eventsggx

Reactive Grails Event-driven architecture made easy

Stephane Maldini – Consultant @ SpringSource/VMware*

* Changes may apply in the next couple of months

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WHY ?!!!!!!!!!!!!!!!!

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In Memory use cases

•  Loosely coupled – Plugin oriented – Testable handlers without mocking

•  Declarative logic – Workflow by contract

•  Threading scalability – Scale to multicores without digging too deep in your code

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In Cloud use cases

•  Sharing workload – And on demand ! – One machine can handle the task: using a shared work queue

•  Synchronizing – All machines need to work: Cache invalidation, indexing...

•  Communicating with Service API – Layering at machine level instead of software level

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The big picture

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Events Bus

Point to point

Service Listener

Service Listener

Service Listener

Service Listener

Service Listener

Application

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The big picture

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Events Bus

Publish/Subscribe

Service Listener

Service Listener

Service Listener

Service Listener

Service Listener

Application

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The big picture

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Events Bus

Publish/Subscribe

App

App

App

App

App

Cloud

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Boring

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Robert Fletcher

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Grails on bus : current plugins

•  Spring Events – Use ApplicationContext to propagate ApplicationEvents – Code boilerplate

•  Routing (Apache Camel) – Super flexible – Simple but powerful – Routing DSL but not so “Grailsy”

•  Falcone Utils – Fully integrated with Grails – Not maintained

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Platform-Core

•  This plugin purpose is to provide key features for todays application development and plugin oriented architecture

•  Provided by Marc Palmer and your guest

•  Initiated mid 2012, currently version 1.0.RC2: – Nearly complete API stabilization – Integrated with grails development

•  Fully extensible, API driven design

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Platform-Core: API

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Navigation Configuration

Injection Events

Security

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Platform-Core : Events

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•  Grails Apps and Plugins can use Platform-Core/Events to:

– Listen for plugins/app events

– Avoid topic name conflicts using namespacing support

– Do in-memory eventing

– Do Asynchronous calls (default)

– Increase in flexibility if required

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•  Add this to your BuildConfig RIGHT NOW :

– compile “:platform-core:1.0.RC2”

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Events : Sending Events

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class UserController{ def registration(){ def user = new User(params).save() if(user){ //non-‐blocking call, will trigger application listeners for this topic event('mailRegistration', user) //blocking call : //event('mailRegistration', user).waitFor() //can also be written like that //event topic:'mailRegistration', data:user //and if you need to reuse the current thread //event topic:'mailRegistration', data:user, fork:false render(view:'sendingRegistrationMail') }else{ render(view:'errorRegistration') } } }

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Events : Listening Events

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class UserService{ //use method name 'mailRegistration' as topic name //can also use custom topic name using topic arg: @Listener(topic='test') @grails.events.Listener def mailRegistration(User user){ sendMail{ to user.mail subject "Confirmation" html g.render(template:"userMailConfirmation") } } //Can also receive an EventMessage to get more information on this particular event) @grails.events.Listener(topic="mailRegistration") def mailRegistration2(org.grails.plugin.platform.events.EventMessage msg){ sendMail{ to msg.data.mail subject "Confirmation" html g.render(template:"userMailConfirmation") } } }

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Events : DSL

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events = { //prevents any events in gorm namespace '*' namespace:'gorm', disabled:true //filters any events on 'testTopic' where data <= 2 testTopic filter:{it > 2} //filters any events on 'testTopic2' where data is not a TestTopic class type testTopic2 filter:TestTopic //filters any events on 'testTopicX' using boolean method from service testTopicX filter:ctx.myService.&someMethod //only if using events-‐push plugin, allows client-‐side listener on this topic testTopic3 browser:true //Default Error Handling, Global Reply Handling, timeout and fork testTopicD onError:{}, onReply:{}, timeout:1000l testTopicD2 fork:false }

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Platform-Core : Events, more!

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•  Listen to GORM events – using the same API

•  Reply handlers – Return values from your listeners to pass them back to caller

•  Errors handler – Listen for any exceptions

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Platform-Core : Simplicity Wins!

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Events : Plugins

•  Leveraging and enriching the Platform-core API

•  May update events registering/dispatching engine

•  Combine them and achieve kool kombos

•  Currently 3 plugins in development – Events-SI : Spring Integration backed events – Events-Push : Events to the browser using Atmosphere – Vertx : Vertx integration and platform-core backed events

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grails-events-si

•  Change in-memory default mechanism:

– @Listener now generates a channel + endpoint

– event methods now send through Spring Integration gateway

– This channel can be overriden using the naming convention

– Super flexible, connect to the world

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grails-events-si

•  SI => Spring Integration – Implements Enterprise Integration Patterns

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grails-events-si + Groovy DSL

•  Based on the excellent module from David Turanski: – https://github.com/SpringSource/spring-integration-dsl-groovy

•  Integration with Events plugin registry and publishing – Easy to add queuing behavior – Easy to transform Pub/Sub to Point 2 Point – Additional declarative logic (filtering, system integration etc)

•  Still possible to fallback to standard BeanBuilder

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grails-events-si + Groovy DSL

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How to send through RabbitMQ in minutes

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beans = { ! xmlns siAmqp: 'http://www.springframework.org/schema/integration/amqp' ! ! siAmqp.'publish-subscribe-channel'(id: 'gorm://afterInsert') ! ! siAmqp.'publish-subscribe-channel'(id: 'gorm://afterDelete') ! ! siAmqp.'publish-subscribe-channel'(id: 'gorm://afterUpdate') ! !}!

With this in BuildConfig : runtime ":rabbitmq:1.0.0 " runtime ":events-si:1.0.M4-SNAPSHOT"

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grails-events-push

•  And if you want to listen for events... in Javascript – Like Socket.IO or Vertx

– Like a free bird

– But not so free, prevent from listening everything

– But which damn protocol using ??

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grails-events-push

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ATMOSPHERE SAVES THE WORLD

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React on server side events

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grails-events-push : Whitelist

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grails-vertx : Hipster time

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grails-vertx

•  No hands clustering – Using Vert.x Hazelcast support

•  Super scalable events processor – Mom’ said Event loop is darn good at handling high concurrent

load

•  Deploying features as “verticles” – WIN for hot reloading plugins/services

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grails-vertx

•  vertxService bean (vertx instance, container)

•  Grails dedicated language factory: – Verticle Hot reloading – Classloader access

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grails-vertx

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Roadmaps

•  Platform-Core – Work Queue / Point to Point eventing – Response Streaming

•  Events-SI – Overridable listeners with Queue channels

•  Events-Push – More on filtering – ... per request security (with PlatformCore security)

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Roadmaps

•  Some more Vertx love: – Better integration

– Specific DSL to manage verticles

– SockJS support

– request dispatching •  Vertx Back / Grails Front •  Vertx Front / Grails Back ?

– Rename it Testx

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Demos!

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More info

•  w: http://bit.ly/platform-core-docs •  w: http://github.com/smaldini

•  Grails Todos source: https://github.com/smaldini/grailsTodos

•  t: @smaldini

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eventsggx

Documents