Deploying Rails (2.0) to Mongrel with Capistrano 2.1
Tags: capistrano,
mongrel,
ruby on rails
Posted 26. October 2007.
Capistrano 2.1 includes some major improvements over the 1.x branch, so everyone should start using it right away. Yet it doesn't work with Mongrel out of the box and it's most likely not backwards compatible with your old deploy recipes. Since there is no official documentation on how to get going with Rails and Mongrel, I put together these instructions.
What follows is a compilation of tips and hacks from mailing lists and different places on the internet that should help you get your Rails app deployed with Capistrano 2.1 in no time.
I have only tested this with Edge Rails (RC1), but it should work the same with your stable Rails 1.2.5 projects.
I assume that you have already setup up Apache and a Mongrel cluster on your web server, as it is described in many places on the net and that you are using Subversion to manage your code base.
First, if you haven't already done so, install or update Capistrano:
Also make sure you have installed the latest version of mongrel_cluster on both your production and deployment machine:
I advise you to have a quick look at the "Getting started with Rails" section on the Capify website, at least the two paragraphs entitled "Enabling Capistrano" and "Project Details". They tell you how to capify your app and show you how your basic config/deploy.rb could look like (It doesn't work yet, though). The rests of the page was not so helpful to me and provides little detail for our specific task, you may safely skip it for now.
First you need to create a spinner script that will start your mongrel servers the first time you deploy. Create a file in you Rails project named "script/spin" and add the following line, replacing "/path" with the real path to your Rails app on the production server:
/usr/bin/mongrel_rails cluster::start -C /path/current/config/mongrel_cluster.yml
You now have to make the spin script executable on the web server to avoid error messages like "script/spin: Permission denied". This is done easiest with subversion. Issue the following command in you working copy:
In your config/deploy.rb, tell Capistrano where to find your mongrel config, assuming deploy_to is set the path of your app on the server:
When I did the cold deploy, I got the following error. Turns out, probably some 37 signals employee forgot to remove private configuration from the code:
command "sudo -p 'sudo password: ' -u app sh -c 'cd /path/to/my/rails/app/current && nohup script/spin'" failed on domain.com
This should be fixed eventually. For now, add the following line to your config/deploy.rb:
Also, the restart task doesn't get executed from mongrel_cluster recipes but instead tries to spawn a FastCGI process when deploying, add this line to your config/deploy.rb to bring things back on track:
task :restart do
restart_mongrel_cluster
end
end
Your complete deploy.rb could now look like this:
set :application, "myapp"
set :repository, "http://my.svnserver.com/svn/myapp"
set :deploy_to, "/path/to/my/rails/#{application}"
set :user, "root"
# Thew new way of telling capistrano 2.1 to use export rather than checkout
set :deploy_via, :export
set :runner, nil
set :mongrel_conf, "#{deploy_to}/current/config/mongrel_cluster.yml"
role :app, "domain.com"
role :web, "domain.com"
role :db, "rdomain.com", :primary => true
namespace :deploy do
task :restart do
restart_mongrel_cluster
end
end
I haven't yet figured out how to use sudo in cap 2.1, so I deploy using root. You could also set :user to an unprivileged user that has write access to your apps releases directory. Don't forget to manually svn checkout on the production machine with the user specified here before you deploy the first time, or else the deploy will fail.
For completeness, here's a sample mongrel_cluster.yml:
cwd: /path/to/my/rails/app/current
log_file: log/mongrel.log
port: "7000"
environment: production
address: 127.0.0.1
pid_file: tmp/pids/mongrel.pid
servers: 2
To ged rid of the deprecation warning when deploying I followed the instructions found in comment #18 on Jamis Buck's weblog. Find the mongrel_cluster recipes file on your system..
$ find / -name recipes.rb
.. and comment out the first line, replacing it with two new lines, so the beginning of the file looks like this:
configuration.load do
# Capistrano.configuration(:must_exist).load do
Hopefully this will be fixed in the mongrel_cluster gem soon, but until then this quick hack will do.
Now you are ready to go. Setup your basic directory structure, fire up mongrel, and start deplyoing..
$ cap deploy:cold
The Cap task names have changed a little, but you can always see the whole list like this:
I tested many common tasks such as deploy, deploy:migrate, deploy:disable:web and restart. All of these should now work with the configuration above. I hope I haven't forgotten anything. If you still get errors when setting things up, please drop a comment and I will try to help you out.
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