11
Applications as Web (Grid) Services and Related Issues
PTLIU Laboratory for Community GridsGeoffrey Fox
Computer Science, Informatics, PhysicsIndiana University, Bloomington IN 47404
http://grids.ucs.indiana.edu/ptliupages
Argonne 10 November 2003
22
Reporting work of Minjun Wang PowerPoint/OpenOffice as a WS Xiaohong Qiu SVG as a WS Bryan Carpenter SVG Javascript games Sangmi Lee, Sunghoon Ko PDA and WS Shrideep Pallickara NaradaBrokering messaging Gurhan Gunduz Messaging performance module Wenjun Wu and Ahmet Uyar Global-MMCS A/V And other students not graduating in next 3 to 9
months
33
Client Applications and O/S I Consider applications like Word, Illustrator, Internet Explorer These haven’t dramatically changed over the last 3 or perhaps
more years
• Some complain that such products are in fact getting worse as they increase in size and complexity and correspondingly decrease in usability
Microsoft has an obvious dominance in both O/S and associated applications
Sun is trying to compete directly with StarOffice/OpenOffice which are competitive with but not clearly better than Microsoft products
• To be compatible with Microsoft Office requires reproducing its bugs?
Mozilla is very competitive with Internet Explorer but not clearly better
44
Client Applications and O/S II Asia – led by China – is aiming at escaping Windows
noose by developing their own (Linux) client• For cost and desire to develop their software industry
Palm O/S and Java are doing rather well in PDA/Cell-phone industry• Doesn’t seem one wants to run same applications on PDA’s
and desktops
• At least don’t want same user interface? Macintosh is doing quite well broadly as a client with a
UNIX based client Linux (Unix?) has rather specialized CLIENT user base
55
Lessons from Web Services Web services are an attractive way of building service side
(Middle-tier) applications with a component model• Expressed by using WSDL and meta-data• All remarks here valid for Grid and Web services!
WSRP, JSR168, Portlets, Jetspeed have taught us to distinguish user-facing and service (resource) ports on Web services and build a corresponding component model for user interfaces• Jetspeed is primitive and standards WSRP, JSR168, portlets are
incomplete• But this will surely rapidly improve as relatively obvious what to do
So Web service based applications are significantly different from classic desktop products like Word• Light weight client which is relatively easily ported between client O/S• Very easy to make collaborative using shared input port (MIMD) or
shared output port (SIMD)• Perhaps hopelessly slow due to service-client interaction (the rule of the
millisecond?)
66
Applications as Web Services? Build “all” classic applications in Web service style with user
interface and “real application” interacting by (WSDL/SOAP) messages and NOT by O/S controlled interrupts• This is “just” MVC (Model View Control) paradigm done very explicitly
• Quite hard because MVC not actually used very systematically
Perhaps the advantages of this architecture could be enough to shake the Microsoft hegemony in both O/S and “productivity” applications• Current challenges of Microsoft applications are trying to do as well and
not easy to see how they can do better
Immediately make a lot easier to support cross O/S applications Form the “Next Generation Client Consortium”?
• There is quite a lot of open source (but not web service based) software with which to begin
77
Classic MVC ParadigmClassic MVC Paradigm
Model View Controller
Model
Controller
ViewMouse eventKeyboard events
Figure MVC Model
Display
8
Web Service Model for Application Development
User Interface
Raw (UI) Events
Logic of Application
Semantic Events
Data
User FacingPorts
Resource Facing Ports
Events as Messages
Rendering as Messages
View
Control
Model
MessagingSystem
Interrupts in traditional monolithic applications become“real messages” not directly method callsNatural for collaboration and universal access
99
Next Generation Client? Access Grid (GlobalMMCS), JXTA, Mozilla (or Firebird for
browser and Thunderbird for mail), Batik SVG, OpenOffice, Better Jetspeed …..
Support Linux, Windows, Palm, Java cellphone Use W3C DOM and “better portlets” What are the principles
• Split at “user interface” events (mouse clicks) or at “semantic” events (slide change)
• What part of rendering on client (AWT, Java2D or …)
• could be different for different clients with server-side adaptors mapping
What general support (tools) do we need?• Event to message mapping and serialization
When is there a performance problem?• How “far” can server be from client?
10
Web Service Model for Application Development
Data
User FacingPorts
Resource Facing Ports
Events as Messages
Rendering as Messages
Another View
Control
Another versionof Model Messaging
System
User Interface (framebuffer)
Raw (UI) Events
Some Semantic Events
Logic of Application
Other Semantic Events
1111
What have we done in this Area? Most of this is work in progress …. PowerPoint only partially as a Web Service SVG as a Web Service and Collaborative SVG
• Example of W3C Document Object Model (DOM) PDA Interfaces and Collaboration using this
architecture Universal Access Publish-subscribe Messaging to link clients and Web
services Global-MMCS: Collaboration as a Web Service Looking at OpenOffice but not perfect
• Not Java and not W3C DOM compliant
1212
Handling Events (Control in MVC) Typically events (Mouse click or change node in DOM)
are handled by setting listeners for produced events• This is publish/subscribe intra-application
Collaboration whether audio-video, text-chat or shared display can be handled by collaborators subscribing to change events published by master• Publish/subscribe inter-clients
Java takes about 0.75 millisecond to handle this on a Linux server
Can handle with uniform publish/subscribe environment• http://www.naradabrokering.org
1313
Role of Portal and User Facing Ports
Application orContent source
WSDL
Web Service
F
I
U
O
F
I
R
O
PortalAggregate
WS-User Facing Fragments
Render
Other WSUser FacingPorts
PossibleFilter
Other WSUser FacingPorts
1414
UserProfile
Application orContent source
WSDL
Web Service
F
I
U
O
F
I
R
O
Render
JetspeedPortal
Selector
Filter
Control Channel
Customized View
SelectionView
Control Channel
Customized View
CustomizedUser-Facing
PortsUniversal AccessWith JetspeedWeb Services,MVC Model for applicationsAsynchronous Messaging
(NaradaBrokering)Event Service
1515
WSDisplay
WSViewer
WS Display
WS ViewerEvent
(Message)Service
Master
WSDisplay
WS Viewer
Collaboration as a WSSet up Session with XGSP
WebServic
e
F
I
U
O
F
I
R
O
Shared Input Port (Replicated WS) Collaboration
OtherParticipants
WebServic
e
F
I
U
O
F
I
R
O
WebServic
e
F
I
U
O
F
I
R
O
1616
WSDisplay
WSViewer
WS Display
WS Viewer
Event(Message)
Service
Master
WSDisplay
WS Viewer
Web Service MessageInterceptor
Collaboration as a WSSet up Session with XGSP
Application orContent source
WSDL
Web Service
F
I
U
O
F
I
R
O
Shared Output Port Collaboration
OtherParticipants
Text ChatWhiteboardMultiplemasters
1717
Collaborative SVG Web Service SVG is W3C 2D Vector Graphics standard and is interesting for
visualization and as a simple PowerPoint like application• Further SVG is built on W3C DOM and one can generalize results
to all W3C DOM-based applications (“all” applications in future?) Apache Batik SVG is Java and open source and so it is practical
to modify it to explore• Real Applications as a Web Service
• Collaboration as a Web Service
• MVC model and web services with implications for portlets We use NaradaBrokering and Global-MMCS to control
collaboration; support PDA Cell-phone and desktop clients; are restructuring Batik as MVC Web Service• Good progress in all areas see
• http://www.svgarena.org for SVG Games
• http://grids.ucs.indiana.edu/ptliupages/projects/carousel/ for PDA
1818
Document Object Model DOM (Document Object Model) defines how documents to be
accessed as distributed objects – especially as a Web service DOM has a particular tree-like specification of the Object
structure of a document It defines
• An application programming interface (API) for documents (e.g. HTML, XML documents) for Java, CORBA, Javascript ….
• Including how to change DOM• The logical structure of documents• The way a document is accessed and manipulated
DOM has a generic event model defining uniform interface for mouse and keyboard actions• Also defines events signifying change in DOM
W3C DOM builds on earlier ad-hoc DOM’s of Internet Explorer and Netscape• Surprisingly unsuccessful so far but critical for this project as allows
general approach to user interfaces
1919
Example of HTML DOM Here is an
example of a fragment of HTML and how it can be thought of as a tree
This is called a “document fragment” in DOM(lightweight tree)
2020
The Node
Interface in
CORBA IDL
Constants
Properties
Methods
2121
Application as a Web serviceApplication as a Web service
Participating Client
RenderingRendering
User Interface
W3C DOM Events
From Master
FromCollaborationAs a WS
Events
Application as a Web serviceApplication as a Web service
Master Client
RenderingRendering
User Interface
W3C DOM Events
To Collaborative Clients
FromCollaborationAs a WS
Events
Control flow for collaborative SVG clients
Figure 3 Control flow for collaborative SVG clients
Collaborative SVG As A Web Service
NaradaBrokering
2222
Collaborative SVG Chess Game in Batik Browser
Players
Observers
2323
Lessons from SVG Web Service This keeps DOM and Javascript Event Handlers on the Server;
keeps the Graphics version of DOM that interfaces with Java2D on client; client captures raw user interface events inside SVG frame; client captures some semantic events (zoom, change URL) in menu-bar
We identified SIMD and MIMD model of collaboration• Program is JavaScript implementing in our case chess or card game• SIMD collaboration is shared output port in Web Services model• MIMD collaboration becomes shared input port model
Internally there are pipelinesAWT/Swing GVT DOM JavaScript new DOM for user inputnew DOM GVT Java2D Framebuffer for rendering
The Graphic Vector Toolkit (GVT) module represents a view of the DOM tree in terms of Java objects that is more suitable for rendering and event handling purposes.
Can share at different points of pipeline based on software engineering issues – where is current software easiest to split
2424
From the Battle Lines Why not easy to convert legacy applications to WS
Although many modern applications adopt MVC (Model-View-Control) paradigm, they may not strictly follow the principles in implementation.
Not faithfully following modularized design principle the applications does not have a clear "control" design which plays the role as the only communication channel between "model" and "view". • there exits direct linkage (not through "control") between Model and
View in the MVC paradigm. • For example, some functional modules
involve information from many stages across the pipeline rather than just provide the linkage between the two modules
Are instantiated in GUI/"view" but execute functions in the backend "model" through direct methods calls
Not providing "Object Serialization" • Object Serialization (the process of reading and writing objects) has many
uses, including remote method invocation (RMI) • In addition to the object streams, java.io has other classes and interfaces
that define the API to help classes perform serialization for its instances. • lacking of serializable feature of the modularized components makes it
hard to split the application into a Web service
2525
SVGBrowser
SVGBrowser
SVGBrowser
SVGBrowser
Identical Programs receiving identical eventsToken determines if browser is moving, waiting for opponent or an observer
SIMD Collaboration
SVGViewer
SVGViewer
SVGViewer
SVGViewer
SVG Model (DOM)
NaradaBrokering
Shared Output portSIMD CollaborativeWeb Service
Non Web ServiceImplementation
NaradaBrokering
2626
MIMD Collaboration
SVGViewer
SVGViewer
SVGViewer
SVGViewer
NaradaBrokering
Shared Input portMIMD CollaborativeWeb Service
SVG Model
SVG Model
SVG Model
SVG Model
NaradaBrokering
2727
PowerPoint as a Sort of Web Service
MasterClient
ConnectableObject
Sink
NaradaBrokering Message Service
User1
1
User2
Usern
PPT as a Web Service
As in Access Grid CollaborativeClient
Holds meta-data(sample of high level semanticevents) like slide number and title
2828
Semantic Events in PPT Web Service One can capture slide and animation semantic events such as
WindowSelectionChange WindowBeforeRightClick, WindowBeforeDoubleClick, PresentationClose, PresentationSave, PresentationOpen, NewPresentation, PresentationNewSlide, WindowActivate, WindowDeactivate, SlideShowBegin, SlideShowNextBuild, SlideShowNextSlide, SlideShowEnd, PresentationPrint, SlideSelectionChanged, ColorSchemeChanged, PresentationBeforeSave, SlideShowNextClick
We don’t know how to capture • Raw UI events such as MouseOver, MouseClicked,
MouseDoubleClicked, KeyDown, KeyUp, KeyStroke, etc.• Sound events such as SoundClipPlayed, SoundFilePlayed, etc.• Some animation events such as AnimationClipPlayed,
MoviesPlayed, AnimationFilePlayed
29
Integration of PDA, Cell phone and Desktop Grid Access
3030
Real-time Community Collaboration Desktop PC, local wireless (802.11b) and the rest of the world (Sprint
PCSVision as glimpse of next generation cell phones) Reconcile different protocols, different display areas, different O/S and
different network bandwidths
Text Chat
3131
Real-time Community Collaboration
PowerPoint via “Shared Pixels”
3232
Real-time Community Collaboration
Scalable Vector Graphics (SVG) via “Shared Web Service”
33
Performance of PDA Client
• Treo 300 Sprint PCS Vision Java MIDP on Palm O/S• 50 Kbit/sec bandwidth both directions• Developing optimized protocol (HHMP) to be built into
NaradaBrokering for fault-tolerance and latency hiding (pre-start HTTP connection)
0
500
1000
1500
2000
2500
3000
3500
4000
4500T
ime
(m
illis
ec
on
ds
)
Publishing Event from PDA to Server
Subscribing to Event from PDA
Latency over successive iterations
3434
Application Web Servicesand Universal Access
NaradaBrokering can link lightweight clients (V in MVC) to Web Services holding as a Web service the “guts of an application” (M in MVC)• This allows customizable user interfaces gotten by mapping
between client profile protocols at NB
• Supports collaboration between diverse clients
Client1
Client2
M
Agent1
Agent2
ProfilesNB
P1
P2
P
Map P to P1
Map P to P2
Web Service
35
NBNB
HHMP
RTP
SVG Web Service ATopic set A
(needs content adapting)
CollaborationPersonal Server
Topic set C
Subscribe/Publish toTopic set B,C
Web Service BTopic set B
(does not need content adaption)
Subscribe/Publish toTopic set A,B
( Subscribe to Topic set A instead of mobile devices and adapt the content to give Topic Set C)
Subscribe/Publish toTopic set A,C
Subscribe/Publish toTopic set A
Subscribe/Publish toTopic set B
Collaboration Personal Server and EventFlow
NB
JMS
HT
TP
HTTP/HHMP Interface (for current 3G phone service)
Page. 36
Web Service to Client Pipeline
• DAT (Data) stage: Data source (facing remote resources)• M&L (Model and Logic) stage: Semantic processing of the data• DTX (Data Transformer) stage: Process of filtering the object
for heterogeneous devices• PCL (Presentation client) stage: Generating abstract
presentation for each client• MCL (Minimal client) stage: Actual drawing onto user device• PDA would “just” have MCL• Desktop might have PDA and MCL• Such diagrams can be analysed formally using Petri nets
Universal user devices
real timemultimedia
I BM
computation unit
DAT M&L DTX PCL MCL
Database
Generating user presentation
User event transmit
Page. 37
Event Processing in Web Service to Client Pipeline
• Events allow Client and service to interact– Transformations in each module MUST be invertible
• Two directions of dataflow – Event transmission– Presentation Generation
DAT M&L DTX PCL MCL
<?xml vers
<!DOCTYPE
<!--local DT
<svg width=
<desc>This
User Event Transmission
SVG document
with the original
size of 1200 x 2000
DOM tree of
SVG
document
Rendered Image
with CSS for PDAs
(resolution of
160 x 160)
SVG browser
for PDAsActual Display
on PDA
Generating Presentation View
3838
Some Simple Principles One must use invertible transformations so that can propagate
information to AND from the client Don’t ever send a position (x,y) for say a mouse click – rather
send position and coordinate system specified by some transformation (as in affine transformations used in graphics)• Or send semantic meaning of click – e.g. open URL
Accumulate mouse-move events into arrays or cumulative events to avoid too many messages
Choose “cutting point” between M and V to support interactivity and performance
Jetspeed is just aggregating lots of different “Views” All messages MUST go through messaging system – it must
support all needed protocols such as those needed to minimize latency for cellphones • Messaging system has routing optimization/firewalls built in
39
NaradaBrokering
Minicomputer
Firewall
ComputerServer
PDA
Modem
Laptop computerWorkstationPeers
Peers
Audio/VideoConferencing Client
Audio/VideoConferencing Client
NaradaBrokering BrokerNetwork
BrokersONLYprocessmessages
4040
“GridMPI” v. NaradaBrokering In parallel computing, MPI and PVM provided “all the features
one needed’ for inter-node messaging NB aims to play same role for the Grid but the requirements and
constraints are very different• NB is not MPI ported to a Grid/Globus environment
Typically MPI aiming at microsecond latency but for Grid, time scales are different• 100 millisecond quite normal network latency• 30 millisecond typical packet time sensitivity (this is one audio or video
frame) but even here can buffer 10-100 frames on client (conferencing to streaming)
• <1 millisecond is time for a Java server to “think” Jitter in latency (transit time through broker) due to routing,
processing (in NB) or packet loss recovery is important property Grids need and can use software supported message functions and
trade-offs between hardware and software routing different from parallel computing
4141
NaradaBrokering Based on a network of cooperating broker nodes
• Cluster based architecture allows system to scale in size• Grid routing topologies are open research issue?
Originally designed to provide uniform software multicast to support real-time collaboration linked to publish-subscribe for asynchronous systems.
Perhaps better thought of as stream not message handler Now has several core functions
• Reliable order-preserving “Optimized” Message transport (based on performance measurement) in heterogeneous multi-link fashion with TCP, UDP, SSL, HTTP, and will add GridFTP
• General publish-subscribe including JMS & JXTA and support for RTP-based audio/video conferencing
• General software routing to avoid network problem• Distributed XML event selection using XPATH metaphor• QoS, Security profiles for sent and received messages• Interface with reliable storage for persistent events
4242
Grid Messaging Substrate
Consumer Service
SOAP+HTTPGridFTPRTP ….
Messaging Substrate
Consumer Service
Standard client-serverstyle communication.
Substrate mediatedcommunication removestransport protocoldependence.
SOAP+HTTPGridFTPRTP ….
Any Protocols satisfying QoS
Messaging Substrate has “intelligence” “any desired fault tolerance” “logging” etc.Hope to demonstrate with multicast fault tolerant GridFTP
4343
Laudable Features of NaradaBrokering Is open source http://www.naradabrokering.org available now;
major new release for SC03 Will have end-point “plug-in” as well as standalone brokers
• end-point is service or user-interface machine Will have a discovery service to find nearest brokers Does tunnel through most firewalls without requiring ports to be
opened Links to NWS (Network Weather Service) style performance
estimation systems Supports JXTA (peer-to-peer network), JMS (Java Message
Service) and more powerful native mode Transit time < 1 millisecond per broker Will have setup and broker network administration module
4444
NaradaBrokering Naturally Supports Filtering of events (streams) to support different end-point
requirements (e.g,. PDA versus desktop, slow lines, different A/V codecs)
Virtualization of addressing, routing, interfaces (OGSI versus pure Web services for example)
Federation and Mediation of multiple instances of Grid services as illustrated by • Composition of Gridlets into full Grids (Gridlets are single computers in
P2P case)
• JXTA with peer-group forming a Gridlet
Monitoring of messages for Service management and general autonomic functions
Fault tolerant data transport Virtual Private Grid with fine-grain Security model
4545
Virtualizing Communication Communication specified in terms of user goal and Quality of
Service – not in choice of port number and protocol Protocols have become overloaded e.g. MUST use UDP for A/V
latency requirements but CAN’t use UDP as firewall will not support ………
A given communication can involve multiple transport protocols and multiple destinations – the latter possibly determined dynamically
Dial-upFilter
SatelliteUDP
FirewallHTTP
A
B1
Hand-HeldProtocol
FastLink
Software MulticastB2
B3NB Broker Client Filtering
NB Brokers
4646
Performance Monitoring Every broker incorporates a Monitoring service that
monitors links originating from the node. Every link measures and exposes a set of metrics
• Average delays, jitters, loss rates, throughput. Individual links can disable measurements for
individual or the entire set of metrics. Measurement
intervals can also be varied
Monitoring Service, returns measured metrics to Performance Aggregator.
BrokerNode
LinkData
BrokerNode
LinkData
Performance AggregationService
Control MessageExchange
Aggregates infofrom nodes in acertain domain
MonitoringService
47
Pentium-3, 1GHz, 256 MB RAM100 Mbps LAN
JRE 1.3 Linux
hop-3
0
1
2
3
4
5
6
7
8
9
100 1000
Tra
nsit
Del
ay
(Mill
isec
onds
)
Message Payload Size (Bytes)
Mean transit delay for message samples in NaradaBrokering: Different communication hops
hop-2
hop-5 hop-7
4848
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
1000 1500 2000 2500 3000 3500 4000 4500 5000
Sta
nd
ard
De
via
tion
(M
illis
eco
nd
s)
Message Payload Size (Bytes)
Standard Deviation for message samples in NaradaBrokering Different communication hops - Internal Machines
hop-2hop-3hop-5hop-7
49
111.5
112
112.5
113
113.5
114
114.5
100 200 300 400 500 600 700 800 900 1000
Me
an
tra
nsi
t d
ela
y (
Mill
ise
con
ds)
Content Payload Size in Bytes
Transit delays for Content Payloads.Broker at Cardiff, Clients at Indiana
Delay
50
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
100 200 300 400 500 600 700 800 900 1000
Sta
nd
ard
De
via
tion
(M
illis
eco
nd
s)
Content Payload Size in Bytes
Standard deviation for Content Payloads.Broker at Cardiff, Clients at Indiana
Standard Deviation
5151
Architecture of Message Layer Need to optimize not only routing of particular messages but classic
publish/subscribe problem of integrating different requests with related topics (subscribe to sports/basketball/lakers and sports)
Related to Akamai, AOL … caching and Server optimization problem
1-> N Grid Clients
Hypercube ofNB Brokers (logicalnot physical)
N≈100 clientsper leaf node for A/V conferencing
Scale usingNB brokernetwork
5252
Global-MMCS 2.0 XGSP based MCU We are building an open source protocol independent Web
Service “MCU” which will scale to an arbitrary number of users and provide integrated thousands of simultaneous users collaboration services.
We will deploy it globally and hope to test with later this year. The function of A/V media server will be distributed using
NaradaBrokering architecture.• Media Servers mix and convert A/V streams and are built as
Web Services Open Global-MMCS MCU based on the following open source
projects• openh323 is basis of H323 Gateway• NIST SIP stack is basis of SIP Gateway• NaradaBrokering is open source messaging from Indiana• Java Media Framework basis of Media Servers
5353
XGSP Web Service MCU Architecture
SIP H323 Access Grid Native XGSPAdmire
Gateways convert to uniform XGSP Messaging
High Performance (RTP)and XML/SOAP and ..
Media ServersFilters
Session ServerXGSP-based Control
NaradaBrokeringAll Messaging
Use Multiple Media servers to scale to many codecs and manyversions of audio/video mixing
NB Scales asdistributed
WebServices
NaradaBrokering
5454
Polycom, Access Grid and RealVideo views of multiple streams using
A/V Web Service integrating SIP and H323
5555
Performance Test : GlobalMMCS1.0 We conducted extensive performance tests on audio and video
servers. Video:
• The test shows that our video server is capable of supporting 100-300 clients if there is only one video sender.
• Video Server Machine : 1.2GHz Intel Pentium III dual CPU, 1GB MEM, RedHat Linux 7.3
Audio: • Our tests show that audio server can support 5 concurrent
sessions (250 participants in total) without any packet droppings. • Audio Server Machine: 2.5GHz Pentium 4 CPU, 512MB memory,
Windows XP machine Scale with logarithmic Broker network
56
0
10
20
30
40
50
60
0 200 400 600 800 1000 1200 1400 1600 1800 2000
De
lay
(Mill
ise
con
ds)
Packet Number
Average delays per packet for 50 video-clients NaradaBrokering Avg=2.23 ms, JMF Avg=3.08 ms
NaradaBrokering-RTP JMF-RTP
57
0
1
2
3
4
5
6
7
8
0 200 400 600 800 1000 1200 1400 1600 1800 2000
Jitte
r (
Mill
ise
con
ds)
Packet Number
Average jitter (std. dev) for 50 video clients.
NaradaBrokering Avg=0.95 ms, JMF Avg=1.10 ms
NaradaBrokering-RTP JMF-RTP
5858
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0 200 400 600 800 1000 1200 1400 1600 1800 2000
Jitt
er
(M
illis
eco
nd
s)
Packet Number
900 audio clientsNaradaBrokering-RTP
JMF-RTP
