Reactive Fault Tolerant Programming with Hystrix and RxJava
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This document discusses reactive fault tolerant programming using Hystrix and RxJava. It begins with an overview of microservices architecture and how latency can occur between services. It then introduces futures and CompletableFutures as ways to allow asynchronous and parallel processing. RxJava is presented as a reactive programming library that can be used to compose asynchronous and event-based programs. Hystrix is discussed as a library for implementing the circuit breaker pattern to handle failures gracefully in distributed systems. The document provides examples of using RxJava and Hystrix to build fault tolerant reactive microservices.
![Hystrix with Spring Cloud
@SpringBootApplication
@EnableDiscoveryClient
@EnableCircuitBreaker
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}](https://image.slidesharecdn.com/reactivefaulttolerant-160413165011/85/Reactive-Fault-Tolerant-Programming-with-Hystrix-and-RxJava-73-320.jpg)
Reactive Fault Tolerant Programming with Hystrix and RxJava
- 1. REACTIVE FAULT TOLERANT PROGRAMMING with Hystrix and RxJava Matt Stine (@mstine)
- 2. Matt StineSenior Product Manager - Pivotal Software, Inc. Author of: http://bit.ly/cloud-native-book
- 3. © Copyright 2015 Pivotal. All rights reserved. 3 MICROSERVICES!!!!!
- 7. public ResponseEntity<Foo> handleIncomingRequest() { Foo foo = new Foo(); foo.addPart(serviceOne.getContributionToFoo()); foo.addPart(serviceTwo.getContributionToFoo()); return new ResponseEntity<>(foo, HttpStatus.OK); } Block and wait!
- 8. Meanwhile in Service Two⊠! ! Ă”S Ă”S Ă”S
- 9. public ResponseEntity<FooPart> handleIncomingRequest() { FooPart fooPart = new FooPart(); fooPart.addSubPart(serviceThree.getContributionToFooPart()); fooPart.addSubPart(serviceFour.getContributionToFooPart()); return new ResponseEntity<>(fooPart, HttpStatus.OK); } Block and wait!
- 11. Futures! ExecutorService executor = createExecutorService(); public ResponseEntity<Foo> handleIncomingRequest() { Foo foo = new Foo(); Future<FooPart> partOne = executor.submit(new CallToServiceOne()); Future<FooPart> partTwo = executor.submit(new CallToServiceTwo()); foo.addPart(partOne.get()); foo.addPart(partTwo.get()); return new ResponseEntity<>(foo, HttpStatus.OK); }
- 12. The service graph changes⊠public ResponseEntity<Foo> handleIncomingRequest() { Foo foo = new Foo(); Future<FooPart> partOne = executor.submit(new CallToServiceOne()); Future<FooPart> partTwo = executor.submit( new CallToServiceTwo(partOne.get())); Future<FooPart> partThree = executor.submit(new CallToServiceThree()) foo.addPart(partTwo.get()); foo.addPart(partThree.get()); return new ResponseEntity<>(foo, HttpStatus.OK); } Block and wait! Blocked until two completes!
- 13. CompletableFutures public ResponseEntity<Foo> handleIncomingRequest() { Foo foo = new Foo(); CompletableFuture<FooPart> partTwo = CompletableFuture.supplyAsync( new CallToServiceOne()) .thenApplyAsync(new CallToServiceTwo()); CompletableFuture<FooPart> partThree = CompletableFuture.supplyAsync( new CallToServiceThree()); foo.addPart(partTwo.get()); foo.addPart(partThree.get()); return new ResponseEntity<>(foo, HttpStatus.OK); }
- 14. As composition becomes more complex, CompletableFuture API is lackingâŠ
- 15. An API like this would be nice⊠List<Integer> transactionsIds = transactions.stream() .filter(t -> t.getType() == Transaction.GROCERY) .sorted(comparing(Transaction::getValue).reversed()) .map(Transaction::getId) .collect(toList());
- 18. RESPONSIVE
- 19. RESILIENT
- 20. ELASTIC
- 21. MESSAGE-DRIVEN
- 24. Observer Pattern
- 25. Hello Observable Observable<Integer> observableString = Observable.create( new Observable.OnSubscribe<Integer>() { public void call(Subscriber<? super Integer> subscriber) { for (int i = 0; i < 5; i++) { subscriber.onNext(i); } subscriber.onCompleted(); } }); Emit an item! Iâm done emitting items!
- 26. Observable<Integer> observableString = Observable.create( subscriber -> { for (int i = 0; i < 5; i++) { subscriber.onNext(i); } subscriber.onCompleted(); }); Hello Observable (JDK 8)
- 27. Hello Subscription Subscription subscription = observableString.subscribe( new Observer<Integer>() { public void onCompleted() { System.out.println("Observable completed"); } public void onError(Throwable throwable) { System.out.println("Oh noes! Something wrong happened!"); } public void onNext(Integer integer) { System.out.println("Item is " + integer); } });
- 28. Hello Subscription (JDK 8) Subscription subscription = observableString.subscribe( item -> System.out.println("Lambda says: " + item), throwable -> System.out.println("Lambda says: Oh noes! Something wrong happened!"), () -> System.out.println("Lambda says: Observable completed"));
- 29. All together now⊠Observable.create( subscriber -> { for (int i = 0; i < 5; i++) { subscriber.onNext(i); } subscriber.onCompleted(); }).subscribe( item -> System.out.println("Lambda says: " + item), throwable -> System.out.println("Lambda says: Oh noes! Something wrong happened!"), () -> System.out.println("Lambda says: Observable completed"));
- 30. Back to Our Service Graph ĂAPI ĂAPI ! ! ! Ă”S Ă”S Ă”S Ă”S Ă”S
- 31. With Callables Observable.fromCallable(new CallToServiceOne()) .flatMap(serviceOneResult -> Observable.fromCallable( new CallToServiceTwo(serviceOneResult))) .zipWith(Observable.fromCallable( new CallToServiceThree()), (FooPart resultFromServiceTwo, FooPart resultFromServiceThree) -> { Foo foo = new Foo(); foo.addPart(resultFromServiceTwo); foo.addPart(resultFromServiceThree); return foo; }).subscribe(System.out::println);
- 32. With Lambdas Observable.<FooPart>create(serviceOneSubscriber -> { serviceOneSubscriber.onNext(new FooPart("one")); serviceOneSubscriber.onCompleted(); }).flatMap(serviceOneResult -> Observable.<FooPart>create(serviceTwoSubscriber -> { serviceTwoSubscriber.onNext(new FooPart(serviceOneResult + " + two")); serviceTwoSubscriber.onCompleted(); })).zipWith(Observable.<FooPart>create(serviceThreeSubscriber -> { serviceThreeSubscriber.onNext(new FooPart("three")); serviceThreeSubscriber.onCompleted(); }), (resultFromServiceTwo, resultFromServiceThree) -> { Foo foo = new Foo(); foo.addPart(resultFromServiceTwo); foo.addPart(resultFromServiceThree); return foo; }).subscribe(System.out::println);
- 34. Combining Observables âą merge() - combine multiple Observables so they act like a single Observable âą zip() - combine sets of items from multiple Observables via a Function, and emit the results https://github.com/ReactiveX/RxJava/wiki/Combining-Observables
- 35. Conditionals âą doWhile() - emit Observable sequence, then repeat the sequence as long as the condition remains true âą ifThen() - only emit Observable sequence if a condition is true, otherwise emit empty or default sequence âą skipUntil() - discard emitted items from Observable until a second Observable emits an item, then emit the remainder âą takeUntil() - emit items from Observable until a second Observable emits or notiïŹes https://github.com/ReactiveX/RxJava/wiki/Conditional-and-Boolean-Operators
- 36. Boolean Operators âą all() - do all the emitted items meet some criteria? âą contains() - does the Observable emit a particular item? âą exists() / isEmpty() - does an Observable emit items or not? âą sequenceEqual() - do two Observables emit equal sequences? https://github.com/ReactiveX/RxJava/wiki/Conditional-and-Boolean-Operators
- 37. Filtering âą ïŹlter() - ïŹlter Observable with a predicate âą take(n) - emit only the ïŹrst n items âą skip(n) - ignore the ïŹrst n items emitted âą sample() - sample items according to a periodic interval https://github.com/ReactiveX/RxJava/wiki/Filtering-Observables
- 38. Transforming âą map() - apply a function to each emitted item âą ïŹatMap() - transform items emitted by Observable into Observables, then ïŹatten âą scan() - apply a function to each emitted item, then feedback result and repeat âą buffer() - gather emitted items into bundles and emit the bundles https://github.com/ReactiveX/RxJava/wiki/Transforming-Observables
- 39. Backpressure!
- 40. â https://github.com/ReactiveX/RxJava/wiki/Backpressure ââŠa quickly-producing Observable meets a slow-consuming observer.â
- 41. Backpressure Observable Observable.create(subscriber -> IntStream.iterate(0, i -> i + 2) .forEach(value -> subscriber.onNext(value))) .onBackpressureBuffer() .subscribe(new BackpressureSubscriber());
- 42. Backpressure Subscriber public class BackpressureSubscriber extends Subscriber<Object> { private int counter = 0; @Override public void onStart() { request(10); } @Override public void onNext(Object o) { if (counter < 9) { processItem(o); } else { processItem(o); resetCounter(); request(10); } } Please only give me this many! OK, I can handle more now.
- 43. Backpressure Subscriber private void processItem(Object o) { try { Thread.sleep(500); } catch (InterruptedException e) { e.printStackTrace(); } counter++; System.out.println(counter + " : " + o); } private void resetCounter() { counter = 0; System.out.println("FETCH MORE"); } Simulate Processing Latency }
- 45. What happens if we cut here? ĂAPI ĂAPI ! ! ! Ă”S Ă”S Ă”S Ă”S Ă”S
- 48. 500 INTERNAL SERVER ERROR
- 49. Fault Tolerance at Netflix http://techblog.netïŹix.com/2012/02/fault-tolerance-in-high-volume.html
- 50. Without taking steps to ensure fault tolerance, 30 dependencies each with 99.99% uptime would result in 2+ hours downtime/ month (99.99%30 = 99.7% uptime = 2.16 hours/month). http://techblog.netïŹix.com/2012/02/fault-tolerance-in-high-volume.html
- 51. The Circuit Breaker Pattern
- 52. Circuit Breaker State Machine Closed on call / pass through call succeeds / reset count call fails / count failure threshold reached / trip breaker Open on call / fail on timeout / attempt reset Half-Open on call / pass through call succeeds / reset call fails / trip breaker trip breaker trip breaker attempt reset reset
- 54. Hello Hystrix World public class CommandHelloWorld extends HystrixCommand<String> { private final String name; public CommandHelloWorld(String name) { super(HystrixCommandGroupKey.Factory.asKey("ExampleGroup")); this.name = name; } @Override protected String run() { // Do something that might fail... return "Hello " + name + "!"; } }
- 55. Synchronous String s = new CommandHelloWorld("Bob").execute(); Block and wait!
- 56. Asynchronous Future<String> s = new CommandHelloWorld("Bob").queue();
- 57. Reactive! Observable<String> s = new CommandHelloWorld("Bob").observe(); s.subscribe(val -> { // value emitted here });
- 58. Fail Fast public class CommandThatFailsFast extends HystrixCommand<String> { private final boolean throwException; public CommandThatFailsFast(boolean throwException) { super(HystrixCommandGroupKey.Factory.asKey("ExampleGroup")); this.throwException = throwException; } @Override protected String run() { if (throwException) { throw new RuntimeException("failure from CommandThatFailsFast"); } else { return "success"; } } }
- 59. Fail Silently public class CommandThatFailsSilently extends HystrixCommand<String> { private final boolean throwException; public CommandThatFailsSilently(boolean throwException) { super(HystrixCommandGroupKey.Factory.asKey("ExampleGroup")); this.throwException = throwException; } @Override protected String run() { if (throwException) { throw new RuntimeException("failure from CommandThatFailsSilently"); } else { return "success"; } } @Override protected String getFallback() { return null; } } Fallback behavior! }
- 60. Static Fallback @Override protected String run() { if (throwException) { throw new RuntimeException("failure from CommandWithStaticFallback"); } else { return "success"; } } @Override protected String getFallback() { return "fallback"; } Fallback behavior! }
- 61. Stubbed Fallback @Override protected UserAccount run() { // fetch UserAccount from remote service // return UserAccountClient.getAccount(customerId); throw new RuntimeException("forcing failure for example"); } @Override protected UserAccount getFallback() { /** * Return stubbed fallback with some static defaults, placeholders, * and an injected value 'countryCodeFromGeoLookup' that we'll use * instead of what we would have retrieved from the remote service. */ return new UserAccount(customerId, "Unknown Name", countryCodeFromGeoLookup, true, true, false); } Fallback behavior! }
- 62. Fallback: Cache via Network
- 63. Primary + Secondary with Fallback
- 67. RxJava + Hystrix
- 68. With Callables Observable.fromCallable(new CallToServiceOne()) .flatMap(serviceOneResult -> Observable.fromCallable( new CallToServiceTwo(serviceOneResult))) .zipWith(Observable.fromCallable( new CallToServiceThree()), (FooPart resultFromServiceTwo, FooPart resultFromServiceThree) -> { Foo foo = new Foo(); foo.addPart(resultFromServiceTwo); foo.addPart(resultFromServiceThree); return foo; }).subscribe(System.out::println);
- 69. With HystrixObservableCommands new CallToServiceOneCommand("callToServiceOne").observe() .flatMap(serviceOneResult -> new CallToServiceTwoCommand("callToServiceTwo", serviceOneResult).observe()) .zipWith(new CallToServiceThreeCommand("callToServiceThree").observe(), (FooPart resultFromServiceTwo, FooPart resultFromServiceThree) -> { Foo foo = new Foo(); foo.addPart(resultFromServiceTwo); foo.addPart(resultFromServiceThree); return foo; }).subscribe(System.out::println);
- 70. Call to Service One public class CallToServiceOneCommand extends HystrixObservableCommand<FooPart> { public CallToServiceOneCommand(String name) { super(HystrixCommandGroupKey.Factory.asKey(name)); } @Override protected Observable<FooPart> construct() { return Observable.create(new Observable.OnSubscribe<FooPart>() { @Override public void call(Subscriber<? super FooPart> subscriber) { subscriber.onNext(new FooPart("one")); subscriber.onCompleted(); } }); } }
- 71. public class CallToServiceTwoCommand extends HystrixObservableCommand<FooPart> { private final FooPart dependencyFromServiceOne; private CallToServiceTwoCommand(String name, FooPart dependencyFromServiceOne) { super(HystrixCommandGroupKey.Factory.asKey(name)); this.dependencyFromServiceOne = dependencyFromServiceOne; } @Override protected Observable<FooPart> construct() { return Observable.create(new Observable.OnSubscribe<FooPart>() { @Override public void call(Subscriber<? super FooPart> subscriber) { subscriber.onNext(new FooPart(dependencyFromServiceOne + " + two")); subscriber.onCompleted(); } }); } } Call to Service Two
- 73. Hystrix with Spring Cloud @SpringBootApplication @EnableDiscoveryClient @EnableCircuitBreaker public class Application { public static void main(String[] args) { SpringApplication.run(Application.class, args); } }
- 74. Hystrix with Spring Cloud @Service @EnableConfigurationProperties(FortuneProperties.class) public class FortuneService { @Autowired FortuneProperties fortuneProperties; @Autowired RestTemplate restTemplate; @HystrixCommand(fallbackMethod = "fallbackFortune") public Fortune randomFortune() { return restTemplate.getForObject("http://fortunes/random", Fortune.class); } private Fortune fallbackFortune() { return new Fortune(42L, fortuneProperties.getFallbackFortune()); } } }
- 75. RxJava + Hystrix + Spring Cloud @HystrixCommand(fallbackMethod = "stubMovie") public Observable<Movie> getMovie(final String mlId) { return new ObservableResult<Movie>() { @Override public Movie invoke() { return restTemplate.getForObject( "http://springbox-catalog/movies/{mlId}", Movie.class, mlId); } }; } private Movie stubMovie(final String mlId) { Movie stub = new Movie(); stub.setMlId(mlId); stub.setTitle("Interesting...the wrong title. Sssshhhh!"); return stub; }
- 76. RxJava + Hystrix + Spring Cloud @RequestMapping("/movie/{mlId}") public Observable<MovieDetails> movieDetails(@PathVariable String mlId) { return Observable.zip( catalogIntegrationService.getMovie(mlId), reviewsIntegrationService.reviewsFor(mlId), recommendationsIntegrationService.getRecommendations(mlId), (movie, reviews, recommendations) -> { MovieDetails movieDetails = new MovieDetails(); movieDetails.setMlId(movie.getMlId()); movieDetails.setTitle(movie.getTitle()); movieDetails.setReviews(reviews); movieDetails.setRecommendations(recommendations); return movieDetails; } ); }
- 78. Reactive Streams http://www.reactive-streams.org/
- 80. JDK 9 Flow API http://download.java.net/jdk9/docs/api/java/util/concurrent/Flow.html
- 81. REACTIVE FAULT TOLERANT PROGRAMMING with Hystrix and RxJava Get your FREE eBook! http://bit.ly/cloud-native-book Matt StineSenior Product Manager - Pivotal Software, Inc.âš @mstineâš [email protected]âš http://mattstine.com