Simple Wordpress cluster backed by MySQL and a Redis object cache, all behind HAProxy

docker-composer.yml

# Main container hosting Wordpress
#
# Can be scaled with `docker-compose scale web=n`
# to spawn `n` Wordpress nodes. A restart
# (`docker-compose restart`) may be required for
# scaled nodes to be added to the HAProxy
# node's configuration.
web:
  build: .
  command: php -S 0.0.0.0:8000 -t /code
  expose:
    - 8000
  links:
    - db
    - redis
  volumes:
    - .:/code

# HAProxy container
haproxy:
  image: tutum/haproxy
  ports:
    - "8000:80"
    - "443:443"
  links:
    - web
  environment:
    BACKEND_PORT: 8000

# MySQL container
db:
  image: orchardup/mysql
  environment:
    MYSQL_DATABASE: wordpress

# Redis container
redis:
  image: redis

Dockerfile

# Basic setup to copy Wordpress files,
# expected to be at '.', into the image
FROM orchardup/php5
ADD . /code

router.php

<?php

// Allows Wordpress permalinks to work
// behind the built-in PHP HTTP server

$root = $_SERVER['DOCUMENT_ROOT'];
chdir($root);
$path = '/'.ltrim(parse_url($_SERVER['REQUEST_URI'])['path'],'/');
set_include_path(get_include_path().':'.__DIR__);
if(file_exists($root.$path))
{
    if(is_dir($root.$path) && substr($path,strlen($path) - 1, 1) !== '/')
        $path = rtrim($path,'/').'/index.php';
    if(strpos($path,'.php') === false) return false;
    else {
        chdir(dirname($root.$path));
        require_once $root.$path;
    }
}else include_once 'index.php';

wp-config.php

<?php

// MariaDB settings
define('DB_NAME', 'wordpress');
define('DB_USER', 'root');
define('DB_PASSWORD', '');
define('DB_HOST', "db:3306");
define('DB_CHARSET', 'utf8');
define('DB_COLLATE', '');
$table_prefix  = 'wp_';

// Redis settings
// only need to override the default host
//
// Works with https://wordpress.org/plugins/redis-cache/,
// not sure about others/
define('WP_REDIS_HOST', 'redis');

// Use your keys/salts
define('AUTH_KEY',         '...');
define('SECURE_AUTH_KEY',  '...');
define('LOGGED_IN_KEY',    '...');
define('NONCE_KEY',        '...');
define('AUTH_SALT',        '...');
define('SECURE_AUTH_SALT', '...');
define('LOGGED_IN_SALT',   '...');
define('NONCE_SALT',       '...');

define('WP_DEBUG', false);

if ( !defined('ABSPATH') )
    define('ABSPATH', dirname(__FILE__) . '/');

require_once(ABSPATH . 'wp-settings.php');