Evented Ruby vs. Node.js

What is evented programming? Why is it useful for server-side web? What are the tradeoffs between using eventmachine and node.js? How can you use evented programming in your Ruby project?

1. Evented Ruby vs Node.js Monday, October 8, 12
2. Hi, I’m Jerry http://github.com/jch @whatcodecraves Monday, October 8, 12
3. Performance Goals ✓ Low hanging fruit ✓ Micro-optimizations (don’t do ‘em) ✓ Sustainable changes ✓ Minimal Monday, October 8, 12
4. Evented... ✓ ... programming ✓ ... server side web ✓ ... Ruby vs Javascript ✓ ... app concurrency Monday, October 8, 12
5. Evented Programming $("body").click(function(e) { $(this).css('color', 'red'); }); Event Callback Event Monday, October 8, 12
6. Reactor Pattern Reactor callbacks callbacks Click Drag Monday, October 8, 12
7. Reactor Pattern ✓ UI events: keyboard, mouse, touch ✓ Reusable reactors: browser, game loop ✓ Other events: network up, disk Monday, October 8, 12
8. Node.js Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient, perfect for data-intensive real-time applications that run across distributed devices. Monday, October 8, 12
9. Blocking I/O If RAM was an F-18 Hornet with a max speed of 1,190 mph, disk access speed is a banana slug with a top speed of 0.007 mph Monday, October 8, 12
10. Blocking I/O data = File.read(‘file.txt’) F = Fast F18 Hornet S = Slow Banana Slug FSSSSSSSSSSSSSSSF CPU is idle Monday, October 8, 12
11. Blocking I/O ✓ Switch between busy processes ✓ OS and hardware caches hides complexity OS Rails Browser iTunes Monday, October 8, 12
12. Blocking I/O OS Node Browser iTunes I/O Node.js switches between I/O within the same process Monday, October 8, 12
13. Web Apps ✓ blocking I/O decreases concurrency ✓ database, filesystem - disk ✓ S3, external APIs - network ✓ ImageMagick - shelling out Monday, October 8, 12
14. Rails Concurrency tweet = Tweet.new(params["tweet"]) # 1. tweet.shorten_links! # 2. network tweet.save # 3. disk Monday, October 8, 12
15. Rails Concurrency Request Request Request Request Green is executing thread Red is waiting on I/O finished request start 2nd request Monday, October 8, 12
16. Rails Concurrency Web Server Rails Rails Rails ✓ Process concurrency ✓ Lots of memory Monday, October 8, 12
17. Node Concurrency tweet = new Tweet(); // 1. tweet.shortenLinks(function(tweet) { // 2. callback tweet.save(function(tweet) { // 3. callback } }) Monday, October 8, 12
18. Node Concurrency Reactor Request Request Reactor Request Request Green is executing thread Red is waiting on I/O Monday, October 8, 12
19. Node Concurrency Reactor Request Request Reactor Request Request Green is executing thread Red is waiting on I/O Start 1st request Monday, October 8, 12
20. Node Concurrency Reactor Request Request Reactor Request Request Green is executing thread Red is waiting on I/O Monday, October 8, 12
21. Node Concurrency Reactor Request Request Reactor Request Request Green is executing thread Red is waiting on I/O Start 2nd request Monday, October 8, 12
22. Node Concurrency Reactor Request Request Reactor Request Request Green is executing thread Red is waiting on I/O Monday, October 8, 12
23. Node Concurrency Reactor Request Request Reactor Request Request Green is executing thread Red is waiting on I/O IO finishes for first request Monday, October 8, 12
24. Node Concurrency Reactor Request Request Reactor Request Request Green is executing thread Red is waiting on I/O Monday, October 8, 12
25. Node Concurrency Reactor Request Request Reactor Request Request Green is executing thread Red is waiting on I/O IO finishes for last request Monday, October 8, 12
26. Node Concurrency Reactor Request Request Reactor Request Request Green is executing thread Red is waiting on I/O Monday, October 8, 12
27. Node Concurrency ✓ One reactor process switches between requests ✓ Fewer processes => Less memory Web Server Node Node Monday, October 8, 12
28. Latency SSSFSSSSSSSSSFSSSS SSSFSSSSSSSSSFSSSS SSSFSSSSSSSSSFSSSS SSSFSSSSSSSSSFSSSS SSSFSSSSSSSSSFSSSS JS Ruby Single request takes the same time ✓ Blocking I/O is not sped up ✓ Optimize response latency first Monday, October 8, 12
29. Code Smell ✓ App code aware of blocking I/O ✓ Ugly syntax, nested contexts tweet = new Tweet(); // 1. tweet.shortenLinks(function(tweet) { // 2. callback tweet.save(function(tweet) { // 3. callback } }) Monday, October 8, 12
30. Evented Ruby ✓ ruby is capable of evented programming ✓ multi-paradigm: procedural, evented, parallel ✓ mix and match paradigms Monday, October 8, 12
31. Ruby Reactors ✓ reactor is just a gem ✓ eventmachine, cool.io, ... # Starting an EventMachine reactor EM.run { # reactor aware code here... } Monday, October 8, 12
32. Add a Reactor Process Concurrency Application Code Reactor Thin, Rainbows!, Passenger (w/ patch) Monday, October 8, 12
33. Add Events http = EM::HttpRequest.new('https://github.com/').get http.callback { # request finished } Monday, October 8, 12
34. Code Smell http = EM::HttpRequest.new('https://github.com/').get http.callback { # request finished } ✓ app code aware of blocking I/O ✓ code doesn’t look like ruby Monday, October 8, 12
35. Procedural Interface, Evented Execution response = Faraday.get 'https://github.com/' Monday, October 8, 12
36. Procedural Interface, Evented Execution response = Faraday.get 'https://github.com/' Faraday.default_adapter = :em_synchrony Monday, October 8, 12
37. Procedural Interface, Evented Execution response = Faraday.get 'https://github.com/' ✓ hides system event callbacks in libraries ✓ keeps app code clean Faraday.default_adapter = :em_synchrony Monday, October 8, 12
38. Procedural Interface, Evented Execution Fibers are primitives for implementing light weight cooperative concurrency in Ruby. Basically they are a means of creating code blocks that can be paused and resumed, much like threads. The main difference is that they are never preempted and that the scheduling must be done by the programmer and not the VM. Monday, October 8, 12
39. Procedural Interface, Evented Execution Reactor Request Fiber1 Fiber2 Monday, October 8, 12
40. Procedural Interface, Evented Execution Reactor Request Fiber1 Fiber2 Start request Monday, October 8, 12
41. Procedural Interface, Evented Execution Reactor Request Fiber1 Fiber2 when blocked on I/O, pause Fiber2, resume Fiber1 Start request Monday, October 8, 12
42. Procedural Interface, Evented Execution Reactor Request Fiber1 Fiber2 when blocked on I/O, pause Fiber2, resume Fiber1 Start request Resume Fiber in I/O callback Monday, October 8, 12
43. Code Smell? ...The main difference is that they are never preempted and that the scheduling must be done by the programmer and not the VM. Monday, October 8, 12
44. Just add Fibers ✓ wrap each request in it’s own fiber ✓ web requests are independent from one another ✓ switch between requests instead of processes Monday, October 8, 12
45. Rack::FiberPool # Rails config.middleware.prepend Rack::FiberPool # Generic rack apps: sinatra, grape, etc use Rack::FiberPool Monday, October 8, 12
46. Recap ✓ App server is reactor-aware ✓ One fiber per request ✓ App code is unchanged Monday, October 8, 12
47. Mixing Paradigms ✓ libraries may block reactor Request Request Request Request Reactor Monday, October 8, 12
48. Mixing Paradigms ✓ libraries may block reactor Request Request Request Request Reactor 1st request Monday, October 8, 12
49. Mixing Paradigms ✓ libraries may block reactor Request Request Request Request Reactor Monday, October 8, 12
50. Mixing Paradigms ✓ libraries may block reactor Request Request Request Request Reactor Blocking library, doesn’t yield to reactor Monday, October 8, 12
51. Mixing Paradigms ✓ libraries may block reactor Request Request Request Request Reactor Monday, October 8, 12
52. Mixing Paradigms ✓ libraries may block reactor Request Request Request Request Reactor 2nd request, reactor blocked, can’t start Monday, October 8, 12
53. Mixing Paradigms ✓ libraries may block reactor Request Request Request Request Reactor Monday, October 8, 12
54. Mixing Paradigms ✓ libraries may block reactor Request Request Request Request Reactor Reactor starts 2nd request Monday, October 8, 12
55. But that’s ok... Web Server Rails Rails Rails Can’t do worse than one request per process Monday, October 8, 12
56. Starting Points ✓ data stores ✓ http ✓ Kernel.system calls Monday, October 8, 12
57. Data Stores ✓ redis ✓ mysql ✓ postgresql ✓ mongo Monday, October 8, 12
58. HTTP ✓ Faraday: use an EM-aware http adapter Monday, October 8, 12
59. System Calls ✓ EM.popen - non-blocking version ✓ EM.defer - run blocking call outside of reactor thread Monday, October 8, 12
60. Final Result Reactor Request Request Fiber1 Fiber2 Fiber3 Green is executing thread Red is waiting on I/O Monday, October 8, 12
61. Why Ruby ✓ Reuse existing code ✓ Performance won’t be worse ✓ Keep procedural syntax ✓ Multi-paradigm Monday, October 8, 12
62. Why Node ✓ Single paradigm consistency ✓ Community Monday, October 8, 12
63. Have cake and eat it too ✓ Don’t go and rewrite your Rails app ✓ Write specific features as an evented subsystem Monday, October 8, 12
64. Example https://github.com/blog/678-meet-nodeload-the-new-download-server Monday, October 8, 12
65. Wrapping Up Monday, October 8, 12
66. Wrapping Up ✓ Evented programming is hard in any language Monday, October 8, 12
67. Wrapping Up ✓ Evented programming is hard in any language ✓ Evented programming for evented problems Monday, October 8, 12
68. Wrapping Up ✓ Evented programming is hard in any language ✓ Evented programming for evented problems ✓ Evented programming doesn’t fix latency Monday, October 8, 12
69. Wrapping Up ✓ Evented programming is hard in any language ✓ Evented programming for evented problems ✓ Evented programming doesn’t fix latency ✓ Avoid evented I/O interface in app code Monday, October 8, 12
70. Thanks! http://github.com/jch @whatcodecraves Monday, October 8, 12