Applying Reactive Programming with RxJava at GOTO Chicago 2015

Rarely do we have a chance to rewrite an application from scratch with the newest techniques. Generally we must work within our existing architectures evolving and refactoring years of code. This can make it seem reactive programming either can’t be introduced or doesn’t play a role.

Netflix has been doing reactive programming with RxJava in production for several years and only recently embarked on “greenfield” development efforts that are fully async. This talk will leverage the experience of introducing reactive programming into existing imperative, blocking codebases to demonstrate how it can be done and when it can make sense to do so. Not all benefits of reactive programming can be obtained without a greenfield, fully async architecture, but many can. Subjects to be covered will include the mental shift from imperative to declarative, working with blocking IO such as JDBC and RPC, service composition, debugging and unit testing.

Presented at GOTO Chicago 2015 http://gotocon.com/chicago-2015/presentation/Applying%20Reactive%20Programming%20with%20Rx

Video: https://www.youtube.com/watch?v=8OcCSQS0tug

Transcript

1. Ben Christensen
   Edge Engineering at Netflix
   @benjchristensen
   http://techblog.netflix.com/
   GOTO Chicago - May 2015
   Applying Reactive Programming with RxJava
   

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7. async + callbacks
   

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8. service composition
   +
   error handling
   developer productivity
   

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9. async + callbacks
   

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10. Future
    Future>
    

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11. Future
    Future>
    

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12. → getListOfListOfMovies
    → forEachList
    → forEachMovie
    → getBookmark
    → getRating
    → getMetadata
    → getSimilars
    → etc
    

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13. Future
    Future>
    Future>>
    

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14. Observable
    Future
    Future>
    Future>>
    

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15. Everything is a Stream
    

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16. List getOrders(int customerId)
    List getProducts(Order order)
    ShippingStatus getShippingStatus(Order o, Product p)
    getOrders → getProducts → getShippingStatus
    

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17. List getOrders(int customerId)
    List getProducts(Order order)
    ShippingStatus getShippingStatus(Order o, Product p)
    getOrders → getProducts → getShippingStatus
    Blocking APIs
    

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18. getOrders → getProducts → getShippingStatus
    

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19. IPC via Apache HTTP
    Memcached
    Cassandra
    Tomcat and Servlets
    

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20. IPC via Apache HTTP
    Memcached
    Cassandra
    Tomcat and Servlets
    All Blocking
    

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21. Many things could not
    realistically change
    

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22. We could change our service layer
    

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23. Async Facade
    

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24. Async Facade
    Blocking Code
    Servlet Sync/Async Bridge
    

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25. Observable getOrders(int customerId)
    Observable getProducts(Order order)
    Observable getShippingStatus(Order o, Product p)
    getOrdersAsync → getProductsAsync → getShippingStatusAsync
    getOrders → getProducts → getShippingStatus
    

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26. Observable getOrders(int customerId)
    Observable getProducts(Order order)
    Observable getShippingStatus(Order o, Product p)
    getOrdersAsync → getProductsAsync → getShippingStatusAsync
    Observable APIs
    getOrders → getProducts → getShippingStatus
    

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27. getOrdersAsync(1)
    .limit(1)
    .flatMap(o -> {
    return getProductsAsync(o)
    .flatMap(p -> {
    return getShippingStatusAsync(o, p);
    });
    })
    .forEach(s -> System.out.println(Thread.currentThread()
    + " [Async] Shipping Status: " + s));
    

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28. getOrdersAsync(1)
    .limit(1)
    .flatMap(o -> {
    return getProductsAsync(o)
    .flatMap(p -> {
    return getShippingStatusAsync(o, p);
    });
    })
    .forEach(s -> System.out.println(Thread.currentThread()
    + " [Async] Shipping Status: " + s));
    an async Observable
    

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29. getOrdersAsync(1)
    .limit(1)
    .flatMap(o -> {
    return getProductsAsync(o)
    .flatMap(p -> {
    return getShippingStatusAsync(o, p);
    });
    })
    .forEach(s -> System.out.println(Thread.currentThread()
    + " [Async] Shipping Status: " + s));
    an async Observable stream
    

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30. getOrdersAsync(1)
    .limit(1)
    .flatMap(o -> {
    return getProductsAsync(o)
    .flatMap(p -> {
    return getShippingStatusAsync(o, p);
    });
    })
    .forEach(s -> System.out.println(Thread.currentThread()
    + " [Async] Shipping Status: " + s));
    another async Observable stream
    

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31. getOrdersAsync(1)
    .limit(1)
    .flatMap(o -> {
    return getProductsAsync(o)
    .flatMap(p -> {
    return getShippingStatusAsync(o, p);
    });
    })
    .forEach(s -> System.out.println(Thread.currentThread()
    + " [Async] Shipping Status: " + s));
    

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32. Observable getShippingStatusAsync(Order o, Product p)
    ShippingStatus getShippingStatus(Order o, Product p)
    

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33. Observable getShippingStatusAsync(Order o, Product p)
    return Observable.defer(() -> {
    return Observable.just(getShippingStatus(o, p));
    }).subscribeOn(Schedulers.io());
    

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34. Observable getShippingStatusAsync(Order o, Product p)
    return Observable.defer(() -> {
    return Observable.just(getShippingStatus(o, p));
    }).subscribeOn(Schedulers.io());
    

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35. Observable getShippingStatusAsync(Order o, Product p)
    return Observable.defer(() -> {
    return Observable.just(getShippingStatus(o, p));
    }).subscribeOn(Schedulers.io());
    

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36. Observable getShippingStatusAsync(Order o, Product p)
    return Observable.defer(() -> {
    return Observable.just(getShippingStatus(o, p));
    }).subscribeOn(Schedulers.io());
    

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37. Observable getShippingStatusAsync(Order o, Product p)
    return Observable.defer(() -> {
    return Observable.just(getShippingStatus(o, p));
    }).subscribeOn(Schedulers.io());
    

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38. Observable getShippingStatusAsync(Order o, Product p)
    return Observable.defer(() -> {
    return Observable.just(getShippingStatus(o, p));
    }).subscribeOn(Schedulers.io());
    

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39. List orders = getOrders(1);
    Observable orders = getOrdersAsync(1);
    

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40. List orders = getOrders(1);
    Observable orders = getOrdersAsync(1);
    

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41. List orders = getOrders(1);
    Observable orders = getOrdersAsync(1);
    

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42. return Observable.defer(() -> {
    return Observable.from(getOrders(customerId));
    }).subscribeOn(Schedulers.io());
    Observable orders = getOrdersAsync(1);
    

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43. return Observable.defer(() -> {
    return Observable.from(getOrders(customerId));
    }).subscribeOn(Schedulers.io());
    Observable orders = getOrdersAsync(1);
    

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44. Observable orders = getOrdersAsync(1);
    return Observable.defer(() -> {
    return Observable.from(getOrders(customerId));
    }).subscribeOn(Schedulers.io());
    

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45. return Observable.defer(() -> {
    return Observable.from(getOrders(customerId));
    }).subscribeOn(Schedulers.io());
    Observable orders = getOrdersAsync(1);
    

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46. return Observable.defer(() -> {
    return Observable.from(getOrders(customerId));
    }).subscribeOn(Schedulers.io());
    Observable orders = getOrdersAsync(1);
    

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47. Wrapped with Threads
    using subscribeOn
    

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48. Wrapped with Threads
    JDBC?
    

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49. List orders = getOrders(1);
    try (Connection c = Database.getConnection()) {
    ResultSet rs = c.createStatement()
    .executeQuery("select * from orders");
    ArrayList orders = new ArrayList<>();
    while (rs.next()) {
    orders.add(new Order(rs.getInt(1)));
    }
    rs.close();
    return orders;
    } catch (Exception e) {
    throw new RuntimeException(e);
    }
    

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50. List orders = getOrders(1);
    try (Connection c = Database.getConnection()) {
    ResultSet rs = c.createStatement()
    .executeQuery("select * from orders");
    ArrayList orders = new ArrayList<>();
    while (rs.next()) {
    orders.add(new Order(rs.getInt(1)));
    }
    rs.close();
    return orders;
    } catch (Exception e) {
    throw new RuntimeException(e);
    }
    

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51. Observable orders = getOrdersAsync(1);
    return Observable. create(o -> {
    try (Connection c = Database.getConnection()) {
    ResultSet rs = c.createStatement()
    .executeQuery("select * from orders");
    while (rs.next() && !o.isUnsubscribed()) {
    o.onNext(new Order(rs.getInt(1)));
    }
    rs.close();
    o.onCompleted();
    } catch (Exception e) {
    o.onError(e);
    }
    }).subscribeOn(Schedulers.io());
    

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52. Observable orders = getOrdersAsync(1);
    return Observable. create(o -> {
    try (Connection c = Database.getConnection()) {
    ResultSet rs = c.createStatement()
    .executeQuery("select * from orders");
    while (rs.next() && !o.isUnsubscribed()) {
    o.onNext(new Order(rs.getInt(1)));
    }
    rs.close();
    o.onCompleted();
    } catch (Exception e) {
    o.onError(e);
    }
    }).subscribeOn(Schedulers.io());
    

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53. return Observable. create(o -> {
    try (Connection c = Database.getConnection()) {
    ResultSet rs = c.createStatement()
    .executeQuery("select * from orders");
    while (rs.next() && !o.isUnsubscribed()) {
    o.onNext(new Order(rs.getInt(1)));
    }
    rs.close();
    o.onCompleted();
    } catch (Exception e) {
    o.onError(e);
    }
    }).subscribeOn(Schedulers.io());
    Observable orders = getOrdersAsync(1);
    

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54. return Observable. create(o -> {
    try (Connection c = Database.getConnection()) {
    ResultSet rs = c.createStatement()
    .executeQuery("select * from orders");
    while (rs.next() && !o.isUnsubscribed()) {
    o.onNext(new Order(rs.getInt(1)));
    }
    rs.close();
    o.onCompleted();
    } catch (Exception e) {
    o.onError(e);
    }
    }).subscribeOn(Schedulers.io());
    Observable orders = getOrdersAsync(1);
    

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55. return Observable. create(o -> {
    try (Connection c = Database.getConnection()) {
    ResultSet rs = c.createStatement()
    .executeQuery("select * from orders");
    while (rs.next() && !o.isUnsubscribed()) {
    o.onNext(new Order(rs.getInt(1)));
    }
    rs.close();
    o.onCompleted();
    } catch (Exception e) {
    o.onError(e);
    }
    }).subscribeOn(Schedulers.io());
    Observable orders = getOrdersAsync(1);
    

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56. return Observable. create(o -> {
    try (Connection c = Database.getConnection()) {
    ResultSet rs = c.createStatement()
    .executeQuery("select * from orders");
    while (rs.next() && !o.isUnsubscribed()) {
    o.onNext(new Order(rs.getInt(1)));
    }
    rs.close();
    o.onCompleted();
    } catch (Exception e) {
    o.onError(e);
    }
    }).subscribeOn(Schedulers.io());
    Observable orders = getOrdersAsync(1);
    

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57. or with “reactive pull” backpressure …
    

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58. return Observable.create(AbstractOnSubscribe. create(s -> {
    ResultSet rs = s.state();
    try {
    if (rs.next()) {
    s.onNext(new Order(rs.getInt(1)));
    } else {
    s.onCompleted();
    }
    } catch (SQLException e) {
    s.onError(e);
    }
    }, s -> {
    Connection c = Database.getConnection();
    try {
    Statement stmt = c.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
    java.sql.ResultSet.CONCUR_READ_ONLY);
    stmt.setFetchSize(Integer.MIN_VALUE);
    return stmt.executeQuery("select * from orders");
    } catch (SQLException e) {
    s.onError(e);
    return null;
    }
    }, rs -> rs.close() } // ignoring try/catch for slide brevity
    )).subscribeOn(Schedulers.io());
    

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59. return Observable.create(AbstractOnSubscribe. create(s -> {
    ResultSet rs = s.state();
    try {
    if (rs.next()) {
    s.onNext(new Order(rs.getInt(1)));
    } else {
    s.onCompleted();
    }
    } catch (SQLException e) {
    s.onError(e);
    }
    }, s -> {
    Connection c = Database.getConnection();
    try {
    Statement stmt = c.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
    java.sql.ResultSet.CONCUR_READ_ONLY);
    stmt.setFetchSize(Integer.MIN_VALUE);
    return stmt.executeQuery("select * from orders");
    } catch (SQLException e) {
    s.onError(e);
    return null;
    }
    }, rs -> rs.close() } // ignoring try/catch for slide brevity
    )).subscribeOn(Schedulers.io());
    

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60. return Observable.create(AbstractOnSubscribe. create(s -> {
    ResultSet rs = s.state();
    try {
    if (rs.next()) {
    s.onNext(new Order(rs.getInt(1)));
    } else {
    s.onCompleted();
    }
    } catch (SQLException e) {
    s.onError(e);
    }
    }, s -> {
    Connection c = Database.getConnection();
    try {
    Statement stmt = c.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
    java.sql.ResultSet.CONCUR_READ_ONLY);
    stmt.setFetchSize(Integer.MIN_VALUE);
    return stmt.executeQuery("select * from orders");
    } catch (SQLException e) {
    s.onError(e);
    return null;
    }
    }, rs -> rs.close() } // ignoring try/catch for slide brevity
    )).subscribeOn(Schedulers.io());
    

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61. return Observable.create(AbstractOnSubscribe. create(s -> {
    ResultSet rs = s.state();
    try {
    if (rs.next()) {
    s.onNext(new Order(rs.getInt(1)));
    } else {
    s.onCompleted();
    }
    } catch (SQLException e) {
    s.onError(e);
    }
    }, s -> {
    Connection c = Database.getConnection();
    try {
    Statement stmt = c.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
    java.sql.ResultSet.CONCUR_READ_ONLY);
    stmt.setFetchSize(Integer.MIN_VALUE);
    return stmt.executeQuery("select * from orders");
    } catch (SQLException e) {
    s.onError(e);
    return null;
    }
    }, rs -> rs.close() } // ignoring try/catch for slide brevity
    )).subscribeOn(Schedulers.io());
    

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62. return Observable.create(AbstractOnSubscribe. create(s -> {
    ResultSet rs = s.state();
    try {
    if (rs.next()) {
    s.onNext(new Order(rs.getInt(1)));
    } else {
    s.onCompleted();
    }
    } catch (SQLException e) {
    s.onError(e);
    }
    }, s -> {
    Connection c = Database.getConnection();
    try {
    Statement stmt = c.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
    java.sql.ResultSet.CONCUR_READ_ONLY);
    stmt.setFetchSize(Integer.MIN_VALUE);
    return stmt.executeQuery("select * from orders");
    } catch (SQLException e) {
    s.onError(e);
    return null;
    }
    }, rs -> rs.close() } // ignoring try/catch for slide brevity
    )).subscribeOn(Schedulers.io());
    

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63. return Observable.create(AbstractOnSubscribe. create(s -> {
    ResultSet rs = s.state();
    try {
    if (rs.next()) {
    s.onNext(new Order(rs.getInt(1)));
    } else {
    s.onCompleted();
    }
    } catch (SQLException e) {
    s.onError(e);
    }
    }, s -> {
    Connection c = Database.getConnection();
    try {
    Statement stmt = c.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
    java.sql.ResultSet.CONCUR_READ_ONLY);
    stmt.setFetchSize(Integer.MIN_VALUE);
    return stmt.executeQuery("select * from orders");
    } catch (SQLException e) {
    s.onError(e);
    return null;
    }
    }, rs -> rs.close() } // ignoring try/catch for slide brevity
    )).subscribeOn(Schedulers.io());
    

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64. return Observable.create(AbstractOnSubscribe. create(s -> {
    ResultSet rs = s.state();
    try {
    if (rs.next()) {
    s.onNext(new Order(rs.getInt(1)));
    } else {
    s.onCompleted();
    }
    } catch (SQLException e) {
    s.onError(e);
    }
    }, s -> {
    Connection c = Database.getConnection();
    try {
    Statement stmt = c.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
    java.sql.ResultSet.CONCUR_READ_ONLY);
    stmt.setFetchSize(Integer.MIN_VALUE);
    return stmt.executeQuery("select * from orders");
    } catch (SQLException e) {
    s.onError(e);
    return null;
    }
    }, rs -> rs.close() } // ignoring try/catch for slide brevity
    )).subscribeOn(Schedulers.io());
    

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65. return Observable.create(AbstractOnSubscribe. create(s -> {
    ResultSet rs = s.state();
    try {
    if (rs.next()) {
    s.onNext(new Order(rs.getInt(1)));
    } else {
    s.onCompleted();
    }
    } catch (SQLException e) {
    s.onError(e);
    }
    }, s -> {
    Connection c = Database.getConnection();
    try {
    Statement stmt = c.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
    java.sql.ResultSet.CONCUR_READ_ONLY);
    stmt.setFetchSize(Integer.MIN_VALUE);
    return stmt.executeQuery("select * from orders");
    } catch (SQLException e) {
    s.onError(e);
    return null;
    }
    }, rs -> rs.close() } // ignoring try/catch for slide brevity
    )).subscribeOn(Schedulers.io());
    

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66. return Observable.create(AbstractOnSubscribe. create(s -> {
    ResultSet rs = s.state();
    try {
    if (rs.next()) {
    s.onNext(new Order(rs.getInt(1)));
    } else {
    s.onCompleted();
    }
    } catch (SQLException e) {
    s.onError(e);
    }
    }, s -> {
    Connection c = Database.getConnection();
    try {
    Statement stmt = c.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
    java.sql.ResultSet.CONCUR_READ_ONLY);
    stmt.setFetchSize(Integer.MIN_VALUE);
    return stmt.executeQuery("select * from orders");
    } catch (SQLException e) {
    s.onError(e);
    return null;
    }
    }, rs -> rs.close() } // ignoring try/catch for slide brevity
    )).subscribeOn(Schedulers.io());
    

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67. return Observable.create(AbstractOnSubscribe. create(s -> {
    ResultSet rs = s.state();
    try {
    if (rs.next()) {
    s.onNext(new Order(rs.getInt(1)));
    } else {
    s.onCompleted();
    }
    } catch (SQLException e) {
    s.onError(e);
    }
    }, s -> {
    Connection c = Database.getConnection();
    try {
    Statement stmt = c.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
    java.sql.ResultSet.CONCUR_READ_ONLY);
    stmt.setFetchSize(Integer.MIN_VALUE);
    return stmt.executeQuery("select * from orders");
    } catch (SQLException e) {
    s.onError(e);
    return null;
    }
    }, rs -> rs.close() } // ignoring try/catch for slide brevity
    )).subscribeOn(Schedulers.io());
    

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68. return Observable.create(AbstractOnSubscribe. create(s -> {
    ResultSet rs = s.state();
    try {
    if (rs.next()) {
    s.onNext(new Order(rs.getInt(1)));
    } else {
    s.onCompleted();
    }
    } catch (SQLException e) {
    s.onError(e);
    }
    }, s -> {
    Connection c = Database.getConnection();
    try {
    Statement stmt = c.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
    java.sql.ResultSet.CONCUR_READ_ONLY);
    stmt.setFetchSize(Integer.MIN_VALUE);
    return stmt.executeQuery("select * from orders");
    } catch (SQLException e) {
    s.onError(e);
    return null;
    }
    }, rs -> rs.close() } // ignoring try/catch for slide brevity
    )).subscribeOn(Schedulers.io());
    

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69. return Observable.create(AbstractOnSubscribe. create(s -> {
    ResultSet rs = s.state();
    try {
    if (rs.next()) {
    s.onNext(new Order(rs.getInt(1)));
    } else {
    s.onCompleted();
    }
    } catch (SQLException e) {
    s.onError(e);
    }
    }, s -> {
    Connection c = Database.getConnection();
    try {
    Statement stmt = c.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
    java.sql.ResultSet.CONCUR_READ_ONLY);
    stmt.setFetchSize(Integer.MIN_VALUE);
    return stmt.executeQuery("select * from orders");
    } catch (SQLException e) {
    s.onError(e);
    return null;
    }
    }, rs -> rs.close() } // ignoring try/catch for slide brevity
    )).subscribeOn(Schedulers.io());
    

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70. return Observable.create(AbstractOnSubscribe. create(s -> {
    ResultSet rs = s.state();
    try {
    if (rs.next()) {
    s.onNext(new Order(rs.getInt(1)));
    } else {
    s.onCompleted();
    }
    } catch (SQLException e) {
    s.onError(e);
    }
    }, s -> {
    Connection c = Database.getConnection();
    try {
    Statement stmt = c.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
    java.sql.ResultSet.CONCUR_READ_ONLY);
    stmt.setFetchSize(Integer.MIN_VALUE);
    return stmt.executeQuery("select * from orders");
    } catch (SQLException e) {
    s.onError(e);
    return null;
    }
    }, rs -> rs.close() } // ignoring try/catch for slide brevity
    )).subscribeOn(Schedulers.io());
    

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71. return Observable.create(AbstractOnSubscribe. create(s -> {
    ResultSet rs = s.state();
    try {
    if (rs.next()) {
    s.onNext(new Order(rs.getInt(1)));
    } else {
    s.onCompleted();
    }
    } catch (SQLException e) {
    s.onError(e);
    }
    }, s -> {
    Connection c = Database.getConnection();
    try {
    Statement stmt = c.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
    java.sql.ResultSet.CONCUR_READ_ONLY);
    stmt.setFetchSize(Integer.MIN_VALUE);
    return stmt.executeQuery("select * from orders");
    } catch (SQLException e) {
    s.onError(e);
    return null;
    }
    }, rs -> rs.close() } // ignoring try/catch for slide brevity
    )).subscribeOn(Schedulers.io());
    

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72. Observable.defer
    Observable.from/just
    Observable.subscribeOn
    Observable.create
    

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73. Async Facade
    Blocking Code
    Servlet Sync/Async Bridge
    

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74. protected void doGet(HttpServletRequest req, HttpServletResponse resp)
    throws ServletException, IOException {
    try {
    // perform service composition asynchronously
    getShippingStatusForCustomerOrdersAsync(req.getParameter(“customerId"))
    .toBlocking() // block on servlet thread
    .forEach(status -> {
    try {
    // write output using blocking IO
    resp.getWriter().write(status.toString());
    } catch (Exception e) {
    throw new RuntimeException("unable to write", e);
    }
    });
    } catch (Exception e) {
    // toBlocking and forEach will convert async onError events into thrown exceptions
    resp.setStatus(500);
    // write and log error ...
    }
    }
    

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75. protected void doGet(HttpServletRequest req, HttpServletResponse resp)
    throws ServletException, IOException {
    try {
    // perform service composition asynchronously
    getShippingStatusForCustomerOrdersAsync(req.getParameter("customerId"))
    .toBlocking() // block on servlet thread
    .forEach(status -> {
    try {
    // write output using blocking IO
    resp.getWriter().write(status.toString());
    } catch (Exception e) {
    throw new RuntimeException("unable to write", e);
    }
    });
    } catch (Exception e) {
    // toBlocking and forEach will convert async onError events into thrown exceptions
    resp.setStatus(500);
    // write and log error ...
    }
    }
    

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76. protected void doGet(HttpServletRequest req, HttpServletResponse resp)
    throws ServletException, IOException {
    try {
    // perform service composition asynchronously
    getShippingStatusForCustomerOrdersAsync(req.getParameter("customerId"))
    .toBlocking() // block on servlet thread
    .forEach(status -> {
    try {
    // write output using blocking IO
    resp.getWriter().write(status.toString());
    } catch (Exception e) {
    throw new RuntimeException("unable to write", e);
    }
    });
    } catch (Exception e) {
    // toBlocking and forEach will convert async onError events into thrown exceptions
    resp.setStatus(500);
    // write and log error ...
    }
    }
    

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77. Observable getShippingStatusForCustomerOrdersAsync(String customerId) {
    return getOrdersAsync(Integer.parseInt(customerId))
    .limit(1)
    .flatMap(o -> {
    return getProductsAsync(o)
    .flatMap(p -> {
    return getShippingStatusAsync(o, p);
    });
    });
    }
    

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78. Observable getShippingStatusForCustomerOrdersAsync(String customerId) {
    return getOrdersAsync(Integer.parseInt(customerId))
    .limit(1)
    .flatMap(o -> {
    return getProductsAsync(o)
    .flatMap(p -> {
    return getShippingStatusAsync(o, p);
    });
    });
    }
    

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79. Observable getShippingStatusForCustomerOrdersAsync(String customerId) {
    return getOrdersAsync(Integer.parseInt(customerId))
    .limit(1)
    .flatMap(o -> {
    return getProductsAsync(o)
    .flatMap(p -> {
    return getShippingStatusAsync(o, p);
    });
    });
    }
    

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80. protected void doGet(HttpServletRequest req, HttpServletResponse resp)
    throws ServletException, IOException {
    try {
    // perform service composition asynchronously
    getShippingStatusForCustomerOrdersAsync(req.getParameter("customerId"))
    .toBlocking() // block on servlet thread
    .forEach(status -> {
    try {
    // write output using blocking IO
    resp.getWriter().write(status.toString());
    } catch (Exception e) {
    throw new RuntimeException("unable to write", e);
    }
    });
    } catch (Exception e) {
    // toBlocking and forEach will convert async onError events into thrown exceptions
    resp.setStatus(500);
    // write and log error ...
    }
    }
    

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81. protected void doGet(HttpServletRequest req, HttpServletResponse resp)
    throws ServletException, IOException {
    try {
    // perform service composition asynchronously
    getShippingStatusForCustomerOrdersAsync(req.getParameter("customerId"))
    .toBlocking() // block on servlet thread
    .forEach(status -> {
    try {
    // write output using blocking IO
    resp.getWriter().write(status.toString());
    } catch (Exception e) {
    throw new RuntimeException("unable to write", e);
    }
    });
    } catch (Exception e) {
    // toBlocking and forEach will convert async onError events into thrown exceptions
    resp.setStatus(500);
    // write and log error ...
    }
    }
    

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82. protected void doGet(HttpServletRequest req, HttpServletResponse resp)
    throws ServletException, IOException {
    try {
    // perform service composition asynchronously
    getShippingStatusForCustomerOrdersAsync(req.getParameter("customerId"))
    .toBlocking() // block on servlet thread
    .forEach(status -> {
    try {
    // write output using blocking IO
    resp.getWriter().write(status.toString());
    } catch (Exception e) {
    throw new RuntimeException("unable to write", e);
    }
    });
    } catch (Exception e) {
    // toBlocking and forEach will convert async onError events into thrown exceptions
    resp.setStatus(500);
    // write and log error ...
    }
    }
    

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83. Observable.toBlocking
    

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84. Observable.toBlocking
    for bridging between async and sync
    

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85. So how did it go adding reactive
    to an existing codebase?
    

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86. First attempt took 3 tries
    

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87. What the *&!@#$^!!!
    

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88. Tech Worked …
    

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89. … but …
    

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90. Needed to relearn idiomatic solutions
    

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91. Iterable is = Arrays.asList("a", "b", "c");
    ArrayList ts = new ArrayList<>();
    for(String s : is) {
    ts.add(s + "-modified");
    }
    // do stuff with ts ...
    Observable os = Observable.just("a", "b", "c");
    os.map(s -> s + "-modified");
    // do stuff with os ...
    

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92. try {
    for (String s : is) {
    ts.add(s + "-modified");
    }
    } catch (Exception e) {
    // do something with exception
    }
    os.map(s -> s + "-modified")
    .onErrorResumeNext(exception -> {
    // do something with exception
    return Observable.empty();
    });
    

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93. Needed to invest in documentation
    

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94. View Slide

95. View Slide

96. Needed to allow for time and mistakes
    

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97. Also … Unit Testing & Debugging
    

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98. Async Unit Tests
    

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99. TestSubscriber ts = new TestSubscriber<>();
    Observable.interval(200, TimeUnit.MILLISECONDS)
    .take(5)
    .map(i -> {
    return i + " value";
    }).subscribe(ts);
    ts.awaitTerminalEvent();
    ts.assertNoErrors();
    ts.assertReceivedOnNext(Arrays.asList("0 value", "1 value",
    "2 value", "3 value", "4 value"));
    

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100. TestSubscriber ts = new TestSubscriber<>();
     Observable.interval(200, TimeUnit.MILLISECONDS)
     .take(5)
     .map(i -> {
     return i + " value";
     }).subscribe(ts);
     ts.awaitTerminalEvent();
     ts.assertNoErrors();
     ts.assertReceivedOnNext(Arrays.asList("0 value", "1 value",
     "2 value", "3 value", "4 value"));
     

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101. TestSubscriber ts = new TestSubscriber<>();
     Observable.interval(200, TimeUnit.MILLISECONDS)
     .take(5)
     .map(i -> {
     return i + " value";
     }).subscribe(ts);
     ts.awaitTerminalEvent();
     ts.assertNoErrors();
     ts.assertReceivedOnNext(Arrays.asList("0 value", "1 value",
     "2 value", "3 value", "4 value"));
     

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102. TestSubscriber ts = new TestSubscriber<>();
     Observable.interval(200, TimeUnit.MILLISECONDS)
     .take(5)
     .map(i -> {
     return i + " value";
     }).subscribe(ts);
     ts.awaitTerminalEvent();
     ts.assertNoErrors();
     ts.assertReceivedOnNext(Arrays.asList("0 value", "1 value",
     "2 value", "3 value", "4 value"));
     

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103. TestSubscriber ts = new TestSubscriber<>();
     Observable.interval(200, TimeUnit.MILLISECONDS)
     .take(5)
     .map(i -> {
     return i + " value";
     }).subscribe(ts);
     ts.awaitTerminalEvent();
     ts.assertNoErrors();
     ts.assertReceivedOnNext(Arrays.asList("0 value", "1 value",
     "2 value", "3 value", "4 value"));
     

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104. TestSubscriber ts = new TestSubscriber<>();
     Observable.interval(200, TimeUnit.MILLISECONDS)
     .take(5)
     .map(i -> {
     return i + " value";
     }).subscribe(ts);
     ts.awaitTerminalEvent();
     ts.assertNoErrors();
     ts.assertReceivedOnNext(Arrays.asList("0 value", "1 value",
     "2 value", "3 value", "4 value"));
     

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105. TestScheduler test = Schedulers.test();
     TestSubscriber ts = new TestSubscriber<>();
     Observable.interval(200, TimeUnit.MILLISECONDS, test)
     .map(i -> {
     return i + " value";
     }).subscribe(ts);
     test.advanceTimeBy(200, TimeUnit.MILLISECONDS);
     ts.assertReceivedOnNext(Arrays.asList("0 value"));
     test.advanceTimeTo(1000, TimeUnit.MILLISECONDS);
     ts.assertReceivedOnNext(Arrays.asList("0 value", "1 value”,
     "2 value", "3 value", "4 value"));
     

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106. TestScheduler test = Schedulers.test();
     TestSubscriber ts = new TestSubscriber<>();
     Observable.interval(200, TimeUnit.MILLISECONDS, test)
     .map(i -> {
     return i + " value";
     }).subscribe(ts);
     test.advanceTimeBy(200, TimeUnit.MILLISECONDS);
     ts.assertReceivedOnNext(Arrays.asList("0 value"));
     test.advanceTimeTo(1000, TimeUnit.MILLISECONDS);
     ts.assertReceivedOnNext(Arrays.asList("0 value", "1 value”,
     "2 value", "3 value", "4 value"));
     

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107. TestScheduler test = Schedulers.test();
     TestSubscriber ts = new TestSubscriber<>();
     Observable.interval(200, TimeUnit.MILLISECONDS, test)
     .map(i -> {
     return i + " value";
     }).subscribe(ts);
     test.advanceTimeBy(200, TimeUnit.MILLISECONDS);
     ts.assertReceivedOnNext(Arrays.asList("0 value"));
     test.advanceTimeTo(1000, TimeUnit.MILLISECONDS);
     ts.assertReceivedOnNext(Arrays.asList("0 value", "1 value”,
     "2 value", "3 value", "4 value"));
     

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108. TestScheduler test = Schedulers.test();
     TestSubscriber ts = new TestSubscriber<>();
     Observable.interval(200, TimeUnit.MILLISECONDS, test)
     .map(i -> {
     return i + " value";
     }).subscribe(ts);
     test.advanceTimeBy(200, TimeUnit.MILLISECONDS);
     ts.assertReceivedOnNext(Arrays.asList("0 value"));
     test.advanceTimeTo(1000, TimeUnit.MILLISECONDS);
     ts.assertReceivedOnNext(Arrays.asList("0 value", "1 value”,
     "2 value", "3 value", "4 value"));
     

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109. TestScheduler test = Schedulers.test();
     TestSubscriber ts = new TestSubscriber<>();
     Observable.interval(200, TimeUnit.MILLISECONDS, test)
     .map(i -> {
     return i + " value";
     }).subscribe(ts);
     test.advanceTimeBy(200, TimeUnit.MILLISECONDS);
     ts.assertReceivedOnNext(Arrays.asList("0 value"));
     test.advanceTimeTo(1000, TimeUnit.MILLISECONDS);
     ts.assertReceivedOnNext(Arrays.asList("0 value", "1 value”,
     "2 value", "3 value", "4 value"));
     

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110. TestScheduler test = Schedulers.test();
     TestSubscriber ts = new TestSubscriber<>();
     Observable.interval(200, TimeUnit.MILLISECONDS, test)
     .map(i -> {
     return i + " value";
     }).subscribe(ts);
     test.advanceTimeBy(200, TimeUnit.MILLISECONDS);
     ts.assertReceivedOnNext(Arrays.asList("0 value"));
     test.advanceTimeTo(1000, TimeUnit.MILLISECONDS);
     ts.assertReceivedOnNext(Arrays.asList("0 value", "1 value”,
     "2 value", "3 value", "4 value"));
     

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111. TestScheduler test = Schedulers.test();
     TestSubscriber ts = new TestSubscriber<>();
     Observable.interval(200, TimeUnit.MILLISECONDS, test)
     .map(i -> {
     return i + " value";
     }).subscribe(ts);
     test.advanceTimeBy(200, TimeUnit.MILLISECONDS);
     ts.assertReceivedOnNext(Arrays.asList("0 value"));
     test.advanceTimeTo(1000, TimeUnit.MILLISECONDS);
     ts.assertReceivedOnNext(Arrays.asList("0 value", "1 value”,
     "2 value", "3 value", "4 value"));
     

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112. TestScheduler test = Schedulers.test();
     TestSubscriber ts = new TestSubscriber<>();
     Observable.interval(200, TimeUnit.MILLISECONDS, test)
     .map(i -> {
     return i + " value";
     }).subscribe(ts);
     test.advanceTimeBy(200, TimeUnit.MILLISECONDS);
     ts.assertReceivedOnNext(Arrays.asList("0 value"));
     test.advanceTimeTo(1000, TimeUnit.MILLISECONDS);
     ts.assertReceivedOnNext(Arrays.asList("0 value", "1 value”,
     "2 value", "3 value", "4 value"));
     

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113. Async Debugging is Hard
     

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114. java.lang.RuntimeException: failure!
     at jdbc.Test.lambda$19(Test.java:63)
     at jdbc.Test$$Lambda$8/888452645.call(Unknown Source)
     at rx.internal.operators.OperatorMap$1.onNext(OperatorMap.java:55)
     at rx.internal.operators.OperatorSubscribeOn$1$1$1.onNext(OperatorSubscribeOn.java:76)
     at rx.observables.AbstractOnSubscribe$SubscriptionState.accept(AbstractOnSubscribe.java:533)
     at rx.observables.AbstractOnSubscribe$SubscriptionProducer.doNext(AbstractOnSubscribe.java:367)
     at rx.observables.AbstractOnSubscribe$SubscriptionProducer.request(AbstractOnSubscribe.java:345)
     at rx.internal.operators.OperatorSubscribeOn$1$1$1$1.request(OperatorSubscribeOn.java:88)
     at rx.Subscriber.setProducer(Subscriber.java:177)
     at rx.Subscriber.setProducer(Subscriber.java:171)
     at rx.internal.operators.OperatorSubscribeOn$1$1$1.setProducer(OperatorSubscribeOn.java:81)
     at rx.observables.AbstractOnSubscribe.call(AbstractOnSubscribe.java:191)
     at rx.observables.AbstractOnSubscribe$LambdaOnSubscribe.call(AbstractOnSubscribe.java:274)
     at rx.Observable.unsafeSubscribe(Observable.java:7495)
     at rx.internal.operators.OperatorSubscribeOn$1$1.call(OperatorSubscribeOn.java:62)
     at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:55)
     at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
     at java.util.concurrent.FutureTask.run(FutureTask.java:266)
     at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)
     at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
     at java.lang.Thread.run(Thread.java:745)
     Caused by: rx.exceptions.OnErrorThrowable$OnNextValue: OnError while emitting onNext value: jdbc.Product.class
     at rx.exceptions.OnErrorThrowable.addValueAsLastCause(OnErrorThrowable.java:98)
     at rx.internal.operators.OperatorMap$1.onNext(OperatorMap.java:58)
     ... 20 more
     Ugly Stacktraces
     

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115. java.lang.RuntimeException: failure!
     at jdbc.Test.lambda$19(Test.java:63)
     at jdbc.Test$$Lambda$8/888452645.call(Unknown Source)
     at rx.internal.operators.OperatorMap$1.onNext(OperatorMap.java:55)
     at rx.internal.operators.OperatorSubscribeOn$1$1$1.onNext(OperatorSubscribeOn.java:76)
     at rx.observables.AbstractOnSubscribe$SubscriptionState.accept(AbstractOnSubscribe.java:533)
     at rx.observables.AbstractOnSubscribe$SubscriptionProducer.doNext(AbstractOnSubscribe.java:367)
     at rx.observables.AbstractOnSubscribe$SubscriptionProducer.request(AbstractOnSubscribe.java:345)
     at rx.internal.operators.OperatorSubscribeOn$1$1$1$1.request(OperatorSubscribeOn.java:88)
     at rx.Subscriber.setProducer(Subscriber.java:177)
     at rx.Subscriber.setProducer(Subscriber.java:171)
     at rx.internal.operators.OperatorSubscribeOn$1$1$1.setProducer(OperatorSubscribeOn.java:81)
     at rx.observables.AbstractOnSubscribe.call(AbstractOnSubscribe.java:191)
     at rx.observables.AbstractOnSubscribe$LambdaOnSubscribe.call(AbstractOnSubscribe.java:274)
     at rx.Observable.unsafeSubscribe(Observable.java:7495)
     at rx.internal.operators.OperatorSubscribeOn$1$1.call(OperatorSubscribeOn.java:62)
     at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:55)
     at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
     at java.util.concurrent.FutureTask.run(FutureTask.java:266)
     at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)
     at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
     at java.lang.Thread.run(Thread.java:745)
     Caused by: rx.exceptions.OnErrorThrowable$OnNextValue: OnError while emitting onNext value: jdbc.Product.class
     at rx.exceptions.OnErrorThrowable.addValueAsLastCause(OnErrorThrowable.java:98)
     at rx.internal.operators.OperatorMap$1.onNext(OperatorMap.java:58)
     ... 20 more
     Ugly Stacktraces
     

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116. java.lang.RuntimeException: failure!
     at jdbc.Test.lambda$19(Test.java:63)
     at jdbc.Test$$Lambda$8/888452645.call(Unknown Source)
     at rx.internal.operators.OperatorMap$1.onNext(OperatorMap.java:55)
     at rx.internal.operators.OperatorSubscribeOn$1$1$1.onNext(OperatorSubscribeOn.java:76)
     at rx.observables.AbstractOnSubscribe$SubscriptionState.accept(AbstractOnSubscribe.java:533)
     at rx.observables.AbstractOnSubscribe$SubscriptionProducer.doNext(AbstractOnSubscribe.java:367)
     at rx.observables.AbstractOnSubscribe$SubscriptionProducer.request(AbstractOnSubscribe.java:345)
     at rx.internal.operators.OperatorSubscribeOn$1$1$1$1.request(OperatorSubscribeOn.java:88)
     at rx.Subscriber.setProducer(Subscriber.java:177)
     at rx.Subscriber.setProducer(Subscriber.java:171)
     at rx.internal.operators.OperatorSubscribeOn$1$1$1.setProducer(OperatorSubscribeOn.java:81)
     at rx.observables.AbstractOnSubscribe.call(AbstractOnSubscribe.java:191)
     at rx.observables.AbstractOnSubscribe$LambdaOnSubscribe.call(AbstractOnSubscribe.java:274)
     at rx.Observable.unsafeSubscribe(Observable.java:7495)
     at rx.internal.operators.OperatorSubscribeOn$1$1.call(OperatorSubscribeOn.java:62)
     at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:55)
     at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
     at java.util.concurrent.FutureTask.run(FutureTask.java:266)
     at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)
     at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
     at java.lang.Thread.run(Thread.java:745)
     Caused by: rx.exceptions.OnErrorThrowable$OnNextValue: OnError while emitting onNext value: jdbc.Product.class
     at rx.exceptions.OnErrorThrowable.addValueAsLastCause(OnErrorThrowable.java:98)
     at rx.internal.operators.OperatorMap$1.onNext(OperatorMap.java:58)
     ... 20 more
     Missing Async Call Chain
     

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117. java.lang.RuntimeException: failure!
     at jdbc.Test.lambda$19(Test.java:63)
     at jdbc.Test$$Lambda$8/888452645.call(Unknown Source)
     at rx.internal.operators.OperatorMap$1.onNext(OperatorMap.java:55)
     at rx.internal.operators.OperatorSubscribeOn$1$1$1.onNext(OperatorSubscribeOn.java:76)
     at rx.observables.AbstractOnSubscribe$SubscriptionState.accept(AbstractOnSubscribe.java:533)
     at rx.observables.AbstractOnSubscribe$SubscriptionProducer.doNext(AbstractOnSubscribe.java:367)
     at rx.observables.AbstractOnSubscribe$SubscriptionProducer.request(AbstractOnSubscribe.java:345)
     at rx.internal.operators.OperatorSubscribeOn$1$1$1$1.request(OperatorSubscribeOn.java:88)
     at rx.Subscriber.setProducer(Subscriber.java:177)
     at rx.Subscriber.setProducer(Subscriber.java:171)
     at rx.internal.operators.OperatorSubscribeOn$1$1$1.setProducer(OperatorSubscribeOn.java:81)
     at rx.observables.AbstractOnSubscribe.call(AbstractOnSubscribe.java:191)
     at rx.observables.AbstractOnSubscribe$LambdaOnSubscribe.call(AbstractOnSubscribe.java:274)
     at rx.Observable.unsafeSubscribe(Observable.java:7495)
     at rx.internal.operators.OperatorSubscribeOn$1$1.call(OperatorSubscribeOn.java:62)
     at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:55)
     at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
     at java.util.concurrent.FutureTask.run(FutureTask.java:266)
     at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)
     at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
     at java.lang.Thread.run(Thread.java:745)
     Caused by: rx.exceptions.OnErrorThrowable$OnNextValue: OnError while emitting onNext value: jdbc.Product.class
     at rx.exceptions.OnErrorThrowable.addValueAsLastCause(OnErrorThrowable.java:98)
     at rx.internal.operators.OperatorMap$1.onNext(OperatorMap.java:58)
     ... 20 more
     Stack Pollution
     

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118. java.lang.RuntimeException: failure!
     at jdbc.Test.lambda$19(Test.java:63)
     at jdbc.Test$$Lambda$8/888452645.call(Unknown Source)
     at rx.internal.operators.OperatorMap$1.onNext(OperatorMap.java:55)
     at rx.internal.operators.OperatorSubscribeOn$1$1$1.onNext(OperatorSubscribeOn.java:76)
     at rx.observables.AbstractOnSubscribe$SubscriptionState.accept(AbstractOnSubscribe.java:533)
     at rx.observables.AbstractOnSubscribe$SubscriptionProducer.doNext(AbstractOnSubscribe.java:367)
     at rx.observables.AbstractOnSubscribe$SubscriptionProducer.request(AbstractOnSubscribe.java:345)
     at rx.internal.operators.OperatorSubscribeOn$1$1$1$1.request(OperatorSubscribeOn.java:88)
     at rx.Subscriber.setProducer(Subscriber.java:177)
     at rx.Subscriber.setProducer(Subscriber.java:171)
     at rx.internal.operators.OperatorSubscribeOn$1$1$1.setProducer(OperatorSubscribeOn.java:81)
     at rx.observables.AbstractOnSubscribe.call(AbstractOnSubscribe.java:191)
     at rx.observables.AbstractOnSubscribe$LambdaOnSubscribe.call(AbstractOnSubscribe.java:274)
     at rx.Observable.unsafeSubscribe(Observable.java:7495)
     at rx.internal.operators.OperatorSubscribeOn$1$1.call(OperatorSubscribeOn.java:62)
     at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:55)
     at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
     at java.util.concurrent.FutureTask.run(FutureTask.java:266)
     at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)
     at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
     at java.lang.Thread.run(Thread.java:745)
     Caused by: rx.exceptions.OnErrorThrowable$OnNextValue: OnError while emitting onNext value: jdbc.Product.class
     at rx.exceptions.OnErrorThrowable.addValueAsLastCause(OnErrorThrowable.java:98)
     at rx.internal.operators.OperatorMap$1.onNext(OperatorMap.java:58)
     ... 20 more
     RxJava Tries
     

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119. Stepping Severely Limited
     

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120. Stepping Severely Limited
     

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121. Stepping Severely Limited
     

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122. orders.flatMap(o -> {
     return getProductsAsync(o)
     .doOnNext(t -> System.out.println("product: " + t))
     .flatMap(p -> {
     return getShippingStatusAsync(o, p)
     .map(s -> {
     return s;
     });
     });
     })
     Debugging via Logging
     

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123. orders.flatMap(o -> {
     return getProductsAsync(o)
     .doOnNext(t -> System.out.println("product: " + t))
     .flatMap(p -> {
     return getShippingStatusAsync(o, p)
     .map(s -> {
     return s;
     });
     });
     })
     :-(
     Debugging via Logging
     

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124. Async Debugging is Hard
     … a work in progress …
     

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125. How about once all done?
     

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126. Async Facade
     Blocking Code
     Servlet Sync/Async Bridge
     Observable APIs Worked Well
     

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127. View Slide

128. 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);  
     }
     ... with an observable api:
     replaced the blocking api ...
     

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129. Async Facade
     Blocking Code
     Servlet Sync/Async Bridge
     Challenges Mixing Approaches
     

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130. Async Facade
     Blocking Code
     Servlet Sync/Async Bridge
     too many threads
     

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131. Async Facade
     Blocking Code
     Servlet Sync/Async Bridge
     hard to tune
     &
     shed load
     

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132. Async Facade
     Blocking Code
     Servlet Sync/Async Bridge
     easy to block
     async code
     

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133. getOrdersAsync(1)
     .flatMap(o -> {
     return getProductsAsync(o)
     .flatMap(p -> {
     return getShippingStatusAsync(o, p);
     });
     });
     getOrdersAsync(1)
     .flatMap(o -> {
     return getProductsAsync(o)
     .map(p -> {
     return getShippingStatus(o, p);
     });
     });
     concurrent →
     sequential →
     

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134. getOrdersAsync(1)
     .flatMap(o -> {
     return getProductsAsync(o)
     .flatMap(p -> {
     return getShippingStatusAsync(o, p);
     });
     });
     getOrdersAsync(1)
     .flatMap(o -> {
     return getProductsAsync(o)
     .map(p -> {
     return getShippingStatus(o, p);
     });
     });
     concurrent →
     sequential →
     

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135. getOrdersAsync(1)
     .flatMap(o -> {
     return getProductsAsync(o)
     .flatMap(p -> {
     return getShippingStatusAsync(o, p);
     });
     });
     getOrdersAsync(1)
     .flatMap(o -> {
     return getProductsAsync(o)
     .map(p -> {
     return getShippingStatus(o, p);
     });
     });
     Async Facade
     only has
     Observable APIs
     

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136. So what about going
     “fully reactive”?
     

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137. View Slide

138. “cause it’s better”
     

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139. “cause it’s better”
     :-/
     

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140. “it’s worse”
     

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141. “it doesn’t matter”
     

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142. green threads, native threads,
     fibers, actors, event loops,
     theoretically equivalent, OS
     kernels, etc, etc, etc …
     

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143. C10k and beyond
     

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144. What to bet future on?
     

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145. What to bet future on?
     

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

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

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

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

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

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151. WSPerfLab: https://github.com/Netflix-Skunkworks/WSPerfLab
     154ms
     

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152. Intel(R) Core(TM) i5-2400 CPU @ 3.10GHz: 4 cores, 1 thread per core
     OpenJDK 8 with frame pointer patch
     RxNetty 0.4.8 with Netty 4.0.25.Final vs Tomcat 7.0.45
     

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153. 0%
     25%
     50%
     75%
     100%
     50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 100010501100
     RxNetty Tomcat
     CPU Usage in Percent
     concurrent clients
     Testing drove both tests near 100% cpu usage
     

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154. 0ms
     0.225ms
     0.45ms
     0.675ms
     0.9ms
     50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 100010501100
     RxNetty Tomcat
     CPU Consumption per Request
     concurrent clients
     • Netty has lower CPU consumption per request
     • Netty keeps getting faster under load, Tomcat gets slower
     

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155. 0rps
     1250rps
     2500rps
     3750rps
     5000rps
     50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 100010501100
     RxNetty Tomcat
     Throughput
     concurrent clients
     • Netty achieves higher throughput
     • Mostly due to lower CPU consumption per request
     

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156. 0ms
     70ms
     140ms
     210ms
     280ms
     50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 100010501100
     RxNetty Tomcat
     Average Latency
     concurrent clients
     Theoretical best possible for test case is 154ms
     

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157. 0ms
     750ms
     1500ms
     2250ms
     3000ms
     50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 100010501100
     RxNetty Tomcat
     Max Latency
     concurrent clients
     Tomcat latency degradation is
     far more severe than Netty
     

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158. 0ipc
     0.175ipc
     0.35ipc
     0.525ipc
     0.7ipc
     50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 100010501100
     RxNetty Tomcat
     CPU Instructions per Cycle
     concurrent clients
     Netty increases instructions
     per cycle as load increases
     

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159. 0
     400000
     800000
     1200000
     1600000
     50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 100010501100
     RxNetty Tomcat
     Thread Migrations
     concurrent clients
     significant divergence
     

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160. 0
     400000
     800000
     1200000
     1600000
     50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 100010501100
     RxNetty Tomcat
     Thread Migrations
     concurrent clients
     Under light load
     both are similar
     

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161. 0
     400000
     800000
     1200000
     1600000
     50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 100010501100
     RxNetty Tomcat
     Thread Migrations
     concurrent clients
     Increased load causes less
     migrations, improving IPC
     and CPU usage per request
     with event loop architecture
     

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162. Why?
     • More efficient framework code
     • object allocation rates and GC costs
     • Event loop architecture
     • reduced thread migrations
     • cache warmth → memory locality → instructions per
     cycle → lower cpu consumption per request
     • Thread pool architecture
     • lock contention
     • thread migrations
     

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163. Why?
     • More efficient framework code
     • object allocation rates and GC costs
     • Event loop architecture
     • reduced thread migrations
     • cache warmth → memory locality → instructions per
     cycle → lower cpu consumption per request
     • Thread pool architecture
     • lock contention
     • thread migrations
     

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164. Why?
     • More efficient framework code
     • object allocation rates and GC costs
     • Event loop architecture
     • reduced thread migrations
     • cache warmth → memory locality → instructions per
     cycle → lower cpu consumption per request
     • Thread pool architecture
     • lock contention
     • thread migrations
     

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165. Why?
     • More efficient framework code
     • object allocation rates and GC costs
     • Event loop architecture
     • reduced thread migrations
     • cache warmth → memory locality → instructions per
     cycle → lower cpu consumption per request
     • Thread pool architecture
     • lock contention
     • thread migrations
     • Many more details …
     

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166. With current JVM and Linux,
     event loops have efficiency benefits.
     

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167. Simpler
     But Not Easier
     

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168. 0ms
     750ms
     1500ms
     2250ms
     3000ms
     50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 100010501100
     RxNetty Tomcat
     Simpler
     But Not Easier
     

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169. A fully async architecture
     does have benefits.
     

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170. Reactive programming
     can be incrementally applied.
     

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171. Mixed Codebases
     

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172. Concurrency via
     Async Service Composition
     

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173. Leverage RxJava Schedulers
     and Threads
     

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174. Leverage RxJava Schedulers
     and Threads
     (or use Hystrix)
     

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175. Concurrency is still non-trivial
     

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176. Rx doesn’t trivialize it
     Concurrency is still non-trivial
     

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177. View Slide

178. 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
     Dragon Image: http://www.clipartpanda.com/clipart_images/you-can-use-this-clip-art-on-2194929
     Greenfield Image: https://kvaes.wordpress.com/2013/06/05/lingo-explained-greenfield-vs-brownfield/
     NY City Image: https://thesandincalifornia.files.wordpress.com/2012/05/newyorkcity-madness.jpg
     Futuristic City: http://i.imgur.com/rPTkr9D.jpg
     

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