Lagom in Practice
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"It’s open source. It’s highly opinionated. Build greenfield microservices and decompose your Java EE monolith like a boss." Lightbend (formerly Typesafe) has come up with their own framework, Lagom, for architecting microservices based systems. With Lagom, Lightbend wants to take up the competition with the Spring Cloud stack. Lagom is built upon Akka and Play and focuses on reactive and message-driven APIs, distributed persistence with Event Sourcing and CQRS and high developer productivity. On the 10th of March a first MVP version has been released with a Java API, the Scala API is being worked on. This workshop acts as an introduction to Lagom during which we will have a look at developing and deploying Lagom microservices. As a warm-up, you could check out the newest blogpost on the JWorks Tech Blog: https://ordina-jworks.github.io/microservices/2016/04/22/Lagom-First-Impressions-and-Initial-Comparison-to-Spring-Cloud.html. Github repo with presentation: https://github.com/yannickdeturck/lagom-shop Blogpost Lagom: First Impressions and Initial Comparison to Spring Cloud: https://ordina-jworks.github.io/microservices/2016/04/22/Lagom-First-Impressions-and-Initial-Comparison-to-Spring-Cloud.html Podcast Lightbend Podcast Ep. 09: Andreas Evers test drives Lagom in comparison with Spring Cloud: https://www.lightbend.com/blog/lightbend-podcast-ep-09-andreas-evers-test-drives-lagom-in-comparison-with-spring-cloud
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Lagom in Practice
- 2. ABOUT ME Yannick De Turck Java Developer Scala and Play enthousiast Ordina Belgium @YannickDeTurck https://github.com/YannickDeTurck
- 3. BLOGPOST LAGOM Lagom: First Impressions and Initial Comparison to Spring Cloud http://bit.ly/1sClupt
- 4. TOPICS Introduction Writing microservices Demo: writing a simple service ES & CQRS Demo: Lagom Shop
- 5. INTRODUCTION
- 6. MEET LAGOM Lightbend's microservices framework Focus on reactiveness MVP version Java API available, Scala API coming soon
- 7. DESIGN PHILOSOPHY Opinionated Message-Driven and Asynchronous Streaming rst-class concept Distributed persistent patterns using ES and CQRS Embraces Domain-Driven Design
- 8. DEVELOPER PRODUCTIVITY Hot code reloading Start up with $ runAll Intra-service communication is managed for you
- 9. ARCHITECTURE AND TECHNOLOGIES Scala Java Play Framework Akka Cluster & Akka Persistence sbt Cassandra Guice ConductR
- 11. PROJECT STRUCTURE helloworld-api → Microservice API submodule └ src/main/java → Java source code interfaces with model objects helloworld-impl → Microservice implementation submodule └ logs → Logs of the microservice └ src/main/java → Java source code implementation of the API submodule └ src/main/resources → Contains the microservice application config └ src/test/java → Java source code unit tests logs → Logs of the Lagom system project → Sbt configuration files └ build.properties → Marker for sbt project └ plugins.sbt → Sbt plugins including the declaration for Lagom itself .gitignore → Git ignore file build.sbt → Application build script
- 12. API INTERFACE public interface HelloService extends Service { ServiceCall<NotUsed, String> hello(String name); ServiceCall<GreetingMessage, String> useGreeting(String id); @Override default Descriptor descriptor() { return named("helloservice").with( restCall(Method.GET, "/api/hello/:name", this::hello), restCall(Method.POST, "/api/hello/:id", this::useGreeting) ).withAutoAcl(true); } }
- 13. API IMPLEMENTATION public class HelloServiceImpl implements HelloService { List<String> savedGreetings = new ArrayList<>(); @Override public ServiceCall<NotUsed, String> hello(String name) { return (request) -> { CompletableFuture.completedFuture("Hello, " + name); }; } @Override public ServiceCall<GreetingMessage, String> useGreeting() { return (request) -> { String greeting = request.getGreeting(); savedGreeting.add(greeting); CompletableFuture.completedFuture("Greeting '" + greeting + "' saved!"); }; } }
- 14. API MODULE public class HelloServiceModule extends AbstractModule implements ServiceGuiceSupport { @Override protected void configure() { bindServices(serviceBinding(HelloService.class, HelloServiceImpl.class)); bindClient(OtherService.class); } }
- 15. API MODULE The module is de ned in the application.con g play.modules.enabled += sample.helloworld.impl.HelloServiceModule
- 16. REGISTERING THE MICROSERVICE build.sbt lazy val helloworldApi = project("helloworld-api") .settings( version := "1.0-SNAPSHOT", libraryDependencies += lagomJavadslApi ) lazy val helloworldImpl = project("helloworld-impl") .enablePlugins(LagomJava) .settings( version := "1.0-SNAPSHOT", libraryDependencies ++= Seq( lagomJavadslPersistence, lagomJavadslTestKit ) ) .settings(lagomForkedTestSettings: _*) .dependsOn(helloworldApi)
- 17. TESTING THE MICROSERVICE $ curl localhost:24266/api/hello/World Hello, World! $ curl -H "Content-Type: application/json" -X POST -d '{"message": "Hello "}' http://localhost:24266/api/hello/World Greeting 'Hello' was saved!
- 18. TESTING THE MICROSERVICE public class HelloServiceTest { private static ServiceTest.TestServer server; @Test public void shouldRespondHello() throws Exception { withServer(defaultSetup(), server -> { HelloService service = server.client(HelloService.class); String hello = service.hello("Yannick") .invoke(NotUsed.getInstance()).toCompletableFuture().get(5, SECONDS); assertEquals("Hello, Yannick", hello); }); } }
- 20. DEMO Implement a new service: capitalise Write a unit test Deploy it to ConductR
- 21. ES & CQRS
- 22. ES AND CQRS
- 24. EVENT SOURCING Capture all changes as domain events Handlers process these events
- 25. EVENT SOURCING BENEFITS All events are stored in an event store No object-relational impedance mismatch Built-in audit mechanism and historical tracing Performance, simpli cation and scalability Testability Debugging by replaying the event log
- 26. CQRS Separation of write- and read-side Scalability Di erent models for write- and read-side Eventual consistency
- 40. ES AND CQRS - PERSISTENTENTITY public class HelloWorld extends PersistentEntity { @Override public Behavior initialBehavior(Optional snapshotState) { BehaviorBuilder b = newBehaviorBuilder( snapshotState.orElse(new WorldState("Hello", LocalDateTime.now().toString()))); b.setCommandHandler(UseGreetingMessage.class, (cmd, ctx) -> ctx.thenPersist(new GreetingMessageChanged(cmd.message), evt -> ctx.reply(Done.getInstance())) ); b.setEventHandler(GreetingMessageChanged.class, evt -> new WorldState(evt.message, LocalDateTime.now().toString())); b.setReadOnlyCommandHandler(Hello.class, (cmd, ctx) -> ctx.reply(state().message + ", " + cmd.name + "!") ); } }
- 41. ES AND CQRS - STATE @Immutable @JsonDeserialize public final class WorldState implements CompressedJsonable { public final String message; public final String timestamp; @JsonCreator public WorldState(String message, String timestamp) { this.message = Preconditions.checkNotNull(message, "message"); this.timestamp = Preconditions.checkNotNull(timestamp, "timestamp"); } // equals, hashcode, toString, ... }
- 42. ES AND CQRS - COMMAND public interface HelloCommand extends Jsonable { @Immutable @JsonDeserialize public final class UseGreetingMessage implements HelloCommand, CompressedJsonable, PersistentEntity.ReplyType { public final String message; @JsonCreator public UseGreetingMessage(String message) { this.message = Preconditions.checkNotNull(message, "message"); } // equals, hashcode, toString,... } }
- 43. ES AND CQRS - EVENT public interface HelloEvent extends Jsonable { @Immutable @JsonDeserialize public final class GreetingMessageChanged implements HelloEvent { public final String message; @JsonCreator public GreetingMessageChanged(String message) { this.message = Preconditions.checkNotNull(message, "message"); } // equals, hashCode, toString }
- 44. ES AND CQRS - SERVICEIMPL @Override public ServiceCall useGreeting(String id) { return (request) -> { PersistentEntityRef ref = persistentEntityRegistry.refFor(HelloWorld.class, id); return ref.ask(new UseGreetingMessage(request.message)); }; }
- 45. DEMO: LAGOM SHOP
- 46. LAGOM SHOP Item Service: Create and lookup items Order Service: Create and lookup orders for items Play front-end
- 47. QUESTIONS? Lagom Shop & Presentation: https://github.com/yannickdeturck/lagom-shop Blogpost Lagom: First Impressions and Initial Comparison to Spring Cloud http://bit.ly/1sClupt Podcast Lightbend Podcast Ep. 09: Andreas Evers test drives Lagom in comparison with Spring Cloud: http://bit.ly/25XVT8w