Tom Hensel - Introduction To Amf

Adobe MAX 2008 

Introduction to AMF



Wednesday, December 3rd



Tom Hensel

®

Copyright 2008 Adobe Systems Incorporated. All Rights Reserved. Adobe Confidential. 1

Terms 

AMF 



Remote Procedure Call (RPC) 



Action Message Format

An inter-process communication technology that allows a computer program to cause a subroutine or procedure to execute in another address space (commonly on another computer on a shared network) without the programmer explicitly coding the details for this remote interaction [wikipedia]

Serialization 

In computer science, in the context of data storage and transmission, serialization is the process of converting an object into a sequence of bits so that it can be stored on a storage medium (such as a file, or a memory buffer) or transmitted across a network connection link. When the resulting series of bits is reread according to the serialization format, it can be used to create a semantically identical clone of the original object [wikipedia] 

Often referred to as decoding and encoding of objects ®

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Definition 

AMF is a binary format based loosely on the Simple Object Access Protocol (SOAP). It is used primarily to exchange data between an Adobe Flash application and a database, using a Remote Procedure Call (RPC)



AMF allows to serialize (and deserialize) ActionScript object graphs



Once serialized an AMF encoded object graph may be used to persist and retrieve the public state of an application across sessions or allow two endpoints to communicate through the exchange of strongly typed data



AMF0 also supports sending complex objects by reference which helps avoid sending redundant instances in an object graph as well as allowing endpoints to restore relationships and avoid circular references

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Purpose - AMF0 

AMF was introduced in Flash Player 6 in 2001 and remained unchanged with the introduction of ActionScript 2.0 in Flash Player 7. The version header of this format was set to 0 and thus this version of the format is referred to as AMF0

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Purpose - AMF3 

In Flash Player 9, Action Script 3.0 was introduced along with a new ActionScript Virtual Machine (AVM+) - the new data types and language features made possible by these improvements prompted AMF to be updated



Given the opportunity to release a new version of AMF, several optimizations were also made to the encoding format to remove redundant information from serialized data



This new version of the format is referred to as AMF3

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Specifications 

Adobe Systems published the AMF binary data protocol specification on December 13, 2007 and announced that it will support the developer community to make this protocol available for every major server platform 

Specification of AMF0 download.macromedia.com/pub/labs/amf/amf0_spec_121207.pdf



Specification of AMF3 download.macromedia.com/pub/labs/amf/amf3_spec_121207.pdf

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Benefits - Efficiency 

AMF objects are very small 

Efficient Encoding and Decoding 





AMF data is parsed directly to and from objects

Small Overhead 

Binary Format



Optional compression (zlib)

Bandwidth and CPU usage is lower compared to 

HTML



JSON



YAML



XML 

SOAP



WDDX ®

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Benefits - Efficiency 

Lower bandwidth and CPU usage means 





Lower latency 

Improved User Experience due to quicker response times  Key Factor for User Acceptance



Essential for Near-Real-Time-Applications, e.g.  Data Processing and Visualization  Multi-User Applications  Online-Games, MMO  Interface and Sensor Input (i.e. Kiosk-Applications)

Bandwidth Usage 

Bandwidth is still not free (and maybe never will)



Scales well (no accumulating overhead)

Suitable for low-bandwidth requirements 

POTS, ISDN, GPRS, ...

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Benefits - Reference Tables 

In AMF 3, Strings, Complex Objects and an Object Type's Traits can be sent by reference 



Complex Objects are defined as 

Anonymous Objects, typed Objects



Arrays



Dates



XMLDocument, XML



ByteArrays

Instead of sending redundant information AMF can simply refer to an earlier occurrence of a complex object 

Transparent Reference Caching  No Client-side logic required  Again, lower bandwidth and CPU usage, lower latency

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Benefits - Ease of Use 



Well-documented 

Specifications available



Many examples and code samples available



Promoted by Adobe (supported)

Easy to implement 

Most of the work is done automagically 

No Parsing required



Less possibly erroneous logic needed  Dont Repeat Yourself (DRY)



Strong-typed result objects  Syntax Completion everywhere  Smooth Team-Work  Error handling is included

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Benefits - Pitfalls 



Ubercomplex types can not be serialized 

DisplayObject



and all of it‘s descendants

Native Types and Custom classes are supported 

Mapping a AMF serialized object back to a custom class is possible, but 



The custom class needs to be instanced when the AMF object is unserialized

Compression (zlib) 

Lower bandwidth usage, but



Higher latency and CPU usage



Compressing binary data is not as efficient as compressing text (i.e. XML)



Do not use compression on larger chunks of data if near real-time response times are required

®

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Downsides (and workarounds) 

Binary Format 





Not readable by humans 

Use a HTTP transport channel for testing, or



Use suitable tools to capture and decode

Less complex clients means a more complex backend 

Higher skill requirements for the backend developers (J2EE, Python, Ruby, ...)



Client design can not fix faulty backend design 

Plan and design both ends carefully and verify your decisions



Create diagrams and documentation



Embrace team-work

Lack of understanding in not-so-agile enterprises 

Do not push your bosses, convince them by facts (they might save time and money)

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Benchmarks 

Apache JMeter 

Capture AMF packets containing the clients requests first (tcpdump, Charles, ...)



JMeter replays packets and measures response times



Produces nicely looking graphs



Integration in NetBeans (great for J2EE Backend Developers)



Not for beginners!

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Benchmarks 

James Ward‘s „Census“ Benchmark www.jamesward.com/census/ 

Source Code available (GPLv2)



Perfect to convince your bosses that AMF is the right thing



Thanks James!

®

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Transport - Basic 



No additional Port required 

Most of the time Port 80 is used



No firewall issues on basic setups

Various Transport Channel Types 

Flex SDK offers fine-grained channel configuration



Simple AMF or HTTP channels 

AMF channels transport data in the binary AMF format and HTTP channels transport data in AMFX, a text-based XML representation of AMF



AMF channels provide better performance Using a HTTP channel instead of an AMF channel is only recommended when  there are auditing or compliance requirements that preclude the use of binary data over the network  or the contents of messages should be easily human-readable over the network (debugging)

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Transport - Advanced 



Advanced HTTP and AMF Channels 

‚Piggybacking‘ provides lightweight pseudo polling: Rather than the client channel polling the server on a fixed interval the client sends a non-command message to the server which sends any pending data along with the response to the client message



‚Long-polling‘ sends a request to the server, but a response is not returned to the client until one is available (similar to „Comet“)

Streaming RTMP, AMF, and HTTP channels 

Less protocol overhead (connection is kept alive)



RTMP allows message pushing  No polling at all  Lowest latency

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Server Side 

PHP 

PHP Extension 



AMFEXT  Written in C, fast encoding and decoding of AMF0 and AMF3 messages  Looking for a new maintainer since July 2008

PHP Frameworks 

AMFPHP  Simple and powerful  Works since Flash MX 2004  Optional support for AMFEXT



CakeAMFPHP  Easy to use with CakePHP, requires AMFEXT  Development stalled

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Server Side 

SabreAMF  Server and Client  PHP5 only  Compliant to PHP Strict Mode



WebORB for PHP  Well documented, commercial support available  Management Console includes Service Browser, Testing and Security Management  Code Generators for ActionScript Remoting, Cairngorm and PureMVC



Zend AMF  Easy to use with Zend Framework  PHP is very widespread  Promoted by Adobe

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Server Side 



Cold Fusion 

Supports serialization to AMF



Easy to use



Supported by Adobe

WebORB for Cold Fusion 

Supports AJAX, Flash, Flex and Silverlight



Provides easy to use interfaces to Features of Cold Fusion



Coming soon!

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Server Side 

.NET 







amf.net 

Implemented as an HttpHandler, easy to install



Very simple

WebORB for .NET 

Easy to install (only on Microsoft IIS)



Commercial support available

FluorineFx 

Supports RTMP



Template based code generator



Includes a Service Browser

Blaze Data Services for .NET (BlazeDS.NET) 

Upcoming port, announced on MAX 2008, stay tuned ®

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Server Side 

Python 

PyAMF 

Integration with Python web frameworks like Django, Pylons, Twisted, CherryPy, ...  Scales well if used with mod_python, mod_wsgi, ...



Possible to run on Google App Engine



RTMPy is a protocol for Twisted  Based on PyAMF  Implementing RTMP  Still in development

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Server Side 

Ruby 



Ruby on Rails 

RubyAMF  Very easy for Rails Developers to get started  Flexible and extensible  Scales well if Rails is used with Thin, lighttpd, nginx, Phusion Passenger (mod_rails), ...



WebORB for Rails  Based on Ruby on Rails  Tight integration of ActiveRecord  Commercial support available

RubyIZUMI 

RTMP Server for streaming Flash video/audio (H.264)



Based on EventMachine (fast single-threaded socket engine)



Experimental - not ready for production use

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Server Side 

Java 



RED5 

Mainly for Audio- and Video Streaming



Supports AMF Remoting, too

Blaze Data Services (BlazeDS) 

Open Source (GPLv3)  Shares codebase (messaging and remoting) with LiveCycle Data Services SE



Rich set of features



Supports streaming channels over HTTP



Includes Tomcat 6 Application Server (easy to deploy)



LiveCycle Data Services Community Edition  Certified builds of BlazeDS  Developer and Enterprise Support ®

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Server Side 



Granite Data Services (GraniteDS) 

Lightweight and stable, scales well



Dedicated Service Factories: integrates with EJB3, Seam, Spring, Guice, Warp, POJO, ...



‚Granite Eclipse Builder‘ for Code Generation in Eclipse



Includes a Client-side framework (‚Tide‘)  Service Locator Pattern (inspired by Cairngorm)  Offline Data Caching (similar to Live Cycle Data Services ES)



Supports ‚Long polling‘ Data Push over HTTP (‚Gravity‘)



Server-side compilation of MXML (‚Granite Web Compiler‘)



Upcoming support for GlassFish and TopLink (instead of Hibernate)

WebORB for Java 

Integrates with Spring, EJB, Pojo, ...



Commerical support available (Enterprise Edition)



Supports Microsoft Silverlight, too ®

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Server Side 

Currently, only Adobe LiveCycle Data Services ES implement all protocols, channel types and security options shown 

Feature Comparison of LiveCycle Data Services ES and BlazeDS 



sujitreddyg.wordpress.com/2008/01/31/blazeds-and-lcds-feature-difference/

Adobe LiveCycle Data Services ES 

Based on J2EE



Very powerful





Data Synchronization



Conflict Resolution



Offline Data Caching

Very expensive 

One-CPU license available for production use (formerly know as LiveCycle Data Services Express); Multi-CPU developer licenses available on request

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Tools 

Client Development 



Flex SDK is everything you need 

Flex Builder



Flash CS4



Powerflasher FDT



Your choice!

Frameworks 

PureMVC



Cairngorm



Guttershark



Mate



Many, many more

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Tools 

Debugging, Testing 



Firebug 

Recommended for every day use



Does not decode AMF



Limited to HTTP (AMFX)

Charles 

Multi-protocol local proxy  Deciphers SSL/TLS  Supports RTMP  Decodes AMF



Easy to use



Affordable Shareware

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Tools 

Debugging, Testing 

ServiceCapture 



tcpdump 



Similar to Charles but more simple, Shareware

Weapon of choice for UNIX experts (geeks)

WireShark 

Full fledged network analyzer



Captures and dissects mostly everything on the wire



Does not decode AMF

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Showcase 

Mercedes Benz - Focus on Fashion 

Server Tiers 

Application Server  MySQL 5  Ruby on Rails 2.0  



ActiveRecord RubyAMF Plugin



Web Server (Assets)



Streaming Server (Videos)

Application 

Adobe Flash Platform  Application built using Flex 3 SDK  



PureMVC Framework (Model-View-Controller Pattern) uses RemoteObject over a AMF channel

Content Modules built in Flash CS3

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Showcase 

mercedes-benz.de/focus-on-fashion

®

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Showcase 

mercedes-benz.de/focus-on-fashion

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Showcase 

User Experience 

Quick response times  Server-side caching of database queries  Application-side caching  



Assets (Browser-Cache) Data (RAM)



Rich and mixed media



Stylish people, fast cars

Developer Experience 

Rapid implementation of a prototype



Lightweight application logic



Transparent, strong-typed data model (Value Objects everywhere) Interdisciplinary team-work PureMVC rocks

 

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Summary 





Efficiency 

Enhanced User Experience



Greater User Acceptance



Helps to save the planet (lower energy consumption)

Ease of Use 

Intuitive way of working with data



Less hassle, higher quality



Have more time for creative ideas, or



Spend more time with your loved ones

AMF is not always the right thing 

Consider alternatives (E4X, SWX, JSON, ...)



Proof your design by a working prototype

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Questions and Answers 

Please ask!

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Keep in touch 

Elephant Seven www.e-7.com



Yeebase Open Source Publishing www.yeebase.com



EMail [email protected]



XING www.xing.com/profile/Tom_Hensel

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