Leonardo Borges

It’s funny how every Rails application I - and possibly you - work on ends up needing some sort of per-environment global constants.

Examples may include the application url - It might be used in account activation emails and thus should be different between the development and production environments.

Or perhaps your application depends on external services that, depending on the environment, are available in different URIs.

There are a couple solutions out there but my needs were simple and straightforward, thus I developed a small rails plugin that is the simplest thing that could possibly work: AppConstants.

It’s been useful for my current project and I hope it can be useful to someone else too

In one of my Rails projects I’m using Sphinx to provide full-text search capabilities. To integrate both worlds I chose Thinking Sphinx, which is just great and so far has met all of my expectations.

Also, as I previously mentioned, I’m using RVM to manage my ruby installations on both my development and production machines and this setup is what motivated this post.

I use Monit to monitor the services running on my production server - nginx, mysql, php - and as of the first deploy of this application, it only made sense to also monitor Sphinx.

In order to create an initialization script, I would need at least a way to start and stop sphinx from the command line, which, using Thinking Sphinx, can be done using these rake tasks:

$ rake thinking_sphinx:stop
$ rake thinking_sphinx:start

It’s worth mentioning now that I don’t run sphinx as root. I run it with the same user my rails application uses. For the purpose of this post, let’s call it deploy.

When I tried using my script I got errors such as these:

Missing the Rails 2.3.5 gem. Please `gem install -v=2.3.5 rails`, update your RAILS_GEM_VERSION setting in config/environment.rb for the Rails version you do have installed, or comment out RAILS_GEM_VERSION to use the latest version installed.

After some digging around I found that the GEM_HOME environment variable for my deploy user wasn’t being set correctly - something to do with rvm, but not quite sure - and to fix this, well, I just had to set it, leaving the final working version of my script somewhat like this - simplified :

#! /bin/sh
 
### BEGIN INIT INFO
### END INIT INFO
 
set_path="cd /your/rails/app/root; export GEM_HOME=/path/to/your/gems; RAILS_ENV=production;"
 
case "$1" in
  start)
        echo -n "Starting sphinx: "
                su - deploy -c "$set_path rake ts:start" >> /var/log/sphinx.log 2>&1
        echo "done."
        ;;
  stop)
        echo -n "Stopping sphinx: "
                su - deploy -c "$set_path rake ts:stop" >> /var/log/sphinx.log 2>&1
        echo "done."
        ;;
      *)
            N=/etc/init.d/sphinx
            echo "Usage: $N {start|stop}" >&2
            exit 1
            ;;
    esac
 
    exit 0

There are 2 things happening here. First, regardless of the user I’m running this init script as, I drop privileges in order to execute the rake task with my deploy user. Second, I set the GEM_HOME environment variable to stop getting the ‘gem not found’ errors.

After that, monit was able not only to monitor my sphinx instance, but also (re)start/stop it with the correct user.

I’m no Linux wizard so if you wanna suggest improvements to this script, feel free to do so!

Today I read a nice post - in Portuguese - by Fábio Akita on how to manage multiple ruby versions on your machine. I’ve tried it once with some tool I can’t even remember the name but failed miserably.

But this time things look very different. The tool here is the rvm - short for Ruby Version manager - and it works just great.

Let’s cut to the chase and imagine that you, like me, want to run/develop/test your code on both ruby 1.8.7 and ruby 1.9.1. These steps would get you up and running in a few minutes:

Install rvm:

$ gem sources -a http://gemcutter.org/
$ gem install rvm
$ rvm-install
$ echo "if [[ ! -z $HOME/.rvm ]] ; then source $HOME/.rvm ; fi" >> ~/.bash_profile
$ source ~/.rvm/scripts/rvm

Install the ruby interpreters you want to use:

$ rvm  install ruby-1.8.7-p160
$ rvm  install ruby-1.9.1

Now it’s important to notice that at this point you have separate gem installations for each of the interpreters you’ve installed in the previous step. That said, just go ahead and switch between your interpreters and use your command line scripts - ruby, gem, etc… - as usual.

Switching between interpreters:

$ rvm ruby-1.8.7-p160  #switch to the specified version 
$ ruby -v
ruby 1.8.7 (2009-04-08 patchlevel 160) [i686-darwin9.8.0]
$ gem install rails  #note I'm not using sudo since the new gem paths point to the user's home directory 
 
$ rvm ruby-1.9.1  #switch to the specified version 
$ ruby -v
ruby 1.9.1p376 (2009-12-07 revision 26041) [i386-darwin9.8.0]
$ gem install rails  #note I'm not using sudo since the new gem paths point to the user's home directory

And that’s it, just go on and install rails, merb, sinatra or whatever rocks your boat!
rvm will work with MRI/YARV, JRuby, Ruby EE and Rubinius. Enjoy and don’t forget to check rvm’s website for the complete documentation!