(Docker-Compose) UnhandledPromiseRejectionWarning when connecting node and postgres - node.js

Question

I am trying to connect the containers for postgres and node. Here is my setup:
yml file:
version: "3"
services:
postgresDB:
image: postgres:alpine
container_name: postgresDB
ports:
- "5432:5432"
environment:
- POSTGRES_DB=myDB
- POSTGRES_USER=postgres
- POSTGRES_PASSWORD=Thisisngo1995!
express-server:
build: ./
environment:
- DB_SERVER=postgresDB
links:
- postgresDB
ports:
- "3000:3000"
Dockerfile:
FROM node:12
WORKDIR /usr/src/app
COPY package.json ./
RUN npm install
COPY . .
COPY ormconfig.docker.json ./ormconfig.json
EXPOSE 3000
CMD ["npm", "start"]
connect to postgres:
let { Pool, Client } = require("pg");
let postgres = new Pool({
host: "postgresDB",
port: 5432,
user: "postgres",
password: "Thisisngo1995!",
database: "myDB",
});
module.exports = postgres;
and here is how I handled my endpoint:
exports.postgres_get_controller = (req, resp) => {
console.log("Reached Here");
postgres
.query('SELECT * FROM public."People"')
.then((results) => {
console.log(results);
resp.send({ allData: results.rows });
})
.catch((e) => console.log(e));
};
Whenever I try to touch the endpoint above, I get this error in the container:
Reasons why?
Note: I am able to have everything functioning on my local machine (without docker) simply by changing "host: localhost"

Answer 1

Your postgres database name and username should be the same

Answer 2

You can use docker-compose-wait to make sure interdependent services are launched in proper order.
See below on how to use it for your case.
update the final part of your Dockerfile as below;
# ...
# this will be used to check if DB is up
ADD https://github.com/ufoscout/docker-compose-wait/releases/download/2.7.3/wait ./wait
RUN chmod +x ./wait
CMD ./wait && npm start
Update some parts of your docker-compose.yml as below:
express-server:
build: ./
environment:
- DB_SERVER=postgresDB
- WAIT_HOSTS=postgresDB:5432
- WAIT_BEFORE_HOSTS=4
links:
- postgresDB
depends_on:
- postgresDB
ports:
- "3000:3000"