SLP: Ruby on Rails: Deployment

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Introduction

This page is for how to deploy your Ruby on Rails apps on an Ubuntu server – specifically, Ubuntu 16.04. This is not needed for your local development, as you can run rails server to test it out locally, or test it out on the course server provided. However, if you do want to get it running through Apache, read on…

These instructions are as of August 2017; you can see an older version of this document online.

This assumes we are running on Ubuntu 16.04, and want to install Ruby 2.4 (2.4.1 is the latest as of this writing) and Rails 5.1 (5.1.3 is the latest as of this writing).

Quick Start

Configuring Apache

  1. Check /etc/apache2/mods-available/passenger.conf. The PassengerDefaultRuby line should be using /usr/bin/ruby, which means (assuming the previous section was completed successfully) that Passenger is using the correct version of Ruby.
  2. Edit your /etc/apache2/sites-available/000-default.conf file, and add the following lines. Here, /home/rails/myapp is where the Rails app is installed on the local file system, and /rails/railstest is the URL for the Rails app (specifically, it will be at http://server/rails/railstest). In this example, all the rails apps are kept in a rails/ directory (and that directory was in the HTML document root, which is likely /var/www/html/), but that need not be the case. The lines to add to 000-default.conf:
RailsEnv development
RailsBaseURI /rails/railstest
<Directory /home/rails/myapp>
  Options -MultiViews
</Directory>
  1. In the HTML document root (likely /var/www/html), make that rails sub-directory. In that directory, run ln -s /home/rails/myapp/public railstest, where /home/rails/myapp and railstest are the values from step 5, above.
  2. Reload apache: sudo service apache2 reload
  3. View the app at http://localhost/rails/railstest. It should show the image displayed at the bottom of the Ruby on Rails getting started (md) page.

Users installing gems

The easist way is to have the users run bundle install --path vendor/bundle instead of bundle install. This will install the gems into their rails app directory (specifically, myapp/vendor/bundle/ruby/2.4.0/gems/). Passenger will look there for the gems, in addition to the system directory (which is /var/lib/gems/2.4.0/gems). Having them install the gems locally will take up more disk space (maybe 50-100 Mb per user), but will be far easier, as the students can manage their own gems without sudo privledges.

Allowing users to reload apache

Reloading apache needs to be run as root. We will allow all users of a given group to execute these functions; we’ll call the group ‘rails’.

Compile this file, and call it reload-apache2:

#include <stdlib.h>
int main() {
  system("service apache2 reload");
  return 0;
}

Take that binaries (reload-apache2), and move it to /usr/local/bin/. The run chown root:rails reload-apache2 and chown 4750 reload-apache2. These commands mean that anybody who runs that binary (which, in this case, can only be done by somebody in the rails group) will execute those commands AS ROOT.

You can add a user to a group via usermod -a -G rails user, but that user will have to completely log out and log back in for that change to take effect.

Deploying multiple Rails apps on one server

Some of these steps were done in the Passenger configuration section, above.

  1. In the HTML document root (which is specified in /etc/apache2/sites-enabled/000-default.conf), create a rails/ directory (this was the same as discussed in steps 5 and 6 in the Configure Passenger section, above).
  2. In that directory, make symlinks to the public folders of each of the apps you want to have on the server: ln -s ~userid/myapp/public user
  3. Edit /etc/apache2/sites-available/000-default.conf
    • Add all of this right above the very last </VirtualHost> line
    • Add the line: RailsEnv development
    • For each rails app to deploy, add the following lines:
    RailsBaseURI /rails/user
<Directory /home/user/myapp>
  Options -MultiViews
</Directory>
    • Here, /rails/user is the symlink (from the apache2 document root done in step 2, above – which means the full path to that symlink is likely something like /var/www/html/rails/user), and /home/user/myapp is where the app itself is stored
    • Alternatively, you can put all of those 4-line stanzas in a separate file, such as /etc/apache2/rails.conf, and then put in the following two lines into /etc/apache2/sites-available/000-default.conf (and, presumably, /etc/apache2/sites-available/default-ssl.conf):
    RailsEnv development
Include rails.conf
  4. Reload the web server (service apache2 reload)
  5. At this point, you should be able to view your app at http://server/rails/user (and possibly the https version of the URL, if that was configured).
  6. If you swtich from development to production in step 3, the app claims it cannot find the file; see the troubleshooting section, below, for details.

Troubleshooting

Generic error with no known cause

Rails apps have a log/ directory (such as /home/rails/myapp/log), and therein provide a lot of detail about what is going wrong.

/usr/lib/ruby/include/ruby.h not found

This should have been solved by installing the ruby2.4-dev package; if not, see the older version of this document.

“The page you were looking for doesn’t exist”

This problem seems to occur when running the Rails apps in production mode. For the reason why (and clues how to fix it), see the answer here