Kubernetes service as env var to frontend usage - kubernetes

Question

I'm trying to configure kubernetes and in my project I've separeted UI and API.
I created one Pod and I exposed both as services.
How can I set API_URL inside pod.yaml configuration in order to send requests from user's browser?
I can't use localhost because the communication isn't between containers.
pod.yaml
apiVersion: v1
kind: Pod
metadata:
name: project
labels:
name: project
spec:
containers:
- image: 'ui:v1'
name: ui
ports:
- name: ui
containerPort: 5003
hostPort: 5003
env:
- name: API_URL
value: <how can I set the API address here?>
- image: 'api:v1'
name: api
ports:
- name: api
containerPort: 5000
hostPort: 5000
env:
- name: DATABASE_URL
valueFrom:
secretKeyRef:
name: postgres-url
key: url
services.yaml
apiVersion: v1
kind: Service
metadata:
name: api
labels:
name: api
spec:
type: NodePort
ports:
- name: 'http'
protocol: 'TCP'
port: 5000
targetPort: 5000
nodePort: 30001
selector:
name: project
---
apiVersion: v1
kind: Service
metadata:
name: ui
labels:
name: ui
spec:
type: NodePort
ports:
- name: 'http'
protocol: 'TCP'
port: 80
targetPort: 5003
nodePort: 30003
selector:
name: project

Answer 1

The service IP is already available in a environment variable inside the pod, because Kubernetes initializes a set of environment variables for each service that exists at that moment.
To list all the environment variables of a pod
kubectl exec <pod-name> env
If the pod was created before the service you must delete it and create it again.
Since you named your service api, one of the variables the command above should list is API_SERVICE_HOST.
But you don't really need to lookup the service IP address inside environment variables. You can simply use the service name as the hostname. Any pod can connect to the service api, simply by calling api.default.svc.cluster (assuming your service is in the default namespace).

Answer 2

I created an Ingress to solve this issue and point to DNS instead of IP.
ingres.yaml
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: project
spec:
tls:
- secretName: tls
backend:
serviceName: ui
servicePort: 5003
rules:
- host: www.project.com
http:
paths:
- backend:
serviceName: ui
servicePort: 5003
- host: api.project.com
http:
paths:
- backend:
serviceName: api
servicePort: 5000
deployment.yaml
apiVersion: v1
kind: Pod
metadata:
name: project
labels:
name: project
spec:
containers:
- image: 'ui:v1'
name: ui
ports:
- name: ui
containerPort: 5003
hostPort: 5003
env:
- name: API_URL
value: https://api.project.com
- image: 'api:v1'
name: api
ports:
- name: api
containerPort: 5000
hostPort: 5000
env:
- name: DATABASE_URL
valueFrom:
secretKeyRef:
name: postgres-url
key: url