Azure disk loss

Azure disk loss detaches the virtual disk from an Azure instance.

• After a specific duration, the virtual disk is re-attached to the instance.
• This fault checks the performance of the application (or process) running on the instance.

Use cases

Azure disk loss:

• Determines the resilience of an application to unexpected disk detachment.
• Determines how quickly the Azure instance recovers from such failures.

Prerequisites

• Kubernetes > 1.16 is required to execute this fault.
• Appropriate Azure access to detach and attach a disk.
• Azure disk should be connected to an instance.
• Use Azure file-based authentication to connect to the instance using Azure GO SDK. To generate auth file, run az ad sp create-for-rbac --sdk-auth > azure.auth Azure CLI command.
• Kubernetes secret should contain the auth file created in the previous step in the CHAOS_NAMESPACE. Below is a sample secret file:

apiVersion: v1
kind: Secret
metadata:
  name: cloud-secret
type: Opaque
stringData:
  azure.auth: |-
    {
      "clientId": "XXXXXXXXX",
      "clientSecret": "XXXXXXXXX",
      "subscriptionId": "XXXXXXXXX",
      "tenantId": "XXXXXXXXX",
      "activeDirectoryEndpointUrl": "XXXXXXXXX",
      "resourceManagerEndpointUrl": "XXXXXXXXX",
      "activeDirectoryGraphResourceId": "XXXXXXXXX",
      "sqlManagementEndpointUrl": "XXXXXXXXX",
      "galleryEndpointUrl": "XXXXXXXXX",
      "managementEndpointUrl": "XXXXXXXXX"
    }

tip

If you change the secret key name from azure.auth to a new name, ensure that you update the AZURE_AUTH_LOCATION environment variable in the chaos experiment with the new name. AZURE_AUTH_LOCATION is variable that describes path to the authetication file which uses the default value in most cases.

Mandatory tunables

Tunable	Description	Notes
VIRTUAL_DISK_NAMES	Name of the virtual disks to target.	Provide comma-separated names for multiple disks. For more information, go to detach virtual disks by name.
RESOURCE_GROUP	Name of the resource group for the target disk(s).	For example, TeamDevops. For more information, go to resource group field in the YAML file.

Optional tunables

Tunable	Description	Notes
SCALE_SET	Checks if the disk is connected to scale set instance.	Defaults to disable. Also supports enable. For more information, go to scale set instances.
TOTAL_CHAOS_DURATION	Duration that you specify, through which chaos is injected into the target resource (in seconds).	Defaults to 30s. For more information, go to duration of the chaos.
CHAOS_INTERVAL	Time interval between two successive instance poweroffs (in seconds).	Defaults to 30s. For more information, go to chaos interval.
SEQUENCE	Sequence of chaos execution for multiple target pods.	Defaults to parallel. Also supports serial sequence. For more information, go to sequence of chaos execution.
DEFAULT_HEALTH_CHECK	Determines if you wish to run the default health check which is present inside the fault.	Default: 'true'. For more information, go to default health check.
RAMP_TIME	Period to wait before and after injecting chaos (in seconds).	For example, 30s. For more information, go to ramp time.

Detach virtual disks by name

It specifies a comma-separated list of disk names that are subject to disk loss. Tune it by using the VIRTUAL_DISK_NAMES environment variable.

Use the following example to tune it:

# detach multiple Azure disks by their names
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: azure-disk-loss
    spec:
      components:
        env:
        # comma separated names of the Azure disks attached to VMs
        - name: VIRTUAL_DISK_NAMES
          value: 'disk-01,disk-02'
        # name of the resource group
        - name: RESOURCE_GROUP
          value: 'rg-azure-disks'

Detach virtual disks attached to scale set instances by name

It specifies a comma-separated list of disk names attached to Scale Set instances subject to disk loss. Tune it by using the VIRTUAL_DISK_NAMES and SCALE_SET environment variables, respectively.

Use the following example to tune it:

# detach multiple Azure disks attached to scale set VMs by their names
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: azure-disk-loss
    spec:
      components:
        env:
        # comma separated names of the Azure disks attached to scaleset VMs
        - name: VIRTUAL_DISK_NAMES
          value: 'disk-01,disk-02'
        # name of the resource group
        - name: RESOURCE_GROUP
          value: 'rg-azure-disks'
        # VM belongs to scaleset or not
        - name: SCALE_SET
          value: 'enable'