Reactor grails realtime web devoxx 2013

Groovy, Reactor, Grails  
& the realtime web
Guillaume Laforge  
@glaforge !

Stéphane Maldini 
@smaldini !

Stéphane
Maldini
Consultant and Reactor committer
at
.
!

@smaldini

Reactor — Housekeeping
!

• Tweet questions during the presentation

– @ProjectReactor
!

• Stop us anywhere if you have a question

– There are no stupid questions, only stupid answers!

@glaforge — @smaldini / #DV13-rtweb

!4

Reactor — Reactive Architecture ?
REACTIVE
AGILE
EVENT DRIVEN
SCALABLE
AVAILABLE


!5

Reactor — Reactive Architecture ?
• A good description is available on:  
http://www.reactivemanifesto.org/

!

• Functional Programming helps as it is stimulus based by nature

!

• Groovy is a perfect candidate:  
Closures and DSL are ﬁrst class citizen

!

• Reactor completes the picture by providing abstractions


!6

Reactor — Threading model matters
• Context switching hurts performances

• Locking hurts performances

• Message passing hurts performances

• Blocking for a thread hurts performances

• Creating Threads needs memory


!7

Reactor — Dealing with performances
• Actors solve the locking and context switching issues  
by becoming state boxes

• One thread assigned per consumer

• One thread will ever access a property 
• Non Blocking Programming solves thread creation and
waiting issues by delaying logic

• Callback will be executed when possible (Lazy)

• Reallocate the blocking time to process something else


!8

Reactor — LMAX Disruptor and Ring Buffer
• LMAX Disruptor deals with message passing issues

• Based on a Ring Buffer structure

• “Mechanical Sympathy” in Disruptor

!

• http://lmax-exchange.github.com/disruptor/ﬁles/
Disruptor-1.0.pdf

• http://mechanitis.blogspot.co.uk/2011/06/dissecting-disruptorwhats-so-special.html


!9

Reactor — Disruptor performances


!10

Reactor — Trisha’s pretty picture of Disruptor
http://mechanitis.blogspot.co.uk/2011/07/dissectingdisruptor-writing-to-ring.html


!11

Reactor — In love with Disruptor
• Reactor best performances are derived from LMAX Disruptor

!

• LMAX Disruptor can be considered  
as an evolution of the Actor Model:

!

• Still avoid locking and deals with context switching

• Producer/Consumer decoupled

• Add Pipelining, Batching and more


!12

Reactor — A foundation part of Spring IO


!13

Reactor — What is it?
!

• Reactor is a distillation of other libraries and best-practices

– Elements of other patterns and libraries  
surface throughout Reactor's abstractions

!

• http://stackoverﬂow.com/questions/16595393/akka-or-reactor


!14

Reactor — What can I build with it?
• Reactor applications are reactive

– Reactive Extensions in .NET

– Netﬂix RxJava

– Observer pattern

!

• Reactor applications route events based on a Selector

– Like a routing topic, but can be any object

– Regex, URI template, Class.isAssingableFrom, custom logic


!15

Reactor — Landscape


!16

Reactor — What does it look like?
Create a reactor context
def
env
=
new
Environment()

!

Build a reactor
parameter

def
reactor
=

Reactors.reactor().env(env).dispatcher(RING_BUFFER).get()

!

reactor.on($('topic')){
Event<String>
ev
-‐>

println
"Hello
$ev.data"

}

React on ‘topic’ events

!

reactor.notify('topic',
Event.wrap('John
Doe'))

Trigger reactor ‘topic’ key

!17

Reactor — Selectors
• Selectors are the left-hand side of an equality comparison

!

– A Selector can be created from any object using $(obj)  
(or the long form: Selectors.object(obj))

!

– A Selector can extract data from the matched key

!

– Predicate<T> Selectors can be created to match on domainspeciﬁc criteria like header values


!18

Reactor — RegexSelector
• A RegexSelector will match a String by executing the regex
over it

– R(“some.(.*)”)
– Selectors.regex(“some.(.*)”)


!19

!

• A RegexSelector will match a String  
by executing the regex over it

!

– R(“some.(.*)”)
!

– Selectors.regex(“some.(.*)”)


!20

Use a Regex Selector and capture group
reactor.on(R('some.(.+)')){
Event<String>
ev
-‐>

def
s
=
ev.headers.get('group1')

}

s will be ‘topic’
!

reactor.notify('some.topic',
Event.wrap('John
Doe'))

Notify a simple String
key to be matched

!21

Reactor — UriSelector
• A UriTemplateSelector will match a String  
by extracting bits from a URI
!

– U(“/some/{path}”)
– Selectors.uri(“/some/{path}”)


!22

Reactor — UriSelector
Use a URI Selector and capture fragment
reactor.on(U('/some/**/{topic}')){
Event<String>
ev
-‐>

def
s
=
ev.headers['topic']

}

s will be ‘topic’
!

reactor.notify('/some/to/topic',
Event.wrap('John
Doe'))

Notify a simple String
URI key to be matched

!23

Reactor — Consumer, Function, Supplier, Predicate
public
interface
Consumer<T>
{

void
accept(T
t);

}

Generic Callback

!

public
interface
Supplier<T>
{

T
get();

}

Object Factory

!

public
interface
Function<T,
V>
{

V
apply(T
t);

}

Map Operation

!

public
abstract
class
Predicate<T>
{

boolean
test(T
t);

}


Filter Operation

!24

Reactor — Streams
●

−
−

Streams allow for composition of functions on data

Callback++

Netﬂix RxJava Observable, JDK 8 Stream
Stream<String>
str
=
obtainStream()

Coerces to Function

!

str.map{
it.toUpperCase()
}

.filter{
someCondition()
}

.consume{
s
-‐>
log.info
"consumed
string
$s"
}

Coerces to Predicate


Coerces to Consumer
!25

Reactor — Promises
●

−
−

Promises supersedes Java Future for composition

Share common functions with Stream
Stateful: only 1 transition allowed
Promise<String>
p
=
doLater()

!

String
s
=
p

.onSuccess
{
s
-‐>
log.info
"consumed
string
$s"
}

.onFailure
{
t
-‐>
log.error
"$t.message"
}

.onComplete
{
log.info
'complete'
}

.await(5,
SECONDS)

!

p.map{
it.toUpperCase()
}.consume{s
-‐>
log.info
"UC:
$s"}

Block for a return value

!26

Reactor — Processor
●

−
−

Thin wrapper around Disruptor RingBuffer
Converts Disruptor API to Reactor API

Uber fast performance for #UberFastData
Processor<Buffer>
proc

!

Operation<Buffer>
op
=
proc.prepare()

op.get().append(data).flip()

op.commit()

!

proc.batch(512)
{
it.append(data).flip()
}

Fill 512 slots and release once

!27

Reactor — Spring
!

Helpers to integrate Reactor into ApplicationContext

●

!

−

@EnableReactor for easy conﬁguration

!

−

Wiring annotated handlers


!28

Reactor — Spring
Setup Environment

@Configuration

@EnableReactor

class
ReactorConfiguration
{

!

@Bean
Reactor
input(Environment
env)
{

Reactors.reactor().env(env)

.dispatcher(RING_BUFFER).get()

}

!

@Bean
Reactor
output(Environment
env)
{

Reactors.reactor().env(env)

.dispatcher(RING_BUFFER).get()

}

}

!29

Reactor — Spring
@Component

class
SimpleHandler
{

Inject reactor

!

@Autowired
Reactor
reactor

!

@Selector('test.topic')
void
onTestTopic(String
s)
{

//
Handle
data

}

}

Register consumer on @reactor


!30

Reactor — Spring
●

−
−
●
●

●

DispatcherTaskExecutor

Not really a high-scale TaskExecutor

Used to get Spring components running in same thread as
Reactor Consumers

ConversionService integration

PromiseHandlerMethodReturnValueHandler (!)

ReactorSubscribableChannel


!31

Reactor — Groovy
●

−
−
−
−

First class citizen language implementation

@CompileStatic ready

Prominent use of Closure as Consumers, Functions and
more

Operator overloading for elegant programming

Full Reactor system Builder


!32

Reactor — Groovy
Works with Groovy 2 CompileStatic

Coerce String to $(string)

@CompileStatic

def
welcome()
{

reactor.on('greetings')
{
String
s
-‐>

reply
"hello
$s"

reply
"how
are
you?"

}

Send data back using
replyTo key header

!

reactor.notify
'greetings',
'Jon'

!

reactor.send('greetings',
'Stephane')
{

println
it

cancel()

}

}

Stop listening for replies


Coerce data arg to
Event.wrap(data)
Notify & Listen for replies
!33

Reactor — Groovy Promises and Streams
Build an async function

def
promise
=
Promises.task
{
longStuff();
1
}
get()

!

def
transformation
=
promise
|
{
it
+
1
}

transformation.await()
==
2

Pipe promise with the
!
def
deferredStream
=
Streams.defer().get()

closure transformation
(deferredStream
&
{
it
>
2
})
<<
{
send(it)
}

!

deferredStream
<<
1
<<
2
<<
3
<<
4

Filter the stream with
the right hand closure
predicate

Add callback after filter
Send data
!34

Reactor — Groovy Environment
Works with Groovy 2
@CompileStatic

Prepare an environment
builder

GroovyEnvironment.create
{

environment
{

defaultDispatcher
=
"test"

!

which dispatcher to use
when creating a reactor

dispatcher('test')
{

type
=
DispatcherType.SYNCHRONOUS

}

}

Build a standard
}.environment()

Return a ready to
use Environment


Dispatcher

!35

Reactor — Groovy Environment
Build a named Reactor

GroovyEnvironment.create
{

reactor('test1')
{

Intercept the data

stream('test')
{

consume
{
ev-‐>

stream coming by the

log.info
ev.data

selector $(‘test’)

}

}

on('test')
{

Stream builder

reply
it

}

}

}

Attach inline consumers


!36

Reactor — Extensive Awesomeness
●

TCP Client/Server, with a Netty 4 implementation

●

Buffer tools

●

Sequencer support, for event ordering

●

Work Queue support with OoB Java Chronicle implementation

●

Log Appender


!37

Reactor — Roadmap
1.1 discussions

●

−

StateBox: a safe tool for concurrent writes

−

Better Timer management

−

Spring XD, Spring 4

−

Exploring Distributed Reactors

●

Voice your interest and your use-case here


!38

Reactor — Roadmap
1.1 discussions

●

−

HTTP helpers

−

Improved RingBuffer API for multithreaded consumers
(slow consumers)

−

More Groovy Love: Buffer, TCP, Processor, Time,


!39

Reactor — Uber Community Contribs
●

−

Meltdown: A Clojure binding by @michaelklishin &
@ifesdjeen

https://github.com/clojurewerkz/meltdown


!40

Reactor — Uber Community Contribs
!

●

−

High Performance Couchbase ingestion by @daschl

http://nitschinger.at/Using-the-Reactor-Processor-for-HighPerformance-TCP

!

●

Beneﬁts of using Reactor Processor, TCP and Batching
facilities


!41

Grails — The Age of Asynchronous
Fact #1:

– HTTP request thread is critical path

– Do the barely necessary for fast rendering

– If it’s long*, do it in a separate thread


!44

Fact #2:

– Creating new Threads needs caution

– Context switching hurts performances

– Concurrent programming is tricky*


!45


Fact #3:

– Burden on your application is never constant

– Scaling Up is a good start…

– …And Scaling Out is only next


!46


So I have to use background threads ?

But using them might lead to issues and headaches ?

And what if I really need to scale out ?


!47

Grails — Reactive Programming Recap
• Adding a level of indirection :  
Driving your application with Events
• Laziness is key
• Scale up/out by tweaking dispatching


!48

Grails — The Big Picture
Application
Service
Consumer
Service
Consumer

Publish/Subscribe
Events
Bus

Service
Consumer


Service
Consumer

Service
Consumer

!49

Grails — The Big Picture
Cloud
App
Publish/Subscribe

App
Events
Bus

App

App
App


!50

Introducing
GRAILS-‐EVENTS
plugin
BOOM!

worse slide ever™

!51

Grails — Origins : Platform-Core plugin
• An initiative to provide modern tools for grails development

!

• Among them: the Events API

• An abstraction used in a few Grails applications today to
decouple logic from producers
!

• grails-events can be considered as  
Platform Core Events API 2.0

!52

Grails — Why a new plugin ?
• New features. And quite a few.

– Streaming data, Selectors, Queue

!

• Based on a new solid foundation – Reactor
– Where Platform-core Events best ideas have leaked

!

• Semantic changes
– But relatively straightforward migration path


!53

Grails — Why a new plugin ?
• Lightweight, only focused on events

!

• Ready to be embedded in a future Grails version

• Complete the asynchronous story

• Could enable runtime plugin deployment


!54

Grails — So what Grails Events is about
• Grails Apps and Plugins can use Events to:

– Listen for plugins/app events

– Start simple with in-memory eventing (#uberfastdata)

– Do Asynchronous calls (default)

– Increase in ﬂexibility if required


!55

Grails — Installing Grails Events
• It’s a binary plugin (!)

• Requires Grails 2.2+
repositories
{

//...

mavenRepo
"http://repo.springsource.org/libs-‐snapshot"

mavenRepo
"http://repo.grails.org/grails/libs-‐snapshots-‐local/"

}

!

dependencies
{

compile
'org.grails.plugins:events:1.0.0.BUILD-‐SNAPSHOT'

}


!56

Grails — Semantics: Consumer
• A Consumer:

– Accepts an Event

– Is registered in a Service or Events artifact, or by calling on()

– Can be thread safe

• Depending on the dispatcher type

• Assuming the consumer is not registered more than once


!57

Grails — Semantics: Selector
• A Selector:

– Matches an event key

– Is paired with a consumer during its registration
– Any bean method can be transformed into consumer
with @Selector


!58

Grails — Semantics: Reactor
• A Reactor:

– Is a dedicated Consumer Registry

– Has an assigned Dispatcher

– Uses a speciﬁc Event Router

!

• Usually, if the Dispatcher doesn’t need to be adapted, reuse the
default reactor grailsReactor


!59

Grails — Pattern Examples : Event Driven CQRS
http://martinfowler.com/bliki/CQRS.html

Save a GORM entity
SaveService
GORM

DB

PostProcessingService

Insert Record


Trigger afterInsert
event

Consume afterInsert events

!60

Grails — Pattern Examples : Modular Architecture
Core application untouched

Trigger ‘request’ event

Main Application

RequestService

Notiﬁcation Plugin

NotiﬁcationService

Create a decoupled module

Consume ‘request’ events
!61

Grails — Pattern Examples : Background Processing
Return immediately
Grails Controller

REST service

Request Service

HTTP Request

Trigger ‘request’
event (async)

Long REST call

!62

Grails — Sending Events (grails-platform-core)
def
user
=
new
User(params).save()

!

event('mailRegistration',
user)

//event('mailRegistration',
user).waitFor()

//event
topic:'mailRegistration',
data:user

//event
topic:'mailRegistration',
data:user,
fork:false

render(view:'sendingRegistrationMail')


!63

Grails — Sending Events (grails-events)
def
user
=
new
User(params).save()

!

user)

user)
{

if(it
==
‘end')
{

cancel()

}

}

Non blocking call to
trigger app consumers

Do things on each reply
Map notation

!

//
event
key:
'mailRegistration',
data:
user

!

render(view:
'sendingRegistrationMail')

!64

Grails — Consuming Events (grails-platform-core)
class
UserService{

@grails.events.Listener

def
mailRegistration(User
user)
{

sendMail
{

to
user.mail

subject
"Confirmation"

html
g.render(template:"userMailConfirmation")

}

}

!

@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")

}

}

}


!65

Grails — Consuming Events (grails-events)
Consume on
Selector(method name)

class
UserService{

@reactor.spring.annotation.Selector

def
mailRegistration(User
user){

sendMail{

to
user.mail

subject
"Confirmation"

html
g.render(template:
"userMailConfirmation")

}

}

Consume on this
specific topic

!

@reactor.spring.annotation.Selector("mailRegistration")

def
mailRegistration2(reactor.event.Event
msg){

sendMail{

to
msg.data.mail

subject
"Confirmation"

html
g.render(template:"userMailConfirmation")

}

}

}


Event typed signature
to inspect enveloppe
(‘headers…)
!66

Grails — A new Artifact conf/XxxxEvents
includes
=
['default']

Merge with DefaultsEvents

!

doWithReactor
=
{

reactor(EventsApi.GRAILS_REACTOR)
{

on('someTopic')
{

reply
'test'

}

}

reactor(‘someGormReactor')
{

dispatcher
=
new
SynchronousDispatcher()

ext
'gorm',
true

Build a GroovyEnvironment

Reactor Groovy Builders

!

Grails extension: accept GORM events

stream
{

consume
{

log.info
"Some
gorm
event
is
flowing
with
data
$it.data"

}.when(Throwable)
{

log.error
"Ow
snap!",
it

}

}

}

}
!67

Grails — Reactor awesomeness : Selectors
• Listen for arbitrary keys

• import static reactor.event.selector.Selectors.*
on(T(SpecificClassType))
{

Listen for SpecificClassType

reply
it

}

!

Send using right key type

event(new
SpecificClassType(),
'data')

!
!

Listen for an URI

on(uri(‘/some/{captureIt}'))
{

reply
it.headers.captureIt

}

!

Send using matching URI

event('/some/hourray',
'data')


!68

Grails — Reactor awesomeness : Stream API
• Reactive Extensions programming style

• Avoid callback hell
Build a Stream to capture any reply
$(‘test’) consumers may reply
withStream
{

event(key:
'test',
data:
1)

}.when(Exception,
{

If a consumer fails

log.info
"exception:$it"

}).map
{

Transform result

callExternalService(it)

}.consume('clientKey',
reactor('browser'))
Reroute to key ‘clientKey’
on Reactor ‘browser’

!69

Grails — Reactor awesomeness: Promise API
• Grails 2.3 Promises become a Reactor Promises

• Beneﬁts from Dispatcher overriding
• Powerful once Combined with Consumers
dispatcher(ReactorPromise.PromiseDispatcher)
{

type
=
DispatcherType.RingBuffer

backlog
=
512

}
task
{

def
res
=

longProcessing()

render
res

}

!70

Grails — Reactor awesomeness : Routing
• During event dispatching, consumers list is selected

• Publish Subscribe is the default

• Possible to assign different routing strategy
reactor('test1')
{

routingStrategy
'round-‐robin'

on('test')
{

reply
'1'

Will reply 1, 2, 1, 2, 1, 2…

}

on('test')
{

reply
'2'

}

}

!71

Grails — Extensibility
!

• Main extension points:

– Dispatcher, Selector, Registry, EventRouter, Consumer
!

• Metadata in Reactor Events DSL:

– ext(‘someExtension’, [ ‘doStuff’: true ])


!72

Grails — GORM events
• GORM is now an extension

– Using ext(‘gorm’, true) on any candidate reactor

– Applicable Selectors: simple topic form (beforeInsert...)

– A boolean reply is evaluated as a cancel directive
reactor('someGormReactor'){

dispatcher
=
new
SynchronousDispatcher()

ext
'gorm',
true

@Selector(reactor
=
'someGormReactor')

}

@ReplyTo

boolean
beforeValidate(Book
b){

false

}

!73

GRAILS-‐EVENTS-‐PUSH
plugin
Eventing over HTTP!


!74

Grails — Pattern Examples : “Realtime” web
Push reply to browser: Websocket, SSE, long-polling…

Reply a new event

ResponseService

Browser

Return immediately


Grails Controller

RequestService

Trigger async event

!75

Grails — An elegant solution to browser push
• Powered by Atmosphere 2

• Automatically picks an adapted protocol:

– WebSockets, ServerSideEvent, Streaming, Polling…

• Consumer bridges for server-to-client push

• Reactor bridge for client-to-server push

• Javascript library


!76

Grails — Installing Grails Events Push
1. Install Grails Events plugin

2. Install Grails Events Push plugin
grails.servlet.version
=
"3.0"

grails.tomcat.nio
=
true

!

Use a “long-connection” friendly
tomcat configuration

grails.project.dependency.resolution
=
{

repositories
{

//...

mavenRepo
"https://oss.sonatype.org/content/repositories/snapshots"

}

dependencies
{

//...

compile
'org.grails.plugins:events:1.0.0.BUILD-‐SNAPSHOT'

}

plugins
{

//...

runtime
":jquery:1.10.2"

runtime
":events-‐push:1.0.0.BUILD-‐SNAPSHOT"

}

}


!77

Grails — grails-events-push Lifecycle 1 - Handshake

Browser

EventsPushHandler

Adapt Protocol and Open
new persistent connection


!78

Grails — grails-events-push Lifecycle 2 - Register
Consumer registered on all Reactor with
‘browser’ extension enabled
Browser

Reactor(s)

Bridge a Client Consumer with a
remote Reactor Consumer


!79

Grails — grails-events-push Lifecycle 3 - Notify
RequestService consumes on matching
Selector within the ‘browser’ Reactor
Browser

‘browser’ Reactor

RequestService

Notify any key


!80

Grails — grails-events-push Lifecycle 4 - Consume
Notify ‘browser’ enabled
Reactor and match key
Browser

Reactor(s)

ResponseService

Push event (WS, SSE…)


!81

Grails — Generating Simple Browsers bridges
includes
=
'push'

!

Conventional name to
override ‘browser’ reactor

doWithReactor
=
{

reactor('browser')
{

ext
'browser',
[

'control',

'move',

'fire',

'leave'

]

}

reactor(‘grailsReactor')
{

ext
'browser',
['sleepBrowser']

Bridge browser to these reactor
consumers $(‘control),…

!

stream(‘sleepBrowser')
{

filter
{

it.data
==
'no'

}

}

}

}


Bridge browser to this reactor
consumer $(‘sleepBrowser)

Prevent data ‘no’ to be
dispatched to browser bridges
!82

Grails — React on server side events
Inject grailsEvents.js (requires resources plugin)
Create a connection
between the browser and
the current Grails app
Listen for $(‘afterInsert’) events


!83

Grails — Generating Advanced Browsers bridges
includes
=
['push']

!

Include PushEvents (configure a
reactor for events from Browsers)

doWithReactor
=
{

reactor(‘grailsReactor')
{

ext
'gorm',
true

ext
'browser',
[

'test':
true,

'afterInsert':
[

browserFilter:
{m,
r
-‐>
true
}

],

(R("sampleBro-‐.*"))
:
true,

]

}

reactor(EventsPushConstants.FROM_BROWSERS)
{

ext
'browser',
[R("sampleBro-‐.*")]

}

}

Listen on GORM events

Extension to bridge
Browsers consumers to
Server-side pair

Events are only routed, from
Browsers to bridged Browsers


Override “From Browsers” reactor
and bridge consumers

!84

Grails — The Bad Stuff
• events-si : Events API on top of Spring Integration

– Not here (just) yet

!

• events-vertx : Abandoned experiment

– Working around Distributed Reactor

!

• Stream DSL could be optimized

– Reducing the number of objects


!85

Grails — Roadmap
• events:

– Document, especially for Migration from Platform Core

– Stick with latest awesome features from Reactor

• Still Many API to expose: Processors, Buffer, TCP, Queues,
Sequencer…

!

• events-push -> events-atmosphere :

– Add support for replyTo

– extract to standalone module : reactor-atmosphere

!86

Grails — Roadmap
• events-sockjs:

– Involves Reactor work here

!

• events-si:

– Supports new events plugin

!

• events-xx:

– The plugin where you are the hero


!87

Groovy, Reactor, Grails and the realtime web
• Embrace modern reactive architectures with Groovy,
Reactor and Grails!

• Groovy is a versatile language, that enables development of
concise and functional oriented applications

• Reactor fuels your asynchronous and reactive applications
with its ultra fast dispatching engine and non-blocking model.

• Grails supports your today's and tomorrow's web app design,
tooled with the right plugins you are prepared for responsive
and interactive applications

!90

Reactor grails realtime web devoxx 2013

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Reactor grails realtime web devoxx 2013

Similar to Reactor grails realtime web devoxx 2013 (20)

More from Stéphane Maldini

More from Stéphane Maldini (14)

Recently uploaded

Recently uploaded (20)

Reactor grails realtime web devoxx 2013