Simulate DNS faults

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 server

Check whether Chaos DNS Server is deployed by running the following command:

kubectl get pods -n chaos-mesh -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-mesh

Simulate fault injections by kbcli

DNS faults can be simulated as random and error. You can select one type for DNS fault injection.

--pattern selects a domain template that matches faults and it is required. Placeholder ? and wildcard * are supported.

DNS random

Run the command below to inject DNS faults into all Pods in the default namespace, which means a random IP address will be returned when a DNS request is sent to the specified domains.

kbcli fault network dns random --patterns=google.com --duration=1m

DNS error

Run the command below to inject DNS faults into all Pods in the default namespace, which means an error will be returned when a DNS request is sent to the specified domains.

kbcli fault network dns error --patterns=google.com --duration=1m

Simulate fault injections by YAML file

This section introduces the YAML configuration file examples. You can view the YAML file by adding --dry-run at the end of the above kbcli commands. Meanwhile, you can also refer to the Chaos Mesh official docs for details.

DNS-random example

1. Write the experiment configuration to the dns-random.yaml file.

   In the following example, Chaos Mesh injects DNS faults into all Pods in the default namespace, which means an IP address will be returned when a DNS request is sent to the specified domains.

   apiVersion: chaos-mesh.org/v1alpha1
   kind: DNSChaos
   metadata:
     creationTimestamp: null
     generateName: dns-chaos-
     namespace: default
   spec:
     action: random
     duration: 1m
     mode: all
     patterns:
     - google.com
     selector:
       namespaces:
       - default

2. Run kubectl to start an experiment.

   kubectl apply -f ./dns-random.yaml

DNS-error example

1. Write the experiment configuration to the dns-error.yaml file.

   In the following example, Chaos Mesh injects DNS faults into all Pods in the default namespace, which means an error will be returned when a DNS request is sent to the specified domains.

   apiVersion: chaos-mesh.org/v1alpha1
   kind: DNSChaos
   metadata:
     creationTimestamp: null
     generateName: dns-chaos-
     namespace: default
   spec:
     action: error
     duration: 1m
     mode: all
     patterns:
     - google.com
     selector:
       namespaces:
       - default

2. Run kubectl to start an experiment.

   kubectl apply -f ./network-partition.yaml

Field description

Parameter	Type	Description	Default value	Required	Example
action	string	Defines the behavior of DNS fault. Optional values: random or error. When the value is random, DNS service returns a random IP address; when the value is error, DNS service returns 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	one
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	1
selector	struct	Specifies the target Pod.	None	Yes