Resolve ip addresses of a headless service
I created a service, which has 3 pods assigned.
I would like to access the service through its hostname by an other service in the same project. How can I do that?
Tried:
alxtbk@dns-test:~$ ping elassandra-0.elassandra
ping: elassandra-0.elassandra: Name or service not known
alxtbk@dns-test:~$ ping elassandra-0.default.svc.cluster.local
ping: elassandra-0.default.svc.cluster.local: Name or service not known
alxtbk@dns-test:~$ ping elassandra.default.svc.cluster.local
ping: elassandra.default.svc.cluster.local: Name or service not knownWhat is the correct way to resolve the ip adresses of the headless service?
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1 Answer
For such Services, a cluster IP is not allocated, kube-proxy does not handle these services, and there is no load balancing or proxying done by the platform for them. How DNS is automatically configured depends on whether the service has selectors defined.
With selectors
For headless services that define selectors, the endpoints controller creates Endpoints records in the API, and modifies the DNS configuration to return A records (addresses) that point directly to the Pods backing the Service.
Without selectors
For headless services that do not define selectors, the endpoints controller does not create Endpoints records. However, the DNS system looks for and configures either:
CNAME records for ExternalName-type services.
A records for any Endpoints that share a name with the service, for all other types.
so you maybe be able to do:
kubectl get epto get the endpoints and then use them inside another kubernetes service.