103 lines
3.1 KiB
Markdown
103 lines
3.1 KiB
Markdown
---
|
|
layout: "docs"
|
|
page_title: "Consul DNS - Kubernetes"
|
|
sidebar_current: "docs-platform-k8s-dns"
|
|
description: |-
|
|
One of the primary query interfaces to Consul is the DNS interface. The Consul DNS interface can be exposed for all pods in Kubernetes using a stub-domain configuration.
|
|
---
|
|
|
|
# Consul DNS on Kubernetes
|
|
|
|
One of the primary query interfaces to Consul is the
|
|
[DNS interface](/docs/agent/dns.html). The Consul DNS interface can be
|
|
exposed for all pods in Kubernetes using a
|
|
[stub-domain configuration](https://kubernetes.io/docs/tasks/administer-cluster/dns-custom-nameservers/#configure-stub-domain-and-upstream-dns-servers).
|
|
|
|
The stub-domain configuration must point to a static IP of a DNS resolver.
|
|
The [Helm chart](/docs/platform/k8s/helm.html) creates a `consul-dns` service
|
|
by default that exports Consul DNS. The cluster IP of this service can be used
|
|
to configure a stub-domain with kube-dns. While the `kube-dns` configuration
|
|
lives in the `kube-system` namepace, the IP just has to be routable so the
|
|
service can live in a different namespace.
|
|
|
|
```
|
|
cat <<EOF | kubectl apply -f -
|
|
apiVersion: v1
|
|
kind: ConfigMap
|
|
metadata:
|
|
labels:
|
|
addonmanager.kubernetes.io/mode: EnsureExists
|
|
name: kube-dns
|
|
namespace: kube-system
|
|
data:
|
|
stubDomains: |
|
|
{"consul": ["$(kubectl get svc consul-dns -o jsonpath='{.spec.clusterIP}')"]}
|
|
EOF
|
|
```
|
|
|
|
-> **Note:** The `stubDomain` can only point to a static IP. If the cluster IP
|
|
of the `consul-dns` service changes, then it must be updated to continue
|
|
working. This can happen if the service is deleted and recreated, such as
|
|
in full cluster rebuilds.
|
|
|
|
## Verifying DNS Works
|
|
|
|
To verify DNS works, run a simple job to query DNS. Save the following
|
|
job to the file `job.yaml` and run it:
|
|
|
|
```yaml
|
|
apiVersion: batch/v1
|
|
kind: Job
|
|
metadata:
|
|
name: dns
|
|
spec:
|
|
template:
|
|
spec:
|
|
containers:
|
|
- name: dns
|
|
image: anubhavmishra/tiny-tools
|
|
command: ["dig", "consul.service.consul"]
|
|
restartPolicy: Never
|
|
backoffLimit: 4
|
|
```
|
|
|
|
```sh
|
|
$ kubectl apply -f job.yaml
|
|
```
|
|
|
|
Then query the pod name for the job and check the logs. You should see
|
|
output similar to the following showing a successful DNS query. If you see
|
|
any errors, then DNS is not configured properly.
|
|
|
|
```
|
|
$ kubectl get pods --show-all | grep dns
|
|
dns-lkgzl 0/1 Completed 0 6m
|
|
|
|
$ kubectl logs dns-lkgzl
|
|
; <<>> DiG 9.11.2-P1 <<>> consul.service.consul
|
|
;; global options: +cmd
|
|
;; Got answer:
|
|
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 4489
|
|
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 4
|
|
|
|
;; OPT PSEUDOSECTION:
|
|
; EDNS: version: 0, flags:; udp: 4096
|
|
;; QUESTION SECTION:
|
|
;consul.service.consul. IN A
|
|
|
|
;; ANSWER SECTION:
|
|
consul.service.consul. 0 IN A 10.36.2.23
|
|
consul.service.consul. 0 IN A 10.36.4.12
|
|
consul.service.consul. 0 IN A 10.36.0.11
|
|
|
|
;; ADDITIONAL SECTION:
|
|
consul.service.consul. 0 IN TXT "consul-network-segment="
|
|
consul.service.consul. 0 IN TXT "consul-network-segment="
|
|
consul.service.consul. 0 IN TXT "consul-network-segment="
|
|
|
|
;; Query time: 5 msec
|
|
;; SERVER: 10.39.240.10#53(10.39.240.10)
|
|
;; WHEN: Wed Sep 12 02:12:30 UTC 2018
|
|
;; MSG SIZE rcvd: 206
|
|
```
|