Command wasn't called in deploy file use Capistrano 3 - capistrano3

Question

I had a problem when i run cap production deploy.
I want to run a command restart unicorn server same as ubuntu service when cap production deploy finished.
But problem was here that it didn't run this command /etc/init.d/unicorn_my_app restart when command cap production deploy finished and the server didn't restart.
And i must ssh to server and start unicorn server /etc/init.d/unicorn_my_app restart manually, so i didn't know the reason.
I research a lot of documents and topics and try a lot, but i was unsuccessful. Hope everybody can help me. Thank you very much.
This is my deploy.rb
lock '3.4.0'
set :application, 'my_app'
set :repo_url, 'git#bitbucket.org:****/my_app.git'
set :branch, 'master'
set :rvm_type, :auto
set :rvm_ruby_version, '2.2.1#my_app'
set :bundle_gemfile, -> { release_path.join('Gemfile') }
set :bundle_dir, -> { shared_path.join('bundle') }
set :bundle_flags, nil
set :bundle_without, %w{development test}.join(' ')
set :bundle_binstubs, nil
set :bundle_roles, :all
set :app_path, '/var/www/my_app/current/'
set :scm, :git
set :pty, true
set :use_sudo, true
set :format, :pretty
set :log_level, :debug
set :keep_releases, 5
set :linked_files, fetch(:linked_files, []).push('config/database.yml', 'config/secrets.yml')
set :linked_dirs, fetch(:linked_dirs, []).push('log', 'tmp/pids', 'tmp/cache', 'tmp/sockets', 'vendor/bundle', 'public/system')
namespace :deploy do
after :restart, :clear_cache do
on roles(:web), in: :groups, limit: 3, wait: 10 do
end
end
task :restart_unicorn do
on roles(:all) do
begin
puts "INFO #{Time.now} starting unicorn"
execute "/etc/init.d/unicorn_my_app restart"
rescue => e
puts "ERROR #{Time.now} error with #{e.inspect}"
end
end
end
after :finishing, "deploy:cleanup", "deploy:restart_unicorn"
end
Update: #Deep: I tried add sudo /etc/init.d/unicorn_my_app restart and it didn't run anyway. Does anybody explain for me why it didn't run ? Thank you.