Play2 Non blocking, composable reactive web programming with - - PowerPoint PPT Presentation

Play2

Non blocking, composable reactive web programming with Iteratees and Promises in Play2

Monday, June 18, 12

@guillaumebort @sadache @hguergachi

Monday, June 18, 12

www.zenexity.com

Web Oriented Architectures

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What is Play?

• The Play framework makes it easier to build

web applications with Java & Scala.

• Play is based on a lightweight, stateless, web-

friendly architecture for highly-scalable applications

• thanks to its reactive model, based on Futures

and Iteratee IO.

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The Web Evolved

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The Web Evolved

• Data distribution and Information Systems

Partitioning

• Streams of Data

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Problem

get x get y

Execution Thread

get x get y

Execution Thread

get x get y

Execution Thread

get x get y

Execution Thread

get x get y

Execution Thread

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Opportunity

get x get y

Execution Thread

get x get y

Execution Thread

get x get y

Execution Thread

get x get y

Execution Thread

get x get y

Execution Thread

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Opportunity

• What if the callee can notify me on completeness of

his task

• A callback

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Callback Hell!

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An Opportunity and a Model

• The service we are calling should support the Non

Blocking Style (ex: NIO)

• A model of programming: Reactive with Futures and

Promises

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Futures and Promises

• val f : Future[A] = ...
• f.map( a => getB(a)) // Eventually transforming A to B
• f.flatMap( a => eventuallyGetB(a))

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Play2’s Action takes the future!

Action { rq => AsyncResult(f.map(a => Ok(a)) }

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Play2’s Action takes the future!

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Play2’s Action takes the future!

• The service we are calling should support the Non

Blocking Style (ex: NIO)

• Webcalls (WS), network, filesystem, datastores

(MongoDb), SQL (async MySQL), disruptor, actors, …)

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Streams of Data

• Streams of data are everywhere
• File uploads, tweets, finance data streams, ...

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InputStream is outdated/too low level

public abstract int read() throws IOException Reads the next byte of data from the input

• stream. [...]

This method blocks until input data is available

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Problem of classic model

• Blocking read and blocking write
• Resources consumption (memory, threads, disk).
• Pro-active waiting.
• Input/Output Stream

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Going Reactive

• Inversion of control.
• Without loosing control.
• Iteratee/Enumerator IO.

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Iteratee

Iteratee[E,A]

Step[E,A] Done[E,A] Cont[E,A] Error[E]

?

Input[E] => Iteratee[E,A]

Step[E,A] Done[E,A] Cont[E,A] Error[E]

? Enumerator[E]

Input[E] is either El[E] or EOF

Enumeratee[EIn,EOut]

is an adapter

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What if the Iteratee’s Input processing is reactive? an opportunity!

Iteratee[E,A]

Promise[Step[E,A]]

Done[E,A] Cont[E,A] Error[E]

?

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Reactive File Upload

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A programming model

• Tools for creating, consuming and adapting streams
• map, filter, fold, unfold, collect, group, scan, foreach, ...
• All in a reactive manner.
• Iteratee, Enumerator and Enumeratee.

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Parsing CSV like file upload

https://gist.github.com/2939230

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How to construct Enumerators (Streams)?

• Pure (from a list of elements)
• generateM and unfoldM
• Push

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Streams

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More

• www.playframework.com
• Check and play with the provided samples
• Ask
• Thanks to @sgodbillon for the MongoDb

example

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