Docker MySQL container unable to wait for MySQL server ready

Question

I am attempting to create a docker container using the mysql:5 docker image. Once the MySQL server is up and running I want to create some databases, users and tables.

My Dockerfile looks like this;

FROM mysql:5

# Add db.data with correct permissions
RUN mkdir /server_data
WORKDIR /server_data
ADD --chown="root:root" ./db.data .

# Copy setup directory
COPY ./setup setup
COPY ./config /etc/mysql/conf.d

CMD ["./setup/setup.sh", "mysql", "-u", "root", "<", "./setup/schema.sql"]

My ./setup/setup.sh script looks like this;

#!/bin/bash
# wait-for-mysql.sh

set -e

shift
cmd="$@"

until mysql -uroot -c '\q'; do
  >&2 echo "mysql is unavailable - sleeping"
  sleep 1
done

>&2 echo "mysql is up - executing command"
exec $cmd

My docker-compose.yml looks like this;

version: "3"

services:
  db:
    build: ./db

    volumes:
      - data-db:/var/lib/mysql

    environment:
      - MYSQL_ROOT_PASSWORD=password

    restart: always

    container_name: db

volumes:
  data-db:

When I run 'docker-compose up --build' I get the following output;

Building db
Step 1/7 : FROM mysql:5
---> 0d16d0a97dd1
Step 2/7 : RUN mkdir /server_data
---> Using cache
---> 087b5ded3a53
Step 3/7 : WORKDIR /server_data
---> Using cache
---> 5a32ea1b0a49
Step 4/7 : ADD --chown="root:root" ./db.data .
---> Using cache
---> 5d453c52a9f1
Step 5/7 : COPY ./setup setup
---> 9c5359818748
Step 6/7 : COPY ./config /etc/mysql/conf.d
---> b663a380813f
Step 7/7 : CMD ["./setup/setup.sh", "mysql", "-u", "root", "<", "./setup/schema.sql"]
---> Running in 4535b2620141
Removing intermediate container 4535b2620141
---> 2d2fb7e308ad
Successfully built 2d2fb7e308ad
Successfully tagged wasdbsandbox_db:latest
Recreating db ... done
Attaching to db
db | ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) db | mysql is unavailable - sleeping
db | ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) db | mysql is unavailable - sleeping

This goes on interminably until I press Ctrl + c.

If I comment out the CMD line in my Dockerfile the output from running 'docker-compose up --build' is the output of the ENTRYPOINT command that is defined in the official mysql Dockerfile.

Why is mysql never starting when I use my own CMD command?

Bret Fisher · Accepted Answer · 2018-06-01 01:33:06Z

2

This is supported already by the official mysql image. No need to make your own custom solution.

Look at the Docker Hub README under "Initializing a fresh instance".

You can see in the official image under the 5.7 Dockerfile (for example) that it copies in a ENTRYPOINT script. That script doesn't run at build time, but at run-time right before the CMD starts the daemon.

In that existing ENTRYPOINT script you'll see that it will process any files you put in /docker-entrypoint-initdb.d/

So in short, when you start a new container from that existing official image it will:

start the mysqld in local-only mode
creates default user, db, pw, etc.
runs any scripts you put in /docker-entrypoint-initdb.d/
stops the mysqld and hands off to the Dockerfile CMD
CMD will run the mysqld to listen on the network

answered Jun 1, 2018 at 1:33

Bret Fisher

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