support primary syntax

README.md

@@ -29,7 +29,9 @@ TODO:
   - [x] support existing significant configuration variables
   - [x] set configuration defaults, add commented out examples to templates
   - [x] basic rollback
-  - [ ] support primary servers `on primary(:db)`
+  - [x] support primary servers `on primary :db`
+  - [ ] rails specific tasks
+  - [ ] auto load tasks for scm based on variable
   - [ ] better descriptions for tasks
   - [ ] add examples to README
 
@@ -78,10 +80,12 @@ To create different stages:
 
     ask :branch, :master
 
-    role :app, %w{example.com}
+    role :app, %w{example.com example2.com}
     role :web, %w{example.com}
     role :db, %w{example.com}
 
+    # the first server in the array is considered primary
+
 ## Tasks
 
 ## Before / After

lib/capistrano/configuration.rb

@@ -33,6 +33,10 @@ module Capistrano
       roles.fetch_roles(names)
     end
 
+    def primary(role)
+      roles.fetch_primary(role)
+    end
+
     def configure_backend
       SSHKit.configure do |sshkit|
         sshkit.format = fetch(:format)
@@ -117,6 +121,10 @@ module Capistrano
         roles_for(names).flatten.uniq
       end
 
+      def fetch_primary(role)
+        fetch(role).first
+      end
+
       def each
         roles.each { |role| yield role }
       end

lib/capistrano/dsl/env.rb

@@ -26,6 +26,10 @@ module Capistrano
         env.roles_for(names)
       end
 
+      def primary(role)
+        env.primary(role)
+      end
+
       def env
         Configuration.env
       end

lib/capistrano/tasks/deploy.rake

@@ -108,8 +108,11 @@ namespace :deploy do
 
   desc 'Clean up old releases'
   task :cleanup do
+    releases = on primary :app do
+      capture(:ls, '-xt', releases_path).split.reverse
+    end
+
     on roles :all do
-      releases = capture(:ls, '-xt', releases_path).split.reverse
       if releases.count >= fetch(:keep_releases)
         info t(:keeping_releases, keep_releases: fetch(:keep_releases), releases: releases.count)
         directories = (releases - releases.last(fetch(:keep_releases))).map { |release|
@@ -121,7 +124,7 @@ namespace :deploy do
 
   desc 'Log details of the deploy'
   task :log_revision do
-    on roles :app do
+    on primary :app do
       within releases_path do
         execute %{echo "#{revision_log_message}" >> #{revision_log}}
       end
@@ -130,11 +133,14 @@ namespace :deploy do
 
   desc 'Rollback to the last release'
   task :rollback do
-    on roles :app do
+    on primary :app do
       last_release = capture(:ls, '-xt', releases_path).split[1]
       set(:rollback_release_timestamp, last_release)
       set(:branch, last_release)
       set(:revision_log_message, rollback_log_message)
+    end
+
+    on roles :app do
       %w{check finalize restart finishing finished}.each do |task|
         invoke "deploy:#{task}"
       end

lib/capistrano/tasks/git.rake

@@ -2,6 +2,7 @@ namespace :git do
 
   desc 'Check that the repository exists'
   task :check do
+    fetch(:branch)
     on roles :all do
       unless test "[ -d #{repo_path} ]"
         within deploy_path do