Docker: "wait-for-it" script does not start the application when MySQL is ready

Question

I am using Docker-Compose and wait-for-it to start my backend with Node.js once the MySQL service is ready to receive connections. My problem is that the script does not realize the connection is ready by itself. I can make it work if I set the timeout to 20s since MySQL would be running by then, but that could change in different environments and the app would crash if it took more time for a specific environment. I want it to check it periodically since I think it is the right thing to do.

This is my docker-compose.yml:

version: "3.8"

services:

  app:
    image: pfmc
    ports:
      - 4005:4005
    working_dir: /usr/src/app
    command: sh -c './wait-for-it.sh -t 0 db:3306 -- npm start'
    environment: 
      MYSQL_ROOT_PASSWORD: pfmc123
      MYSQL_HOST: mysql
      MYSQL_USER: root
      MYSQL_PASSWORD: pfmc123
      MYSQL_DATABASE: pfmc

  mysql:
    image: mysql:5
    command: --default-authentication-plugin=mysql_native_password
    restart: always
    volumes:
      - ./db-startup:/docker-entrypoint-initdb.d
    environment:
      MYSQL_ROOT_PASSWORD: pfmc123
      MYSQL_DATABASE: pfmc

The logs:

app_1    | wait-for-it.sh: waiting for db:3306 without a timeout
mysql_1  | 2020-05-25 19:59:58+00:00 [Note] [Entrypoint]: Entrypoint script for MySQL Server 5.7.30-1debian10 started.
mysql_1  | 2020-05-25 19:59:58+00:00 [Note] [Entrypoint]: Switching to dedicated user 'mysql'
mysql_1  | 2020-05-25 19:59:58+00:00 [Note] [Entrypoint]: Entrypoint script for MySQL Server 5.7.30-1debian10 started.
mysql_1  | 2020-05-25 19:59:58+00:00 [Note] [Entrypoint]: Initializing database files

and it stays at this point:

mysql_1  | 2020-05-25T20:00:08.243448Z 0 [Note] mysqld: ready for connections.
mysql_1  | Version: '5.7.30'  socket: '/var/run/mysqld/mysqld.sock'  port: 3306  MySQL Community Server (GPL)

Thank you very much for your help.

@NiteshSharma the file is the one included in the repo link I posted. — Manuel Carballido
– Manuel Carballido, Commented May 25, 2020 at 20:37

β.εηοιτ.βε · Accepted Answer · 2020-05-25 20:44:41Z

1

You do have one issues in here: your MySQL container is a service named mysql not db you should either adapt the service to be named db or the wait-for-it invocation to poll on a connection to mysql:3306

All together, your docker-compose.yml should look like this – I added the fix with comment stating @fixme:

version: "3.8"

services:

  app:
    image: pfmc
    ports:
      - 4005:4005
    working_dir: /usr/src/app
    command: sh -c './wait-for-it.sh -t 0 db:3306 -- npm start'
    environment: 
      MYSQL_ROOT_PASSWORD: pfmc123
      # A first @fixme is here 
      MYSQL_HOST: db
      MYSQL_USER: root
      MYSQL_PASSWORD: pfmc123
      MYSQL_DATABASE: pfmc

  # And a second @fixme is here
  db: 
    image: mysql:5
    command: --default-authentication-plugin=mysql_native_password
    restart: always
    volumes:
      - ./db-startup:/docker-entrypoint-initdb.d
    environment:
      MYSQL_ROOT_PASSWORD: pfmc123
      MYSQL_DATABASE: pfmc

edited May 25, 2020 at 20:44

answered May 25, 2020 at 20:26

β.εηοιτ.βε

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1 Comment

Manuel Carballido Over a year ago

Fantastic! One thing though before accepting this answer. I had to change the value of MYSQL_HOST: from mysql to db to match the new container name. Now it works like a charm, thank you very much!

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