Ben Christensen Software Engineer – Edge Engineering at Netflix @benjchristensen http://www.linkedin.com/in/benjchristensen ! ! ! ! ! http://techblog.netflix.com/ New York Times - September 2014 Reactive Programming with Rx

Reactive Extensions for Async Programming RxJava http://github.com/ReactiveX/RxJava http://reactivex.io

Reactive Extensions for Async Programming RxJava http://github.com/ReactiveX/RxJava http://reactivex.io Single Multiple Sync T getData() Iterable getData() Async Future getData() Observable getData()

Single Multiple Sync T getData() Iterable getData() Async Future getData() Observable getData() Observable.create(subscriber -> { subscriber.onNext("Hello world!"); subscriber.onCompleted(); }).forEach(System.out::println); Synchronous single value

Single Multiple Sync T getData() Iterable getData() Async Future getData() Observable getData() Observable.create(subscriber -> { subscriber.onNext("Hello"); subscriber.onNext("world"); subscriber.onNext("!"); subscriber.onCompleted(); }).forEach(System.out::println); Synchronous multi-value

Single Multiple Sync T getData() Iterable getData() Async Future getData() Observable getData() 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 with error handling

Single Multiple Sync T getData() Iterable getData() Async Future getData() Observable getData() Observable.create(subscriber -> { int i = 0; while (!subscriber.isUnsubscribed()) { subscriber.onNext(i++); } }).take(10).forEach(System.out::println); Synchronous multi-value with unsubscribe

Single Multiple Sync T getData() Iterable getData() Async Future getData() Observable getData() 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 multi-valued source that thread-hops with “reactive pull” backpressure

Single Multiple Sync T getData() Iterable getData() Async Future getData() Observable getData() Observable.from(iterable) .observeOn(Schedulers.newThread()) .take(10).forEach(System.out::println); Synchronous multi-valued source that thread-hops with “reactive pull” backpressure

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Abstract Concurrency

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  VideoList  getPersonalizedListOfMovies(userId);        def  VideoBookmark  getBookmark(userId,  videoId);        def  VideoRating  getRating(userId,  videoId);        def  VideoMetadata  getMetadata(videoId);   } class  VideoService  {        def  Observable  getPersonalizedListOfMovies(userId);        def  Observable  getBookmark(userId,  videoId);        def  Observable  getRating(userId,  videoId);        def  Observable  getMetadata(videoId);   } ... create an observable api: instead of a blocking api ...

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))); }); } 1 2 3 4 5 6

Non-Opinionated Concurrency

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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))); }); }

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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))); }); }

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Decouples Consumption from Production // 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); })

Decouples Consumption from Production // 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); })

Decouples Consumption from Production // 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); })

Decouples Consumption from Production Event Loop API Request API Request API Request API Request API Request Dependency REST API new Command().observe() new Command(). observe() new Command(). observe() new Command(). observe() new Command(). observe() Collapser

Decouples Consumption from Production // 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); }) 1 2 3 4 5

class  VideoService  {        def  Observable  getPersonalizedListOfMovies(userId);        def  Observable  getBookmark(userId,  videoId);        def  Observable  getRating(userId,  videoId);        def  Observable  getMetadata(videoId);   } Clear API Communicates Potential Cost

class  VideoService  {        def  Observable  getPersonalizedListOfMovies(userId);        def  Observable  getBookmark(userId,  videoId);        def  Observable  getRating(userId,  videoId);        def  Observable  getMetadata(videoId);   } Implementation Can Differ BIO Network Call Local Cache Collapsed Network Call

class  VideoService  {        def  Observable  getPersonalizedListOfMovies(userId);        def  Observable  getBookmark(userId,  videoId);        def  Observable  getRating(userId,  videoId);        def  Observable  getMetadata(videoId);   } Implementation Can Differ and Change Local Cache Collapsed Network Call Collapsed Network Call BIO NIO Network Call

Retrieval, Transformation, Combination all done in same declarative manner

Front Controller and Web Service Endpoints Service Layer Impl & Service Clients Observable APIs & Reactive Programming

Front Controller and Web Service Endpoints Service Layer Impl & Service Clients Imperative & Blocking Service Layer Impl & Service Clients

Front Controller and Web Service Endpoints Service Layer Impl & Service Clients Can we do better here? Service Layer Impl & Service Clients

Service Layer Impl & Service Clients RxNetty +

WSPerfLab https://github.com/Netflix-Skunkworks/WSPerfLab

Latency in Milliseconds 0 1,250 2,500 3,750 5,000 Latency Percentile 50th 66th 75th 80th 90th 95th 98th 99th 100th Tomcat -c200: 969 r/s Tomcat -c400: 1142 r/s RxNetty -c200: 1264 r/s RxNetty -c400: 2077 r/s

Latency in Milliseconds 0 100 200 300 400 Latency Percentile 50th 66th 75th 80th 90th 95th 98th 99th 100th Tomcat -c200: 969 r/s Tomcat -c400: 1142 r/s RxNetty -c200: 1264 r/s RxNetty -c400: 2077 r/s

Latency in Milliseconds 0 1,250 2,500 3,750 5,000 Latency Percentile 50th 66th 75th 80th 90th 95th 98th 99th 100th Tomcat -c200: 969 r/s Tomcat -c400: 1142 r/s RxNetty -c200: 1264 r/s RxNetty -c400: 2077 r/s

Latency in Milliseconds 0 1,250 2,500 3,750 5,000 Latency Percentile 50th 66th 75th 80th 90th 95th 98th 99th 100th Tomcat -c200: 969 r/s Tomcat -c400: 1142 r/s RxNetty -c200: 1264 r/s RxNetty -c400: 2077 r/s 458 1217

Latency in Milliseconds 0 150 300 450 600 Latency Percentile 50th 66th 75th 80th 90th 95th 98th 99th 100th Tomcat -c200: 969 r/s Tomcat -c400: 1142 r/s RxNetty -c200: 1264 r/s RxNetty -c400: 2077 r/s Tomcat -c400: 1142 r/s RxNetty -c200: 1264 r/s RxNetty -c400: 2077 r/s Tomcat -c200: 969 r/s

Latency in Milliseconds 0 150 300 450 600 Latency Percentile 50th 66th 75th 80th 90th 95th 98th 99th 100th Tomcat -c200: 969 r/s Tomcat -c400: 1142 r/s RxNetty -c200: 1264 r/s RxNetty -c400: 2077 r/s Tomcat -c400: 1142 r/s RxNetty -c200: 1264 r/s RxNetty -c400: 2077 r/s Tomcat -c200: 969 r/s

Latency in Milliseconds 0 150 300 450 600 Latency Percentile 50th 66th 75th 80th 90th 95th 98th 99th 100th Tomcat -c200: 969 r/s Tomcat -c400: 1142 r/s RxNetty -c200: 1264 r/s RxNetty -c400: 2077 r/s Tomcat -c400: 1142 r/s Tomcat -c200: 969 r/s RxNetty -c200: 1264 r/s RxNetty -c400: 2077 r/s 458 1217

Current status … moving on to production testing with Netty-based IPC

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Note: This is a mockup

Note: This is a mockup

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)); }); }

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)); }); }

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 ! ! ! ! Ben Christensen @benjchristensen http://www.linkedin.com/in/benjchristensen RxJava https://github.com/ReactiveX/RxJava @RxJava RxJS http://reactive-extensions.github.io/RxJS/ @ReactiveX jobs.netflix.com