deploying with mina using gateways

Capistrano allows you to deploy through a gateway server using a :gateway attribute. When migrating from capistrano to mina you might wonder how mina does this.

Mina relies on a properly setup ssh config file, in particular the use of ProxyCommand.

For example lets assume you want to deploy to intranet.example.com using a gateway at gateway.example.com.

Your mina config will look something like this:

require 'mina/bundler'
require 'mina/git'

set :domain, 'intranet.example.com'
set :deploy_to, '/var/very/secret'
set :repository, 'git://git.example.com/very/secret'
set :branch, 'master'
set :user, 'secret'

desc "Deploys the current version to the server."
task :deploy => :environment do
  deploy do
    invoke :'git:clone'
    invoke :'bundle:install'

    to :launch do
      queue "touch #{deploy_to}/tmp/restart.txt"
    end
  end
end

Note the use of intranet.example.com as host even though it’s only accessible through gateway.example.com!

To make this work you need to setup your $HOME/.ssh/config using a ProxyCommand effectivly telling SSH to connect to gateway.example.com first when connecting to intranet.example.com:

Host gateway.example.com
  IdentityFile ~/.ssh/id_rsa
  User administrator
  ProxyCommand none

Host intranet.example.com
  ForwardAgent yes
  ProxyCommand ssh gateway.example.com nc %h %p

That’s all. Now you can deploy with mina using a gateway.

You might ask why this fact is so obfuscated.
If you’ve ever taken a look at the simulated output of mina it’s actually very obvious:

$ bundle exec mina deploy -S
#!/usr/bin/env bash
# Executing the following via 'ssh [email protected] -A -t':
…

There you go: a simple bash script executed over SSH.

If you ever run into problems when deploying with mina, check the deployment script step by step to find the culprite.

To sum up the important points:

• your :domain from your deploy.rb and the Host from ssh config need to be the same (NOT Hostname and :domain).
• gateway.example.com needs to be able to resolve intranet.example.com. If this is not the case, add a Hostname property with a correct ip.

Happy deploying :)