Rails is A Follower

what we can learn from dRuby’s metaprogramming magic.
@ dRubyConf2012

Transcript

1. Rails is A Follower what we can learn from dRuby’s metaprogramming magic Masatoshi SEKI Makoto Inoue
2. Makoto Inoue Web Developer @ New Bamboo (UK) Translator of “The dRuby Book”
3. Masatoshi Seki Ruby committer Author of dRuby/Rinda Author of ERB Pokemon Master The ERB Book Embed ruby script in any document using ERB
4. Seki san @ Work Embedded RealTime Network GUI
5. Seki san @ RubyKaigi (06 - 11) 2006 dRuby as a session storage 2007 Rinda: Distributed TupleSpace 2008 RIP ERB 2009 dRuby and BigTable 2010 dRuby and Object Database 2011 Drip: A stream based database
6. History of dRuby 1999-3 ERB 1999-9 DRb 2003 committer 2010 pokemon-master 2000 Rinda 1998 started ruby 2006 - 2011 Ruby Kaigi
7. Thank you to Our Sponsors Ruby No Kai new bamboo
8. Thank you to Our Sponsors @PUPRL @ayumin @arika @mame @ vestige_ @track8 @ nagachika "ruby trunk changes" @ktou Powered by Rabbit @tsuboi @ayako119 @hisashim
9. Table Of Contents What is dRuby ? Before dRuby (BD) Designing dRuby Q&A
10. What is dRuby? Distributed Object System Can invoke methods in different processes Can send objects between processes Pure Ruby Ruby standard library
11. Demo1 Starting up
12. Demo2 Which is the server?
13. Demo3 Distributed Queue
14. dRuby usage: distributed RSpec Used at Cookpad Ask @mrkn for the detail
15. dRuby usage: prototyping
16. Before dRuby (BD)
17. Old-fashioned programmer (BD8) Used to program in old Unix style IPC (Inter-Process Communication) fork/pipe, SystemV IPC
18. Simple world of CGI (BD5) request/response, stateless Converted my IPC programs to CGI
19. Ruby & shttpsrv (BD1) 1998-9 Met Ruby & shttpsrv
20. Ruby & shttpsrv Web server written in Ruby Before WEBrick Small and extensible
21. Embedding HTTP into processes Embedding web server into small apps are fun Application communication via HTTP
22. Ruby everywhere I used to play with various languages with CGI, but now everything is Ruby
23. Not so cool because... Converting Ruby way into Web way HTTP restricts how to exchange objects Server - Client relationship Functional APIʢRPCʣ Cool URL No REST at that time
24. I just want Ruby to talk each other Converting Ruby world to Web world is restricting Too much abstraction?
25. Back to Ruby They are Ruby objects. Let’s call them in Ruby-ish way
26. Back to Ruby Distributed objects acting like Ruby RPC -> RMI Extending Ruby’s method invocation to socket programming
27. Why metaprogramming? Need a perfect proxy acting like Ruby Perfect fake that acts like normal Ruby
28. Designing dRuby method_missing Marshal ObjectSpace._id2ref & send Other Techniques
29. method_missing Respond to unknown methods Used for Proxies to catch method calls
30. class DRbObject ... def method_missing(msg_id, *a) succ, result = DRbConn.new(@uri).send_message(self, msg_id, *a) raise result if ! succ result end ... end
31. Marshal Serializes objects
32. module DRbProtocol ... def dump(obj, soc) begin str = Marshal::dump(obj) rescue ro = DRbObject.new(obj) str = Marshal::dump(ro) end soc.write(str) if soc str end ... end
33. Marshal File, Thread, Proc raise exceptions If you can not serialize, then serialize its proxy Send Object references
34. module DRbProtocol ... def dump(obj, soc) begin str = Marshal::dump(obj) rescue ro = DRbObject.new(obj) str = Marshal::dump(ro) end soc.write(str) if soc str end ... end
35. ObjectSpace._id2ref & send Find a object using object id The server finds the object and dispatches the method to it
36. class DRbServer ... ! ro, msg, argv = recv_request(s) ! if ro and ro.ref ! obj = ObjectSpace._id2ref(ro.ref) ! else ! obj = DRb.front ! end ! result = obj.__send__(msg.intern, *argv) ! succ = true ... end
37. class DRbServer ... ! ro, msg, argv = recv_request(s) ! if ro and ro.ref ! obj = ObjectSpace._id2ref(ro.ref) ! else ! obj = DRb.front ! end ! result = obj.__send__(msg.intern, *argv) ! succ = true ... end
38. Other techniques How do you recover unknown objects? Multithreading Handling method call with block
39. Demo4 DRbUnknown
40. What has just happened? Who did replace Foo with DRbUnknown?
41. class DRbMessage ... def load(soc) ... begin ... Marshal.load(str) rescue NameError, ArgumentError DRbUnknown.new($!, str) ensure ... end ... end end
42. class DRbUnknown def initialize(err, buf) case err.to_s when /uninitialized constant (\S+)/ @name = $1 when /undefined class\/module (\S+)/ @name = $1 else @name = nil end @buf = buf end
43. class DRbUnknown ... def _dump(lv) @buf end ... end
44. What has just happened? How does DRbUnkown#reload work?
45. class DRbUnknown ... def self._load(s) begin Marshal::load(s) rescue NameError, ArgumentError DRbUnknown.new($!, s) end end def reload self.class._load(@buf) end end
46. Multithreading Ruby socket programming patterns from shttpsrv
47. Thread.start(@soc.accept) do |s| begin ro, msg, arg = recv_request(s) ... send_response(s, succ, result) ensure s.close end end
48. Handling method call with block kvs.each do |k,v| p v end
49. ro, msg, argv, block = recv_request(s) obj = ro_to_obj(ro) if block result = obj.__send__(msg.intern, *argv) do |*x| block.call(*x) end else result = obj.__send__(msg.intern, *argv) end
50. break? kvs.each do |k,v| break if k == "foo" p v end LocalJumpError: break from proc-closure ! from (druby://eleven.local:61018) ..... ! from (druby://eleven.local:61018) ..... ! from (druby://eleven.local:61018) .....
51. def perform_with_block @obj.__send__(@msg_id, *@argv) do |*x| jump_error = nil begin block_value = block_yield(x) rescue LocalJumpError jump_error = $! end if jump_error case jump_error.reason when :break break(jump_error.exit_value) else raise jump_error end end block_value end endɹ
52. Did you get it?
53. Summary IPC -> http RPC -> dRuby dRuby metaprogramming techniques It’s your turn now.
54. My thoughts on Metaprogramming Isn’t metaprogramming too magical? Magic should not look like magic. Your magic is complete if no one notices it
55. You have everything you need Now it’s your turn