docker-compose wait-for.sh fails for waiting mongodb - node.js

Question

I am trying to set up a docker network with simple nodejs and mongodb services by following this guide, however, when building nodejs it fails because it can't connect to mongodb.
docker-compose.yml
version: "3"
services:
nodejs:
container_name: nodejs # How the container will appear when listing containers from the CLI
image: node:10 # The <container-name>:<tag-version> of the container, in this case the tag version aligns with the version of node
user: node # The user to run as in the container
working_dir: "/app" # Where to container will assume it should run commands and where you will start out if you go inside the container
networks:
- app # Networking can get complex, but for all intents and purposes just know that containers on the same network can speak to each other
ports:
- "3000:3000" # <host-port>:<container-port> to listen to, so anything running on port 3000 of the container will map to port 3000 on our localhost
volumes:
- ./:/app # <host-directory>:<container-directory> this says map the current directory from your system to the /app directory in the docker container
command: # The command docker will execute when starting the container, this command is not allowed to exit, if it does your container will stop
- ./wait-for.sh
- --timeout=15
- mongodb:27017
- --
- bash
- -c
- npm install && npm start
env_file: ".env"
environment:
- MONGO_USERNAME=$MONGO_USERNAME
- MONGO_PASSWORD=$MONGO_PASSWORD
- MONGO_HOSTNAME=mongodb
- MONGO_PORT=$MONGO_PORT
- MONGO_DB=$MONGO_DB
depends_on:
- mongodb
mongodb:
image: mongo:4.1.8-xenial
container_name: mongodb
restart: unless-stopped
env_file: .env
environment:
- MONGO_INITDB_ROOT_USERNAME=$MONGO_USERNAME
- MONGO_INITDB_ROOT_PASSWORD=$MONGO_PASSWORD
volumes:
- dbdata:/data/db
networks:
- app
networks:
app:
driver: bridge
volumes:
dbdata:
app.js
const express = require('express');
var server = express();
var bodyParser = require('body-parser');
// getting-started.js
var mongoose = require('mongoose');
mongoose.connect('mongodb://simpleUser:123456#mongodb:27017/simpleDb', {useNewUrlParser: true});
server.listen(3000, function() {
console.log('Example app listening on port 3000');
});
Here is the common wait-for.sh script that I was using. https://github.com/eficode/wait-for/blob/master/wait-for
docker logs -f nodejs gives;
Operation timed out
Thanks for your help!

Answer 1

In this case I believe the issue is that you are using the wait-for.sh script which makes use of netcat command (see https://github.com/eficode/wait-for/blob/master/wait-for#L24), but the node:10 image does not have netcat installed...
I would suggest either creating a custom image based on the node:10 image and adding netcat or use a different approach (preferably a nodejs based solution) for checking if the mongodb is accessible
A sample Dockerfile for creating your own custom image would look something like this
FROM node:10
RUN apt update && apt install -y netcat
Then you can build this image by replacing image: node:10 with
build:
dockerfile: Dockerfile
context: .
and you should be fine

Answer 2

I found the problem which was because of the image node:10 doesn't have nc command installed so it was failing. I switched to image node:10-alpine and it worked.