How to connect two docker containers together - docker

Question

I have a reactjs front end application and a simple python flask. And I am using a docker-compose.yml to spin up both the containers, and it is like this:
version: "3.2"
services:
frontend:
build: .
environment:
CHOKIDAR_USEPOLLING: "true"
ports:
- 80:80
links:
- "backend:backend"
depends_on:
- backend
backend:
build: ./api
# volumes:
# - ./api:/usr/src/app
environment:
# CHOKIDAR_USEPOLLING: "true"
FLASK_APP: /usr/src/app/server.py
FLASK_DEBUG: 1
ports:
- 8083:8083
I have used links so the frontend service can talk to backend service using axios as below:
axio.get("http://backend:8083/monitors").then(res => {
this.setState({
status: res.data
});
});
I used docker-compose up --build -d to build and start the two containers and they are started without any issue and running fine.
But now the frontend cannot talk to backend.
I am using an AWS ec2 instance. When the page loads, I tried to see the for any console errors and I get this error:
VM167:1 GET http://backend:8083/monitors net::ERR_NAME_NOT_RESOLVED
Can someone please help me?
The backend service is up and running.

Answer 1

You can use a nginx as reverse proxy for both
The compose file
version: "3.2"
services:
frontend:
build: .
environment:
CHOKIDAR_USEPOLLING: "true"
depends_on:
- backend
backend:
build: ./api
# volumes:
# - ./api:/usr/src/app
environment:
# CHOKIDAR_USEPOLLING: "true"
FLASK_APP: /usr/src/app/server.py
FLASK_DEBUG: 1
proxy:
image: nginx
volumes:
- ./nginx.conf:/etc/nginx/conf.d/example.conf
ports:
- 80:80
minimal nginx config (nginx.conf):
server {
server_name example.com;
server_tokens off;
location / {
proxy_pass http://frontend:80;
}
}
server {
server_name api.example.com;
server_tokens off;
location / {
proxy_pass http://backend:8083;
}
}
The request hits the nginx container and is routed according the domain to the right container.
To use example.com and api.example.com you need to edit your hosts file:
Linux: /etc/hosts
Windows: c:\windows\system32\drivers\etc\hosts
Mac: /private/etc/hosts
127.0.0.1 example.com api.example.com