Nodejs cannot connect to Postgresdb container - node.js

Question

I am currently working on an angular app using Rest API (Express, Nodejs) and Postgresql. Everything worked well when hosted on my local machine. After testing, I moved the images to Ubuntu server so the app can be hosted on an external port. I am able to access the angular frontend using the https://serveripaddress:80 but when trying to login, the api is not connecting to Postgresql. I am getting an error message: ERR_CONNECTION_REFUSED. Here is my docker-compose file:
version: '3.0'
services:
db:
image: postgres:9.6-alpine
environment:
POSTGRES_DB: myDatabase
POSTGRES_PASSWORD: myPwd
POSTGRES_PORT: 5432
POSTGRES_HOST: db
ports:
- 5434:5432
restart: always
volumes:
- ./postgres-data:/var/lib/postgresql/data
backend: # name of the second service
image: myid/nodeapi
ports:
- 3000:3000
environment:
POSTGRES_DB: myDatabase
POSTGRES_PASSWORD: myPwd
POSTGRES_PORT: 5432
POSTGRES_HOST: db
depends_on:
- db
command: bash -c "sleep 20 && node server.js"
myapp-portal:
image: myId/angular-app
ports:
- "80:80"
depends_on:
- backend
volumes:
postgres-data:
The code to connect to database:
const { Client } = require('pg')
const client = new Client({
database: process.env.POSTGRES_DB,
user: 'postgres',
password: process.env.POSTGRES_PASSWORD,
host: process.env.POSTGRES_HOST,
port: process.env.POSTGRES_PORT
})
client.connect()
.then(
() => {
console.log("db connected");
})
and the docker-compose log for backend:
backend_1 | db connected
When I exec into the database docker container and connect to psql, I see that my database is created(used pg_dump manually) with all the tables and data. My guess is that node.js is connecting to the default Postgres database created at the time of the installation. I had the same issue on my local machine but I resolved it by creating a new server group in pgAdmin4 and creating a new db on port 5434. I prefer not to do this on server as it defeats the purpose of the concept of docker. Another thought is perhaps node.js is attempting to connect to the database even before it is up. That is the reason I added the line 'sleep 20' which worked on my local machine. Any thoughts on how I can fix this? TIA!

Answer 1

If you want to wait on the availability of a host and TCP port, you can use this script https://github.com/vishnubob/wait-for-it
In your docker file you can copy this file into container and change mode
RUN chmod +x wait-for-it.sh
Then in your docker compose run this script on service which you want to wait
entrypoint: bash -c "./wait-for-it.sh --timeout=0 service_name:service_port && node server.js"