This is a presentation for International Lisp Conference 2012 which was held in Kyoto, Japan. Clack is a web application environment for Common Lisp to make your web applications be portable and reusable by abstracting HTTP into a simple API. In this paper, I describe what are problems in web development and how Clack solves them.

1. About Clack
Hatena Co., Ltd.
Eitarow Fukamachi
Oct 24, 2012
International Lisp Conference @ Kyoto, Japan

2. About Me
• Eitarow FUKAMACHI (≒ eight arrow)
• Live in Kyoto, Japan
• Common Lisp user since 2010
• Attended ILC2010 @ Reno
• (I’m using Clozure CL)
• Web application developer at Hatena Co., Ltd.
• Using Perl at work

3. Products
• Clack • CL-Markup
• Caveman • CL-Project
• ningle • Shelly
• CL-TEST-MORE etc.
• CL-DBI
See github.com/fukamachi

4. What’s “Clack”?

5. What’s Clack?
• Web application environment
• Foundation for Web application framework
• Equivalent to...
• Python’s WSGI, Ruby’s Rack, Perl’s Plack/PSGI and
Clojure’s Ring

6. What’s Clack?
• Web application environment
• Foundation for Web application framework
• Equivalent to...
• Python’s WSGI, Ruby’s Rack, Perl’s Plack/PSGI and
Clojure’s Ring
• Abstract HTTP into a simple API (Portability)
• Share code across web frameworks (Reusability)

7. Clack’s
“Portability”

8. “Portability”
• Abstract a web server
※Application includes Web frameworks.

9. “Portability”
• Abstract a web server
※Application includes Web frameworks.

10. “Portability”
(clack:clackup app)
;-> Hunchentoot server is started.
; Listening on localhost:5000.
; # #x30200A102B3D

11. “Portability”
(clack:clackup app)
;-> Hunchentoot server is started.
; Listening on localhost:5000.
; # #x30200A102B3D
(clack:clackup app :server :hunchentoot) ;; default
(clack:clackup app :server :fcgi)
(clack:clackup app :server :apache)

12. Clack’s
“Reusability”

13. “Reusability”
• Application takes Request and returns Response

14. “Reusability”
• Application takes Request and returns Response
• Extension mechanism called “Middleware”
• “Middleware” can be reused

15. “Show me how to use it!”

16. Example 1
“Hello, World!”

17. Example: Hello, World!
(defun app (env)
(declare (ignore env))
'(200
(:content-type "text/plain")
("Hello, World!")))
(clack:clackup #'app)

18. Example: Hello, World!
(defun app (env)
(declare (ignore env))
'(200
‘(200
(:content-type "text/plain")
“text/plain”)
("Hello, World!")))
(“Hello, World!”))
(clack:clackup #'app)

19. Example: Hello, World!
(defun app (env)
(declare (ignore env))
'(200
‘(200
(:request-method :GET
:script-name "" (:content-type "text/plain")
“text/plain”)
:path-info "/sns/member"
("Hello, World!")))
(“Hello, World!”))
:query-string "id=3"
:server-name "localhost"
:server-port 5000
(clack:clackup #'app)
:request-uri "/sns/member?id=3"
:server-protocol :HTTP/1.1
:http-user-agent "Mozilla/5.0 (Macintosh..."
:remote-addr "127.0.0.1"
:remote-port 26077
:http-referer nil
:http-host "localhost:5000"
:http-cookies nil)

20. Example: Hello, World!

21. Example 2
“Conditional flow”

22. Example: Conditional flow
(defun app (env)
(cond
((string= (getf env :path-info) "/favicon.ico")
'(200
(:content-type "image/x-icon")
#p"/path/to/favicon.ico"))
((string= (getf env :path-info) "/")
'(200
(:content-type "text/html")
("Hello again")))
(t '(404 (:content-type "text/plain") ("Not found")))))
(clack:clackup #'app)

23. Example 3
“Basic Auth”

24. Example: Basic Auth
(import ‘(clack.builder:builder
clack.middleware.auth.basic:<clack-middleware-auth-basic>))
(defun app (env)
(declare (ignore env))
'(200
(:content-type "text/plain")
("Hello, World!")))
(clack:clackup
(builder
(<clack-middleware-auth-basic>
:authenticator
(lambda (user pass)
(and (string= user "johnmccarthy")
(string= password "password"))))
#'app))

25. Example: Basic Auth

26. Example 4
“Static files”

27. Example: Static files
(import ‘(clack.builder:builder
clack.middleware.static:<clack-middleware-static>))
(defun app (req)
(declare (ignore req))
'(200
(:content-type "text/plain")
("Hello, World!")))
(clack:clackup
(builder
(<clack-middleware-static>
:path (lambda (path)
(when (ppcre:scan "^/(?:images|css|js)/" path)
(ppcre:regex-replace "^/[^/]+" path "")))
:root #p"static/")
#'app))

28. What are the benefits of using Clack?

29. Clack allows you to:
• If you’re a “Web framework developer”...
• Clack provides server interfaces.
• Reuse code from other web frameworks.

30. Clack allows you to:
• If you’re a “Web framework developer”...
• Clack provides server interfaces.
• Reuse code from other web frameworks.
• If you’re a “Web application engineer”...
• Reuse code in your projects
• Extensible

31. Frameworks

32. Frameworks
• Caveman
• A Sinatra-like micro framework
• ningle
• A really micro framework

33. Frameworks
• Caveman (fukamachi.github.com/caveman/)
• A Sinatra-like micro framework
• ningle (fukamachi.github.com/ningle/)
• A really micro framework

34. Future Work

35. Future Work
• More Middlewares
• More Servers
• non-blocking web server?
• preforking web server?

36. Future Work
• More Middlewares
• More Servers
• non-blocking web server?
• preforking web server?
• More Frameworks
• Ruby on Rails?

37. THE END
Thank you for listening

38. Maybe we still have time.
Any questions in easy English?
To Japanese speakers:
Please translate a question for me if it looks I don't understand it.
僕が質問を理解できていなさそうだったら翻訳してください＞＜