Not a toy! The Play Framework for Scalable Web Applications

Martin Lehmann: „Not a toy! The Play Framework for Scalable Web Applications”. Eclipse Democamp, 30. November 2015

https://wiki.eclipse.org/Eclipse_DemoCamp_November_2015/Frankfurt

Transcript

1. 1 Kein Spielzeug! Das Play Framework für skalierbare Web-Anwendungen Martin Lehmann, Accso GmbH – Eclipse Democamp, Frankfurt 30.11.2015
2. 2 Not a toy! The Play Framework for Scalable Web Applications Martin Lehmann, Accso GmbH – Eclipse Democamp, Frankfurt Nov 30th, 2015
3. 3  Computer science  Since 2010 member of management board and CTO at Accso – Accelerated Solutions GmbH in Darmstadt, www.accso.de  Since end of the 90s working in several projects with scope on individual software development, focussing mainly on technical architecture  Java, SW architecture, SW Engineering, Distributed Systems  Active member of iSAQB and IASA # who am i
4. 4 Copyright © Accso GmbH Requirements on Performance: short response times, low latency, high throughput Requirements on Scalability: growing numbers of named/concurrent users, multi-core Requirements on Availability: 24x7, failover, fault-tolerancy What are the Requirements? Reactive Manifesto: Responsive, Resilient, Elastic, Message-Driven Event based Many parallel requests Lots of subscribers Pipelining, Data chains
5. 5 Copyright © Accso GmbH Traditional concurrent programming model is too low-level, too complex, too error-prone! Another Requirement: Control the Complexity Traditional concurrent programming model does not get the optimum out of available resources. Actor Model Reactor Pattern
6. 6 Copyright © Accso GmbH Actor Model Carl Hewitt, 1973 Model for concurrent programming Actors as the executables in the system Shared-Nothing architecture (no global state) Asynchronous messaging Actor Actor Actor State State State
7. 7 Copyright © Accso GmbH Design Pattern for event handling Reactor = Dispatcher (of events to callback handlers) Decouples application logic from execution logic Reactor Pattern: 1 Event-Loop-Thread Multi-Reactor Pattern: Scale to n ELTs Handler has to avoid to block the ELT at all cost! (Multi-)Reactor Pattern Douglas Schmidt et al, 1996f Client Client Client Event Loop
8. 8 Copyright © Accso GmbH (Multi-)Reactor Pattern Douglas Schmidt et al, 1996f loop { // you control the flow doSomething(); } registerHandler(doSomething); loop { // event loop controls the flow // calls registered callback event = getEventFromEventQueue(); dispatch(event); } Event Driven Normal
9. 9 Copyright © Accso GmbH Good old stuff from the 70s and 90s used nowadays
10. Copyright © Accso GmbH 10 Overview Play-Framework Since 2007 Currently V2.4 (V3 expected soon) (don‘t mix up with Play 1.x) Web- Framework (MVC) Open-Source (Apache 2) reactive Typesafe Reactive Platform extendable > 80 modules listed at https://www.playframework.com/documen tation/2.4.x/ModuleDirectory
11. Copyright © Accso GmbH 11 sbt Build System Resource Handling View Templates (Scala, HTML) Sonstige Libraries JSON, Security, … Play Core (MVC) Persistence (EBeans or JPA, h2 database) Netty (Web- server) Play Application JUnit, Selenium Akka Java or Scala CoffeeScript / JavaScript CSS / LESS Overview Play-Framework
12. 12 Demo
13. Copyright © Accso GmbH Play Web Applications are based on MVC: routes Configuration and Controller in Java 13 # Routes GET /presents controllers.XMasController.getPresentList() GET /daysToXMas controllers.XMasController.howManyDaysUntilXMas() Route: URL to Controller method Call the View public class XMasController extends Controller { @Inject Initialize init; public Result getPresentList() { List<Present> presents = Present.list(); return ok(showPresentList.render(presents)); } public Result howManyDaysUntilXMas() { LocalDate xMasDay = LocalDate.of(2015, Month.DECEMBER, 24); LocalDate now = LocalDate.now(); … int days = (Period.between(now, xMasDay)).getDays(); return ok(daysToGo.render(days)); } } Controller-Methode (public, static) Controller method
14. Copyright © Accso GmbH @(presents: List[Present]) @* showPresentList.scala.html *@ @main("XMasPresents") { <h1>List of XMas presents</h1> <p> <ul> @for(present <- presents) { <li>@present.name is for @present.presentee</li> } </ul> } Play Web Applications are based on MVC: View Templates in HTML & Scala Main elements: for loop, iterator, if-then-else and Template composition 13 Parameter from Controller Scala-Code Starts with @
15. Copyright © Accso GmbH Play Web Applications are based on MVC: Persistence with ORM via EBeans (or Hibernate/JPA) 15 import javax.persistence.*; @Entity public class Present extends Model { @Id @GeneratedValue @Column(nullable = false) private Long id; @Column(nullable = false) public String name; @Column(nullable = false) public String presentee; ... private static Model.Find<Long, Present> finder = new Model.Find<Long, Present>(){}; public static List<Present> list() { return finder.findList(); } } EBeans-Model super class plus enhancement Annotations from javax.persistence Finder methods, Query API EBeans is pretty simple. No session. Attention: Still usable though Ebeans seems (is?) kind of dead meanwhile.
16. Copyright © Accso GmbH Configuration and Modularization of a Play Web Application 16 Central config file in application.conf Divide to and include of other config files Modularization of a Play App
17. Copyright © Accso GmbH 17 What about the Development Tool Chain? • Integration with Eclipse / Scala IDE easy • Hot-Deployment and Debugging straight forward • Tests with JUnit and Selenium • Build with sbt, Ivy • Integration with Maven possible but tricky • Templates, routes etc are compiled, too • Eclipse 4.4.2 (Luna) • Scala IDE 4.2.0 • Scala 2.11.7 and Scala 2.10.5 • Sbt 0.13.8 • Scala Worksheet 0.4.0 • Play Framework support 0.5.0 • ScalaTest support 2.9.3 • Scala Refactoring 0.7.0 • Scala Search 0.2.5 • access to the full Scala IDE ecosystem
18. Copyright © Accso GmbH 18 Table visualization taken from: Lutz Huehnken, Typesafe, JAX 2015: „Von Enterprise zu Reactive“ http://de.slideshare.net/lutzh/von-enterprise-zu-reactive Traditional Servlet Model: Thread per Request Dispatching (n Threads per m Requests) Attention Don‘t rely on ThreadLocal! Blocking IO (e.g. JDBC) blocks the thread! Play standalone or via Plugin in Servlet Container? Plugin see https://github.com/play2war/play2-war-plugin/
19. Copyright © Accso GmbH Play uses Akka under the hood for Asynchronous Web Processing 19 Browser Server Proc. Unit Proc. Unit Proc. Unit Proc. Unit Proc. Unit Proc. Unit
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