Customized port is not functional in Docker-compose - docker

Question

I'm having a dumb question regarding to using docker-compose.
Current scenario is I'm trying use my reverse_proxy to talk to my frontend_server. Inside the reverse_proxy, It redirects to frontend_server just like the following:
Suppose I receive http://${REV_IP}:${REV_PORT} It should redirect me to http://${FE_IP}:${FE_PORT} but it redirect me to 15000
(PROXIED_FRONTEND is http://${FE_IP}:${FE_PORT}, this environment veriable is used for this redirection)
Here is the code snippet for my docker-compose.yml
version: '3'
services:
reverse_proxy:
image: "${ARTIFACTORY}/template-reverse-proxy:${BRANCH}-${REV_TAG}"
networks:
nucleus-network:
ipv4_address: ${REV_IP}
ports:
- "${REV_PORT}:15999"
environment:
- KEYFILE_REVPROXY=${REV_KEY}
- CERTFILE_REVPROXY=${REV_CERT}
- PUBLIC_URL=${PUBLIC_URL}
- PUBLIC_API_URL=${PUBLIC_API_URL}
- PROXIED_FRONTEND=${PROXIED_FRONTEND}
- PROXIED_PDF=${PROXIED_PDF}
depends_on:
- frontend_server
frontend_server:
image: "${ARTIFACTORY}/fe_server:${BRANCH}-${PDF_TAG}"
ports:
- "${FE_PORT}:15000"
networks:
nucleus-network:
ipv4_address: ${FE_IP}
environment:
- FILEPATH_FE_SERVER=${FILEPATH_FE_SERVER}
volumes:
- "/home/lluo/dist_share:/app/dist"
depends_on:
- frontend_static
networks:
nucleus-network:
driver: bridge
ipam:
driver: default
config:
- subnet: ${SUB_NET}

Answer 1

It's no need for you to publish frontend_server port to outside world (via ports:), unless you want to access it directly (i.e. for debugging)
Since you use docker-compose and depends_on, it will create you a inner docker network, in which containers will see each other.
Only thing for you to do is to setup your reverse proxy to have the proxied backend pointing to http://frontend_server:15000 and your good to go. inner docker DNS will resolve the frontend_sever service name to appropriate container IP address.
for reference and more info see this question and links provided there: https://serverfault.com/questions/800689/how-to-use-haproxy-in-load-balancing-and-as-a-reverse-proxy-with-docker