Dockerizing Pligg with Fig

by Álex 2014-11-24 devops docker pligg fig

For a pet project I needed Pligg which is kinda a social network site in the style of the old-digg (with karma and this kind of things).

Installing a LAMP system is kinda boring stuff, so, for that and for the sake of learning I decided to go with Docker & Fig. Sadly or luckily, every time that I dockerize something I find a lot of unexpected problems that slow me down, but… you always learn something!

This post is to explain a little bit the process and the problems that I found and how I solved them. It’s not a how to, it’s more a explanation of what I did and perhaps you can provide a better solution on the comments.

What do I need?

The site is “simple” so the only required stuff will be a MySQL server and an Apache2 server. You could run 2 Docker instances manually, or… use the magic provided by Fig. This is the fig.yml file that explains my service:

web:
  build: .
  links:
   - db
  volumes:
   - /var/log:/var/www/logs
  ports:
   - "80:80"
  environment:
   - MYSQL_PASSWORD
   - MY_BASE_URL
db:
  image: mysql
  volumes:
   - /var/lib/mysql:/var/lib/mysql
  environment:
   - MYSQL_DATABASE=dbpligg
   - MYSQL_USER=pligguser
   - MYSQL_ROOT_PASSWORD
   - MYSQL_PASSWORD
  ports:
   - "3306:3306"

Basically I am saying that I will have 2 servers: “web” & “db” and specifying their volumes, environment variables and exported ports.

Problem?

First thing that we see here: MY_BASE_URL & MYSQL_{,ROOT_}PASSWORD don’t have any value, this is because Fig is going to got those values from the current Docker host. I need them for specified some settings file that originally were written in a normal file (difficult to change while deploying).

Also, MY_BASE_URL is a small/ugly trick. It seems that Pligg requires to know the host were it’s running to serve static assets as CSS or JS.

If you take a look to my repo config folder you will see the slightly modified versions of two configuration files for Pligg that are making use of this environment variables.

More problems?

For running Pligg we need a minimal DB structure I’ve found 2 different ways of creating this data in my data container, but none of them are optimal for me, mainly because they require an extra step:

I think that perhaps creating a script that checks is the DB if empty and if it is it uses the SQL to dump the DB back would be an option, but seems kinda dangerous to automate that process in a live environment (anybody said delete data by a mistaken dump?).

@eloycoto has recommended me to use inheritance of containers. But I am not happy with that solution either: I would need two Dockerfiles and possibly two fig.yml files as well or add some weird magic to replace one container with the other after the installation.

Third thing that I don’t really like

After the first time that you run the installation you need to manually remove the install path (this seems quite common in PHP apps?). I am doing that running a docker exec to that container, but I would prefer to manually remove it with the Dockerfile. Why I don’t do so? Because if I remove that folder I am forcing all the users of my configuration to use the dump SQL method explained above and I don’t give them any change.

So…

I suspect that it’s normal to have that kind of problems trying to “migrate” an application that was never used before in a Docker container.

To be honest with Pligg, the only changes that I required were minimal, but I don’t know if that “install” part could be just removed with my own settings file, I tried that and it was asking me to repeat values that were already set in the settings.php.

I am not happy with the dump/install solution that I’ve found, but it works™!

I am sure that if you were using Docker or Fig before you will have plenty of complaints about my article, let me know leaving a comment or just tweet me something.


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