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Available containers

It is best to use the hostnames and not to rely on the ip addresses as they might change. In most cases however you can even use 127.0.0.1 or localhost (See background section below).

E.g.: When you want to setup a MySQL database connection use mysql or 127.0.0.1 as the hostname.

Container	Container name	Hostname	IP Address
PHP / HHVM	php	php	172.16.238.10
Apache / Nginx	http	http	172.16.238.11
MySQL / MariaDB	mysql	mysql	172.16.238.12
PostgreSQL	pgsql	pgsql	172.16.238.13
Redis	redis	redis	172.16.238.14
Memcahed	memcached	memcached	172.16.238.15

Background

Background - PHP Container

The php container is the center of all container. Everything happens in there. This is also the reason it does some more magic than actually required.

Remote ports and remote sockets are made available to the php container.

The PHP container is using socat to

forward the remote mysql port 3306 (on the mysql container) to its own 127.0.0.1:3306
forward the remote pgsql port 5432 (on the mysql container) to its own 127.0.0.1:5432
forward the remote redis port 6379 (on the mysql container) to its own 127.0.0.1:6379

The PHP container is using volumes to

mount the remote mysql.sock to its own filesystem into a path configured in its php.ini

Background - Docker Host

The docker host (your computer) does exactly the same as the php container.

container mysql port 3306 is exposed to the host on port 127.0.0.1:3306
container pgsql port 5432 is exposed to the host on port 127.0.0.1:5432
container redis port 6379 is exposed to the host on port 127.0.0.1:6379

Also the database sockets from the container are mounted into the host.

Background - Benefit of the above

With the PHP container and the docker host (your computer) behaving the same it is possible to write your php applications like this:

<?php
mysql_connect('127.0.0.1', 'user', 'pass');
// or using sockets
mysql_connect('localhost', 'user', 'pass');

This setup can then either be served by the docker or by your host computer (if you shutdown docker and start your local lamp stack)

Background - Implications

Messing around with socket mounts has caused some problems in the past and it might be subject of change. In order to stay compatible it is your best choice to use 127.0.0.1 instead of localhost.

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