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: <code>kubectl get pods -o wide</code> Cordon the node <code>kubectl cordon &lt;nodename&gt;</code> ??? info "View the default validations" The target nodes should be in ready 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: node-drain-sa namespace: default labels: name: node-drain-sa app.kubernetes.io/part-of: litmus apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRole metadata: name: node-drain-sa labels: name: node-drain-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","pods/eviction"] verbs: ["get","list","create"] apiGroups: ["apps"] resources: ["daemonsets"] verbs: ["list","get","delete"] apiGroups: ["batch"] resources: ["jobs"] verbs: ["create","list","get","delete","deletecollection"] apiGroups: ["litmuschaos.io"] resources: ["chaosengines","chaosexperiments","chaosresults"] verbs: ["create","list","get","patch","update","delete"] apiGroups: [""] resources: ["nodes"] verbs: ["get","list","patch"] apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRoleBinding metadata: name: node-drain-sa labels: name: node-drain-sa app.kubernetes.io/part-of: litmus roleRef: apiGroup: rbac.authorization.k8s.io kind: ClusterRole name: node-drain-sa subjects: kind: ServiceAccount name: node-drain-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> TARGET_NODE </td> <td> Name of the node to be tainted</td> <td> </td> </tr> <tr> <td> NODE_LABEL </td> <td> It contains node label, which will be used to filter the target node if TARGET_NODE ENV is not set </td> <td>It is mutually exclusive with the TARGETNODE ENV. If both are provided then it will use the TARGETNODE</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 time duration for chaos insertion (seconds) </td> <td> Defaults to 60s </td> </tr> <tr> <td> LIB </td> <td> The chaos lib used to inject the chaos </td> <td> Defaults to `litmus` </td> </tr> <tr> <td> RAMP_TIME </td> <td> Period to wait before injection of chaos in sec </td> <td> </td> </tr> </table> Refer the and to tune the common tunables for all experiments and node specific tunables. It contains name of target node subjected to the chaos. It can be tuned via `TARGET_NODE` ENV. Use the following example to tune this: ```yaml apiVersion: litmuschaos.io/v1alpha1 kind: ChaosEngine metadata: name: engine-nginx spec: engineState: "active" annotationCheck: "false" chaosServiceAccount: node-drain-sa experiments: name: node-drain spec: components: env: name: TARGET_NODE value: 'node01' name: TOTALCHAOSDURATION value: '60' ```