How to make docker-compose services accesible with each other? - node.js

Question

I'm trying to make a frontend app accesible to the outside. It depends on several other modules, serving as services/backend. This other services also rely on things like Kafka and OpenLink Virtuoso (Database).
How can I make all of them all accesible with each other and how should I expose my frontend to outside internet? Should I also remove any "localhost/port" in my code, and replace it with the service name? Should I also replace every port in the code for the equivalent port of docker?
Here is an extraction of my docker-compose.yml file.
version: '2'
services:
zookeeper:
image: confluentinc/cp-zookeeper:latest
environment:
ZOOKEEPER_CLIENT_PORT: 2181
ZOOKEEPER_TICK_TIME: 2000
ports:
- 22181:2181
kafka:
image: confluentinc/cp-kafka:latest
depends_on:
- zookeeper
ports:
- 29092:29092
environment:
KAFKA_BROKER_ID: 1
KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://kafka:9092,PLAINTEXT_HOST://localhost:29092
KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: PLAINTEXT:PLAINTEXT,PLAINTEXT_HOST:PLAINTEXT
KAFKA_INTER_BROKER_LISTENER_NAME: PLAINTEXT
KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 1
frontend:
build:
context: ./Frontend
dockerfile: ./Dockerfile
image: "jcpbr/node-frontend-app"
ports:
- "3000:3000"
# Should I use links to connect to every module the frontend access and for the other modules as well?
links:
- "auth:auth"
auth:
build:
context: ./Auth
dockerfile: ./Dockerfile
image: "jcpbr/node-auth-app"
ports:
- "3003:3003"
(...)

Answer 1

How can I make all of [my services] all accesible with each other?
Do absolutely nothing. Delete the obsolete links: block you have. Compose automatically creates a network named default that you can use to communicate between the containers, and they can use the other Compose service names as host names; for example, your auth container could connect to kafka:9092. Also see Networking in Compose in the Docker documentation.
(Some other setups will advocate manually creating Compose networks: and overriding the container_name:, but this isn't necessary. I'd delete these lines in the name of simplicity.)
How should I expose my frontend to outside internet?
That's what the ports: ['3000:3000'] line does. Anyone who can reach your host system on port 3000 (the first port number) will be able to access the frontend container. As far as an outside caller is concerned, they have no idea whether things are running in Docker or not, just that your host is running an HTTP server on port 3000.
Setting up a reverse proxy, maybe based on Nginx, is a little more complicated, but addresses some problems around communication from the browser application to the back-end container(s).
Should I also remove any "localhost/port" in my code?
Yes, absolutely.
...and replace it with the service name? every port?
No, because those settings will be incorrect in your non-container development environment, and will probably be incorrect again if you have a production deployment to a cloud environment.
The easiest right answer here is to use environment variables. In Node code, you might try
const kafkaHost = process.env.KAFKA_HOST || 'localhost';
const kafkaPort = process.env.KAFKA_PORT || '9092';
If you're running this locally without those environment variables set, you'll get the usually-correct developer defaults. But in your Docker-based setup, you can set those environment variables
services:
kafka:
image: confluentinc/cp-kafka:latest
environment:
KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://kafka:9092 # must match the Docker service name
app:
build: .
environment:
KAFKA_HOST: kafka
# default KAFKA_PORT is still correct