Docker(docker-compose) node + MySQL: ECONNREFUSED - mysql

Question

I have a docker-compose.yml file, that is running three containers. My problem is when I start my containers it seems like my node(api) container is starting before my MySQL container, even if I declare depends_on on my docker-compose.yml, giving me the following error:
error connecting: Error: connect ECONNREFUSED xxx.xx.x.x:3306
at TCPConnectWrap.afterConnect [as oncomplete]
After I got this error I can see in my console that the MySQL container is just starting. My database is ok, I can access it without any problems. If I make some change in my nodejs code, then this will make my node server to refresh and when the server is up again I don't have any connections problems, because the MySQL container is already up.
I even tried to use solutions as wait-for-it.sh (https://github.com/vishnubob/wait-for-it/blob/master/wait-for-it.sh), but the result was the same, my node backend tries to make a mysql connection, but the mysql container is not ready.
This is my docker-compose.yml
version: "3"
services:
mysql:
image: my_mysql
build: ./db
restart: always
container_name: my_mysql
volumes:
- /var/lib/mysql
- ./db:/db
ports:
- "3307:3306"
environment:
- MYSQL_ROOT_PASSWORD=x
- MYSQL_USER=x
- MYSQL_PASSWORD=x
- MYSQL_DATABASE=x
networks:
- my_network
command: --default-authentication-plugin=mysql_native_password
api:
container_name: my_api
build: ./api
restart: always
ports:
- "9000:9000"
environment:
DB_HOSTNAME: mysql
working_dir: /api
volumes:
- ./api:/api
depends_on:
- mysql
networks:
- my_network
client:
container_name: my_client
image: mhart/alpine-node:12
build: ./client
restart: always
ports:
- "3000:3000"
working_dir: /client
volumes:
- ./client:/client
entrypoint: ["npm", "start"]
depends_on:
- api
networks:
- my_network
networks:
my_network:
driver: bridge
Dockerfile for my nodejs backend:
FROM mhart/alpine-node:12
WORKDIR /api
COPY package*.json /api/
RUN npm i -G nodemon
RUN npm install
COPY . /api/
EXPOSE 9000
CMD ["npm", "run", "dev"]
Dockerfile for my react front:
FROM mhart/alpine-node:12
WORKDIR /client
COPY package*.json /client/
RUN npm install
COPY . /client/
EXPOSE 3000
CMD ["npm", "start"]
and Dockerfile for mysql:
FROM mysql:8.0.19
Calling mysql connection in nodejs:
const config = require('config');
const express = require('express');
const router = express.Router();
const mysql = require('mysql');
const connection = mysql.createConnection({
host : config.get('mysql.config.host'),
user : config.get('mysql.config.user'),
password : config.get('mysql.config.password'),
database : config.get('mysql.config.database'),
port : config.get('mysql.config.port')
});
connection.connect(function(err) {
if (err) {
console.error('error connecting: ' + err.stack);
return;
}
console.log('connected as id ' + connection.threadId);
});
router.get("/", function(req, res, next) {
connection.query('SELECT 1 + 1 AS solution', function (error, results, fields) {
if (error) {
throw error;
}
res.send(`MySQL OK: ${results[0].solution}`);
});
});
module.exports = router;
Thanks for any help.

Answer 1

I could not test it, but the docker recommendation is to create a script to wait until the other container accepts connections.
Alternatively, write your own wrapper script to perform a more application-specific health check. For example, you might want to wait until Postgres is definitely ready to accept commands:
#!/bin/sh
# wait-for-postgres.sh
set -e
host="$1"
shift
cmd="$#"
until PGPASSWORD=$POSTGRES_PASSWORD psql -h "$host" -U "postgres" -c '\q'; do
>&2 echo "Postgres is unavailable - sleeping"
sleep 1
done
>&2 echo "Postgres is up - executing command"
exec $cmd
You could check the documentation here:
Control startup and shutdown order in Compose
Hope this helps.