Modernization of legacy systems with microservices, Hystrix and RxJava

Presented at Javadays Kiev, November 4, 2015

As a software developer you are not very often in the situation where you develop a completely new system from scratch based on recent techonologies. More often just small features have to be integrated in already existing systems. A change of the basic software architecture and an introduction of new programming paradigms are very difficult in this context. It is all the more important to make the modernization of a legacy systems an ongoing part of the feature-driven development process. In this talk I will show step by step how to transform a big, monolithic legacy system towards a modern microservice based architecture. And I will demonstrate how two open libraries from Netflix can support this process. Hystrix will help us to improve the overall stability of the system and RxJava will help us to handle asynchronous processes in a more elegant way. Based on examples, I will show how the suggested modernization process could be realised.

Transcript

1. Modernizing Systems with Microservices, Hystrix and RxJava Holger Kraus Javadays Kiev, Nov 4, 2015
2. A typical System
3. The context
4. Current problems > Maintenance is difficult > New features need a lot of time > Very unstable > Outdated technology > Doesn’t scale + frustrated developers :(
5. Current problems > Maintenance is difficult > New features need a lot of time > Very unstable > Outdated technology > Doesn’t scale Microservices FTW ! not yet …
6. Stabilize first!
7. External dependencies here! here! and also here!
8. Cascading Failures https://www.flickr.com/photos/benstassen/2991003141/
9. Stability patterns > Timeouts > Circuit Breaker > Bulkhead … Fail Fast, Steady State, Handshaking, Test Harness, Decoupling Middleware
10. Timeout https://www.flickr.com/photos/55293400@N07/15564061004
11. Bulkheads https://www.flickr.com/photos/10413717@N08/6935206524
12. Ships http://de.wikipedia.org/wiki/RMS_Titanic#/media/File:Titanic_Structure_de.svg
13. Bulkheads and IT > Thread pools > Database connection pools > Instances > Server > Data center
14. Circuit Breaker https://www.flickr.com/photos/leafbug/409950515/
15. Circuit Breaker http://martinfowler.com/bliki/CircuitBreaker.html
16. Hystrix > Library from Netflix > Resilience Library > Command Pattern > Metrics > Dashboard
17. Use Cases let’s pick this one!
18. Search Products 2. find external products 1. search products 3. find internal products 4. return internal + external products
19. Search Products
20. Call without Hystrix cascading failures incoming!
21. Simple Command
22. Execute it!
23. Execute it asynchronously
24. Fallback
25. In case Merchant 2 is down something is missing here
26. The stabilized system
27. Demo
28. And now?
29. Current Problems > Maintenance is difficult > New features need a lot of time > Very unstable => enables further distribution > Outdated technology > Doesn’t scale
30. © 2015 innoQ Deutschland GmbH We need a clear cut! https://www.flickr.com/photos/taefit/8528632756
31. Microservices! but how to get started ????
32. Architectural Decisions
33. Domain Architecture which boxes do we need ? let the monolith guide you!
34. Macro Architecture > Integration > Deployment > Formats > Protocols > Reduce Choices what’s the same for all boxes ? = API + UI = Docker = JSON = HTTP + AMQP = Java, Go Monozon: pick your own!
35. Micro Architecture
36. Migration Path ? pick one [big bang, strangler, wonder]
37. Big Bang a.k.a REVOLUTION only call old monolith meanwhile build new systems: Step 1
38. Big Bang a.k.a REVOLUTION only call new shiny systems Step2 delete this one!
39. Strangler a.k.a EVOLUTION Step 0 your monolith a.k.a „Big Ball of Mud“
40. Strangler a.k.a EVOLUTION Step 1 give your monolith internal structure and interfaces … if possible.
41. Strangler a.k.a EVOLUTION Step 2 - Extract your new Service
42. Strangler a.k.a EVOLUTION Step3 - Extract your new Service
43. Is it really so easy?
44. Time to connect boxes
45. Synchronous vs. Async/Parallel
46. Try this with futures blocking! blocking!
47. Time for RxJava > Reactive Extensions for the JVM > Asynchronous streams > Elements of > Iterator pattern > Observable pattern > Functional programming
48. https://speakerdeck.com/benjchristensen/functional-reactive-programming-with-rxjava-javaone-2013
49. Everything is a stream! https://www.flickr.com/photos/gruesome/3010529489
50. RxJava in one picture https://speakerdeck.com/benjchristensen/functional-reactive-programming-with-rxjava-javaone-2013
51. Creating Observables
52. Transforming with map http://reactivex.io/RxJava/javadoc/rx/Observable.html
53. map in action
54. Combining with merge http://reactivex.io/RxJava/javadoc/rx/Observable.html
55. merge in action
56. Combining streams with zip http://reactivex.io/RxJava/javadoc/rx/Observable.html
57. zip in action
58. Collecting details with flatMap http://reactivex.io/RxJava/javadoc/rx/Observable.html
59. flatMap in action
60. Why not map?
61. Concurrency
62. Easier with Hystrix
63. Converting into a stream
64. Returning a result
65. Summary > Use Hystrix to stabilize your system! > Use RxJava to increase the amount of async/ parallel processes in an easy way! > Introduce Microservices to get control over your system again! > Have fun :)
66. Thank you! holger.kraus@innoq.com Always worth a visit: innoq.com