Getting IP into env variable via DNS in kubernetes - kubernetes

Question

I'm trying to get my head around K8s coming from docker compose. I would like to setup my first pod with two containers which I pushed to a registry. Following question:
How do I get the IP via DNS into a environment variable, so that registrator can connect to consul? See container registrtor in args consul://consul:8500. The consul needs to be changed with the env.
{
"kind": "Pod",
"apiVersion": "v1",
"metadata": {
"name": "service-discovery",
"labels": {
"name": "service-discovery"
}
},
"spec": {
"containers": [
{
"name": "consul",
"image": "eu.gcr.io/{myproject}/consul",
"args": [
"-server",
"-bootstrap",
"-advertise=$(MY_POD_IP)"
],
"env": [{
"name": "MY_POD_IP",
"valueFrom": {
"fieldRef": {
"fieldPath": "status.podIP"
}
}
}],
"imagePullPolicy": "IfNotPresent",
"ports": [
{
"containerPort": 8300,
"name": "server"
},
{
"containerPort": 8400,
"name": "alt-port"
},
{
"containerPort": 8500,
"name": "ui-port"
},
{
"containerPort": 53,
"name": "udp-port"
},
{
"containerPort": 8443,
"name": "https-port"
}
]
},
{
"name": "registrator",
"image": "eu.gcr.io/{myproject}/registrator",
"args": [
"-internal",
"-ip=$(MY_POD_IP)",
"consul://consul:8500"
],
"env": [{
"name": "MY_POD_IP",
"valueFrom": {
"fieldRef": {
"fieldPath": "status.podIP"
}
}
}],
"imagePullPolicy": "Always"
}
]
}
}

Answer 1

Exposing pods to other applications is done with a Service in Kubernetes. Once you've defined a service you can use environment variables related to that services within your pods. Exposing the Pod directly is not a good idea as Pods might get rescheduled.
When e.g. using a service like this:
apiVersion: v1
kind: Service
metadata:
name: consul
namespace: kube-system
labels:
name: consul
spec:
ports:
- name: http
port: 8500
- name: rpc
port: 8400
- name: serflan
port: 8301
- name: serfwan
port: 8302
- name: server
port: 8300
- name: consuldns
port: 8600
selector:
app: consul
The related environment variable will be CONSUL_SERVICE_IP
Anyways it seems others actually stopped using that environment variables for some reasons as described here