K
Q

make pod resolve external service name via DNS

7/3/2019

I have a client applicationg running in a pod, on kubernetes 1.11.1., that should connect to a rabbitMQ cluster.

I would like to create a service that should round robin among two IP addresses of two hosts. The hosts are not pods, they are external virtual machines acting as a cluster of rabbitMQ.

I created a service and an endpoint that share the name (rabbitmq-service) in order to match. Now, from a pod it is not possibile to resolve via DNS the servicename.default.svc, while it is possible to resolve both host names via a name that contains the service name, as in: N-N-N-N.servicename.namespace.svc.clusterdomain. (where N-N-N-N is similar to an ip address).

service.yaml:

apiVersion: v1
kind: Service
metadata:
  name: rabbitmq-service
spec:
  ports:
  - name: http
    protocol: TCP
    port: 5672
    targetPort: 5672

endpoints.yaml:

apiVersion: v1
kind: Endpoints
metadata:
  name: rabbitmq-service
  namespace: default
subsets:
  - addresses:
      - ip: 10.112.63.98
      - ip: 10.112.63.99
    ports:
    - name: http
      port: 5672
      protocol: TCP

How can I configure the servicename.default.svc resolution?

Thank you.

-- eppesuig
coredns
kubernetes
rabbitmq

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1 Answer

7/3/2019

I applied your configurations and this is what I get:

kubectl get endpoints
NAME               ENDPOINTS                             AGE
kubernetes         192.168.99.116:8443                   45s
rabbitmq-service   10.112.63.98:5672,10.112.63.99:5672   13s

Also I tried to resolve the dns of rabbitmq-service from another pod using the below commands:

kubectl apply -f https://k8s.io/examples/admin/dns/busybox.yaml
kubectl exec -ti busybox -- nslookup rabbitmq-service.default

The above nslookup command in the pod gave the output:

Defaulting container name to busybox.
Use 'kubectl describe pod/busybox -n default' to see all of the containers in this pod.
Server:    10.96.0.10
Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local


Name:      rabbitmq-service.default
Address 1: 10.101.126.122 rabbitmq-service.default.svc.cluster.local

which means that the service is resolvable. I hope there should be problem in accessing your rabbitmq service from your machines running the kubernetes cluster.

Please refer to this document if you suspect an issue with kubernetes coreDNS.

-- Malathi
Source: StackOverflow