Reactive Spring 5: WebFlux & Reactor

Transcript

1. Spring 5 & Reactive systems Project Reactor
2. Reactive Programming what is it?
3. Imperative programming expression is evaluated once value is assigned to a variable Reactive programming is all about responding to value changes
4. Reactive programming Who has done it?
5. You have probably done some reactive programming, even if you didn’t realise it at that time: - Defining cell values in spreadsheets is similar to defining variables in imperative programming - Defining cell expressions in spreadsheets is similar to defining and operating on reactive types Reactive programming
6. Previous example in spreadsheet: - assign cell B1 with value of 2 - assign cell B2 with value of 3 - assign cell B3 with an expression that multiplies B1 value with B2 value - when value of either referenced component in the expression changes -> expression is re-evaluated automagically in B3
7. Spring 5 WebFlux
8. Spring 5 Embraced different perspective on modern day web architecture
9. Spring 5 Embraced different perspective on modern day web architecture Spring WebFlux = parallel web architecture next to the servlet-based Spring MVC
10. Non-Blocking Event
 Queue IO
 Calls Schedule Schedule Callback Callback Request Response EVENT
 LOOP
11. Load test milliseconds (95th percentile) 0 500 1000 1500 2000 2500 3000 3500 4000 Concurrent users 1 10 100 200 500 1000 2000 Synchronous Reactive (500ms backend service)
12. Load test requests served per second (parallellism : 100) 0 25 50 75 100 1 8 32 96 768 Blocking WebFlux (Reactive)
13. Project Reactor history
14. Dutch computer scientist Erik Meijer @Microsoft: C#, LINQ Reactive Extensions (RX) Currently Director Of Engineering @ Facebook Bearer of extremely cool tie-dyed shirts reactivex.io
15. Reactive Manifesto
16. Reactive Manifesto Responsive
17. Reactive Manifesto Responsive Resilient
18. Reactive Manifesto Responsive Resilient Elastic
19. Reactive Manifesto Responsive Resilient Elastic Message Driven
20. Reactive Manifesto To be reactive, according to The Reactive Manifesto, you have to be Responsive, Resilient, Elastic, and Message Driven. The last criteria in this list caused big movement into the asynchronous way of communications.
21. Reactive Streams
22. rxjava 1.x rx reactive streams commons rxjava 2.x reactive streams akka reactor 2.x reactor 3.x spring
23. Reactive Streams
24. Reactive Streams
25. Reactive Streams
26. Reactive Streams standard for asynchronous stream processing with non-blocking back pressure
27. Goal of Reactive Streams exchange of data across an asynchronous boundary while ensuring that the receiving side is not forced to buffer arbitrary amounts of data (back pressure)
31. Publisher
32. Subscriber
33. Subscription
34. Processor
35. Pull?
36. PUSH! Pull?
37. Iterator Subscriber Comparison Iterable VS Publisher
38. Java 9 2015 Start Reactive Streams 1.0 2016 Growth Akka, Spring, Pivotal Project Reactor, RxJava, MongoDB, Kafka, … 2017 Java The interfaces available in JDK9’s java.util.concurrent.Flow, are 1:1 semantically equivalent
40. Reactive Streams PUBLISHER SUBSCRIBER Subscribe then
 request(n) data
 (Backpressure) 0..N data then
 0..1 (Error | Complete)
42. Reactive Streams implementations
47. Reactive core Typed [0|1|N] sequences Non-blocking IPC non-blocking foundation
 interacts with Java 8
 functional API, Completable
 Future, Streams reactive composable API
 Flux[N]
 Mono[0/1]
 implements Reactive Extensions suited for microservices architecture
 backpressure-ready network engines
 (HTTP / Websockets / TCP / UDP)
 reactive encoding/decoding Reactor
48. Operators work with the stream
53. 5 6 7
54. 5 6 7 8 9 10
55. 5 6 7 8 9 10 8 10
56. 5 6 7 8 9 10 8 10 [8,10]
57. SUBSCRIBE! Nothing happens until you
58. Function composition
59. Function composition map collect sorted filter Original list of machines List of model names
60. Nothing happens until you subscribe Assembly Time
61. Nothing happens until you subscribe Execution Time
62. Assembly time
63. subscription Execution time
64. AGNOSTIC! Reactor is threading
65. Concurrency … but facilitates switching
66. Schedulers elastic, parallel, single, …
67. publishOn / subscribeOn determine threading
68. publishOn switch rest of Flux on a thread
69. Flux.op1.op2.publishOn.op3.op4.subscribe
70. Flux.op1.op2.publishOn.op3.op4.subscribe 1 2 Thread calling subscribe()
 is where data flows initially 1 After publishOn() data flows in Thread 2 2
71. subscribeOn make subscription happen on particular thread
72. Flux.op1.op2.subscribeOn.op3.op4.subscribe
73. Flux.op1.op2.subscribeOn.op3.op4.subscribe 1 2 SubscribeOn() changes where sequence subscription happens… 1 … which is also where data flows initially 2
74. and the two together? knock yourself out…
75. But… Frameworks, libraries & operators build on top might be opinionated
76. HARD! Async debugging is
77. When you shift to asynchronous code, things can get more complicated: - Ugly stack traces - Missing async call chain - Stack pollution Debugging
78. java.lang.ArithmeticException: / by zero at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:107) at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:115) at reactor.core.publisher.FluxJust$WeakScalarSubscription.request(FluxJust.java:99) at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.request(FluxMapFuseable.java:156) at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.request(FluxMapFuseable.java:156) at reactor.core.publisher.BlockingSingleSubscriber.onSubscribe(BlockingSingleSubscriber.java:49) at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onSubscribe(FluxMapFuseable.java:90) at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onSubscribe(FluxMapFuseable.java:90) at reactor.core.publisher.FluxJust.subscribe(FluxJust.java:70) at reactor.core.publisher.FluxMapFuseable.subscribe(FluxMapFuseable.java:63) at reactor.core.publisher.FluxMapFuseable.subscribe(FluxMapFuseable.java:63) at reactor.core.publisher.Flux.subscribe(Flux.java:6873) at mycode.test(MyTest.java:xx) Debugging
79. Spring WebFlux Spring WebFlux vs Spring MVC
80. Spring WebFlux
81. Spring 5 WebFlux
82. Servlet Container Netty, Tomcat, Jetty, Undertow HTTP / Reactive Streams spring-webflux Servlet API spring-webmvc Router Functions @Controller, @RequestMapping Spring 5
83. Demo Spring WebFlux application Testing Reactive Mongo Server-Sent Events
84. Real-life example Measuring time with Reactor (NTP)
85. Network Time Protocol
86. S1 S2 S3
88. SNTP time Client time Server 135ms 137ms 298ms 231ms t1 t2 t0 t3 δ=65ms time offset ϑ = (t1 − t0 ) + (t2 − t3 ) 2 round − trip delay δ = (t3 − t0 ) − (t2 − t1 )
89. Less than ideal network —UDP
90. DNS Resolution IP1 IP2 IP3 IP4 SNTP Request 1 NTP POOL Least Roundtrip Delay SNTP Request 2 SNTP Request 3 SNTP Request 4 SNTP Request 5 Statistical analysis Sort by clock offset + median NTP Time Best possible approximation of 5 . . .
91. Everything is a STREAM !!! ⋎ almost
92. DNS Resolution IP1 IP2 IP3 IP4 SNTP Request 1 NTP POOL Least Roundtrip Delay SNTP Request 2 SNTP Request 3 SNTP Request 4 SNTP Request 5 Statistical analysis Sort by clock offset + median NTP Time Best possible approximation of 5 . . .
95. testability++ Reactive approach pure functions elegant concise
96. Spring 5 WebFlux
97. Summarizing Reactor
98. Reactor is awesome! Asynchronous, non-blocking, reactive data flows Event-based programs
99. Reactor is so so… Reactor is not the holy grail.
100. Reactor is so so… Reactor is not the holy grail. Should be used for streams processing, for general asynchronous non-blocking computation, see coroutines (Spring 5.2+)
101. Reactor has downsides? Mindshift (also when testing)
 Debugging & stacktraces are harder For the DDD people: (small) pollution of your domain with Mono/Flux
105. request / stream finite stream of many RSocket request / response stream of 1 fire and forget channel no response bi-directional streams
106. Questions with(out) answers
107. Simplicity does not precede complexity but follows it Alan Perlis
108. Thank you! Spring WebFlux projectreactor.io