Maybe you’ve heard of Capistrano a tool written by Jamis Buck in Ruby that helps you automate deployment to multiple servers.

Capistrano & Deprec

This ‘gem’ of a gem is huge time saver. Believe me, anyone who has used it has surely reaped the benefits of

$ cap --apply-to .
$ cap setup
$ cap deploy
$ cap rollback
$ cap update_current
$ cap watch_load
$ cap uptime
$ cap disable/enable_web
$ cap some_long_complex_task_that_would_normally_take_more_than_a_couple_of_hours_if_done_manually

etc....

This beauty is such a versatile beast (pun intended) that you can easily automate tasks for a range of use cases (app deployment, system administration, backups, profiling, benchmarking etc etc)

And many people have gone ahead and extended capistrano to do their bidding with evermore complex tasks.

One such person is Mike Bailey who was obviously really pissed off at having to setup the same old software on every new VPS he was configuring for his clients. (Please note that this is pure speculation and the real reason may in fact be very different). In any case, he decided to remedy the situation and wrote the deprec gem.

What does deprec do?

It basically augments capistrano to allow you to do things like:

$ cap setup_ssh_keys   # copy out your public keys
$ cap install_rails_stack # install apache, ruby & rubygems, mongrel, rails on the hosts defined in your capistrano recipe etc.
$ deprec --apply-to . --name bailey --domain bailey.net.au
$ cap deprec_setup #setup your application to allow easy server setups
$ cap deploy_with_migrations #deploy your application
$ cap restart_mongrel_cluster #start app server
$ cap restart_apache #start web server

i.e with this gem you can very easily setup a brand new VPS with a full rails stack including the MySQL database and Apache 2 web server.

Customizing Deprec

When I first discovered deprec, I immediately realised that this was going to be saving me a lot of time when setting up our own clients VPS’, but I wasn’t really enamoured of the choices of web server or database. Furthermore I wanted to be able to select the right tools for the job. For one client I may use MySQL but for another I’d use postgres (Well actually I prefer using postgres always but maybe you’d like to do that :).

My current preference for a rails stack is the following very lightweight setup:

Nginx => Mongrel => Rails => Postgres

So as we had a couple of small new clients whose servers needed setting up I spent a couple of days and wrote my own extensions to deprec that added support for nginx (see this for details) and PostgreSQL. I also added a few other bits and pieces that allowed me to do things that I like to do with every new VPS I setup.

Exploring Capistrano Server Extensions

So first off we install the Capistrano Server Extensions gem (very lame name I know) via:

sudo gem install -y capserverext

That’ll bring down all required dependencies including capistrano and deprec if you don’t already have them.

So once capserverext has been installed your first action is to

$ cap show_tasks

Which will show you a bewildering list of possible tasks to perform.

From this list you can pick and choose, mix and match different tasks for every occasion.

But let’s run through what you’d need to do to get a rails stack setup with nginx and postgres (currently only on a Ubuntu server but I’m working on supporting debian and Gentoo).

First let’s ask capistrano to tell us what we should do to use this thing. Type:

$ cap capserverext_usage
 * executing task capserverext_usage
      * rails myproject
      * cd /path/to/myproject
      * deprec --apply-to . --name user --domain myprojectsdomain.com
      * Add following entries to deploy.rb:
          require 'capserverext/recipes'
          require 'capistrano/ext/monitor'

      * Edit deploy.rb appropriately:
        * set deprec_combination to either (:nginx_postgres, :nginx_mysql, :apache_mysql, :apache_postgres)
          for a combination other than the default: ':nginx_postgres'
        * set ssh_security_port for an ssh port other than the default 22 (Defaults to: '8888')
        * set mongrel options (best to accept the defaults)
        * set repository
        * any other custom options

      * run: "cap prepare_ssh" 
      * set ssh_options[:port] to the value of ssh_security_port in deploy.rb
      * run: "cap prepare_host" 

Using Capistrano Server Extensions

Thanks, that was handy. Now let me type the following:

On my local machine:

$ cd ~/dev/freelance
$ rails amicmuseuprecolombi.org   #A domain for one of my apps
$ cd amicsmuseuprecolombi.org
$ deprec --apply-to . --name saimon --domain amicsmuseuprecolombi.org

This’ll create a deploy.rb capistrano recipe for us in ./config/deploy.rb.

Quickly edit it to add:

  require 'capserverext/recipes'
  set :deprec_combination, :nginx_postgres
  set :repository, "http://www.webtypes.com/svn/projects/#{application}/trunk" 

  set :mongrel_servers, nginx_proxy_servers
  set :mongrel_port, nginx_proxy_port
  set :mongrel_address, nginx_proxy_address

Now type:

  $ cap prepare_ssh

And set the secure_ssh_port in deploy.rb to 8888 like so:

set ssh_options[:port], 8888

Now finally type:

  $ cap prepare_host

When that’s done type:

  $ cap deploy_with_migrations
  $ cap restart_mongrel_cluster
  $ cap restart_nginx

That takes about a total of 10 minutes from start to finish!

And visit http://amicsmuseuprecolombi.org (Our latest creation based on a globalized version of Mephisto) to see the result of having typed in those few commands. Well we also wrote the code for the site but you get the gist :)

Yep that’s all it takes to get a lean rails stack setup on your server .

Variations on the same theme

“I haven’t heard of nginx before. Can’t I use Apache?” someone says.

No problem. Set:

  set :deprec_combination, :apache_postgres

  $ cap prepare_host

“I prefer MySQL.” another says.

No problem. Set:

  set :deprec_combination, :nginx_mysql

  $ cap prepare_host

“No I meant with Apache.” they say again.

No problem. Set:

  set :deprec_combination, :apache_mysql

  $ cap prepare_host

Under the cover

Some of you will be asking what do these commands do exactly and I’ll point those of you to the very readable source code of the capserverext gem and the deprec gem. (Capistrano code is also very readable but you don’t need to go that far.)

So what will capserverext do remotely:

The prepare_ssh task will:

• Connect via root and set root’s password
• Change ssh port for security reasons
• Create a deployment user, add it to the ‘deploy’ group

The prepare_host task will:

• Connect with the deployment user and copy over your local machines public ssh keys.
• Reconnect without asking for passwords anymore (apart from the first time it uses sudo)
• Give the deployment user sudo privileges.
• enable the ubuntu ‘universe’ repository
• Install requisites allowing compilation of other packages, ruby, subversion, openssl
• Install the PostgreSQL database server (8.1)
• Install rubygems
• Install rails, mongrel, mongrel_cluster and builder
• Install nginx
• setup generic deployment paths
• setup app specific deployment paths
• Configure nginx for production
• Configure postgres for production (Creates a new database according to the name given for the production environment in database.yml, a database user and gives access privileges to that user)

That’s it. And you can do this again and again, over and over, on any number of hosts.

The beauty of this is that many tasks are composed of other smaller tasks so you can execute a specific task without having to run the whole lot.

Say you want to just install and configure nginx:

$ cap install_nginx
$ cap setup_web_for_nginx

or just apache

$ cap install_apache
$ cap setup_web  (deprec task)

Conclusion

Let me conclude by saying that I hope this article has shown you the flexibility and usefullness that Capistrano can be put to and how easily you can now setup your VPS servers for most combinations of setup.

Of course there’ll be a lot of you that need to tweak things for their own purposes, just create a ~/.caprc file and customize away (That’s how I did it)

I’m going to continue working on this to add support for more linux distributions. Mac server users will have to wait until I decide to make the jump (It’ll inevitably come but I’m not sure when yet).

If you found this handy or useful please provide feedback and also let Mike Bailey know and then we can perhaps integrate this stuff into deprec (so you don’t need to be installing two separate gems).

Thanks for reading,

Saimon Moore