Trying to create rolling deploy via capistrano.

deploy_via_methods.rb

role :servers, "server1", "server2"
set :user, 'ubuntu'

def stop_load_balancer
  run "echo service registerelb stop"
end

def start_load_balancer
  run "echo service registerelb start"
end

def stop_app
  run "echo service app stop"
end

def start_app
  run "echo service app start"
end

namespace :deploy do
  desc "Deploy"
  task :default, :roles => :servers, :max_hosts => 1 do
    stop_load_balancer
    stop_app
    start_app
    start_load_balancer
  end
end

__END__

Here is the output of running the command. As you can see it runs each
remote command on both servers (consecutively) before getting to the next
remote command. This WILL cause downtime!

╭─haim@sunra  ~/cap_tests ‹1.8.7-p352›
╰─$ cap -f deploy_via_methods.rb deploy                                                                                                                                          1 ↵
  * executing `deploy'
  * executing "echo service registerelb stop"
    servers: ["server1", "server2"]
    [server1] executing command
 ** [out :: server1] service registerelb stop
    command finished in 1404ms
    [server2] executing command
 ** [out :: server2] service registerelb stop
    command finished in 1124ms
  * executing "echo service app stop"
    servers: ["server1", "server2"]
    [server1] executing command
 ** [out :: server1] service app stop
    command finished in 1515ms
    [server2] executing command
 ** [out :: server2] service app stop
    command finished in 1239ms
  * executing "echo service app start"
    servers: ["server1", "server2"]
    [server1] executing command
 ** [out :: server1] service app start
    command finished in 969ms
    [server2] executing command
 ** [out :: server2] service app start
    command finished in 823ms
  * executing "echo service registerelb start"
    servers: ["server1", "server2"]
    [server1] executing command
 ** [out :: server1] service registerelb start
    command finished in 1759ms
    [server2] executing command
 ** [out :: server2] service registerelb start
    command finished in 664ms

rolling.rb

role :servers, 'server1', 'server2'
set :user, 'ubuntu'

namespace :deploy do
  desc "Deploy"
  task :default do
    find_servers(:roles => :servers).each do |server|
      run "echo service registerelb stop", :hosts => server
      run "echo service app stop", :hosts => server
      run "echo service app start", :hosts => server
      run "echo service registerelb start", :hosts => server
    end
  end
end

__END__

This setup actually works as I want it to work (rolling deploy without
downtime) but it will cause code duplication because I want to be able
to run each command separately.

╭─haim@sunra  ~/cap_tests ‹1.8.7-p352›
╰─$ cap -f rolling.rb deploy
  * executing `deploy'
  * executing "echo service registerelb stop"
    servers: ["server1"]
    [server1] executing command
 ** [out :: server1] service registerelb stop
    command finished in 1095ms
  * executing "echo service app stop"
    servers: ["server1"]
    [server1] executing command
 ** [out :: server1] service app stop
    command finished in 337ms
  * executing "echo service app start"
    servers: ["server1"]
    [server1] executing command
 ** [out :: server1] service app start
    command finished in 338ms
  * executing "echo service registerelb start"
    servers: ["server1"]
    [server1] executing command
 ** [out :: server1] service registerelb start
    command finished in 352ms
  * executing "echo service registerelb stop"
    servers: ["server2"]
    [server2] executing command
 ** [out :: server2] service registerelb stop
    command finished in 1127ms
  * executing "echo service app stop"
    servers: ["server2"]
    [server2] executing command
 ** [out :: server2] service app stop
    command finished in 347ms
  * executing "echo service app start"
    servers: ["server2"]
    [server2] executing command
 ** [out :: server2] service app start
    command finished in 325ms
  * executing "echo service registerelb start"
    servers: ["server2"]
    [server2] executing command
 ** [out :: server2] service registerelb start
    command finished in 330ms