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title
Simulate DNS Faults

import PickHelmVersion from '@site/src/components/PickHelmVersion'

This document describes how to create DNSChaos experiments in Chaos Mesh to simulate DNS faults.

DNSChaos Introduction

DNSChaos is used to simulate wrong DNS responses. For example, DNSChaos can return an error or return a random IP address when receiving a DNS request.

Deploy Chaos DNS Service

Before creating a DNSChaos experiment using Chaos Mesh, you need to deploy a special DNS service to inject faults:

{helm upgrade chaos-mesh chaos-mesh/chaos-mesh --namespace=chaos-testing --version latest --set dnsServer.create=true}

After executing the above commands, check if the DNS service status is normal:

kubectl get pods -n chaos-testing -l app.kubernetes.io/component=chaos-dns-server

Make sure that the Pod status is Running.

Notes

  1. Currently, DNSChaos only supports record types A and AAAA.

  2. The chaos DNS service runs CoreDNS with the k8s_dns_chaos plugin. If the CoreDNS service in your Kubernetes cluster contains some special configurations, you can edit configMap dns-server-config to make the configuration of the chaos DNS service consistent with that of the K8s CoreDNS service using the following command:

    kubectl edit configmap dns-server-config -n chaos-testing

Create experiments using Chaos Dashboard

  1. Open Chaos Dashboard, and click NEW EXPERIMENT on the page to create a new experiment:

    Create Experiment

  2. In the Choose a Target area, choose DNS FAULT and select a specific behavior, such as ERROR. Then fill out the matching rules.

    DNSChaos Experiment

    According to the matching rules configured in the screenshot, the DNS FAULT takes effect for domains including google.com, chaos-mesh.org, and github.com, which means that an error will be returned when a DNS request is sent to these three domains. For details of specific matching rules, refer to the description of the patterns field in Configuration Description.

  3. Fill out the experiment information, and specify the experiment scope and the scheduled experiment duration:

    Experiment Information

  4. Submit the experiment information.

Create experiments using the YAML file

  1. Write the experiment configuration to the dnschaos.yaml file:

    apiVersion: chaos-mesh.org/v1alpha1
kind: DNSChaos
metadata:
  name: dns-chaos-example
  namespace: chaos-testing
spec:
  action: random
  mode: all
  patterns:
    - google.com
    - chaos-mesh.*
    - github.?om
  selector:
    namespaces:
      - busybox

    This configuration can take effect for domains including google.com, chaos-mesh.org, and github.com, which means that an IP address will be returned when a DNS request is sent to these three domains. For specific matching rules, refer to the patterns description in Configuration Description.

  2. After the configuration file is prepared, use kubectl to create an experiment:

    kubectl apply -f dnschaos.yaml

Configuration Description

Parameter Type Description Default value Required Example
action string Defines the behavior of DNS fault. The value can be random or error. When the value is random, DNS service will return a random IP address; when the value is error, DNS service will return an error. None Yes random or error
patterns String array Selects a domain template that matches faults. Placeholder ? and wildcard are supported. * [] No google.com, chaos-mesh.org, github.com
mode string Specifies the mode of the experiment. The mode options include one (selecting a random Pod), all (selecting all eligible Pods), fixed (selecting a specified number of eligible Pods), fixed-percent (selecting a specified percentage of Pods from the eligible Pods), and random-max-percent (selecting the maximum percentage of Pods from the eligible Pods). None Yes 1
value string Provides parameters for the mode configuration, depending on mode. For example, when mode is set to fixed-percent, value specifies the percentage of Pods. None No 2
selector struct Specifies the target Pod. For details, refer to Define the Scope of Chaos Experiments. None Yes

:::note

  • The wildcard in patterns configuration must be at the end of string. For example, chaos-mes*.org. is an invalid configuration.

  • When patterns is not configured, faults will be injected for all domains.

:::