How do I separate roles in Capistrano?

I am trying to deploy my RoR application with Capistrano. Everything was fine until I introduced another role in my Capistrano config, the :web role, which supposedly would be my HTTP/reverse proxy server.

My understanding is that the :app role should refer to the application server (thin, mongrel, whatever) and the :web role should refer to the frontend server (nginx, apache), so I'm rather confused by the choice of running all tasks on all roles, even though开发者_如何学C capistrano separates them by default.

Right now my problem is that I'm not able to make the deploy:update_code run only on the servers that have an :app role, for example, and capistrano errors out because it tries to run update_code on my web server, where I didn't even install git (I don't need it ...). Has anyone suceeded in doing that? Can someone share the code?

TIA, ngw

This problem arises because the built-in tasks don't respect the role limitations on your custom tasks that invoke them, i.e.,

task my_task, :roles => :web do
    run "some command"  # will only be executed on servers with the :web role
    update              # will be executed for all roles
end

You will, as you intuited, have to override all the built-in tasks. Or you can try Rodney Koch's patch to Capistrano.

Are you explicitly specifying the role in the task name?

task :task_A, :roles => :web do
  #do stuff here
end

task :task_B, :roles => :app do
  #do stuff here
end