TRACKING SATELLITES STATION PEERS - …schmidt/PDF/ACE4.pdfSp onso rs NSF, D ARP A, Bellco re, Bo...

Using the ACE Framework and Patterns to

Develop OO Communication Software

Douglas C. Schmidt

[email protected]

Washington University, St. Louis

http://www.cs.wustl.edu/�schmidt/

Sponsors

NSF, DARPA, Bellcore, Boeing, CDI/GDIS,

Kodak, Lockheed, Lucent, Microsoft, Motorola, OTI, SAIC,

Siemens SCR, Siemens MED, Siemens ZT, Sprint, USENIX

Douglas C. Schmidt Distributed Object Computing Group

Motivation: the Distributed Software Crisis

WIDE AREA

NETWORK

SATELLITESSATELLITESTRACKINGTRACKINGSTATIONSTATION

PEERSPEERS

STATUS INFO

COMMANDS BULK DATA

TRANSFER

LOCAL AREA NETWORK

GROUNDSTATION

PEERS

GATEWAY� Symptoms

{ Hardware gets smaller,

faster, cheaper

{ Software gets larger, slower,

more expensive

� Culprits

{ Accidental and inherent

complexity

� Solutions

{ Frameworks, components,

and patterns

Washington University, St. Louis 1


Techniques for Improving Software

Quality and Productivity

APPLICATIONAPPLICATION

SPECIFICSPECIFIC

LOGICLOGIC

USERUSER

INTERFACEINTERFACE

((AA)) CLASS LIBRARY CLASS LIBRARY

ARCHITECTUREARCHITECTURE

NETWORKINGNETWORKING

MATHMATH ADTADTSS

DATADATA

BASEBASE


SPECIFICSPECIFIC

LOGICLOGIC

MATHMATH

((BB)) APPLICATION FRAMEWORK APPLICATION FRAMEWORK

ARCHITECTUREARCHITECTURE

ADTADTSS

INVOKESINVOKES

CALLCALL

BACKSBACKS

NETWORKINGNETWORKING USERUSER

INTERFACEINTERFACE

DATABASEDATABASE

INVOKESINVOKES

EVENTEVENT

LOOPLOOP

EVENTEVENT

LOOPLOOP

� Proven solutions

{ Components

� Self-contained, \pluggable"

ADTs

{ Frameworks

� Reusable, \semi-complete"

applications

{ Patterns

� Problem/solution pairs in a

context

{ Architecture

� Families of related patterns

and components



Why We Need Communication Middleware

� System call-level programming is wrong abstraction for

application developers

{ Too low-level ! error codes, endless reinvention

{ Error-prone ! HANDLEs lack type-safety, thread cancellation woes

{ Mechanisms do not scale ! Win32 TLS

{ Steep learning curve ! Win32 Named Pipes

{ Non-portable ! socket bugs

{ Ine�cient ! i.e., tedious for humans

� GUI frameworks are inadequate for communication software

{ Ine�cient ! excessive use of virtual methods

{ Lack of features ! minimal threading and synchronization

mechanisms, no network services


DouglasC.Schmidt

DistributedObjectComputingGroup

TheADAPTIVECommunicationEnvironment(ACE)

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ER

http://www.cs.wustl.edu/�

schmidt/ACE.html

�

ACEOverview

{AconcurrentOO

networking

framework

{AvailableinC++

andJava

{Portedto

VxWorks,POSIX,

andWin32

�

Relatedwork

{x-Kernel

{SysVSTREAMS

WashingtonUniversity,St.Louis

4

DouglasC.Schmidt


ACEStatistics

�

ACEcontain>

135,000linesofC++

{Over15person-yearsofe�ort

�

PortedtoUNIX,Win32,MVS,and

embeddedplatforms

{e.g.,VxWorks,LynxOS,pSoS

�

Largeusercommunity

{www.cs.wustl.edu/�

schmidt/ACE-

users.html

�

Currentlyusedbydozens

ofcompanies

{Bellcore,Boeing,

Ericsson,Kodak,

Lockheed,Lucent,

Motorola,SAIC,

Siemens,StorTek,etc.

�

Supportedcommercially

{www.riverace.com


5

DouglasC.Schmidt


PatternsforCommunicationMiddleware

Acc

epto

rA

ccep

tor

Con

nec

tor

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nec

tor

Th

read

-per

Th

read

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alf-

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or

Pro

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�

Observation

{Failuresrarelyresult

fromunknownscienti�c

principles,butfrom

failingtoapplyproven

engineeringpracticesand

patterns

�

Bene�tsofPatterns

{Facilitatedesignreuse

{Preservecrucialdesign

information

{Guidedesignchoices


6

DouglasC.Schmidt


ActiveObjectswithACETasks

AC

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IVE

:: M

essa

ge

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sage

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eue

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euett 22

: :

Task

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ACETaskFeatures

{Queueing

{Eventdemultiplexing

{Concurrency

{Dynamiclinking


7


The ACE Stream Class Category

NETWORK INTERFACE

OR PSEUDO-DEVICES

STREAMSTREAMTailTail

MultiplexorMultiplexor


StreamStream

STREAMSTREAMHeadHead


StreamStream

UPSTREAMD

OWNSTREAM

MESSAGEMESSAGE

OBJECTOBJECT

WRITEWRITE

TASKTASK

OBJECTOBJECT

READREAD

TASKTASK

OBJECTOBJECT

MODULEMODULE

OBJECTOBJECT

open()=0close()=0put()=0svc()=0

� ACE Stream Features

{ Layered service

composition

{ Synchronous and

asynchronous messaging

{ Dynamic con�guration



Alternative Concurrency ModelsModuleModule

AA

PROCESS ORPROCESS OR

THREADTHREAD

READ TASKREAD TASK

OBJECTOBJECT

READ TASKREAD TASK

OBJECTOBJECT

MODULEMODULE

OBJECTOBJECT

ModuleModuleBB

ModuleModuleCC

ModuleModuleAA

ModuleModuleBB

ModuleModuleCC

2: svc()2: svc()

1: put()1: put()

4: svc()4: svc()

3: put()3: put()

ACTIVEACTIVE

ACTIVEACTIVE

ACTIVEACTIVE

ACTIVEACTIVE

2: put()2: put()

1: put()1: put()

ACTIVEACTIVEACTIVEACTIVE

TASKTASK--BASEDBASED

THREAD ARCHITECTURETHREAD ARCHITECTURE

MESSAGEMESSAGE--BASEDBASED

THREAD ARCHITECTURETHREAD ARCHITECTURE

MESSAGEMESSAGE

OBJECTOBJECT

� Message-based

Evaluation

{ Low overhead

{ Harder to program

� Task-based Features

{ Higher overhead

{ Easier to program



Use-cases for ACE

APPLICATIONSAPPLICATIONAPPLICATION--SPECIFICSPECIFIC

APPLICATIONAPPLICATION--INDEPENDENTINDEPENDENT

APPLICATIONSAPPLICATIONSAPPLICATIONSAPPLICATIONS

ConcurrencyConcurrencyglobalglobal

ReactorReactor

ServiceServiceInitializationInitialization

ServiceServiceConfiguratorConfigurator

StreamStreamFrameworkFramework

InterprocessInterprocessCommunicationCommunication

NetworkNetworkServicesServices

� Domains

{ Medical imaging

{ Network

management

{ Wireless

communications

{ Real-time avionics

{ Multimedia services



Applying ACE to Medical Imaging

DDIIAAGGNNOOSSTTIICC

SSTTAATTIIOONNSS

AATTMMMMAANN

AATTMMLLAANN

AATTMMLLAANN

MMOODDAALLIITTIIEESS

((CCTT,, MMRR,, CCRR)) CCEENNTTRRAALL

IIMMAAGGEESSTTOORREE

CCLLUUSSTTEERRIIMMAAGGEESSTTOORREE

DDXXIIMMAAGGEESSTTOORREE

� Domain Challenges

{ Large volume of \Blob"

data

� e.g., 10 to 40 Mbps

{ \Lossy compression"

isn't viable

{ Prioritization of requests

� �schmidt/COOTS-96.ps.gz

� �schmidt/av.ps.gz



Applying ACE to Network Management

Session RouterModule

PresentationModule

Event FilterModule

Event AnalysisModule

PresentationModule

Switch RouterModule

Reactor

MD110MD110 ERICSSONERICSSON

TELECOMTELECOM

SWITCHESSWITCHES

SUPERSUPER

VISORSVISORS



SUPERSUPER

VISORSVISORS

SUPERSUPER

VISORSVISORS

Switch IO

Session IO


{ Low latency

{ Multi-platform

{ Family of related

services

{ �schmidt/DSEJ-

94.ps.gz



Applying ACE to Global PCS

WIDE AREA

NETWORK

SATELLITESSATELLITESTRACKINGTRACKINGSTATIONSTATION

PEERSPEERS

STATUS INFO

COMMANDS BULK DATA

TRANSFER

LOCAL AREA NETWORK

GROUNDSTATION

PEERS

GATEWAY� Domain Challenges

{ Long latency satellite links

{ High reliability

{ Prioritization

{ �schmidt/TAPOS-95.ps.gz



Applying ACE to Real-time Avionics

Consumers

I/O Facade

SensorProxy

SensorProxy

SensorProxy

SensorProxy

1: I/O via interrupts

I/O Facade I/O Facade

EventChannel

2: push (demarshaled data)

AircraftSensors

3: push (demarshaled data)

Suppliers


{ Real-time periodic

processing

{ Complex dependencies

{ Very low latency

{ �schmidt/JSAC-

98.ps.gz



The ACE ORB (TAO)

NETWORKNETWORK

ORBORB RUN RUN--TIMETIME

SCHEDULERSCHEDULER

REALREAL--TIMETIMEORBORB CORECORE

operation()operation()

RIDLRIDLSTUBSSTUBS

REALREAL--TIMETIME

OBJECTOBJECT

ADAPTERADAPTER

RIDLRIDLSKELETONSKELETON

in argsin args

out args + return valueout args + return value

CLIENTCLIENT

OS KERNELOS KERNEL

HIGHHIGH--SPEEDSPEED

NETWORK INTERFACENETWORK INTERFACE

REALREAL--TIME ITIME I//OOSUBSYSTEMSUBSYSTEM

RIOPRIOP

OBJECTOBJECT((SERVANTSERVANT))

OS KERNELOS KERNEL

HIGHHIGH--SPEEDSPEED

NETWORK INTERFACENETWORK INTERFACE

REALREAL--TIME ITIME I//OOSUBSYSTEMSUBSYSTEM

� TAO Overview

{ High-performance,

real-time ORB

� Networking and

avionics focus

{ Leverages ACE

� Runs on VxWorks,

POSIX, and Win32

� �schmidt/TAO.html


DouglasC.Schmidt


JAWSAdaptiveWebServer

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{Ahigh-performance

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�

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concurrencyand

eventdispatching

mechanisms

�

FullHTTP1.0and

CGIsupport

{LeveragestheACE

framework

�

PortedtomostOS

platforms


16

DouglasC.Schmidt


JavaACE

FR

AM

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KS

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M)

�

schmidt/JACE.html

�

schmidt/MedJava.ps.gz

�

schmidt/C++2java.html

�

JavaACEOverview

{AversionofACE

writteninJava

{Usedformedical

imagingprototype


17

DouglasC.Schmidt


LessonsLearnedBuildingACE

�

Goodcomponents,frameworks,andsoftwarearchitecturestaketimeto

develop

�

Reuse-in-the-largeworksbestwhen:

{Themarketplaceiscompetitive

{Thedomainiscomplex

{Buildingmiddlewarein-housecoststoomuch

{Corporatecultureissupportive

�

Producereusablecomponentsbygeneralizingfromworkingapplications

{i.e.,don'tbuildcomponentsinisolation

�

Thebestcomponents(andsystemsresearch)comefromsolvingreal

problems


18

DouglasC.Schmidt


ConcludingRemarks

�

Developersofcommunicationsoftwareconfrontrecurringchallenges

thatarelargelyapplication-independent

{e.g.,serviceinitializationanddistribution,errorhandling, ow

control,eventdemultiplexing,concurrencycontrol

�

Successfuldevelopersresolvethesechallengesbyapplyingappropriate

designpatternstocreatecommunicationframeworks

�

Applicationframeworksareane�ectivewaytoachievebroadreuseof

software


19

DouglasC.Schmidt


ObtainingACE

�

ACEisanOOframeworkthatrei�eskeycommunicationsoftware

patterns

�

AllsourcecodeforACEisfreelyavailable

{www.cs.wustl.edu/�

schmidt/ACE.html

�

Mailinglists

{[email protected]

{[email protected]

{[email protected]

{[email protected]

�

Newsgroup

{comp.soft-sys.ace


20

TRACKING SATELLITES STATION PEERS - …schmidt/PDF/ACE4.pdfSp onso rs NSF, D ARP A, Bellco re, Bo...

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Transcript of TRACKING SATELLITES STATION PEERS - …schmidt/PDF/ACE4.pdfSp onso rs NSF, D ARP A, Bellco re, Bo...