Ben Christensen Developer – Edge Engineering at Netflix @benjchristensen ! ! ! ! ! ! http://techblog.netflix.com/ JavaOne - September 2014 Reactive Streams with Rx

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RxJava http://github.com/ReactiveX/RxJava http://reactivex.io

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Single Multiple Sync T getData() Iterable getData() Async Future getData() Observable getData()

public interface Observer { public abstract void onCompleted() public abstract void onError(Throwable e) public abstract void onNext(T t) } public class Observable { public static Observable create(OnSubscribe f) public Subscription subscribe(Observer super T> subscriber) } Lazy Cold or Hot Asynchronous Push *onNext (onError | onCompleted)?

public interface Observer { public abstract void onCompleted() public abstract void onError(Throwable e) public abstract void onNext(T t) } public class Observable { public static Observable create(OnSubscribe f) public Subscription subscribe(Observer super T> subscriber) } Lazy Cold or Hot Asynchronous (or Synchronous) Push (or Pull) *onNext (onError | onCompleted)?

public interface Observer { public abstract void onCompleted() public abstract void onError(Throwable e) public abstract void onNext(T t) } public class Observable { public static Observable create(OnSubscribe f) public Subscription subscribe(Observer super T> subscriber) } Lazy Cold or Hot Asynchronous (or Synchronous) Push (or Pull) *onNext (onError | onCompleted)?

public interface Subscriber implements Observer { public abstract void onCompleted() public abstract void onError(Throwable e) public abstract void onNext(T t) } public class Observable { public static Observable create(OnSubscribe f) public Subscription subscribe(Subscriber super T> subscriber) } Lazy Cold or Hot Asynchronous (or Synchronous) Push (or Pull) *onNext (onError | onCompleted)?

public abstract class Subscriber implements Observer, Subscription public abstract void onCompleted() public abstract void onError(Throwable e) public abstract void onNext(T t) ! public final void add(Subscription s) public void setProducer(Producer producer) } ! public interface Producer { public void request(long n); }

public abstract class Subscriber implements Observer, Subscription public abstract void onCompleted() public abstract void onError(Throwable e) public abstract void onNext(T t) ! public final void add(Subscription s) public void setProducer(Producer producer) } ! public interface Producer { public void request(long n); }

public abstract class Subscriber implements Observer, Subscription public abstract void onCompleted() public abstract void onError(Throwable e) public abstract void onNext(T t) ! public final void add(Subscription s) public void setProducer(Producer producer) } ! public interface Producer { public void request(long n); }

public abstract class Subscriber implements Observer, Subscription public abstract void onCompleted() public abstract void onError(Throwable e) public abstract void onNext(T t) ! public final void add(Subscription s) public void setProducer(Producer producer) } ! public interface Producer { public void request(long n); }

public abstract class Subscriber implements Observer, Subscription public abstract void onCompleted() public abstract void onError(Throwable e) public abstract void onNext(T t) ! public final void add(Subscription s) public void setProducer(Producer producer) } ! public interface Producer { public void request(long n); } “reactive pull” dynamic push/pull for flow control (backpressure)

public class Observable { public static Observable create(OnSubscribe f) public Subscription subscribe(Subscriber super T> subscriber) } public static interface OnSubscribe { public void call(Subscriber super T> subscriber); } public abstract class Subscriber implements Observer, Subscription public abstract void onCompleted() public abstract void onError(Throwable e) public abstract void onNext(T t) ! public final void add(Subscription s) public void setProducer(Producer producer) } ! public interface Producer { public void request(long n); }

public class Observable { public static Observable create(OnSubscribe f) public Subscription subscribe(Subscriber super T> subscriber) } public static interface OnSubscribe { public void call(Subscriber super T> subscriber); } public abstract class Subscriber implements Observer, Subscription public abstract void onCompleted() public abstract void onError(Throwable e) public abstract void onNext(T t) ! public final void add(Subscription s) public void setProducer(Producer producer) } ! public interface Producer { public void request(long n); }

public class Observable { public static Observable create(OnSubscribe f) public Subscription subscribe(Subscriber super T> subscriber) } public static interface OnSubscribe { public void call(Subscriber super T> subscriber); } public abstract class Subscriber implements Observer, Subscription public abstract void onCompleted() public abstract void onError(Throwable e) public abstract void onNext(T t) ! public final void add(Subscription s) public void setProducer(Producer producer) } ! public interface Producer { public void request(long n); }

Observable.create(subscriber -> { subscriber.onNext("Hello world!"); subscriber.onCompleted(); }).forEach(System.out::println); synchronous single value public static interface OnSubscribe { public void call(Subscriber super T> subscriber); } public abstract class Subscriber implements Observer, Subscription public abstract void onCompleted() public abstract void onError(Throwable e) public abstract void onNext(T t) ! public final void add(Subscription s) public void setProducer(Producer producer) } ! public interface Producer { public void request(long n); } public class Observable { public static Observable create(OnSubscribe f) public Subscription subscribe(Subscriber super T> subscriber) }

Observable.create(subscriber -> { subscriber.onNext("Hello"); subscriber.onNext("world"); subscriber.onNext("!"); subscriber.onCompleted(); }).forEach(System.out::println); synchronous multiple values public static interface OnSubscribe { public void call(Subscriber super T> subscriber); } public abstract class Subscriber implements Observer, Subscription public abstract void onCompleted() public abstract void onError(Throwable e) public abstract void onNext(T t) ! public final void add(Subscription s) public void setProducer(Producer producer) } ! public interface Producer { public void request(long n); } public class Observable { public static Observable create(OnSubscribe f) public Subscription subscribe(Subscriber super T> subscriber) }

Observable.create(subscriber -> { try { subscriber.onNext(doSomething()); subscriber.onCompleted(); } catch (Throwable e) { subscriber.onError(e); } }).subscribeOn(Schedulers.io()) .forEach(System.out::println); asynchronous single value error notification public static interface OnSubscribe { public void call(Subscriber super T> subscriber); } public abstract class Subscriber implements Observer, Subscription public abstract void onCompleted() public abstract void onError(Throwable e) public abstract void onNext(T t) ! public final void add(Subscription s) public void setProducer(Producer producer) } ! public interface Producer { public void request(long n); } public class Observable { public static Observable create(OnSubscribe f) public Subscription subscribe(Subscriber super T> subscriber) }

Observable.create(subscriber -> { int i = 0; while (!subscriber.isUnsubscribed()) { subscriber.onNext(i++); } }).take(10).forEach(System.out::println); synchronous multiple values with unsubscribe public static interface OnSubscribe { public void call(Subscriber super T> subscriber); } public abstract class Subscriber implements Observer, Subscription public abstract void onCompleted() public abstract void onError(Throwable e) public abstract void onNext(T t) ! public final void add(Subscription s) public void setProducer(Producer producer) } ! public interface Producer { public void request(long n); } public class Observable { public static Observable create(OnSubscribe f) public Subscription subscribe(Subscriber super T> subscriber) }

Observable.create(subscriber -> { AtomicInteger i = new AtomicInteger(); AtomicLong requested = new AtomicLong(); subscriber.setProducer(r -> { if (requested.getAndAdd(r) == 0) { do { if (subscriber.isUnsubscribed()) { break; } subscriber.onNext(i.incrementAndGet()); } while (requested.decrementAndGet() > 0); } }); }).observeOn(Schedulers.newThread()) .take(10).forEach(System.out::println); synchronous multiple values flow control with “reactive pull” backpressure thread scheduling public static interface OnSubscribe { public void call(Subscriber super T> subscriber); } public abstract class Subscriber implements Observer, Subscription public abstract void onCompleted() public abstract void onError(Throwable e) public abstract void onNext(T t) ! public final void add(Subscription s) public void setProducer(Producer producer) } ! public interface Producer { public void request(long n); } public class Observable { public static Observable create(OnSubscribe f) public Subscription subscribe(Subscriber super T> subscriber) }

Observable.create(subscriber -> { AtomicInteger i = new AtomicInteger(); AtomicLong requested = new AtomicLong(); subscriber.setProducer(r -> { if (requested.getAndAdd(r) == 0) { do { if (subscriber.isUnsubscribed()) { break; } subscriber.onNext(i.incrementAndGet()); } while (requested.decrementAndGet() > 0); } }); }).observeOn(Schedulers.newThread()) .take(10).forEach(System.out::println); public static interface OnSubscribe { public void call(Subscriber super T> subscriber); } public abstract class Subscriber implements Observer, Subscription public abstract void onCompleted() public abstract void onError(Throwable e) public abstract void onNext(T t) ! public final void add(Subscription s) public void setProducer(Producer producer) } ! public interface Producer { public void request(long n); } public class Observable { public static Observable create(OnSubscribe f) public Subscription subscribe(Subscriber super T> subscriber) }

Observable.from(iterable) .observeOn(Schedulers.newThread()) .take(10).forEach(System.out::println); public static interface OnSubscribe { public void call(Subscriber super T> subscriber); } public abstract class Subscriber implements Observer, Subscription public abstract void onCompleted() public abstract void onError(Throwable e) public abstract void onNext(T t) ! public final void add(Subscription s) public void setProducer(Producer producer) } ! public interface Producer { public void request(long n); } public class Observable { public static Observable create(OnSubscribe f) public Subscription subscribe(Subscriber super T> subscriber) }

finite

infinite finite

finite infinite distributed

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public Observable handle(HttpServerRequest request, HttpServerResponse response) { // first request User object return new UserCommand(request.getQueryParameters().get("userId")).observe().flatMap(user -> { // then fetch personal catalog Observable> catalog = new PersonalizedCatalogCommand(user).observe() .flatMap(catalogList -> { return catalogList.videos().> flatMap(video -> { Observable bookmark = new BookmarkCommand(video).observe(); Observable rating = new RatingsCommand(video).observe(); Observable metadata = new VideoMetadataCommand(video).observe(); return Observable.zip(bookmark, rating, metadata, (b, r, m) -> { return combineVideoData(video, b, r, m); }); }); }); // and fetch social data in parallel Observable> social = new SocialCommand(user).observe().map(s -> { return s.getDataAsMap(); }); // merge the results return Observable.merge(catalog, social); }).flatMap(data -> { // output as SSE as we get back the data (no waiting until all is done) return response.writeAndFlush(new ServerSentEvent(SimpleJson.mapToJson(data))); }); }

public Observable handle(HttpServerRequest request, HttpServerResponse response) { // first request User object return new UserCommand(request.getQueryParameters().get("userId")).observe().flatMap(user -> { // then fetch personal catalog Observable> catalog = new PersonalizedCatalogCommand(user).observe() .flatMap(catalogList -> { return catalogList.videos().> flatMap(video -> { Observable bookmark = new BookmarkCommand(video).observe(); Observable rating = new RatingsCommand(video).observe(); Observable metadata = new VideoMetadataCommand(video).observe(); return Observable.zip(bookmark, rating, metadata, (b, r, m) -> { return combineVideoData(video, b, r, m); }); }); }); // and fetch social data in parallel Observable> social = new SocialCommand(user).observe().map(s -> { return s.getDataAsMap(); }); // merge the results return Observable.merge(catalog, social); }).flatMap(data -> { // output as SSE as we get back the data (no waiting until all is done) return response.writeAndFlush(new ServerSentEvent(SimpleJson.mapToJson(data))); }); }

public Observable handle(HttpServerRequest request, HttpServerResponse response) { // first request User object return new UserCommand(request.getQueryParameters().get("userId")).observe().flatMap(user -> { // then fetch personal catalog Observable> catalog = new PersonalizedCatalogCommand(user).observe() .flatMap(catalogList -> { return catalogList.videos().> flatMap(video -> { Observable bookmark = new BookmarkCommand(video).observe(); Observable rating = new RatingsCommand(video).observe(); Observable metadata = new VideoMetadataCommand(video).observe(); return Observable.zip(bookmark, rating, metadata, (b, r, m) -> { return combineVideoData(video, b, r, m); }); }); }); // and fetch social data in parallel Observable> social = new SocialCommand(user).observe().map(s -> { return s.getDataAsMap(); }); // merge the results return Observable.merge(catalog, social); }).flatMap(data -> { // output as SSE as we get back the data (no waiting until all is done) return response.writeAndFlush(new ServerSentEvent(SimpleJson.mapToJson(data))); }); }

 Observable  b  =  Observable.flatMap({  T  t  -­‐>            Observable  r  =  ...  transform  t  ...          return  r;    }) flatMap

 Observable  b  =  Observable.flatMap({  T  t  -­‐>            Observable  r  =  ...  transform  t  ...          return  r;    }) flatMap

public Observable handle(HttpServerRequest request, HttpServerResponse response) { // first request User object return new UserCommand(request.getQueryParameters().get("userId")).observe().flatMap(user -> { // then fetch personal catalog Observable> catalog = new PersonalizedCatalogCommand(user).observe() .flatMap(catalogList -> { return catalogList.videos().> flatMap(video -> { Observable bookmark = new BookmarkCommand(video).observe(); Observable rating = new RatingsCommand(video).observe(); Observable metadata = new VideoMetadataCommand(video).observe(); return Observable.zip(bookmark, rating, metadata, (b, r, m) -> { return combineVideoData(video, b, r, m); }); }); }); // and fetch social data in parallel Observable> social = new SocialCommand(user).observe().map(s -> { return s.getDataAsMap(); }); // merge the results return Observable.merge(catalog, social); }).flatMap(data -> { // output as SSE as we get back the data (no waiting until all is done) return response.writeAndFlush(new ServerSentEvent(SimpleJson.mapToJson(data))); }); }

public Observable handle(HttpServerRequest request, HttpServerResponse response) { // first request User object return new UserCommand(request.getQueryParameters().get("userId")).observe().flatMap(user -> { // then fetch personal catalog Observable> catalog = new PersonalizedCatalogCommand(user).observe() .flatMap(catalogList -> { return catalogList.videos().> flatMap(video -> { Observable bookmark = new BookmarkCommand(video).observe(); Observable rating = new RatingsCommand(video).observe(); Observable metadata = new VideoMetadataCommand(video).observe(); return Observable.zip(bookmark, rating, metadata, (b, r, m) -> { return combineVideoData(video, b, r, m); }); }); }); // and fetch social data in parallel Observable> social = new SocialCommand(user).observe().map(s -> { return s.getDataAsMap(); }); // merge the results return Observable.merge(catalog, social); }).flatMap(data -> { // output as SSE as we get back the data (no waiting until all is done) return response.writeAndFlush(new ServerSentEvent(SimpleJson.mapToJson(data))); }); }

public Observable handle(HttpServerRequest request, HttpServerResponse response) { // first request User object return new UserCommand(request.getQueryParameters().get("userId")).observe().flatMap(user -> { // then fetch personal catalog Observable> catalog = new PersonalizedCatalogCommand(user).observe() .flatMap(catalogList -> { return catalogList.videos().> flatMap(video -> { Observable bookmark = new BookmarkCommand(video).observe(); Observable rating = new RatingsCommand(video).observe(); Observable metadata = new VideoMetadataCommand(video).observe(); return Observable.zip(bookmark, rating, metadata, (b, r, m) -> { return combineVideoData(video, b, r, m); }); }); }); // and fetch social data in parallel Observable> social = new SocialCommand(user).observe().map(s -> { return s.getDataAsMap(); }); // merge the results return Observable.merge(catalog, social); }).flatMap(data -> { // output as SSE as we get back the data (no waiting until all is done) return response.writeAndFlush(new ServerSentEvent(SimpleJson.mapToJson(data))); }); }

public Observable handle(HttpServerRequest request, HttpServerResponse response) { // first request User object return new UserCommand(request.getQueryParameters().get("userId")).observe().flatMap(user -> { // then fetch personal catalog Observable> catalog = new PersonalizedCatalogCommand(user).observe() .flatMap(catalogList -> { return catalogList.videos().> flatMap(video -> { Observable bookmark = new BookmarkCommand(video).observe(); Observable rating = new RatingsCommand(video).observe(); Observable metadata = new VideoMetadataCommand(video).observe(); return Observable.zip(bookmark, rating, metadata, (b, r, m) -> { return combineVideoData(video, b, r, m); }); }); }); // and fetch social data in parallel Observable> social = new SocialCommand(user).observe().map(s -> { return s.getDataAsMap(); }); // merge the results return Observable.merge(catalog, social); }).flatMap(data -> { // output as SSE as we get back the data (no waiting until all is done) return response.writeAndFlush(new ServerSentEvent(SimpleJson.mapToJson(data))); }); }

public Observable handle(HttpServerRequest request, HttpServerResponse response) { // first request User object return new UserCommand(request.getQueryParameters().get("userId")).observe().flatMap(user -> { // then fetch personal catalog Observable> catalog = new PersonalizedCatalogCommand(user).observe() .flatMap(catalogList -> { return catalogList.videos().> flatMap(video -> { Observable bookmark = new BookmarkCommand(video).observe(); Observable rating = new RatingsCommand(video).observe(); Observable metadata = new VideoMetadataCommand(video).observe(); return Observable.zip(bookmark, rating, metadata, (b, r, m) -> { return combineVideoData(video, b, r, m); }); }); }); // and fetch social data in parallel Observable> social = new SocialCommand(user).observe().map(s -> { return s.getDataAsMap(); }); // merge the results return Observable.merge(catalog, social); }).flatMap(data -> { // output as SSE as we get back the data (no waiting until all is done) return response.writeAndFlush(new ServerSentEvent(SimpleJson.mapToJson(data))); }); }

public Observable handle(HttpServerRequest request, HttpServerResponse response) { // first request User object return new UserCommand(request.getQueryParameters().get("userId")).observe().flatMap(user -> { // then fetch personal catalog Observable> catalog = new PersonalizedCatalogCommand(user).observe() .flatMap(catalogList -> { return catalogList.videos().> flatMap(video -> { Observable bookmark = new BookmarkCommand(video).observe(); Observable rating = new RatingsCommand(video).observe(); Observable metadata = new VideoMetadataCommand(video).observe(); return Observable.zip(bookmark, rating, metadata, (b, r, m) -> { return combineVideoData(video, b, r, m); }); }); }); // and fetch social data in parallel Observable> social = new SocialCommand(user).observe().map(s -> { return s.getDataAsMap(); }); // merge the results return Observable.merge(catalog, social); }).flatMap(data -> { // output as SSE as we get back the data (no waiting until all is done) return response.writeAndFlush(new ServerSentEvent(SimpleJson.mapToJson(data))); }); }

public Observable handle(HttpServerRequest request, HttpServerResponse response) { // first request User object return new UserCommand(request.getQueryParameters().get("userId")).observe().flatMap(user -> { // then fetch personal catalog Observable> catalog = new PersonalizedCatalogCommand(user).observe() .flatMap(catalogList -> { return catalogList.videos().> flatMap(video -> { Observable bookmark = new BookmarkCommand(video).observe(); Observable rating = new RatingsCommand(video).observe(); Observable metadata = new VideoMetadataCommand(video).observe(); return Observable.zip(bookmark, rating, metadata, (b, r, m) -> { return combineVideoData(video, b, r, m); }); }); }); // and fetch social data in parallel Observable> social = new SocialCommand(user).observe().map(s -> { return s.getDataAsMap(); }); // merge the results return Observable.merge(catalog, social); }).flatMap(data -> { // output as SSE as we get back the data (no waiting until all is done) return response.writeAndFlush(new ServerSentEvent(SimpleJson.mapToJson(data))); }); }

public Observable handle(HttpServerRequest request, HttpServerResponse response) { // first request User object return new UserCommand(request.getQueryParameters().get("userId")).observe().flatMap(user -> { // then fetch personal catalog Observable> catalog = new PersonalizedCatalogCommand(user).observe() .flatMap(catalogList -> { return catalogList.videos().> flatMap(video -> { Observable bookmark = new BookmarkCommand(video).observe(); Observable rating = new RatingsCommand(video).observe(); Observable metadata = new VideoMetadataCommand(video).observe(); return Observable.zip(bookmark, rating, metadata, (b, r, m) -> { return combineVideoData(video, b, r, m); }); }); }); // and fetch social data in parallel Observable> social = new SocialCommand(user).observe().map(s -> { return s.getDataAsMap(); }); // merge the results return Observable.merge(catalog, social); }).flatMap(data -> { // output as SSE as we get back the data (no waiting until all is done) return response.writeAndFlush(new ServerSentEvent(SimpleJson.mapToJson(data))); }); }

public Observable handle(HttpServerRequest request, HttpServerResponse response) { // first request User object return new UserCommand(request.getQueryParameters().get("userId")).observe().flatMap(user -> { // then fetch personal catalog Observable> catalog = new PersonalizedCatalogCommand(user).observe() .flatMap(catalogList -> { return catalogList.videos().> flatMap(video -> { Observable bookmark = new BookmarkCommand(video).observe(); Observable rating = new RatingsCommand(video).observe(); Observable metadata = new VideoMetadataCommand(video).observe(); return Observable.zip(bookmark, rating, metadata, (b, r, m) -> { return combineVideoData(video, b, r, m); }); }); }); // and fetch social data in parallel Observable> social = new SocialCommand(user).observe().map(s -> { return s.getDataAsMap(); }); // merge the results return Observable.merge(catalog, social); }).flatMap(data -> { // output as SSE as we get back the data (no waiting until all is done) return response.writeAndFlush(new ServerSentEvent(SimpleJson.mapToJson(data))); }); }

       Observable.zip(a,  b,  {  a,  b,  -­‐>                ...  operate  on  values  from  both  a  &  b  ...              return  [a,  b];  //  i.e.  return  tuple          })

public Observable handle(HttpServerRequest request, HttpServerResponse response) { // first request User object return new UserCommand(request.getQueryParameters().get("userId")).observe().flatMap(user -> { // then fetch personal catalog Observable> catalog = new PersonalizedCatalogCommand(user).observe() .flatMap(catalogList -> { return catalogList.videos().> flatMap(video -> { Observable bookmark = new BookmarkCommand(video).observe(); Observable rating = new RatingsCommand(video).observe(); Observable metadata = new VideoMetadataCommand(video).observe(); return Observable.zip(bookmark, rating, metadata, (b, r, m) -> { return combineVideoData(video, b, r, m); }); }); }); // and fetch social data in parallel Observable> social = new SocialCommand(user).observe().map(s -> { return s.getDataAsMap(); }); // merge the results return Observable.merge(catalog, social); }).flatMap(data -> { // output as SSE as we get back the data (no waiting until all is done) return response.writeAndFlush(new ServerSentEvent(SimpleJson.mapToJson(data))); }); }

public Observable handle(HttpServerRequest request, HttpServerResponse response) { // first request User object return new UserCommand(request.getQueryParameters().get("userId")).observe().flatMap(user -> { // then fetch personal catalog Observable> catalog = new PersonalizedCatalogCommand(user).observe() .flatMap(catalogList -> { return catalogList.videos().> flatMap(video -> { Observable bookmark = new BookmarkCommand(video).observe(); Observable rating = new RatingsCommand(video).observe(); Observable metadata = new VideoMetadataCommand(video).observe(); return Observable.zip(bookmark, rating, metadata, (b, r, m) -> { return combineVideoData(video, b, r, m); }); }); }); // and fetch social data in parallel Observable> social = new SocialCommand(user).observe().map(s -> { return s.getDataAsMap(); }); // merge the results return Observable.merge(catalog, social); }).flatMap(data -> { // output as SSE as we get back the data (no waiting until all is done) return response.writeAndFlush(new ServerSentEvent(SimpleJson.mapToJson(data))); }); }

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public Observable handle(HttpServerRequest request, HttpServerResponse response) { // first request User object return new UserCommand(request.getQueryParameters().get("userId")).observe().flatMap(user -> { // then fetch personal catalog Observable> catalog = new PersonalizedCatalogCommand(user).observe() .flatMap(catalogList -> { return catalogList.videos().> flatMap(video -> { Observable bookmark = new BookmarkCommand(video).observe(); Observable rating = new RatingsCommand(video).observe(); Observable metadata = new VideoMetadataCommand(video).observe(); return Observable.zip(bookmark, rating, metadata, (b, r, m) -> { return combineVideoData(video, b, r, m); }); }); }); // and fetch social data in parallel Observable> social = new SocialCommand(user).observe().map(s -> { return s.getDataAsMap(); }); // merge the results return Observable.merge(catalog, social); }).flatMap(data -> { // output as SSE as we get back the data (no waiting until all is done) return response.writeAndFlush(new ServerSentEvent(SimpleJson.mapToJson(data))); }); }

public Observable handle(HttpServerRequest request, HttpServerResponse response) { // first request User object return new UserCommand(request.getQueryParameters().get("userId")).observe().flatMap(user -> { // then fetch personal catalog Observable> catalog = new PersonalizedCatalogCommand(user).observe() .flatMap(catalogList -> { return catalogList.videos().> flatMap(video -> { Observable bookmark = new BookmarkCommand(video).observe(); Observable rating = new RatingsCommand(video).observe(); Observable metadata = new VideoMetadataCommand(video).observe(); return Observable.zip(bookmark, rating, metadata, (b, r, m) -> { return combineVideoData(video, b, r, m); }); }); }); // and fetch social data in parallel Observable> social = new SocialCommand(user).observe().map(s -> { return s.getDataAsMap(); }); // merge the results return Observable.merge(catalog, social); }).flatMap(data -> { // output as SSE as we get back the data (no waiting until all is done) return response.writeAndFlush(new ServerSentEvent(SimpleJson.mapToJson(data))); }); }

class  VideoService  {        def  Observable  getPersonalizedListOfMovies(userId);        def  Observable  getBookmark(userId,  videoId);        def  Observable  getRating(userId,  videoId);        def  Observable  getMetadata(videoId);   } an observable api: finite Treat everything like a stream

public Observable handle(HttpServerRequest request, HttpServerResponse response) { // first request User object return new UserCommand(request.getQueryParameters().get("userId")).observe().flatMap(user -> { // then fetch personal catalog Observable> catalog = new PersonalizedCatalogCommand(user).observe() .flatMap(catalogList -> { return catalogList.videos().> flatMap(video -> { Observable bookmark = new BookmarkCommand(video).observe(); Observable rating = new RatingsCommand(video).observe(); Observable metadata = new VideoMetadataCommand(video).observe(); return Observable.zip(bookmark, rating, metadata, (b, r, m) -> { return combineVideoData(video, b, r, m); }); }); }); // and fetch social data in parallel Observable> social = new SocialCommand(user).observe().map(s -> { return s.getDataAsMap(); }); // merge the results return Observable.merge(catalog, social); }).flatMap(data -> { // output as SSE as we get back the data (no waiting until all is done) return response.writeAndFlush(new ServerSentEvent(SimpleJson.mapToJson(data))); }); } 1 2 3 4 5 6

public Observable handle(HttpServerRequest request, HttpServerResponse response) { // first request User object return new UserCommand(request.getQueryParameters().get("userId")).observe().flatMap(user -> { // then fetch personal catalog Observable> catalog = new PersonalizedCatalogCommand(user).observe() .flatMap(catalogList -> { return catalogList.videos().> flatMap(video -> { Observable bookmark = new BookmarkCommand(video).observe(); Observable rating = new RatingsCommand(video).observe(); Observable metadata = new VideoMetadataCommand(video).observe(); return Observable.zip(bookmark, rating, metadata, (b, r, m) -> { return combineVideoData(video, b, r, m); }); }); }); // and fetch social data in parallel Observable> social = new SocialCommand(user).observe().map(s -> { return s.getDataAsMap(); }); // merge the results return Observable.merge(catalog, social); }).flatMap(data -> { // output as SSE as we get back the data (no waiting until all is done) return response.writeAndFlush(new ServerSentEvent(SimpleJson.mapToJson(data))); }); } 3 4 5

public Observable handle(HttpServerRequest request, HttpServerResponse response) { // first request User object return new UserCommand(request.getQueryParameters().get("userId")).observe().flatMap(user -> { // then fetch personal catalog Observable> catalog = new PersonalizedCatalogCommand(user).observe() .flatMap(catalogList -> { return catalogList.videos().> flatMap(video -> { Observable bookmark = new BookmarkCommand(video).observe(); Observable rating = new RatingsCommand(video).observe(); Observable metadata = new VideoMetadataCommand(video).observe(); return Observable.zip(bookmark, rating, metadata, (b, r, m) -> { return combineVideoData(video, b, r, m); }); }); }); // and fetch social data in parallel Observable> social = new SocialCommand(user).observe().map(s -> { return s.getDataAsMap(); }); // merge the results return Observable.merge(catalog, social); }).flatMap(data -> { // output as SSE as we get back the data (no waiting until all is done) return response.writeAndFlush(new ServerSentEvent(SimpleJson.mapToJson(data))); }); }

infinite

private static Observable>> aggregateUsingPivot(Observable>> instanceStreams) { return instanceStreams.map(instanceStream -> { return createGroupedObservable(instanceStream.getKey(), instanceStream .groupBy((Map json) -> { return TypeAndNameKey.from(String.valueOf(json.get("type")), String.valueOf(json.get("name"))); })); }).lift(OperatorPivot.create()).map(commandGroup -> { // merge all instances per group into a single stream of deltas and sum them return createGroupedObservable(commandGroup.getKey(), commandGroup.flatMap(instanceGroup -> { return instanceGroup.startWith(Collections. emptyMap()) .buffer(2, 1) .map(StreamAggregator::previousAndCurrentToDelta) .filter(data -> data != null && !data.isEmpty()); }).scan(new HashMap(), StreamAggregator::sumOfDelta) .skip(1)); }); }

private static Observable>> aggregateUsingPivot(Observable>> instanceStreams) { return instanceStreams.map(instanceStream -> { return createGroupedObservable(instanceStream.getKey(), instanceStream .groupBy((Map json) -> { return TypeAndNameKey.from(String.valueOf(json.get("type")), String.valueOf(json.get("name"))); })); }).lift(OperatorPivot.create()).map(commandGroup -> { // merge all instances per group into a single stream of deltas and sum them return createGroupedObservable(commandGroup.getKey(), commandGroup.flatMap(instanceGroup -> { return instanceGroup.startWith(Collections. emptyMap()) .buffer(2, 1) .map(StreamAggregator::previousAndCurrentToDelta) .filter(data -> data != null && !data.isEmpty()); }).scan(new HashMap(), StreamAggregator::sumOfDelta) .skip(1)); }); }

No content

private static Observable>> aggregateUsingPivot(Observable>> instanceStreams) { return instanceStreams.map(instanceStream -> { return createGroupedObservable(instanceStream.getKey(), instanceStream .groupBy((Map json) -> { return TypeAndNameKey.from(String.valueOf(json.get("type")), String.valueOf(json.get("name"))); })); }).lift(OperatorPivot.create()).map(commandGroup -> { // merge all instances per group into a single stream of deltas and sum them return createGroupedObservable(commandGroup.getKey(), commandGroup.flatMap(instanceGroup -> { return instanceGroup.startWith(Collections. emptyMap()) .buffer(2, 1) .map(StreamAggregator::previousAndCurrentToDelta) .filter(data -> data != null && !data.isEmpty()); }).scan(new HashMap(), StreamAggregator::sumOfDelta) .skip(1)); }); }

No content

private static Observable>> aggregateUsingPivot(Observable>> instanceStreams) { return instanceStreams.map(instanceStream -> { return createGroupedObservable(instanceStream.getKey(), instanceStream .groupBy((Map json) -> { return TypeAndNameKey.from(String.valueOf(json.get("type")), String.valueOf(json.get("name"))); })); }).lift(OperatorPivot.create()).map(commandGroup -> { // merge all instances per group into a single stream of deltas and sum them return createGroupedObservable(commandGroup.getKey(), commandGroup.flatMap(instanceGroup -> { return instanceGroup.startWith(Collections. emptyMap()) .buffer(2, 1) .map(StreamAggregator::previousAndCurrentToDelta) .filter(data -> data != null && !data.isEmpty()); }).scan(new HashMap(), StreamAggregator::sumOfDelta) .skip(1)); }); }

No content

data: {“type":"HystrixCommand","name":"GetPredictions","requestCount":317,"rollingCountSuccess":327,"reportingHosts":1} data: {“type":"HystrixCommand","name":"GetPredictions","requestCount":1376,"rollingCountSuccess":1432,"reportingHosts":4}

data: {“type":"HystrixCommand","name":"GetPredictions","requestCount":317,"rollingCountSuccess":327,"reportingHosts":1} data: {“type":"HystrixCommand","name":"GetPredictions","requestCount":1376,"rollingCountSuccess":1432,"reportingHosts":4}

data => {"rollingCountFallbackFailure":0,"rollingCountFallbackSuccess": 0,"propertyValue_circuitBreakerRequestVolumeThreshold":"20","propertyValue_circuitBreakerForceOpen":false,"propertyValue_metricsRol lingStatisticalWindowInMilliseconds":"10000","latencyTotal_mean":32,"type":"HystrixCommand","rollingCountResponsesFromCache": 0,"rollingCountTimeout":0,"propertyValue_executionIsolationStrategy":"SEMAPHORE","instanceId":"34567","rollingCountFailure": 0,"rollingCountExceptionsThrown":0,"latencyExecute_mean":32,"isCircuitBreakerOpen":false,"errorCount": 0,"rollingCountSemaphoreRejected":0,"latencyTotal":{"0":0,"25":0,"50":12,"75":48,"90":68,"95":96,"99":192,"99.5":1452,"100": 1560},"requestCount":1376,"rollingCountCollapsedRequests":94516,"rollingCountShortCircuited":0,"latencyExecute":{"0":0,"25":0,"50": 12,"75":48,"90":68,"95":96,"99":192,"99.5":1452,"100": 1560},"propertyValue_circuitBreakerSleepWindowInMilliseconds":"5000","currentConcurrentExecutionCount": 0,"propertyValue_executionIsolationSemaphoreMaxConcurrentRequests":"10","errorPercentage":0,"rollingCountThreadPoolRejected": 0,"propertyValue_circuitBreakerEnabled":true,"propertyValue_executionIsolationThreadInterruptOnTimeout":true,"propertyValue_request CacheEnabled":true,"rollingCountFallbackRejection":0,"propertyValue_requestLogEnabled":true,"rollingCountSuccess": 1432,"propertyValue_fallbackIsolationSemaphoreMaxConcurrentRequests":"10","propertyValue_circuitBreakerErrorThresholdPercentage":"5 0","propertyValue_circuitBreakerForceClosed":false,"name":"GetPredictions","reportingHosts": 4,"propertyValue_executionIsolationThreadPoolKeyOverride":"null","propertyValue_executionIsolationThreadTimeoutInMilliseconds":"100 0"} data: {“type":"HystrixCommand","name":"GetPredictions","requestCount":317,"rollingCountSuccess":327,"reportingHosts":1} data: {“type":"HystrixCommand","name":"GetPredictions","requestCount":1376,"rollingCountSuccess":1432,"reportingHosts":4}

Flow Control

Flow Control (backpressure)

no backpressure needed Observable.from(iterable).take(1000).map(i -> "value_" + i).subscribe(System.out::println);

Observable.from(iterable).take(1000).map(i -> "value_" + i).subscribe(System.out::println); no backpressure needed synchronous on same thread (no queueing)

Observable.from(iterable).take(1000).map(i -> "value_" + i) .observeOn(Schedulers.computation()).subscribe(System.out::println); backpressure needed

Observable.from(iterable).take(1000).map(i -> "value_" + i) .observeOn(Schedulers.computation()).subscribe(System.out::println); backpressure needed asynchronous (queueing)

Flow Control Options

Block (callstack blocking and/or park the thread)

Temporal Operators (batch or drop data using time)

Observable.range(1, 1000000).sample(10, TimeUnit.MILLISECONDS).forEach(System.out::println); 110584 242165 544453 942880

Observable.range(1, 1000000).throttleFirst(10, TimeUnit.MILLISECONDS).forEach(System.out::println); 1 55463 163962 308545 457445 592638 751789 897159

Observable.range(1, 1000000).debounce(10, TimeUnit.MILLISECONDS).forEach(System.out::println); 1000000

Observable.range(1, 1000000).buffer(10, TimeUnit.MILLISECONDS) .toBlocking().forEach(list -> System.out.println("batch: " + list.size())); batch: 71141 batch: 49488 batch: 141147 batch: 141432 batch: 195920 batch: 240462 batch: 160410

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/* The following will emit a buffered list as it is debounced */ // first we multicast the stream ... using refCount so it handles the subscribe/unsubscribe Observable burstStream = intermittentBursts().take(20).publish().refCount(); // then we get the debounced version Observable debounced = burstStream.debounce(10, TimeUnit.MILLISECONDS); // then the buffered one that uses the debounced stream to demark window start/stop Observable> buffered = burstStream.buffer(debounced); // then we subscribe to the buffered stream so it does what we want buffered.toBlocking().forEach(System.out::println); [0, 1, 2] [0, 1, 2] [0, 1, 2, 3, 4, 5, 6] [0, 1, 2, 3, 4] [0, 1] []

/* The following will emit a buffered list as it is debounced */ // first we multicast the stream ... using refCount so it handles the subscribe/unsubscribe Observable burstStream = intermittentBursts().take(20).publish().refCount(); // then we get the debounced version Observable debounced = burstStream.debounce(10, TimeUnit.MILLISECONDS); // then the buffered one that uses the debounced stream to demark window start/stop Observable> buffered = burstStream.buffer(debounced); // then we subscribe to the buffered stream so it does what we want buffered.toBlocking().forEach(System.out::println); [0, 1, 2] [0, 1, 2] [0, 1, 2, 3, 4, 5, 6] [0, 1, 2, 3, 4] [0, 1] []

/* The following will emit a buffered list as it is debounced */ // first we multicast the stream ... using refCount so it handles the subscribe/unsubscribe Observable burstStream = intermittentBursts().take(20).publish().refCount(); // then we get the debounced version Observable debounced = burstStream.debounce(10, TimeUnit.MILLISECONDS); // then the buffered one that uses the debounced stream to demark window start/stop Observable> buffered = burstStream.buffer(debounced); // then we subscribe to the buffered stream so it does what we want buffered.toBlocking().forEach(System.out::println); [0, 1, 2] [0, 1, 2] [0, 1, 2, 3, 4, 5, 6] [0, 1, 2, 3, 4] [0, 1] []

/* The following will emit a buffered list as it is debounced */ // first we multicast the stream ... using refCount so it handles the subscribe/unsubscribe Observable burstStream = intermittentBursts().take(20).publish().refCount(); // then we get the debounced version Observable debounced = burstStream.debounce(10, TimeUnit.MILLISECONDS); // then the buffered one that uses the debounced stream to demark window start/stop Observable> buffered = burstStream.buffer(debounced); // then we subscribe to the buffered stream so it does what we want buffered.toBlocking().forEach(System.out::println); [0, 1, 2] [0, 1, 2] [0, 1, 2, 3, 4, 5, 6] [0, 1, 2, 3, 4] [0, 1] []

/* The following will emit a buffered list as it is debounced */ // first we multicast the stream ... using refCount so it handles the subscribe/unsubscribe Observable burstStream = intermittentBursts().take(20).publish().refCount(); // then we get the debounced version Observable debounced = burstStream.debounce(10, TimeUnit.MILLISECONDS); // then the buffered one that uses the debounced stream to demark window start/stop Observable> buffered = burstStream.buffer(debounced); // then we subscribe to the buffered stream so it does what we want buffered.toBlocking().forEach(System.out::println); [0, 1, 2] [0, 1, 2] [0, 1, 2, 3, 4, 5, 6] [0, 1, 2, 3, 4] [0, 1] []

/* The following will emit a buffered list as it is debounced */ // first we multicast the stream ... using refCount so it handles the subscribe/unsubscribe Observable burstStream = intermittentBursts().take(20).publish().refCount(); // then we get the debounced version Observable debounced = burstStream.debounce(10, TimeUnit.MILLISECONDS); // then the buffered one that uses the debounced stream to demark window start/stop Observable> buffered = burstStream.buffer(debounced); // then we subscribe to the buffered stream so it does what we want buffered.toBlocking().forEach(System.out::println); [0, 1, 2] [0, 1, 2] [0, 1, 2, 3, 4, 5, 6] [0, 1, 2, 3, 4] [0, 1] [] https://gist.github.com/benjchristensen/e4524a308456f3c21c0b

Observable.range(1, 1000000).window(50, TimeUnit.MILLISECONDS) .flatMap(window -> window.count()) .toBlocking().forEach(count -> System.out.println("num items: " + count)); num items: 477769 num items: 155463 num items: 366768

Observable.range(1, 1000000).window(500000) .flatMap(window -> window.count()) .toBlocking().forEach(count -> System.out.println("num items: " + count)); num items: 500000 num items: 500000

Reactive Pull (dynamic push-pull)

Push when consumer keeps up with producer. ! Switch to Pull when consumer is slow. ! Bound all* queues.

Push when consumer keeps up with producer. ! Switch to Pull when consumer is slow. ! Bound all* queues. *vertically, not horizontally

Observable Subscriber Observable.create(subscriber -> { // emit to subscriber }).subscribe(new Subscriber() { ! public void onCompleted() { // do stuff } ! public void onError(Throwable e) { // handle error } ! public void onNext(String t) { ! } ! });

observable.subscribe Observable.create(subscriber -> { // emit to subscriber }).subscribe(new Subscriber() { ! public void onCompleted() { // do stuff } ! public void onError(Throwable e) { // handle error } ! public void onNext(String t) { ! } ! });

observable.subscribe subscriber.setProducer Observable.create(subscriber -> { subscriber.setProducer(request -> { }); }).subscribe(new Subscriber() { ! public void onCompleted() { // do stuff } ! public void onError(Throwable e) { // handle error } ! public void onNext(String t) { ! } ! });

Observable.create(subscriber -> { subscriber.setProducer(request -> { }); }).subscribe(new Subscriber() { ! public void onStart() { request(5); } ! public void onCompleted() { // do stuff } ! public void onError(Throwable e) { // handle error } ! public void onNext(String t) { ! } ! }); observable.subscribe subscriber.setProducer producer.request(n)

Observable.create(subscriber -> { subscriber.setProducer(request -> { subscriber.onNext(t); // 5 times }); }).subscribe(new Subscriber() { ! public void onStart() { request(5); } ! public void onCompleted() { // do stuff } ! public void onError(Throwable e) { // handle error } ! public void onNext(String t) { ! } ! }); observable.subscribe subscriber.setProducer producer.request(n) subscriber.onNext(t) …

Observable.create(subscriber -> { subscriber.setProducer(request -> { subscriber.onNext(t); // 5 times }); }).subscribe(new Subscriber() { ! public void onStart() { request(5); } ! public void onCompleted() { // do stuff } ! public void onError(Throwable e) { // handle error } ! public void onNext(String t) { doStuffWith(t); if(requested—- == 0) request(5); } ! }); observable.subscribe subscriber.setProducer producer.request(n) subscriber.onNext(t) … producer.request(n)

Observable.create(subscriber -> { subscriber.setProducer(request -> { … previous logic … subscriber.onCompleted(); }); }).subscribe(new Subscriber() { ! public void onStart() { request(5); } ! public void onCompleted() { // do stuff } ! public void onError(Throwable e) { // handle error } ! public void onNext(String t) { doStuffWith(t); if(requested—- == 0) request(5); } ! }); observable.subscribe subscriber.setProducer producer.request(n) subscriber.onNext(t) … producer.request(n) subscriber.onCompleted/onError unsubscribe

Observable Subscriber Observable Subscriber observable.subscribe observable.subscribe

Observable.from(iterable) .observeOn(Schedulers.computation()) .subscribe(System.out::println);

Observable.from(iterable) .observeOn(Schedulers.computation()) .subscribe(System.out::println);

Observable Subscriber Observable Subscriber observable.subscribe observable.subscribe

Observable Subscriber Observable Subscriber subscriber.setProducer subscriber.setProducer

Observable Subscriber Observable Subscriber producer.request(n) producer.request(5) outstanding requested = 5

Observable Subscriber Observable Subscriber producer.request(n) producer.request(5) outstanding requested = 5

Observable Subscriber Observable Subscriber producer.request(n) producer.request(5) outstanding requested = 5

Observable Subscriber Observable Subscriber subscriber.onNext outstanding requested = 5

Observable Subscriber Observable Subscriber outstanding requested = 5 subscriber.onNext

Observable Subscriber Observable Subscriber outstanding requested = 4 subscriber.onNext

Observable Subscriber Observable Subscriber outstanding requested = 3 subscriber.onNext

Observable Subscriber Observable Subscriber outstanding requested = 3 subscriber.onNext producer.request(1) request(1)

Observable Subscriber Observable Subscriber outstanding requested = 4 subscriber.onNext producer.request(1)

Observable Subscriber Observable Subscriber outstanding requested = 4 subscriber.onNext subscriber.onNext

Observable Subscriber Observable Subscriber outstanding requested = 0 subscriber.onNext

Observable Subscriber Observable Subscriber outstanding requested = 0 subscriber.onNext

Observable Subscriber Observable Subscriber outstanding requested = 0 subscriber.onNext

Observable Subscriber Observable Subscriber outstanding requested = 0 subscriber.onNext

Observable Subscriber Observable Subscriber outstanding requested = 0 subscriber.onNext

Observable Subscriber Observable Subscriber outstanding requested = 2 subscriber.onNext request(2) producer.request(2)

someObservable.subscribe(new Subscriber() { @Override public void onStart() { request(1); } ! @Override public void onCompleted() { // gracefully handle sequence-complete } ! @Override public void onError(Throwable e) { // gracefully handle error } ! @Override public void onNext(T n) { // do something with the emitted item "n" // request another item: request(1); } });

someObservable.subscribe(new Subscriber() { @Override public void onStart() { request(1); } ! @Override public void onCompleted() { // gracefully handle sequence-complete } ! @Override public void onError(Throwable e) { // gracefully handle error } ! @Override public void onNext(T n) { // do something with the emitted item "n" // request another item: request(1); } });

someObservable.subscribe(new Subscriber() { @Override public void onStart() { request(1); } ! @Override public void onCompleted() { // gracefully handle sequence-complete } ! @Override public void onError(Throwable e) { // gracefully handle error } ! @Override public void onNext(T n) { // do something with the emitted item "n" // request another item: request(1); } });

someObservable.subscribe(new Subscriber() { @Override public void onStart() { request(1024); } ! @Override public void onCompleted() { // gracefully handle sequence-complete } ! @Override public void onError(Throwable e) { // gracefully handle error } ! @Override public void onNext(T n) { enqueue(n); // elsewhere the queue is drained // and request(m) is called } ! });

someObservable.subscribe(new Subscriber() { @Override public void onStart() { request(1024); } ! @Override public void onCompleted() { // gracefully handle sequence-complete } ! @Override public void onError(Throwable e) { // gracefully handle error } ! @Override public void onNext(T n) { enqueue(n); // elsewhere the queue is drained // and request(m) is called } ! });

someObservable.subscribe(new Subscriber() { @Override public void onStart() { request(1024); } ! @Override public void onCompleted() { // gracefully handle sequence-complete } ! @Override public void onError(Throwable e) { // gracefully handle error } ! @Override public void onNext(T n) { enqueue(n); // elsewhere the queue is drained // and request(m) is called } ! });

Reactive Pull hot vs cold?

Reactive Pull … or when source doesn’t support request(n)?

hotSourceStream.onBackpressureBuffer().observeOn(aScheduler);

hotSourceStream.onBackpressureBuffer().observeOn(aScheduler);

hotSourceStream.onBackpressureBuffer().observeOn(aScheduler);

hotSourceStream.onBackpressureBuffer().observeOn(aScheduler);

hotSourceStream.onBackpressureDrop().observeOn(aScheduler);

stream.onBackpressure(strategy).subscribe

distributed

MantisJob .source(NetflixSources.moviePlayAttempts()) .stage(playAttempts -> { return playAttempts.groupBy(playAttempt -> { return playAttempt.getMovieId(); }) }) .stage(playAttemptsByMovieId -> { playAttemptsByMovieId .window(10,TimeUnit.MINUTES, 1000) // buffer for 10 minutes, or 1000 play attempts .flatMap(windowOfPlayAttempts -> { return windowOfPlayAttempts .reduce(new FailRatioExperiment(playAttemptsByMovieId.getKey()), (experiment, playAttempt) -> { experiment.updateFailRatio(playAttempt); experiment.updateExamples(playAttempt); return experiment; }).doOnNext(experiment -> { logToHistorical("Play attempt experiment", experiment.getId(),experiment); // log for offline analysis }).filter(experiment -> { return experiment.failRatio() >= DYNAMIC_PROP("fail_threshold").get(); }).map(experiment -> { return new FailReport(experiment, runCorrelations(experiment.getExamples())); }).doOnNext(report -> { logToHistorical("Failure report", report.getId(), report); // log for offline analysis }) }) }) .sink(Sinks.emailAlert(report -> { return toEmail(report)})) // anomalies trigger events (simple email here)

MantisJob .source(NetflixSources.moviePlayAttempts()) .stage(playAttempts -> { return playAttempts.groupBy(playAttempt -> { return playAttempt.getMovieId(); }) }) .stage(playAttemptsByMovieId -> { playAttemptsByMovieId .window(10,TimeUnit.MINUTES, 1000) // buffer for 10 minutes, or 1000 play attempts .flatMap(windowOfPlayAttempts -> { return windowOfPlayAttempts .reduce(new FailRatioExperiment(playAttemptsByMovieId.getKey()), (experiment, playAttempt) -> { experiment.updateFailRatio(playAttempt); experiment.updateExamples(playAttempt); return experiment; }).doOnNext(experiment -> { logToHistorical("Play attempt experiment", experiment.getId(),experiment); // log for offline analysis }).filter(experiment -> { return experiment.failRatio() >= DYNAMIC_PROP("fail_threshold").get(); }).map(experiment -> { return new FailReport(experiment, runCorrelations(experiment.getExamples())); }).doOnNext(report -> { logToHistorical("Failure report", report.getId(), report); // log for offline analysis }) }) }) .sink(Sinks.emailAlert(report -> { return toEmail(report)})) // anomalies trigger events (simple email here)

MantisJob .source(NetflixSources.moviePlayAttempts()) .stage(playAttempts -> { return playAttempts.groupBy(playAttempt -> { return playAttempt.getMovieId(); }) }) .stage(playAttemptsByMovieId -> { playAttemptsByMovieId .window(10,TimeUnit.MINUTES, 1000) // buffer for 10 minutes, or 1000 play attempts .flatMap(windowOfPlayAttempts -> { return windowOfPlayAttempts .reduce(new FailRatioExperiment(playAttemptsByMovieId.getKey()), (experiment, playAttempt) -> { experiment.updateFailRatio(playAttempt); experiment.updateExamples(playAttempt); return experiment; }).doOnNext(experiment -> { logToHistorical("Play attempt experiment", experiment.getId(),experiment); // log for offline analysis }).filter(experiment -> { return experiment.failRatio() >= DYNAMIC_PROP("fail_threshold").get(); }).map(experiment -> { return new FailReport(experiment, runCorrelations(experiment.getExamples())); }).doOnNext(report -> { logToHistorical("Failure report", report.getId(), report); // log for offline analysis }) }) }) .sink(Sinks.emailAlert(report -> { return toEmail(report)})) // anomalies trigger events (simple email here)

MantisJob .source(NetflixSources.moviePlayAttempts()) .stage(playAttempts -> { return playAttempts.groupBy(playAttempt -> { return playAttempt.getMovieId(); }) }) .stage(playAttemptsByMovieId -> { playAttemptsByMovieId .window(10,TimeUnit.MINUTES, 1000) // buffer for 10 minutes, or 1000 play attempts .flatMap(windowOfPlayAttempts -> { return windowOfPlayAttempts .reduce(new FailRatioExperiment(playAttemptsByMovieId.getKey()), (experiment, playAttempt) -> { experiment.updateFailRatio(playAttempt); experiment.updateExamples(playAttempt); return experiment; }).doOnNext(experiment -> { logToHistorical("Play attempt experiment", experiment.getId(),experiment); // log for offline analysis }).filter(experiment -> { return experiment.failRatio() >= DYNAMIC_PROP("fail_threshold").get(); }).map(experiment -> { return new FailReport(experiment, runCorrelations(experiment.getExamples())); }).doOnNext(report -> { logToHistorical("Failure report", report.getId(), report); // log for offline analysis }) }) }) .sink(Sinks.emailAlert(report -> { return toEmail(report)})) // anomalies trigger events (simple email here)

MantisJob .source(NetflixSources.moviePlayAttempts()) .stage(playAttempts -> { return playAttempts.groupBy(playAttempt -> { return playAttempt.getMovieId(); }) }) .stage(playAttemptsByMovieId -> { playAttemptsByMovieId .window(10,TimeUnit.MINUTES, 1000) // buffer for 10 minutes, or 1000 play attempts .flatMap(windowOfPlayAttempts -> { return windowOfPlayAttempts .reduce(new FailRatioExperiment(playAttemptsByMovieId.getKey()), (experiment, playAttempt) -> { experiment.updateFailRatio(playAttempt); experiment.updateExamples(playAttempt); return experiment; }).doOnNext(experiment -> { logToHistorical("Play attempt experiment", experiment.getId(),experiment); // log for offline analysis }).filter(experiment -> { return experiment.failRatio() >= DYNAMIC_PROP("fail_threshold").get(); }).map(experiment -> { return new FailReport(experiment, runCorrelations(experiment.getExamples())); }).doOnNext(report -> { logToHistorical("Failure report", report.getId(), report); // log for offline analysis }) }) }) .sink(Sinks.emailAlert(report -> { return toEmail(report)})) // anomalies trigger events (simple email here)

(movieId) movieId=12345 movieId=34567

MantisJob .source(NetflixSources.moviePlayAttempts()) .stage(playAttempts -> { return playAttempts.groupBy(playAttempt -> { return playAttempt.getMovieId(); }) }) .stage(playAttemptsByMovieId -> { playAttemptsByMovieId .window(10,TimeUnit.MINUTES, 1000) // buffer for 10 minutes, or 1000 play attempts .flatMap(windowOfPlayAttempts -> { return windowOfPlayAttempts .reduce(new FailRatioExperiment(playAttemptsByMovieId.getKey()), (experiment, playAttempt) -> { experiment.updateFailRatio(playAttempt); experiment.updateExamples(playAttempt); return experiment; }).doOnNext(experiment -> { logToHistorical("Play attempt experiment", experiment.getId(),experiment); // log for offline analysis }).filter(experiment -> { return experiment.failRatio() >= DYNAMIC_PROP("fail_threshold").get(); }).map(experiment -> { return new FailReport(experiment, runCorrelations(experiment.getExamples())); }).doOnNext(report -> { logToHistorical("Failure report", report.getId(), report); // log for offline analysis }) }) }) .sink(Sinks.emailAlert(report -> { return toEmail(report)})) // anomalies trigger events (simple email here)

MantisJob .source(NetflixSources.moviePlayAttempts()) .stage(playAttempts -> { return playAttempts.groupBy(playAttempt -> { return playAttempt.getMovieId(); }) }) .stage(playAttemptsByMovieId -> { playAttemptsByMovieId .window(10,TimeUnit.MINUTES, 1000) // buffer for 10 minutes, or 1000 play attempts .flatMap(windowOfPlayAttempts -> { return windowOfPlayAttempts .reduce(new FailRatioExperiment(playAttemptsByMovieId.getKey()), (experiment, playAttempt) -> { experiment.updateFailRatio(playAttempt); experiment.updateExamples(playAttempt); return experiment; }).doOnNext(experiment -> { logToHistorical("Play attempt experiment", experiment.getId(),experiment); // log for offline analysis }).filter(experiment -> { return experiment.failRatio() >= DYNAMIC_PROP("fail_threshold").get(); }).map(experiment -> { return new FailReport(experiment, runCorrelations(experiment.getExamples())); }).doOnNext(report -> { logToHistorical("Failure report", report.getId(), report); // log for offline analysis }) }) }) .sink(Sinks.emailAlert(report -> { return toEmail(report)})) // anomalies trigger events (simple email here)

Stage 1 Stage 2 groupBy Event Streams sink

Stage 1 Stage 2 12345 56789 34567

Stage 1 Stage 2 12345 56789 34567

Stage 1 Stage 2 12345 56789 34567

Stage 1 Stage 2 12345 56789 34567

Stage 1 Stage 2 12345 56789 34567 12345 56789 34567

Stage 1 Stage 2 12345 56789 34567 12345 56789 34567

Stage 1 Stage 2 12345 56789 34567 12345 56789 34567

Stage 1 Stage 2 12345 56789 34567 12345 56789 34567

MantisJob .source(NetflixSources.moviePlayAttempts()) .stage(playAttempts -> { return playAttempts.groupBy(playAttempt -> { return playAttempt.getMovieId(); }) }) .stage(playAttemptsByMovieId -> { playAttemptsByMovieId .window(10,TimeUnit.MINUTES, 1000) // buffer for 10 minutes, or 1000 play attempts .flatMap(windowOfPlayAttempts -> { return windowOfPlayAttempts .reduce(new FailRatioExperiment(playAttemptsByMovieId.getKey()), (experiment, playAttempt) -> { experiment.updateFailRatio(playAttempt); experiment.updateExamples(playAttempt); return experiment; }).doOnNext(experiment -> { logToHistorical("Play attempt experiment", experiment.getId(),experiment); // log for offline analysis }).filter(experiment -> { return experiment.failRatio() >= DYNAMIC_PROP("fail_threshold").get(); }).map(experiment -> { return new FailReport(experiment, runCorrelations(experiment.getExamples())); }).doOnNext(report -> { logToHistorical("Failure report", report.getId(), report); // log for offline analysis }) }) }) .sink(Sinks.emailAlert(report -> { return toEmail(report)})) // anomalies trigger events (simple email here)

10mins || 1000 4:40-4:50pm 4:50-5:00pm 5:00-5:07pm (burst to 1000) 5:07-5:17pm

10mins || 1000 4:40-4:50pm 4:50-5:00pm 5:00-5:07pm (burst to 1000) 5:07-5:17pm

MantisJob .source(NetflixSources.moviePlayAttempts()) .stage(playAttempts -> { return playAttempts.groupBy(playAttempt -> { return playAttempt.getMovieId(); }) }) .stage(playAttemptsByMovieId -> { playAttemptsByMovieId .window(10,TimeUnit.MINUTES, 1000) // buffer for 10 minutes, or 1000 play attempts .flatMap(windowOfPlayAttempts -> { return windowOfPlayAttempts .reduce(new FailRatioExperiment(playAttemptsByMovieId.getKey()), (experiment, playAttempt) -> { experiment.updateFailRatio(playAttempt); experiment.updateExamples(playAttempt); return experiment; }).doOnNext(experiment -> { logToHistorical("Play attempt experiment", experiment.getId(),experiment); // log for offline analysis }).filter(experiment -> { return experiment.failRatio() >= DYNAMIC_PROP("fail_threshold").get(); }).map(experiment -> { return new FailReport(experiment, runCorrelations(experiment.getExamples())); }).doOnNext(report -> { logToHistorical("Failure report", report.getId(), report); // log for offline analysis }) }) }) .sink(Sinks.emailAlert(report -> { return toEmail(report)})) // anomalies trigger events (simple email here)

flatMap

flatMap

MantisJob .source(NetflixSources.moviePlayAttempts()) .stage(playAttempts -> { return playAttempts.groupBy(playAttempt -> { return playAttempt.getMovieId(); }) }) .stage(playAttemptsByMovieId -> { playAttemptsByMovieId .window(10,TimeUnit.MINUTES, 1000) // buffer for 10 minutes, or 1000 play attempts .flatMap(windowOfPlayAttempts -> { return windowOfPlayAttempts .reduce(new FailRatioExperiment(playAttemptsByMovieId.getKey()), (experiment, playAttempt) -> { experiment.updateFailRatio(playAttempt); experiment.updateExamples(playAttempt); return experiment; }).doOnNext(experiment -> { logToHistorical("Play attempt experiment", experiment.getId(),experiment); // log for offline analysis }).filter(experiment -> { return experiment.failRatio() >= DYNAMIC_PROP("fail_threshold").get(); }).map(experiment -> { return new FailReport(experiment, runCorrelations(experiment.getExamples())); }).doOnNext(report -> { logToHistorical("Failure report", report.getId(), report); // log for offline analysis }) }) }) .sink(Sinks.emailAlert(report -> { return toEmail(report)})) // anomalies trigger events (simple email here)

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MantisJob .source(NetflixSources.moviePlayAttempts()) .stage(playAttempts -> { return playAttempts.groupBy(playAttempt -> { return playAttempt.getMovieId(); }) }) .stage(playAttemptsByMovieId -> { playAttemptsByMovieId .window(10,TimeUnit.MINUTES, 1000) // buffer for 10 minutes, or 1000 play attempts .flatMap(windowOfPlayAttempts -> { return windowOfPlayAttempts .reduce(new FailRatioExperiment(playAttemptsByMovieId.getKey()), (experiment, playAttempt) -> { experiment.updateFailRatio(playAttempt); experiment.updateExamples(playAttempt); return experiment; }).doOnNext(experiment -> { logToHistorical("Play attempt experiment", experiment.getId(),experiment); // log for offline analysis }).filter(experiment -> { return experiment.failRatio() >= DYNAMIC_PROP("fail_threshold").get(); }).map(experiment -> { return new FailReport(experiment, runCorrelations(experiment.getExamples())); }).doOnNext(report -> { logToHistorical("Failure report", report.getId(), report); // log for offline analysis }) }) }) .sink(Sinks.emailAlert(report -> { return toEmail(report)})) // anomalies trigger events (simple email here)

MantisJob .source(NetflixSources.moviePlayAttempts()) .stage(playAttempts -> { return playAttempts.groupBy(playAttempt -> { return playAttempt.getMovieId(); }) }) .stage(playAttemptsByMovieId -> { playAttemptsByMovieId .window(10,TimeUnit.MINUTES, 1000) // buffer for 10 minutes, or 1000 play attempts .flatMap(windowOfPlayAttempts -> { return windowOfPlayAttempts .reduce(new FailRatioExperiment(playAttemptsByMovieId.getKey()), (experiment, playAttempt) -> { experiment.updateFailRatio(playAttempt); experiment.updateExamples(playAttempt); return experiment; }).doOnNext(experiment -> { logToHistorical("Play attempt experiment", experiment.getId(),experiment); // log for offline analysis }).filter(experiment -> { return experiment.failRatio() >= DYNAMIC_PROP("fail_threshold").get(); }).map(experiment -> { return new FailReport(experiment, runCorrelations(experiment.getExamples())); }).doOnNext(report -> { logToHistorical("Failure report", report.getId(), report); // log for offline analysis }) }) }) .sink(Sinks.emailAlert(report -> { return toEmail(report)})) // anomalies trigger events (simple email here)

MantisJob .source(NetflixSources.moviePlayAttempts()) .stage(playAttempts -> { return playAttempts.groupBy(playAttempt -> { return playAttempt.getMovieId(); }) }) .stage(playAttemptsByMovieId -> { playAttemptsByMovieId .window(10,TimeUnit.MINUTES, 1000) // buffer for 10 minutes, or 1000 play attempts .flatMap(windowOfPlayAttempts -> { return windowOfPlayAttempts .reduce(new FailRatioExperiment(playAttemptsByMovieId.getKey()), (experiment, playAttempt) -> { experiment.updateFailRatio(playAttempt); experiment.updateExamples(playAttempt); return experiment; }).doOnNext(experiment -> { logToHistorical("Play attempt experiment", experiment.getId(),experiment); // log for offline analysis }).filter(experiment -> { return experiment.failRatio() >= DYNAMIC_PROP("fail_threshold").get(); }).map(experiment -> { return new FailReport(experiment, runCorrelations(experiment.getExamples())); }).doOnNext(report -> { logToHistorical("Failure report", report.getId(), report); // log for offline analysis }) }) }) .sink(Sinks.emailAlert(report -> { return toEmail(report)})) // anomalies trigger events (simple email here)

MantisJob .source(NetflixSources.moviePlayAttempts()) .stage(playAttempts -> { return playAttempts.groupBy(playAttempt -> { return playAttempt.getMovieId(); }) }) .stage(playAttemptsByMovieId -> { playAttemptsByMovieId .window(10,TimeUnit.MINUTES, 1000) // buffer for 10 minutes, or 1000 play attempts .flatMap(windowOfPlayAttempts -> { return windowOfPlayAttempts .reduce(new FailRatioExperiment(playAttemptsByMovieId.getKey()), (experiment, playAttempt) -> { experiment.updateFailRatio(playAttempt); experiment.updateExamples(playAttempt); return experiment; }).doOnNext(experiment -> { logToHistorical("Play attempt experiment", experiment.getId(),experiment); // log for offline analysis }).filter(experiment -> { return experiment.failRatio() >= DYNAMIC_PROP("fail_threshold").get(); }).map(experiment -> { return new FailReport(experiment, runCorrelations(experiment.getExamples())); }).doOnNext(report -> { logToHistorical("Failure report", report.getId(), report); // log for offline analysis }) }) }) .sink(Sinks.emailAlert(report -> { return toEmail(report)})) // anomalies trigger events (simple email here)

MantisJob .source(NetflixSources.moviePlayAttempts()) .stage(playAttempts -> { return playAttempts.groupBy(playAttempt -> { return playAttempt.getMovieId(); }) }) .stage(playAttemptsByMovieId -> { playAttemptsByMovieId .window(10,TimeUnit.MINUTES, 1000) // buffer for 10 minutes, or 1000 play attempts .flatMap(windowOfPlayAttempts -> { return windowOfPlayAttempts .reduce(new FailRatioExperiment(playAttemptsByMovieId.getKey()), (experiment, playAttempt) -> { experiment.updateFailRatio(playAttempt); experiment.updateExamples(playAttempt); return experiment; }).doOnNext(experiment -> { logToHistorical("Play attempt experiment", experiment.getId(),experiment); // log for offline analysis }).filter(experiment -> { return experiment.failRatio() >= DYNAMIC_PROP("fail_threshold").get(); }).map(experiment -> { return new FailReport(experiment, runCorrelations(experiment.getExamples())); }).doOnNext(report -> { logToHistorical("Failure report", report.getId(), report); // log for offline analysis }) }) }) .sink(Sinks.emailAlert(report -> { return toEmail(report)})) // anomalies trigger events (simple email here)

MantisJob .source(NetflixSources.moviePlayAttempts()) .stage(playAttempts -> { return playAttempts.groupBy(playAttempt -> { return playAttempt.getMovieId(); }) }) .stage(playAttemptsByMovieId -> { playAttemptsByMovieId .window(10,TimeUnit.MINUTES, 1000) // buffer for 10 minutes, or 1000 play attempts .flatMap(windowOfPlayAttempts -> { return windowOfPlayAttempts .reduce(new FailRatioExperiment(playAttemptsByMovieId.getKey()), (experiment, playAttempt) -> { experiment.updateFailRatio(playAttempt); experiment.updateExamples(playAttempt); return experiment; }).doOnNext(experiment -> { logToHistorical("Play attempt experiment", experiment.getId(),experiment); // log for offline analysis }).filter(experiment -> { return experiment.failRatio() >= DYNAMIC_PROP("fail_threshold").get(); }).map(experiment -> { return new FailReport(experiment, runCorrelations(experiment.getExamples())); }).doOnNext(report -> { logToHistorical("Failure report", report.getId(), report); // log for offline analysis }) }) }) .sink(Sinks.emailAlert(report -> { return toEmail(report)})) // anomalies trigger events (simple email here)

stream.onBackpressure(strategy?).subscribe

stream.onBackpressure(buffer).subscribe

stream.onBackpressure(drop).subscribe

stream.onBackpressure(sample).subscribe

stream.onBackpressure(scaleHorizontally).subscribe

finite infinite distributed

Single Multiple Sync T getData() Iterable getData() Async Future getData() Observable getData()

RxJava http://github.com/ReactiveX/RxJava http://reactivex.io

! Reactive Programming in the Netflix API with RxJava http://techblog.netflix.com/2013/02/rxjava-netflix-api.html ! Optimizing the Netflix API http://techblog.netflix.com/2013/01/optimizing-netflix-api.html ! Reactive Extensions (Rx) http://www.reactivex.io ! Reactive Streams https://github.com/reactive-streams/reactive-streams ! ! ! ! ! Ben Christensen @benjchristensen RxJava https://github.com/ReactiveX/RxJava @RxJava RxJS http://reactive-extensions.github.io/RxJS/ @ReactiveX jobs.netflix.com