Learn more about Replicated to operationalize your application
/

DNS

Collect data to troubleshoot DNS Resolution

The dns collector can be used to help diagnose DNS resolution problems, such as detecting search domain misconfiguration. During execution, the collector does the following:

  • Output Kubernetes Service Cluster IP retrieved from kube-apiserver
  • Run a test pod of image registry.k8s.io/e2e-test-images/jessie-dnsutils:1.3, do nslookup to kubernetes Service and output content of /etc/resolv.conf
  • Check if DNS pods are running
  • Check if DNS service is up
  • Check if DNS endpoints are populated
  • Output CoreDNS/KubeDNS config

Parameters

In addition to the shared collector properties, the dns collector accepts the following parameters:

The name of the collector. The collector name is used as filename of the output in the support bundle.

See the examples below for use cases.

Example Collector Definition

apiVersion: troubleshoot.sh/v1beta2
kind: SupportBundle
metadata:
  name: sample
spec:
  collectors:
    - dns:
        collectorName: "dns-troubleshoot"

Example data collected

=== Kubernetes Cluster IP from API Server: 172.20.0.1
=== Test DNS resolution in pod registry.k8s.io/e2e-test-images/jessie-dnsutils:1.3:
+ cat /etc/resolv.conf
search default.svc.cluster.local svc.cluster.local cluster.local ec2.internal
nameserver 172.20.0.10
options ndots:5
+ nslookup -debug kubernetes
Server:		172.20.0.10
Address:	172.20.0.10#53
------------
    QUESTIONS:
	kubernetes.default.svc.cluster.local, type = A, class = IN
    ANSWERS:
    ->  kubernetes.default.svc.cluster.local
	internet address = 172.20.0.1
	ttl = 5
    AUTHORITY RECORDS:
    ADDITIONAL RECORDS:
------------
Name:	kubernetes.default.svc.cluster.local
Address: 172.20.0.1
+ exit 0
=== Running kube-dns pods: coredns-7dc65fd6c5-tqfff, coredns-7dc65fd6c5-w2dsg
=== Running kube-dns service: 172.20.0.10
=== kube-dns endpoints: 10.0.37.5:53, 10.0.8.255:53
=== CoreDNS config:
.:53 {
    errors
    health {
        lameduck 5s
      }
    ready
    kubernetes cluster.local in-addr.arpa ip6.arpa {
      pods insecure
      fallthrough in-addr.arpa ip6.arpa
    }
    prometheus :9153
    forward . /etc/resolv.conf
    cache 30
    loop
    reload
    loadbalance
}

Included resources

When this collector is executed, it includes the following file in a support bundle:

/dns/[collector-name]

Edit on GitHub