litmus/mkdocs/docs/experiments/categories/nodes/node-drain.md

Introduction

• 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"

Uses

??? info "View the uses of the experiment" coming soon

Prerequisites

??? info "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 that the node-drain experiment resource is available in the cluster by executing kubectl get chaosexperiments in the desired namespace. If not, install from here - Ensure that the node specified in the experiment ENV variable TARGET_NODE (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: kubectl get pods -o wide - Cordon the node kubectl cordon <nodename>

Default Validations

??? info "View the default validations" The target nodes should be in ready state before and after chaos injection.

Minimal RBAC configuration example (optional)

!!! 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 litmus-admin RBAC, which is pre installed in the cluster as part of the agent setup.

??? note "View the Minimal RBAC permissions"

    [embedmd]:# (https://raw.githubusercontent.com/litmuschaos/chaos-charts/master/charts/generic/node-drain/rbac.yaml yaml)
    ```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","events"]
      verbs: ["create","list","get","patch","update","delete","deletecollection"]
    - apiGroups: [""]
      resources: ["pods/exec","pods/log","pods/eviction"]
      verbs: ["list","get","create"]
    - apiGroups: ["batch"]
      resources: ["jobs"]
      verbs: ["create","list","get","delete","deletecollection"]
    - apiGroups: ["apps"]
      resources: ["daemonsets"]
      verbs: ["list","get","delete"]
    - apiGroups: ["litmuschaos.io"]
      resources: ["chaosengines","chaosexperiments","chaosresults"]
      verbs: ["create","list","get","patch","update"]
    - apiGroups: [""]
      resources: ["nodes"]
      verbs: ["patch","get","list"]
    ---
    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.

Experiment tunables

??? info "check the experiment tunables"

Mandatory Fields

<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 TARGET_NODE ENV. If both are provided then it will use the TARGET_NODE</td>
  </tr>
</table>

<h2>Optional Fields</h2>

<table>
  <tr>
    <th> Variables </th>
    <th> Description </th>
    <th> Notes </th>
  </tr>
  <tr>
    <td> TOTAL_CHAOS_DURATION </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>

Experiment Examples

Common and Node specific tunables

Refer the common attributes and Node specific tunable to tune the common tunables for all experiments and node specific tunables.

Drain Node

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:

# drain the targeted node
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 of the target node
        - name: TARGET_NODE
          value: 'node01'
        - name: TOTAL_CHAOS_DURATION
          VALUE: '60'