Benefits of Reactive Programming with Reactor and Spring Boot 2 by Violeta Georgieva at SpringOne Tour 2019

1. Benefits of Reactive Programming
with Reactor and Spring Boot 2
Violeta Georgieva
@violeta_g_g

2. Violeta Georgieva
• Pivotal
• Spring Framework contributor
• Reactor Netty committer
• Tomcat committer
2

3. Agenda
• Intro
• Blocking vs. Non-blocking
• Use cases
• Performance
• Challenges
3

4. Intro
• Spring Framework 5
• WebFlux
• WebFlux.fn
• Functional, reactive WebClient
• Reactive types support for Web MVC (still asynchronous and blocking)
• Project Reactor
• Reactor Core
• Reactor Netty
• Spring Boot 2
4

5. Blocking vs Non-blocking

6. Synchronous Processing
Blocking - Remote Call
6
Processing
Latency
Network
Latency

7. Synchronous Processing
Blocking - Slow Client
7
Network
Latency

8. Asynchronous Processing
Blocking - Remote Call
8
Processing
Latency
Network
Latency

9. Asynchronous Processing
Blocking - Slow Client
9
Network
Latency

10. Non-blocking and Event Loops
10
worker
IO
selector
Delegate
Callback

11. Use Cases

12. Reactive Programming Model
• Ability to react on a change
• Control the amount of data/events - backpressure
12

13. Web MVC vs. WebFlux
• Web MVC
• Synchronous processing
• Asynchronous processing
• Supports reactive types Flux/Mono (based on asynchronous processing)
• WebFlux
• Non-blocking processing
13

14. Use Cases
• High Traffic
• Remote Call to Database with non-blocking driver
• Remote Call to Microservice
• Streaming
• Mobile applications and backends
14

15. Performance

16. Load Scenario
16
128 users
32 steps
4k users

17. Scenario 1 - Hello World
• WebFlux.Fn - Reactor Netty with 4 threads
• Web MVC - Tomcat with 200 threads
4k 15min 5min
17

18. Scenario 1 - Hello World
WebFlux.fn
18
Web MVC Synchronous

19. Metrics
WebFlux.fn - 4 Threads Web MVC Synchronous - 200 Threads
19

20. Metrics
20
WebFlux.fn - 4 Threads Web MVC Synchronous - 200 Threads

21. Scenario 2 - Hello World with Delay
• WebFlux.Fn - Reactor Netty with 4 threads
• Web MVC - Tomcat with 200 threads
• Web MVC - Tomcat with 600 threads
• Simulate slow client - 100ms delay
4k 15min 5min
21

22. Scenario 2 - Hello World with Delay
22
WebFlux.fn
100ms

23. Scenario 2 - Hello World with Delay
23
Web MVC Asynchronous
100ms

24. Metrics
24
WebFlux.fn - 4 Threads Web MVC Asynchronous - 200 Threads

25. Metrics
25
WebFlux.fn - 4 Threads Web MVC Asynchronous - 200 Threads

26. Metrics
26
WebFlux.fn - 4 Threads Web MVC Asynchronous - 600 Threads

27. Metrics
27
WebFlux.fn - 4 Threads Web MVC Asynchronous - 600 Threads

28. Scenario 3 - Streaming
• WebFlux.Fn - Reactor Netty with 4 threads
• MVC - Tomcat with 200 threads
4k 15min 5min
28

29. Scenario 3 - Streaming
29
WebFlux.fn
50
1k

30. Scenario 3 - Streaming
30
Web MVC Asynchronous
50
1k

31. Metrics
31
WebFlux.fn - 4 Threads Web MVC Asynchronous - 200 Threads

32. Metrics
32
WebFlux.fn - 4 Threads Web MVC Asynchronous - 200 Threads

33. Scenario 4 - Streaming with Delay
• WebFlux.Fn - Reactor Netty with 4 threads
• MVC - Tomcat with 200 threads
• Streaming with delay - 100ms
4k 15min 5min
33

34. Scenario 4 - Streaming with Delay
34
WebFlux.fn
50
1k
100ms

35. Scenario 4 - Streaming with Delay
35
Web MVC Asynchronous
50
1k
100ms

36. Metrics
36
WebFlux.fn - 4 Threads Web MVC Asynchronous - 200 Threads

37. Metrics
37
WebFlux.fn - 4 Threads Web MVC Asynchronous - 200 Threads

38. Scenario 5 - Remote Call
• WebFlux.Fn - Reactor Netty with 4 threads
• MVC - Tomcat with 200 threads; RestTemplate
• MVC - Tomcat with 200 threads; WebClient
4k 15min 5min
38

39. Scenario 5 - Remote Call
39
WebFlux.fn

40. Scenario 5 - Remote Call
40
Web MVC RestTemplate/WebClient

41. Metrics
41
Web MVC Synchronous -
WebFlux.fn - 4 Threads RestTemplate; 200 Threads

42. Metrics
42
Web MVC Synchronous -
WebFlux.fn - 4 Threads RestTemplate; 200 Threads

43. Metrics
43
Web MVC Asynchronous -
WebFlux.fn - 4 Threads WebClient; 200 Threads

44. Metrics
44
Web MVC Asynchronous -
WebFlux.fn - 4 Threads WebClient; 200 Threads

45. Scenario 6 - Remote Call with Delay
• WebFlux.Fn - Reactor Netty with 4 threads
• MVC - Tomcat with 200 threads; RestTemplate
• MVC - Tomcat with 200 threads; WebClient
• Delay on the Remote system - 100ms
4k 15min 5min
45

46. Scenario 6 - Remote Call with Delay
46
WebFlux.fn
Remote call with delay
100ms

47. Scenario 6 - Remote Call with Delay
47
Web MVC RestTemplate/WebClient
Remote call with delay
100ms
Remote call with delay
100ms

48. Metrics
48
Web MVC Synchronous -
WebFlux.fn - 4 Threads RestTemplate; 200 Threads

49. Metrics
49
Web MVC Synchronous -
WebFlux.fn - 4 Threads RestTemplate; 200 Threads

50. Metrics
50
Web MVC Asynchronous -
WebFlux.fn - 4 Threads WebClient; 200 Threads

51. Metrics
51
Web MVC Asynchronous -
WebFlux.fn - 4 Threads WebClient; 200 Threads

52. Benefits
• Connection volume scalability
• Less threads, less memory
• Ability to serve mixed traffic
52

53. Challenges

54. Challenges
• Learning curve is higher
• Servlet API is not available
• ThreadLocal -> Context from Reactor Core
• Exceptions as we know them from imperative programming
• Blocking calls
54

55. Reactor Debug Agent
• When something goes wrong it’s often hard to determine what happened
• Extensive framework results in overloaded stack traces
• Asynchronous execution results in partial stack traces
• Reactor Debug Agent gives you Reactor flow traces, with near-zero runtime
performance overhead
55

56. Reactor Debug Agent
56

57. BlockHound
• Reactive programming requires that your application be non-blocking throughout
its entire execution
• Blocking one of the very few threads has a massive impact
• But given all your dependencies it’s often hard to determine if something in your
application is blocking
• BlockHound watches your code, executes and throws an error any time a
blocking API is called, identifying and preventing blocking
57

58. DEMO

59. THANK YOU
@violeta_g_g
violetagg
https://github.com/violetagg/web-benchmarks/tree/experimental