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Building SOA City by Lynton Grice Logosworld SOA India 17.Nov 2008 Bangalore

Building SOA CityAtomic SOA Patterns

Elementary Middleware Communication Patterns for a Succesful SOA ImplementationSOA India Certication Course – Part 1By Axel Angeli – SOA Evangelist - [email protected]

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Any complex communication throughmiddleware can be efficiently built froma small number of atomic patterns

Atomic Communication PatternsEnhance Middleware Development Quality

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Communications is a three step process

Receive

Process

Send

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Von Neumann Computers do The Same

János von Neumann zu Margitta

Father of modern computer architecture Input

Process

Output

János von Neumann zu MargittaFather of modern computer architecture

http://de.wikipedia.org/w/index.php?title=Bild:JohnvonNeumann-LosAlamos.jpg&filetimestamp=20041104122452

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Canonical Data Transport

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As a pre-requisite make sure that dataexchange within a layer happens always

using a Canonical Format

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Use separate technologies forInput/Output (=Adapters)Process Logic

Split development across layersOne developer for I/OOne developer for Process Logic

How can a project leader enforce component use and

segregation of duties?

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SOA Application Layer Model (non-OSI)

• Canonical Content representationContent

• HTML, XML, JSON, ASCIIEnvelope

• HTTP, FTP, WebDAV, SteganographieTransport

• TCP, UDP, IPXDelivery

• IPData Linkage

• Ethernet, Token-RingNetwork

• WLAN, Cable, Sound, File-SystemPhysical

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Example: How we copy a file

The quick & dirty approach

• Procedure CopyFile

• Read the input file

• Convert encoding

• Save the file

The atomic approach• Procedure readFile• Read the input file

• Procedure convertEncoding• Convert encoding

• Procedure saveFile• Save the file

• Procedure CopyFile• Call inputFile• Call convertEncoding• Call saveFile

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Axel Angeli - (c) 2008 logosworld.com - Building the SOA City

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Data Transport in Envelopes

Canonical Format

• Internal container

Transport Envelope

• Protocol specific

• HTML, JSON, Text Physical Format

• Transport protocol

• HTTP, FTP, FileSys

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Conversion in Adapters

Physical Format Adapter

Transport envelope Adapter

Canonical Format Data ready for program

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Communication Categories

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Request & Response

Fire & Forget

Broadcast

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Communication Categories

Request and Response

HTTP, FTP

Fire and Forget

Maildrop,Triggers

SMTP

Broadcast

MQ, Database, website

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Request and Response

• HTTP, FTP

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Client Server

Request

Response

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Fire and Forget

• Sender does not accept a response• Mail drop; Message Queue

• SMTP

• Infrastructure can supervise the delivery

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SenderServer

Fire &Forget

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Broadcast

• One sender, unknown number of receivers• Website

• Message Queue, Database

• Event Triggers

• Sender Does not know, who is listening

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Sender

Publish

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Communication Patterns

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Filter Pattern

Receive

Transform

Send

Sender

Ad

ap

ter

Ad

ap

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FilterReceiver

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Basic Communication Pattern

All follow the same communication flow Sender

• Format Conversion

Internal Format• Format conversion

Receiver

Sender AdapterInternal Format

Adapter Receiver

SpeechSound

EARBrain

ElectricMOUTH

SpeechSound

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Because we always revert to some pre-thought algorithm

Patterns reduce complexity

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Especially the reuse of tools andmonitoring components

Patterns allow reuse

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Patterns Ancestry

Pass Filter (A-1-B)

Null Filter (A-0-B) Proxy (A-1-B) Request/Reply (A-1-A) Throttling (A-time-B)

Fan Out (1:n)

Fan out (1:n) Fan out & collect (1:n:1) Load balance (1-1/n)

Message queue

Queue-in/out

Queue and Forward

Campaign

Queue and reply

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Layers

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Data Layer versus Transport layer

In Process Out

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HTTP XML SOAP

Data layer

Transport Layer

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Content strictly separate from Envelope

Content

EDIFACT

IDOC

Envelope

SOAP

XML

HTML

JSON

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Interaction Transport/Data-Layer

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Atomic Patterns

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Atom: Pass Filter

Message is handled and filtered by an algorithm during pass through

Sender

Ad

ap

ter

Ad

ap

ter

FilterReceiver

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Pass Filter Variation: Transformation

Message payload is changed by the filter

Sender

Ad

ap

ter

Ad

ap

ter

ProcessReceiver

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Pass Filter Variation: Mapping

Message payload is changed by the filter

Sender

Ad

ap

ter

Ad

ap

ter

ProcessReceiver

Fox

Wolf

Hound

Hyane

Tiger

Dogs

Cats

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Pa

tie

nt

Fil

e

Pass Filter: Content based routing

Receiver depends on message content

Sender

Ad

apte

r

Ad

apte

r

ProcessReceiver

Age=45

Female

Age=12

Male

Pregnant

Gynecologist

Psychatrist

Pediatric

12yr old girl

35yr old lady

A man

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Null Filter

A special case of a pass filter that would not change the message‘s payload Usages: Protocol converter

Bridge between media

Decouple sender and receiver to avoid impact

Ad

ap

ter

Ad

ap

ter

Null-Filter

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Atom: Proxy - Asynchronous Capsule

Services are activated asynchronously only Proxy provides emulation of synchronous processing

Ad

ap

ter

Ad

ap

ter

Requester Collector

Service

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Atom: Request Reply Pattern

Request-reply patterns are filter where sender and receiver are the same entity

Ad

ap

ter

Service

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Atom: Fanout

A fan-out distributes a message to list of registered subscribers

Ad

apte

r

Ad

apte

r

ProcessSubscription

Handler

Ad

apte

rA

dap

ter

Sender ProcessDetermineSubscriber

Fan-OutReceivers

Receiver

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Atom: Fanout and Collect

This pattern fans out the messages and then waits for all tasks to terminate

Ad

apte

rDistributor

Ad

apte

rA

dap

ter

Synchronizer

Ad

apte

rA

dap

ter

Ad

apte

r

SenderDistri-bute

Fan-Out Re-Sync Receiver

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Dispatcher

Atom: Load Balancing

Receive a message and assign to the next available ressource to process from

Ad

apte

r

Ad

apte

rA

dap

ter

Ad

apte

r

Process

Process

Process

Ad

apte

r

SenderMQ-

InboxProcess Receiver

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Atom: Load Throttling

Messages are stored in an MQ and then dispatched to processes that signal availability

Ad

apte

r

QueueJanitor

Ad

apte

rA

dap

ter

MQ

Process

Process

Process

Ad

apte

r

SenderMQ-

InboxProcess Receiver

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Passive Dispatching

Receiver peeks messages

Active Dispatching

Messages are forwarded

Active and Passive Throttling

Messages are normally fetched by a free handler If processor is unable to poll, MQ may forward messages

QueueJanitor

MQ

Process

Process

Process

QueueJanitor

MQ

Process

Process

Process

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Atom: Galvanic Decoupling (Q&Forward)

The process will deploy the response into a message queue for next process to pick up

MQ Process

Process

MQ

SenderMQ-

InboxProcess

MQ-Outbox

NextProcess

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Atom: Campaigning

Message will be made public in a queue A watchdog will remove the queue after expiration

QueueJanitor

MQ

Process Process

WatchDog

Sender MQ-Inbox Published Withdraw

Process

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Atom: Sorting & Merging Queues

Messages need to be sorted

Queues need to be merged I to one queue

QueueMerger

MQ

Process

Ad

apte

r

SenderMQ-

InboxesMerger Process Receiver

MQ

MQ

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Merged Queues

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Merge Difficulties

Allow hysteresis of merge keys

• E.g. time stamps differ by up to 1 second

Wait before starting merge

Some queue may take longer to fill up

• E.g. snapshots taken every x seconds only

Calculate Default drop out values

• E.g. RFID tag is not read

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Atom: Bucketing

• Process is halted until a number of messages arrive

• Lock prevention needs to be configurable• E.g Timeout, trigger message („joker“)

Process

SenderMQ-

InboxesWait for

fillProcess Receiver

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