My capistrano deployment

deploy.rb

require File.join(File.dirname(__FILE__), 'deploy/nginx')
require File.join(File.dirname(__FILE__), 'deploy/log')

default_run_options[:pty] = true
set :ssh_options, { :forward_agent => true }

set :application, "appname"
set :repository,  "git@giturl"

set :scm, :git
set :user, "deploy"
set :deploy_to, "/var/applications/appname"
set :rails_env, "production"
set :branch, "master"

server "appname.com", :web, :app, :db, :primary => true

namespace :deploy do
  desc "Deploy the MFer"
  task :default do
    update
    restart
    cleanup
  end

  desc "Setup a GitHub-style deployment."
  task :setup, :except => { :no_release => true } do
    run "git clone #{repository} #{current_path}"
    update
    run "mkdir -p #{current_path}/tmp/sockets && mkdir -p #{current_path}/tmp/pids"
    db.setup
    migrate
    db.seed
    start
    cleanup
    nginx.start
  end
  
  desc "Update the deployed code."
  task :update_code, :except => { :no_release => true } do
    #run "cd #{current_path}; git fetch origin; git reset --hard #{branch}"
    run "cd #{current_path}; git reset --hard; git pull origin master"
  end
  
  desc "Deploy and run migrations"
  task :migrations, :except => { :no_release => true } do
    update
    migrate
    restart
    cleanup
  end
  
  desc "Run pending migrations on already deployed code"
  task :migrate, :only => {:primary => true}, :except => { :no_release => true } do
    run "cd #{current_path}; RAILS_ENV=#{rails_env} bundle exec rake db:migrate"
  end   
  
  task :symlink, :roles => :app, :except => { :no_release => true } do
    #nothing yet - only exists to wipe out symlink task from super
  end
  
  namespace :db do 
      
    desc "Seed the database on already deployed code"
    task :seed, :only => {:primary => true}, :except => { :no_release => true } do
      run "cd #{current_path}; RAILS_ENV=#{rails_env} bundle exec rake db:seed"
    end     
  
    desc "Setup application schema"
    task :setup do
      run "cd #{current_path}; RAILS_ENV=#{rails_env} bundle exec rake db:create"  
    end
    
    desc "Wipe tables then rerun all migrations and seed database"
    task :remigrate, :only => {:primary => true}, :except => { :no_release => true } do
      run "cd #{current_path}; RAILS_ENV=#{rails_env} bundle exec rake db:remigrate"
    end    
  end
  
  namespace :rollback do
    desc "Rollback"
    task :default, :except => { :no_release => true } do
      code
    end
    
    desc "Rollback a single commit."
    task :code, :except => { :no_release => true } do
      set :branch, "HEAD^"
      default
    end
  end
  
  task :cleanup, :roles => :app, :except => { :no_release => true } do
    # nothing yet
  end    

  # override default tasks to make capistrano happy
  desc "Start unicorn"
  task :start, :roles => :app do
    run "cd #{current_path} && bundle exec unicorn -c #{current_path}/config/unicorn.rb -E #{rails_env} -D"
  end

  desc "Kick unicorn"
  task :restart, :roles => :app do
    run "kill -USR2 `cat #{current_path}/tmp/pids/unicorn.pid`"
  end

  desc "Kill a unicorn"
  task :stop, :roles => :app do
    run "kill -QUIT `cat #{current_path}/tmp/pids/unicorn.pid`"
  end
end

namespace :restore do
  task :db, :roles => :db do
    # from http://www.thegeekstuff.com/2009/01/how-to-backup-and-restore-postgres-database-using-pg_dump-and-psql/
    # 
    # psql -U {user-name} -d {desintation_db}-f {dumpfilename.sql}
  end
end

namespace :backup do
  desc "Backup the database"
  task :db, :roles => :db do
    run "mkdir -p #{current_path}/backups"
    run "cd #{current_path}; pg_dump -U #{user} #{application}_production -f backups/#{Time.now.utc.strftime('%Y%m%d%H%M%S')}.sql"
  end

  desc "Backup the database and download the script"
  task :download, :roles => :app do
    db
    timestamp = Time.now.utc.strftime('%Y%m%d%H%M%S') 
    run "mkdir -p backups"
    run "cd #{current_path}; tar -cvzpf #{timestamp}_backup.tar.gz backups"
    get "#{current_path}/#{timestamp}_backup.tar.gz", "#{timestamp}_backup.tar.gz"
  end
end

namespace :assets do
  task :precompile, :roles => :web do
    run "cd #{current_path}; RAILS_ENV=#{rails_env} bundle exec rake assets:precompile"
  end
  
  task :clean, :roles => :web do
    run "cd #{current_path}; RAILS_ENV=#{rails_env} bundle exec rake assets:clean"
  end
end

namespace :bundler do
  task :bundle_new_release, :roles => :app do
    run "cd #{current_path} && bundle install --deployment --quiet --without development test cucumber"
  end
end
  
after 'deploy:update_code', 'bundler:bundle_new_release'
after 'deploy:update_code', 'assets:precompile'

log.rb

Capistrano::Configuration.instance.load do
  namespace :log do
    desc "Tail all application log files"
    task :tail, :roles => :app do
      run "tail -f #{current_path}/log/*.log" do |channel, stream, data|
        puts "#{channel[:host]}: #{data}"
        break if stream == :err
      end
    end
  end
end

nginx.rb

Capistrano::Configuration.instance.load do
  namespace :nginx do
    desc "Restart nginx"
    task :restart, :roles => :app , :except => { :no_release => true } do
      sudo "/etc/init.d/nginx restart"
    end
    
    desc "Stop nginx"
    task :stop, :roles => :app , :except => { :no_release => true } do
      sudo "/etc/init.d/nginx stop"
    end
    
    desc "Start nginx"
    task :start, :roles => :app , :except => { :no_release => true } do
      sudo "/etc/init.d/nginx start"
    end

    desc "Show nginx status"
    task :status, :roles => :app , :except => { :no_release => true } do
      sudo "/etc/init.d/nginx status"
    end
  end
end  

Hi, would you mind posting your unicorn.rb as well? I'm trying to wrap my head around unicorn continuous deploys. The migrate task you have: is it possible that some users will see the old unicorn process and the old version of code, and some will see the new process and new updated code? Then, assuming your before_fork block kills the old unicorn in your unicorn.rb, things will finally sync up?