Building Reactive Applications With Akka And Java
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Reactive applications share four key traits: responsive, resilient, message-driven, and elastic. The Akka framework supports building reactive systems using the actor model which represents processing, storage, and communication as actors that receive messages asynchronously. Actors can send messages to other known actors, create new actors, and handle the next received message. This allows reactive applications to scale dynamically to meet demand and tolerate failures through message passing and supervision hierarchies.
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Building Reactive Applications With Akka And Java
- 1. Building Reactive Systems with Akka Tu Pham CTO @ Dyno.me Google Developer Expert on Cloud Technology
- 2. The rules of thegame have changed
- 3. Apps inthe 60s-90s were writtenfor Apps today are writtenfor Single machines Single coreprocessors Expensive RAM Expensive disk Slow networks Few concurrent users Small data sets Latency in seconds Clusters ofmachines Multicore processors Cheap RAM Cheap disk Fast networks Lots of concurrentusers Large data sets Latency in milliseconds 3
- 5. Reactive applications share four traits ReactiveApplications 5
- 6. Reactive applications enrich the user experience with low latencyresponse.
- 7. Responsive • Real-time, engaging, rich andcollaborative • Create an open and ongoing dialog with users • More efficient workflow; inspires a feeling of connectedness • Fully Reactive enabling push instead of pull “The move to these technologies is already paying off. Response times are down for processor intensive code–such as image andPDF generation–by around 75%.” Brian Pugh, VP of Engineering, Lucid Software 7
- 8. Reactive applications react to changes in the world around them.
- 9. Message-Driven • Loosely coupled architecture, easier to extend, maintain, evolve • Asynchronous and non-blocking • Concurrent by design, immutablestate • Lower latency and higher throughput “Clearly, the goal is to do these operations concurrently and non-blocking, so that entire blocks of seats or sections are not locked. We’re able to find and allocate seats under load in less than 20ms without trying very hard to achieve it.” Andrew Headrick, Platform Architect,Ticketfly 9
- 11. Acomputational model thatembodies: 11 ✓Processing ✓Storage ✓Communication Supports 3 axioms—when an Actor receives a message it can: 1.Create newActors 2.Send messages to Actors it knows 3.Designate how it should handle the next message it receives The ActorModel
- 12. Theessence of an actor from Akka’sperspective 12 1. DEFINE 2. CREATE 3. SEND 4. BECOME 5. SUPERVISE
- 13. public abstract class BaseEvent implements Serializable { private final String id; private final JsonElement data; // Can be Json Primitive, Object, Array private int created; public BaseEvent(String id, JsonElement data) { this.id = id; this.data = data; this.created = DateTimeUtil.getCurrentUnixTime(""); } // getter & setter here } X 0.DEFINE
- 14. public class Event extends BaseEvent { private EventType eventType; public Event(String id, JsonElement data){ super(id, data); } public Event(String id, EventType eventType, JsonElement data) { super(id, data); this.eventType = eventType; } } X 0.DEFINE
- 15. public class SimpleActor extends UntypedActor { @Override public void onReceive(Object msg) throws Exception { if (msg instanceof Event) { // Say hello System.out.println(“Hello ” + msg.getId()) } } } X 0.DEFINE
- 16. Give it a name 1.CREATE Yougetan ActorRef back Create theActor Create an Actor system Actorconfiguration ActorSystem system = ActorSystem.create("MySystem"); ActorRef greeter = system.actorOf(Props.create(SimpleActor.class), “greeter");
- 17. Guardian SystemActor Actors can formhierarchies
- 18. Guardian SystemActor system.actorOf(Props.create(Foo.class), “Foo”); Actors can formhierarchies
- 19. Foo Guardian SystemActor system.actorOf(Props.create(Foo.class), “Foo”); Actors can formhierarchies
- 20. A Foo Guardian SystemActor Actors can formhierarchies
- 21. A Foo Guardian SystemActor context().actorOf(Props.create(A.class), “A”); Actors can formhierarchies
- 22. A B BarFoo C B E A D C Guardian SystemActor Actors can formhierarchies
- 23. A B BarFoo C B E A C D Guardian SystemActor Actors can formhierarchies
- 24. A B BarFoo C B E A C D Guardian SystemActor Name resolution—like a file-system
- 25. A B BarFoo C B E A C /Foo D Guardian SystemActor Name resolution—like a file-system
- 27. A B BarFoo C B E A C /Foo /Foo/A /Foo/A/B D Guardian SystemActor Name resolution—like a file-system
- 28. A B BarFoo C B E A C /Foo /Foo/A /Foo/A/B Guardian SystemActor /Foo/A/D D Name resolution—like a file-system
- 29. 2.SEND X simpleRef.tell(new Event(new UUID().toString(), null, jsonObject), null); Send the message asynchronously Passin the senderActorRef
- 30. Reactive applications are architected to handle failure at all levels.
- 31. Resilient • Failure is embraced as a natural state in the app lifecycle • Resilience is a first-class construct • Failure is detected, isolated, and managed • Applications selfheal “The Typesafe Reactive Platform helps us maintain a very aggressive development and deployment cycle, all in a fail-forward manner. It’s now the default choice for developing all new services.” Peter Hausel, VP Engineering, Gawker Media 21
- 35. Coffee Machine Programmer Inserts coins Add morecoins Think VendingMachine
- 36. Coffee Machine Programmer Inserts coins Gets coffee Add morecoins Think VendingMachine
- 39. Coffee Machine Programmer Inserts coins Think VendingMachine Out of coffee beans error
- 40. Coffee Machine Programmer Inserts coins Think VendingMachine Out of coffee beans error Wrong
- 42. Coffee Machine Programmer Inserts coins Out of coffee beans error Think VendingMachine
- 43. Coffee Machine Programmer Service Guy Inserts coins Out of coffee beans error Think VendingMachine
- 44. Coffee Machine Programmer Service Guy Inserts coins Out of coffee beans error Adds more beans Think VendingMachine
- 45. Coffee Machine Programmer Service Guy Inserts coins Gets coffee Out of coffee beans error Adds more beans Think VendingMachine
- 54. • Isolate the failure • Compartmentalize • Manage failure locally • Avoid cascading failures Use Bulkheads
- 55. • Isolate thefailure • Compartmentalize • Manage failurelocally • Avoid cascadingfailures Use Bulkheads
- 56. EnterSupervision
- 57. A B BarFoo C B E A D C Supervisor hierarchies Automatic and mandatory supervision
- 58. Reactive applications scale up and down to meet demand.
- 59. Elastic • Elasticity and Scalability to embrace the Cloud • Adaptive Scale on Demand • Clustered servers support joining and leaving of nodes • More cost-efficient utilization of hardware “Our traffic can increase by as much as 100x for 15 minutes each day. Until a couple of years ago, noon was a stressful time. Nowadays, it’s usually a non-event.” Eric Bowman, VP Architecture, Gilt Groupe 33
- 62. 1.Minimize Contention 2.Maximize Locality ofReference 35 Weneedto
- 64. Fully event-drivenapps are a necessity Amdahl’s Law will hunt you down X
- 66. Typesafe ReactivePlatform • • Actors are asynchronous and communicate via message passing Supervision and clustering in support of fault tolerance • • Purely asynchronous and non-blocking webframeworks No container required, no inherent bottlenecks in session management • • Asynchronous and immutable programmingconstructs Composable abstractions enabling simpler concurrency and parallelism 48
- 67. Reactive is being adopted across a wide range of industries.
- 68. Finance Internet/Social Media Mfg/Hardware Government Retail
- 69. DEMO TIMEAsimple game of ping pong
- 70. 3.BECOME X
Hinweis der Redaktion
- Tôi có 1 người bạn trước đây là cựu giám đốc Kiến trúc của VM Ware, là hiện là Kĩ sư trưởng tại Google, ông ấy bắt đầu lập trình chuyên nghiệp từ năm 1983, khi tôi hỏi sự khác biệt lớn nhất giữa LTV năm 83 và bây giờ là gì, ông ấy trả lời là phần cứng
- Đặc điểm: Responsive: Reacting or replying quickly or favourably, as to a suggestion, initiative Resilient: Returning to the original form or position after being bent, compressed, or stretched Elastic: Able to encompass variety and change; flexible and adaptable. Message driven: Messaging is one way to communicate events raised by producers to consumers in a reliable, guaranteed manner.