How to set the server variable on the fly using capistrano 3 - capistrano3

Question

we're trying to make our deployment scripts as generic as possible. Is it possible to have capistrano 3 prompt for the server address rather than setting it in the config files.
So far i have a capistrao task that does
namespace :config do
task :setup do
ask(:db_user, 'db_user')
ask(:db_pass, 'db_pass')
ask(:db_name, 'db_name')
ask(:db_host, 'db_host')
ask(:application, 'application')
ask(:web_server, 'server')
setup_config = <<-EOF
#{fetch(:rails_env)}:
adapter: postgresql
database: #{fetch(:db_name)}
username: #{fetch(:db_user)}
password: #{fetch(:db_pass)}
host: #{fetch(:db_host)}
EOF
on roles(:app) do
execute "mkdir -p #{shared_path}/config"
upload! StringIO.new(setup_config), "# {shared_path}/config/database.yml"
end
end
end
and in my production.rb file i have
set :application, "#{fetch(:application)}"
set :server_name, "#{fetch(:application)}.#{fetch(:server)}"
set :app_port, "80"
But when I do cap production config:setup to run the config script I get an error asking me for a password. If i hard code the server address in the production.rb file it works fine...how can I resolve this?
Thanks

Answer 1

I hope that someone else offers a more elegant solution, but if not:
I've done this in some cases with environment variables. If you want, you can also use a Makefile to simplify some of the env combinations.