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VMware DNS chaos

VMware DNS chaos causes DNS errors in the VMware VMs which results in the DNS server being unavailable or malfunctioning for a specific duration.

  • It checks the performance of the application (or process) running on the VMware VMs.

VMware DNS Chaos

Usage​

View fault usage
This fault causes DNS errors on the target VMs which results in unavailability (or distorted) network connectivity from the VM to the target hosts. This fault provides a hypothesis wherein certain services of an application could be unreachable from the VM. This fault determines how DNS errors impact the infrastructure and standalone tasks in the application. It simulates unavailability of DNS server (loss of access to any external domain from a given microservice) and malfunctioning of DNS server (loss of access to specific domains from a given microservice, access to cloud provider dependencies, and access to specific third party services).

Prerequisites​

  • Kubernetes > 1.16
  • Execution plane is connected to vCenter and the hosts on port 443.
  • VMware tool is installed on the target VM with remote execution enabled.
  • Adequate vCenter permissions to access the hosts and the VMs.
  • Create a Kubernetes secret that has the Vcenter credentials in the CHAOS_NAMESPACE. Below is a sample secret file:
apiVersion: v1
kind: Secret
metadata:
  name: vcenter-secret
  namespace: litmus
type: Opaque
stringData:
    VCENTERSERVER: XXXXXXXXXXX
    VCENTERUSER: XXXXXXXXXXXXX
    VCENTERPASS: XXXXXXXXXXXXX

Note​

You can pass the VM credentials as secrets or as a ChaosEngine environment variable.

Default validations​

The VM should be in a healthy state before and after injecting chaos.

Fault tunables​

Fault tunables

Mandatory fields

Variables Description Notes
VM_USER_NAME Username of the target VM(s). Multiple usernames can be provided as comma-separated values (when there are multiple VMs subject to chaos). It also helps run the govc command.
VM_PASSWORD Password for the target VM(s). It helps run the govc command.
PORT DNS Port Defaults to 54

Optional fields

Variables Description Notes
TOTAL_CHAOS_DURATION Duration that you specify, through which chaos is injected into the target resource (in seconds). Defaults to 30s.
CHAOS_INTERVAL Time interval between two successive instance terminations (in seconds). Defaults to 30s.
SEQUENCE Sequence of chaos execution for multiple instances. Defaults to parallel. Supports serial sequence as well.
RAMP_TIME Period to wait before and after injecting chaos (in seconds). For example, 30s.
TARGET_HOSTNAMES List of the target host names. If it is not provided, all host names (or domains) are targeted. For example, '["litmuschaos","chaosnative.com"]'.
MATCH_SCHEME Determines whether the DNS query should exactly match the targets or can be a substring. Defaults to exact.
UPSTREAM_SERVER Custom upstream server to which the intercepted DNS requests will be forwarded. Defaults to the server mentioned in resolv.conf file.

Secret Fields

Variables Description Notes
GOVC_URL vCenter server URL used to perform API calls using the govc command. It is derived from a secret.
GOVC_USERNAME Username of the vCenter server used for authentication purposes. It can be set up using a secret.
GOVC_PASSWORD Password of the vCenter server used for authentication purposes. It can be set up using a secret.
GOVC_INSECURE Runs the govc command in insecure mode. It is set to true. It can be set up using a secret.

Fault examples​

Common fault tunables​

Refer to the common attributes to tune the common tunables for all the faults.

Run DNS chaos with port​

It specifies the DNS port where DNS chaos is injected. You can tune it using the PORT environment variable.

Use the following example to tune it:

# induces DNS chaos on the VMware VM
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: VMware-engine
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: VMware-DNS-chaos
    spec:
      components:
        env:
        - name: PORT
          value: '54'
        - name: VM_NAME
          value: 'vm-1,vm-2'
        - name: VM_USER_NAME
          value: 'ubuntu,debian'
        - name: VM_PASSWORD
          value: '123,123'

Run DNS chaos with target host names​

It contains the list of the target host names into which DNS chaos is injected. You can tune it using the TARGET_HOSTNAMES environment variable.

Use the following example to tune it:

# induces DNS chaos on the VMware VMs
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: VMware-DNS-chaos
    spec:
      components:
        env:
        # list of target host names
        - name: TARGET_HOSTNAMES
          value: '["litmuschaos","chaosnative.com"]'
        - name: VM_NAME
          value: 'vm-1,vm-2'
        - name: VM_USER_NAME
          value: 'ubuntu,debian'
        - name: VM_PASSWORD
          value: '123,123'

Run DNS chaos with match scheme​

It determines whether the DNS query should exactly match the targets or can be a substring. You can tune it using the MATCH_SCHEME environment variable.

Use the following example to tune it:

# induces DNS chaos on the VMware VMs
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: VMware-DNS-chaos
    spec:
      components:
        env:
        # match scheme type
        - name: MATCH_SCHEME
          value: 'exact'
        - name: VM_NAME
          value: 'vm-1,vm-2'
        - name: VM_USER_NAME
          value: 'ubuntu,debian'
        - name: VM_PASSWORD
          value: '123,123'

Run DNS chaos with upstream server​

It specifies the custom upstream server to which the intercepted DNS requests are forwarded. It defaults to the server mentioned in the resolv.conf file. The value can be provided using UPSTREAM_SERVER environment variable.

Use the following example to tune it:

# induces DNS chaos on the VMware VMs
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: VMware-DNS-chaos
    spec:
      components:
        env:
        # name of the upstream server
        - name: UPSTREAM_SERVER
          value: '8.8.8.8'
        - name: VM_NAME
          value: 'vm-1,vm-2'
        - name: VM_USER_NAME
          value: 'ubuntu,debian'
        - name: VM_PASSWORD
          value: '123,123'