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Truly madly deeply parallel ruby applications

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  • 1. Truly Madly Deeply Parallel Ruby (Web)* Applications @harikrishnan83 * Thanks @headius
  • 2. How many of you are building web applications?
  • 3. How many of you have more than 1 user using it at a time?
  • 4. How many of you use scaling out as the way hit scale?
  • 5. How many of you are scaling up to hit scale?
  • 6. What is a parallel environment?
  • 7. Parallelism
  • 8. Concurrency Thread A - load Thread B - load Thread A - increment Thread B - increment Thread A - save Thread B - save i = 0 i = 0 i = 1 i = 1
  • 9. Ruby web application deployment
  • 10. Process Parallelism Reverse Proxy Unicorn Processes Database Layer
  • 11. On my current project
  • 12. We only use EC2 small instances
  • 13. Because it is very hard to utilize a high spec machine Process Context Switch is Expensive
  • 14. Today... ● We have 4 small EC2 instances ● 2 Puma processes run on each ● Handles about 100,000 requests per hour ● And this is our Private alpha
  • 15. We need to... ● Handle about 1 million requests per hour ● Which means about 40-45 EC2 small instances
  • 16. This is not trivial ● Costs a lot of money ● Lot of time required to maintain these boxes ● Being elastic will become very important ● Cost also in terms of more Devops time
  • 17. In general
  • 18. It is easier to baby sit few boxes
  • 19. Than a lot!
  • 20. Ideally, we would like to both scale up and scale out
  • 21. i.e. we want to achieve the same throughput with, say, just 5 large instances
  • 22. Enter thread based parallelism
  • 23. Why were we not doing this till now?
  • 24. Threads are hard* They share memory and mutate thingsThey share memory and mutate things * - Supposedly
  • 25. And there is the ubiquitous issue ‘Thread Safety’
  • 26. Before we go there, first lets look at some code
  • 27. The real question is...
  • 28. Are you “Safe for Parallelization”
  • 29. Understanding this will take you a long way in “getting parallel”
  • 30. Things to remember while moving to threaded parallelism
  • 31. #1 - Always identify the shared resources
  • 32. Shared Resource ● Objects ● DB rows ● Caches ● Log files!
  • 33. #2 - Bank on thread safe libraries
  • 34. Libraries ● Data structures ● JSON, XML parsing, HTTP clients etc ● Generally, auditing all the gems you use for thread safety is a good idea
  • 35. If you only use thread safe libraries are you ‘safe for parallelism’?
  • 36. Rails is thread safe right? Why is everyone concerned about thread safety in the first place?
  • 37. #3 - If two libraries are thread safe, code that uses both of them need not be
  • 38. Rails thread safety model ● Instantiate everything for every request ● No shared state (global objects) ● Different from, say, Java (single servlet object per container, IOC with singletons etc.)
  • 39. #4 - Try and stick to Rails’ way of handling requests
  • 40. Are you ‘Safe for parallelism’ if you follow these steps?
  • 41. Well, it depends...
  • 42. Validating, say, through a green bar is very hard.
  • 43. Always give yourself some time to stabilize. The move is definitely not overnight!
  • 44. Speaking of the move, move where?
  • 45. Since Rubinius is mostly MRI like, its simpler
  • 46. I personally love JRuby more because of my JVM background
  • 47. Lots of good things have been spoken about JRuby
  • 48. Some gotchas based on my experience
  • 49. JRuby impacts Developers ● The JRuby startup time (mostly because of the JVM startup time) can sometimes kill red- green cycle time ● Sometimes, you should be OK with stooping down to Java code to figure out why something is not working
  • 50. JRuby impacts OPs ● You no longer have a ruby app in prod, its a Java app ● GC tuning, Process monitoring, Profiling etc. are very different on a JVM
  • 51. Thread Parallelism Reverse Proxy Puma Instance Database LayerThreads
  • 52. Thank you! @harikrishnan83