title: docker-compose mysql container denies access to wordpress container
body: <p>I have a problem with mysql 5.7 container denying access to wordpress container. I'm using docker-compose and I'm running docker on Mac OSX. Docker should be on latest version available.</p>
  
  <p>Here's my docker-compose.yml</p>
  
  <pre><code>version: '2'
  
  services:
    wordpress:
      depends_on:
        - db
      image: wordpress:latest
      container_name: wordpress
      ports:
        - "8000:80"
        - "443:443"
      restart: always
      environment:
        WORDPRESS_DB_HOST: db:3306
        WORDPRESS_DB_NAME: blog
        WORDPRESS_DB_USER: blog_admin
        WORDPRESS_DB_PASSWORD: userpasswd
      networks:
        - wordpress_net
    db:
      image: mysql:5.7
      container_name: db
      ports:
        - "3306:3306"
      volumes:
        - db_data:/var/lib/mysql
      restart: always
      environment:
        MYSQL_ROOT_PASSWORD: rootpasswd
        MYSQL_DATABASE: blog
        MYSQL_USER: blog_admin
        MYSQL_PASSWORD: userpasswd
      networks:
        - wordpress_net
  networks:
    wordpress_net:
  volumes:
    db_data:
  </code></pre>
  
  <p>Logs from db container are: </p>
  
  <pre><code>2017-05-12T23:28:06.138429Z 321 [Note] Access denied for user 'blog_admin'@'172.19.0.3' (using password: YES)
  </code></pre>
  
  <p>Logs from wordpress container are:</p>
  
  <pre><code>MySQL Connection Error: (1045) Access denied for user 'blog_admin'@'172.19.0.3' (using password: YES)
  Warning: mysqli::mysqli(): (HY000/1045): Access denied for user 'blog_admin'@'172.19.0.3' (using password: YES) in - on line 22
  </code></pre>
  
  <p>docker ps:</p>
  
  <pre><code>CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                                        NAMES
  1b02f0146fe7        wordpress:latest    "docker-entrypoint..."   25 minutes ago      Up 26 seconds       0.0.0.0:443-&gt;443/tcp, 0.0.0.0:8000-&gt;80/tcp   wordpress
  5d932ed6c269        mysql:5.7           "docker-entrypoint..."   25 minutes ago      Up 25 minutes       0.0.0.0:3306-&gt;3306/tcp                       db
  </code></pre>
  
  <p>What have I tried:</p>
  
  <ol>
  <li>Restarting docker host.</li>
  <li>docker-compose rm -v and then docker-compose up -d again.</li>
  <li>Logging in with those user credentials and root credentials outside of wordpress container.</li>
  <li>Removing docker images and pulling them again from scratch.</li>
  <li>Using root credentials in  <code>WORDPRESS_DB_HOST, WORDPRESS_DB_USER</code></li>
  </ol>
  
  <p>I can see all the env vars for db when I connect to db container. Wordpress container keeps restarting it self. I saw one answer on stack overflow which recommended flushing privileges and setting new user account but I want to know if I'm doing something wrong that could cause this problem to appear again on other machine.</p>