synatic|blog by Benedikt Deicke

Yesterday I decided to give Phusion Passenger aka mod_rails a try and installed it. It was dead simple to set it up and to deploy rails applications with it. I’m now using it for several “small” applications, for which the whole overhead of setting up a cluster of mongrels and a proxy doesn’t seem to be adequate. I’ll give you a short summary on how to install mod_rails for apache2 on Debian Etch.

First, install the passenger gem using RubyGems (if you don’t have Ruby and RubyGems running on your server, install them first – of course):

   1  gem install passenger

Afterwards, run the passenger apache2 module installer using this command:

   1  passenger-install-apache2-module

It’ll check for the required software to install the module, compile it and copy it to the correct folders. If some software is missing install it using aptitude (ie. aptitude install g++ if you’re missing the GNU C++ Compiler).

Next, create two new files in the /etc/apache2/mods-available directory. One called mod_rails.load:

   1  LoadModule passenger_module /usr/lib/ruby/gems/1.8/gems/passenger-2.0.2/ext/apache2/mod_passenger.so

... and the other one called mod_rails.conf:

   1  PassengerRoot /usr/lib/ruby/gems/1.8/gems/passenger-2.0.2
   2  PassengerRuby /usr/bin/ruby1.8

Now you can enable the module using a2enmod and restart apache.

   1  a2enmod mod_rails
   2  apache2ctl restart

That’s it! Now simply deploy your rails application, just make sure apache’s document root is pointing to your applications public folder. Passenger will automatically detect your rails application and start up processes as needed. You can check it’s status and stats using the passenger-status and passenger-memory-stats commands. For more details on mod_rails, take a look at it’s documentation.

Andreas Wolff recently released RSpactor, a (up to now) command line tool similar to autotest. Nevertheless it differs from autotest in two points. First it’s focused on RSpec and secondly it’s using Mac OS’ FSEvents to monitor file changes. According to this it only runs on Mac OS. To get it running on Linux you’ll have to change RSpactor’s Listener class to use Linux’ equivalent to FSEvents called inotify. Luckily there’s a gem called RInotify which introduces a simple class to access the inotify events within ruby. I rewrote the Listeners class yesterday to get it running on my Linux notebook:

   1  # inotify_listener.rb
   2  
   3  class Listener
   4  
   5    def initialize(&block)
   6      require 'rinotify'
   7      begin
   8        @spec_run_time = Time.now
   9        @watching      = {}
  10  
  11        notify = RInotify.new
  12        Dir.glob(File.join(Dir.pwd, '**')).each do |dir|
  13          watch_desc = notify.add_watch(dir, RInotify::MODIFY | RInotify::CREATE | RInotify::DELETE)
  14          @watching[watch_desc] = dir
  15        end
  16  
  17        while true do
  18          changed_files = []
  19          notify.each_event do |event|
  20            changed_files << build_path_from_event(event)
  21          end
  22          changed_files.uniq!
  23          unless changed_files.empty?
  24            @spec_run_time = Time.now
  25            yield changed_files
  26          end
  27          sleep(5)
  28        end
  29      rescue Interrupt
  30        @watching.each_key { |key| notify.rm_watch(key) }
  31      end
  32    end
  33  
  34    def build_path_from_event(event)
  35      File.join(@watching[event.watch_descriptor], event.name || '')
  36    end
  37  
  38  end

To get it running you simply have to install the RInotify gem and change one line in bin/rspactor:

   1  # from
   2  require File.join(File.dirname(__FILE__), '..', 'lib', 'listener')
   3  # to
   4  require File.join(File.dirname(__FILE__), '..', 'lib', 'inotify_listener')

That’s it! RSpactor should be running on Linux now and consuming much less CPU than autotest.

(You might also want to change the system()-call in lib/resulting.rb as it’s currently using growl to notify you about the test results.)

Typing SSH passwords again and again can be a real pain. For example: Lately I started to use Capistrano to deploy my rails applications. If I want to set up the maintenance-page on the server I’ll type cap deploy:web:disable which of course prompts me for the SSH password. Then I want to deploy my application with cap deploy and again will be prompted for the password. Finally I have to cap deploy:web:enable to remove the maintenance page which – as mindful readers might have guessed already – prompts for the password. This was just one reason for me to set up SSH authentication keys. At first I was a little worried that setting it up might be a bit complicated. Luckily I was disabused. If you want to switch to key based authentication too follow these simple steps:

Key generation

The first thing you need is – of course – a pair of keys: your private key and the associated public key. To generate both fire up our favorite shell (for me it’s bash) and type:

   1  ssh-keygen

This will generate both keys and ask you where to store it. Usually the default would be something like ~/.ssh/id_rsa. Simply accept the default by pressing return. Next you’ll have to enter a password for your key and confirm it. Afterwards you’ve to tell the server to accept your key on authentication. Do so by uploading the public key to the server.

   1  scp ~/.ssh/id_rsa yourserver.com:~/.ssh/authenticated_keys2

If you want to add multiple keys, be sure to append it to the authenticated_keys2 file and don’t overwrite it.

First login

That’s all you have to do to switch to key based SSH authentication. Try to log in as usual by typing:

   1  ssh yourserver.com

This will prompt you for your key’s password and log you in to your server afterwards. “But wait! I’m still having to type my password every time I want to log in!” you shout, and you’re right – up to now. What you need to do is running ssh-agent, adding your key and typing your password. ssh-agent will then ask for the password and store it until you shut it down. You’ll have to do this everytime you open up a new shell or put the commands into your i.e. ~/.bash_profile. Quite comfortable but we can do better.

Keychain

There is a nice little tool called keychain that will smooth the process a little for you. It’s originally developed by the Gentoo people but it’s available on other linux distributions, too. Simply install it by typing your system’s equivalent to

   1  # Gentoo
   2  emerge keychain
   3  # Debian
   4  aptitude install keychain

and it’ll be available in no time. To set it up you need to put these two lines in our ~/.bash_profile:

   1  keychain ~/.ssh/id_rsa
   2  source ~/.keychain/$HOSTNAME-sh

That’s it. The first time you open up a shell keychain will start ssh-agent, prompt you for your keys password and remember the running ssh-agent for all new shells. On your next SSH authentication no more password typing is required. Wasn’t complicated at all, was it?

Note the fork! Recognizing someone?