An introduction to deploying rails applications with capistrano I gave at RailsToItaly in 2007

1. Capistrano 2
Beyond Hassle-Free Deployment
Luca Mearelli
Pisa - Oct. 27, 2007

3. Rails is fun

4. Rails is fun
Rails is TOO MUCH fun

5. Deployment

6. System Administration

7. Rails : Web development
=
Capistrano : Sys.administration

8. Capistrano basics
•SSH to the remote machines
•Posix compatible shell
•Same password or public key
•a bit of ruby knowledge
•works from a command line

9. Capistrano basics
•Capfile (makefile, rakefile, ...)
•It’s ruby
task :dump_db, :hosts => quot;database.spazidigitali.comquot; do
run quot;mysqldump -u deploy sd_production > /home/luca/dumps/db.sqlquot;
end
cap dump_db

10. role :sd_db, quot;database.spazidigitali.comquot;
task :dump_db do
run quot;mysqldump -u deploy sd_production > /home/luca/dumps/db.sqlquot;
end
task :free_space do
run quot;df -hquot;
end
cap dump_db

11. set :gateway, quot;firewall.spazidigitali.comquot;
role :sd_db, quot;database.spazidigitali.comquot;
task :dump_db do
run quot;mysqldump -u deploy sd_production > /home/luca/dumps/db.sqlquot;
end
task :free_space do
run quot;df -hquot;
end
cap dump_db

12. set :gateway, quot;firewall.spazidigitali.comquot;
role :sd_db, quot;database.spazidigitali.comquot;, quot;replica.spazidigitali.comquot;
task :dump_db do
run quot;mysqldump -u deploy sd_production > /home/luca/dumps/db.sqlquot;
end
task :free_space do
run quot;df -hquot;
end
cap dump_db

13. set :gateway, quot;firewall.spazidigitali.comquot;
role :sd_db, quot;database.spazidigitali.comquot;, quot;replica.spazidigitali.comquot;
role :sd_app, quot;mongrels.spazidigitali.comquot;
task :dump_db, :roles=>:sd_db do
run quot;mysqldump -u deploy sd_production > /home/luca/dumps/db.sqlquot;
end
task :free_space, :roles=>[:sd_db, :sd_app ] do
run quot;df -hquot;
end
cap dump_db

14. set :gateway, quot;firewall.spazidigitali.comquot;
role :sd_db, quot;database.spazidigitali.comquot;, quot;replica.spazidigitali.comquot;
role :sd_app, quot;mongrels.spazidigitali.comquot;
namespace :spazidig do
desc quot;Dumping our DBsquot;
task :dump_db, :roles=>:sd_db do
run quot;mysqldump -u deploy sd_production > /home/luca/dumps/db.sqlquot;
end
desc quot;Checking free spacequot;
task :free_space, :roles=>[:sd_db, :sd_app ]do
run quot;df -hquot;
end
end
cap spazidig:dump_db

15. set :gateway, quot;firewall.spazidigitali.comquot;
role :sd_db, quot;database.spazidigitali.comquot;, quot;replica.spazidigitali.comquot;
role :sd_app, quot;mongrels.spazidigitali.comquot;
namespace :spazidig do
desc quot;What??quot;
task :default do
run quot;uname -aquot;
end
desc quot;Dumping our DBsquot;
task :dump_db, :roles=>:sd_db do
run quot;mysqldump -u deploy sd_production > /home/luca/dumps/db.sqlquot;
end
desc quot;Checking free spacequot;
task :free_space, :roles=>[:sd_db, :sd_app ]do
run quot;df -hquot;
end
end
cap spazidig
spazidig:dump_db
cap dump_db
cap spazidig:free_space

16. set :gateway, quot;firewall.spazidigitali.comquot;
role :sd_db, quot;database.spazidigitali.comquot;, quot;replica.spazidigitali.comquot;
role :sd_app, quot;mongrels.spazidigitali.comquot;
set :destination, quot;db.sqlquot;
namespace :spazidig do
desc quot;Dumping our DBsquot;
task :dump_db, :roles=>:sd_db do
run quot;mysqldump -u deploy sd_production > /home/luca/dumps/#{destination}.sqlquot;
end
end
cap spazidig:dump_db

17. set :gateway, quot;firewall.spazidigitali.comquot;
role :sd_db, quot;database.spazidigitali.comquot;, quot;replica.spazidigitali.comquot;
role :sd_app, quot;mongrels.spazidigitali.comquot;
set :destination, quot;db.sqlquot;
set(:database) do
Capistrano::CLI.ui.ask quot;Which database?: quot;
end
namespace :spazidig do
desc quot;Dumping our DBsquot;
task :dump_db, :roles=>:sd_db do
run quot;mysqldump -u deploy #{database} > /home/luca/dumps/#{destination}.sqlquot;
end
end
cap spazidig:dump_db

18. task :deploy do
transaction do
try_this
then_do_that
end
end
task :try_this do
on_rollback { run quot;do_cleanupquot; }
#...
end
task :then_do_that do
on_rollback { run quot;do_super_cleanupquot; }
#...
end

19. on :event, :callback, :only => %w(tasks_to_do)
# :load, :exit, :start, :finish, :begin, :after
trigger :notify, current_task
on :notify, :callback

20. load_paths << quot;config/deployquot;
case ENV['STAGE']
when quot;productionquot; then
load quot;productionquot;
when quot;stagingquot; then
load quot;stagingquot;
else
abort quot;unknown stage: #{ENV['STAGE']}quot;
end

21. before :deploy, :run_tests
after quot;deploy:update_codequot;, :link_database_yml
task :run_tests do
system quot;rakequot; or abort quot;tests failedquot;
end
task :link_database_yml do
run quot;ln -s #{release_path}/config/database.yml #{shared_path}/database.ymlquot;
end

22. Cap
•cap -T
•cap <some task>
•cap invoke COMMAND=quot;df -hquot;
•cap invoke COMMAND=quot;df -hquot; ROLES=sd_db
•cap invoke COMMAND=quot;df -hquot; HOSTS=www.spazidigitali.com
•cap shell

23. Capify
capify .
•Creates a Capfile
•Creates a deploy “configuration” file

24. Cap
•cap deploy:setup •cap deploy
•cap deploy:check •cap deploy:rollback
•cap deploy:cold •cap deploy:migrations
•cap deploy:update •cap deploy:web:disable
•cap deploy:migrate •cap deploy:web:enable
•cap deploy:start •cap deploy:cleanup

25. deploy:setup
•<deploy_to>
•current
•releases
•200706060120
•200702020815
•shared
•log
•pids
•system

26. deploy:check
depend :remote, :gem, 'rpdf', '>=1.1.4'
depend :remote, :directory, quot;/tmp/railsquot;
depend :remote, :writable, quot;/dir/file.logquot;
depend :local, :command, quot;gemquot;
depend :remote, :command, quot;mysqldumpquot;

27. deploy:cold
•copies the code - cap deploy:update
•migrates the database - cap deploy:migrate
•starts the service - cap deploy:start

28. Variables
•:ssh_options •:use_sudo
•:application •:group_writable
•:repository •:rake
•:scm •:current_path
•:deploy_via •:release_path
•:deploy_to •:shared_path
•:revision

29. Deployment strategies
•Checkout (classic capistrano)
•Remote cache (svn up)
•Export
•Copy (via checkout or export, with compression)

30. Example*
*sorta real

31. That’s all folks
•Luca Mearelli
•http://spazidigitali.com
•lucamea@gmail.com