Silent Revolution by Max Voronoy (Senior Consultant, Engineering, Globallogic)
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The document provides examples of reactive programming concepts using Reactor.IO and Spring. It shows how to run simple Flux examples to transform and print string values. It also shows a more complicated example using Spring Data and MongoDB to retrieve Person objects reactively from a repository. The key aspects are running long operations asynchronously and non-blockingly using reactive streams instead of blocking the thread.
![LET’S RUN SIMPLE
Flux.just("red", "white", "blue")
.log()
.map(value -> value.toUpperCase())
.subscribe(System.out::println);
Flux.just("red", "white", "blue")
.subscribeOn(Schedulers.parallel()) // !!!!
.log()
.map(value -> value.toUpperCase())
.subscribe(System.out::println);
01:37:18.678 [main] INFO reactor.core.publisher.FluxLog -
ON_SUBSCRIBE(reactor.core.publisher.FluxArray$ArraySubscription@35bbe5e8)
01:37:18.681 [main] INFO reactor.core.publisher.FluxLog - REQUEST(unbounded)
01:37:18.682 [main] INFO reactor.core.publisher.FluxLog - ON_NEXT(red)
RED
01:37:18.682 [main] INFO reactor.core.publisher.FluxLog - ON_NEXT(white)
WHITE
01:37:18.682 [main] INFO reactor.core.publisher.FluxLog - ON_NEXT(blue)
BLUE
01:37:18.682 [main] INFO reactor.core.publisher.FluxLog - ON_COMPLETE()
...
17:26:15.184 [main] INFO reactor.Flux.SubscribeOn.1 - request(unbounded)
17:26:15.189 [parallel-1] INFO reactor.Flux.SubscribeOn.1 - onNext(red)
RED
17:26:15.189 [parallel-1] INFO reactor.Flux.SubscribeOn.1 - onNext(white)
WHITE
17:26:15.189 [parallel-1] INFO reactor.Flux.SubscribeOn.1 - onNext(blue)
BLUE
17:26:15.190 [parallel-1] INFO reactor.Flux.SubscribeOn.1 - onComplete()](https://image.slidesharecdn.com/silentrevolutionbymaxvoronoy-190916112432/85/Silent-Revolution-by-Max-Voronoy-Senior-Consultant-Engineering-Globallogic-7-320.jpg)
Silent Revolution by Max Voronoy (Senior Consultant, Engineering, Globallogic)
- 2. BAD MT EXAMPLES try(Transaction t = db.startTransaction()){ List<User> all = db.select10000Users(); all.forEach(u->{ String text = template.formatEmail(u); smtp.send(u.email, text); }); } Future<?> future = executorService.submit(() -> { String threadName = Thread.currentThread().getName(); System.out.println("Hello " + threadName); }); future.get(); • NO MT CODE private Lock synchro = new ReentrantLock(); public void wrong2(Map<String, String> sharedResource) { synchro.lock(); try{ sharedResource.put("Key1", "Value1"); }finally { synchro.unlock(); } } • ERROR IN PRIMITIVE USE • ERROR IN RESPONSIBILITY AND TRANSACTION SCOPE class Singleton //doublecheck { static volatile Singleton instance; static Object accessor… static Singleton get() { if(instance == null){ lock(accessor){ if(instance == null) instance = new; } } return instance; } } • BROKEN PATTERN
- 3. WHERE IS MY CPU • BAD CPU UTILIZATION • NO LOAD RESERVE
- 4. EVERYBODY LIKES SPRING ( ) ReactiveX Reactor IO • NETTY, JETTY, TOMCAT, UNDERTOW (SERVLET 3.1 ) • JDK 9 AS JAVA.UTIL.CONCURRENT.FLOW • > JAVA.NIO.FILE.*(AsynchronousFileChannel) • HTTP | WEBSOCKET | TCP | UDP Streams
- 5. THINK REACTIVE event Iterable (pull) Observable (push) retrieve data T next() onNext(T) discover error throws Exception onError(Exception) complete !hasNext() onCompleted()
- 6. BASIC PLAYERS (FROM REACTOR.IO) • SUBSCRIBER • PUBLISHER • FLUX -> 0:N (∞) • MONO -> 0:1 public void subscribe(Subscriber<? super T> s); // Factory for Subscription interface void onSubscribe(Subscription s); void onNext(T t); void onError(Throwable t); void onComplete();
- 7. LET’S RUN SIMPLE Flux.just("red", "white", "blue") .log() .map(value -> value.toUpperCase()) .subscribe(System.out::println); Flux.just("red", "white", "blue") .subscribeOn(Schedulers.parallel()) // !!!! .log() .map(value -> value.toUpperCase()) .subscribe(System.out::println); 01:37:18.678 [main] INFO reactor.core.publisher.FluxLog - ON_SUBSCRIBE(reactor.core.publisher.FluxArray$ArraySubscription@35bbe5e8) 01:37:18.681 [main] INFO reactor.core.publisher.FluxLog - REQUEST(unbounded) 01:37:18.682 [main] INFO reactor.core.publisher.FluxLog - ON_NEXT(red) RED 01:37:18.682 [main] INFO reactor.core.publisher.FluxLog - ON_NEXT(white) WHITE 01:37:18.682 [main] INFO reactor.core.publisher.FluxLog - ON_NEXT(blue) BLUE 01:37:18.682 [main] INFO reactor.core.publisher.FluxLog - ON_COMPLETE() ... 17:26:15.184 [main] INFO reactor.Flux.SubscribeOn.1 - request(unbounded) 17:26:15.189 [parallel-1] INFO reactor.Flux.SubscribeOn.1 - onNext(red) RED 17:26:15.189 [parallel-1] INFO reactor.Flux.SubscribeOn.1 - onNext(white) WHITE 17:26:15.189 [parallel-1] INFO reactor.Flux.SubscribeOn.1 - onNext(blue) BLUE 17:26:15.190 [parallel-1] INFO reactor.Flux.SubscribeOn.1 - onComplete()
- 8. COMPLICATED EXAMPLE@Document class Person { @Id String id; String name; } interface PersonRepository extends MongoRepository<Person, String> { @Query("{}") Stream<Person> all(); CompletableFuture<Person> findById(String id); } @Controller class PersonController { @Autowired PersonRepository personRepository; @GetMapping("/person") public Flux<Person> all(){ return Flux.fromStream( personRepository.all() ); } @GetMapping("/person/{id}") public Mono<Person> byId(@PathVariable String userId){ return Optional .ofNullable(userId) .map(id -> personRepository.findById(id)) .map(person-> Mono.fromFuture(person)) .orElseThrow(() -> new IllegalStateException("error - null id")) ; } }
- 9. UNDER THE HOOD Thread HTTP Request Thread HTTP Request 100 . . . @GetMapping("/person") List<Person> get(){ List<Person> result = db.longOperation(); return Response.ok(result); } HTTP HTTP HTTPHTTP HTTP < 100 @GetMapping("/person") public Flux<Person> all(){ return Flux.fromStream( personRepository.all() ); }
- 10. COMMON INTERVIEW MISTAKE • ASYNC REQUEST AS AN ANSWER FOR LONG REQUESTS (WRONG) JavaScript queries process Long Running server Display results • PULLING OR PUSHING (RIGHT) Client query Pull status of Job Display Result Server Render Job ID Track Status of Job
- 11. DO IT IN REACTIVE WAY @RequestMapping(value = "/report/{userId}", method = RequestMethod.PUT) @ResponseStatus(HttpStatus.OK) public void longReport(@PathVariable String userId){ Mono.just(userId) .subscribeOn(Schedulers.parallel()) // MOST IMPORTANT LINE .log() .subscribe( personRepository::longOperation, websocketRegistry::notifyError, //use WebSockets to report error websocketRegistry::notifySuccess //use WebSockets to report success ); ; //here we return to client status OK }
- 12. {FINALIZE} • REACTIVE REVOLUTIONIZE MULTITHREADING BY EXPOSING GOOD DESIGN PATTERNS; • SPRING PUTS ALL TOGETHER; • CHANGE YOUR MIND TO BE REACTIVE. • ANY QUESTIONS?