Grid Technology A Web Services Globus OGSA

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Grid Technology AWeb ServicesGlobus OGSA Grid
ArchitectureCERN GenevaApril 1-3 2003

• Geoffrey Fox
• Community Grids Lab
• Indiana University
• gcf_at_indiana.edu

2
With Thanks to

• Tony Hey my co-speaker and
• I adapted presentations from
• Marlon Pierce
• Dennis Gannon
• Globus
• Malcolm Atkinson
• David de Roure

3
Fermilab Experiments 1975-1980
Regge Theory 1978
Hadron Jets in 1977 Compared to Feynman Field
(Fox) Model
E350
-t
E260
200 GeV hp
4
Caltech Hypercube
JPL Mark II 1985 Chuck Seitz 1983
Hypercube as a cube
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History New York Times 1984

• One of today's fastest computers is the Cray 1,
  which can do 20 million to 80 million operations
  a second. But at 5 million, they are expensive
  and few scientists have the resources to tie one
  up for days or weeks to solve a problem.
• Poor old Cray and Cyber (another super
  computer) don't have much of a chance of getting
  any significant increase in speed,'' Fox said.
  Our ultimate machines are expected to be at
  least 1,000 times faster than the current fastest
  computers.'' (80 gigaflops predicted. Earth
  Simulator is 40,000 gflops)
• But not everyone in the field is as impressed
  with Caltech's Cosmic Cube as its inventors are.
  The machine is nothing more nor less than 64
  standard, off-the-shelf microprocessors wired
  together, not much different than the innards of
  64 IBM personal computers working as a unit.
• The Caltech Hypercube was just a cluster of
  PCs!

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History New York Times 1984

• We are using the same technology used in PCs
  (personal computers) and Pacmans,'' Seitz said.
  The technology is an 8086 microprocessor capable
  of doing 1/20th of a million operations a second
  with 1/8th of a megabyte of primary storage.
  Sixty-four of them together will do 3 million
  operations a second with 8 megabytes of storage.
• Computer scientists have known how to make such a
  computer for years but have thought it too
  pedestrian to bother with.
• It could have been done many years ago,'' said
  Jack B. Dennis, a computer scientist at the
  Massachusetts Institute of Technology who is
  working on a more radical and ambitious approach
  to parallel processing than Seitz and Fox.
• There's nothing particularly difficult about
  putting together 64 of these processors,'' he
  said. But many people don't see that sort of
  machine as on the path to a profitable result.'
• So clusters are a trivial architecture (1984)
• So architecture is unchanged unfortunately
  after 20 years research, programming model is
  also the same (message passing)

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What is a Grid I?

• Collaborative Environment (Ch2.2,18)
• Combining powerful resources, federated computing
  and a security structure (Ch38.2)
• Coordinated resource sharing and problem solving
  in dynamic multi-institutional virtual
  organizations (Ch6)
• Data Grids as Managed Distributed Systems for
  Global Virtual Organizations (Ch39)
• Distributed Computing or distributed systems
  (Ch2.2,10)
• Enabling Scalable Virtual Organizations (Ch6)
• Enabling use of enterprise-wide systems, and
  someday nationwide systems, that consist of
  workstations, vector supercomputers, and parallel
  supercomputers connected by local and wide area
  networks. Users will be presented the illusion of
  a single, very powerful computer, rather than a
  collection of disparate machines. The system will
  schedule application components on processors,
  manage data transfer, and provide communication
  and synchronization in such a manner as to
  dramatically improve application performance.
  Further, boundaries between computers will be
  invisible, as will the location of data and the
  failure of processors. (Ch10)

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What is a Grid II?

• Supporting e-Science representing increasing
  global collaborations of people and of shared
  resources that will be needed to solve the new
  problems of Science and Engineering (Ch36)
• As infrastructure that will provide us with the
  ability to dynamically link together resources as
  an ensemble to support the execution of
  large-scale, resource-intensive, and distributed
  applications. (Ch1)
• Makes high-performance computers superfluous
  (Ch6)
• Metasystems or metacomputing systems (Ch10,37)
• Middleware as the services needed to support a
  common set of applications in a distributed
  network environment (Ch6)
• Next Generation Internet (Ch6)
• Peer-to-peer Network (Ch10, 18)
• Realizing thirty year dream of science fiction
  writers that have spun yarns featuring worldwide
  networks of interconnected computers that behave
  as a single entity. (Ch10)

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What is Grid Technology?

• Grids support distributed collaboratories or
  virtual organizations integrating concepts from
• The Web
• Distributed Objects (CORBA Java/Jini COM)
• Globus Legion Condor NetSolve Ninf and other High
  Performance Computing activities
• Peer-to-peer Networks
• With perhaps the Web being the most important for
  Information Grids and Globus for Compute
  Grids
• Use Information Grids and not usual Data Grids as
  distributed file systems (holding lots of
  data!) are handled in Compute Grids

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PPPH Paradigms Protocols Platforms and Hosting I

• We will start from the Web view and assert that
  basic paradigm is
• Meta-data rich Web Services communicating via
  messages
• These have some basic support from some runtime
  such as .NET, Jini (pure Java), Apache
  TomcatAxis (Web Service toolkit), Enterprise
  JavaBeans, WebSphere (IBM) or GT3 (Globus Toolkit
  3)
• These are the distributed equivalent of operating
  system functions as in UNIX Shell
• Called Hosting Environment or platform

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Some Basic Observations

• Grids manage and share asynchronous resources in
  a rather centralized fashion
• Peer-to-peer networks are just like Grids with
  different implementations of services like
  registration and look-up
• Web Services interact with messages
• Everything (including applications like
  PowerPoint will be a WS?) see later short
  discussion
• Computers are fast and getting faster. One can
  afford many strategies that used to be
  unrealistic
• All messages can be publish/subscribe
• Software message routing
• XML will be used for most interesting data and
  meta-data
• One will store/consider data and meta-data
  separately but often use same technology to
  manage both of them.
• Need Synchronous and Asynchronous Resource
  Sharing
• Integrate Grid and Collaboration technology

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Classic Grid Architecture
Resources
Content Access
Composition
Middle TierBrokers Service Providers
Netsolve
Security
Collaboration
Computing
Middle Tier becomes Web Services
Clients
Users and Devices
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What is a Web Service I

• A web service is a computer program running on
  either the local or remote machine with a set of
  well defined interfaces (ports) specified in XML
  (WSDL)
• In principle, computer program can be in any
  language (Fortran .. Java .. Perl .. Python) and
  the interfaces can be implemented in any way what
  so ever
• Interfaces can be method calls, Java RMI
  Messages, CGI Web invocations, totally compiled
  away (inlining) but
• The simplest implementations involve XML messages
  (SOAP) and programs written in net friendly
  languages like Java and Python
• Web Services separate the meaning of a port
  (message) interface from its implementation
• Enhances/Enables Re-usable component model of ANY
  electronic resource

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Raw Data
RawResources
Raw Data
(Virtual) XML Data Interface
WS
WS
etc.
XML WS to WS Interfaces
(Virtual) XML Knowledge (User) Interface
Render to XML Display Format
(Virtual) XML Rendering Interface
Clients
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What is a Web Service II

• Web Services have important implication that ALL
  interfaces are XML messages based. In contrast
• Most Windows programs have interfaces defined as
  interrupts due to user inputs
• Most software have interfaces defined as methods
  which might be implemented as a message but this
  is often NOT explicit

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What is a Web Service III

• Everything electronic is a resource
• Computers Programs People
• Data (from sensors to this presentation to email
  to databases)
• Everything electronic is a distributed object
• All resources have interfaces which are defined
  in XML for both properties (data-structure) and
  methods (service, function, subroutine)
  (Resources are Services)
• We can assume that a data-structure property has
  getproperty() and setproperty(value) methods to
  act as interface
• All resources are linked by messages with
  structure, which must be specifiable in XML
• All resources have a URI such as unique//a/b/c
  .

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WSDL Abstractions

• WSDL abstracts a program as an entity that does
  something given one or more inputs with its
  results defined by streams on one or more
  outputs.
• Functions are defined by method name and
  parametersmethodname(parm1,parm2, parmN)
• Where parameters are Input Output or both
• In WSDL, we will have a Web Service which like a
  (Java or CORBA Program) can be thought of as a
  (distributed) object with many methods
• Instead of a function call, the calling routine
  sends an XML message to the Web Service
  specifying methodname and values of the
  parameters
• Note name of function is just another parameter

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Details of WSDL Protocol Stack

• UDDI finds where programs are
• remote( (distributed) programs are just Web
  Services
• (not a great success)
• WSFL links programs together(under revision as
  BPEL4WS)
• WSDL defines interface (methods, parameters, data
  formats)
• SOAP defines structure of message including
  serialization of information
• HTTP is negotiation/transport protocol
• TCP/IP is layers 3-4 of OSI
• Physical Network is layer 1 of OSI

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Education as a Web Service

• Can link to Science as a Web Service and
  substitute educational modules
• Learning Object XML standards already exist
  from IMS/ADL http//www.adlnet.org need to
  update architecture
• Web Services for virtual university include
• Registration
• Performance (grading)
• Authoring of Curriculum
• Online laboratories for real and virtual
  instruments
• Homework submission
• Quizzes of various types (multiple choice, random
  parameters)
• Assessment data access and analysis
• Synchronous Delivery of Curricula
• Scheduling of courses and mentoring sessions
• Asynchronous access, data-mining and knowledge
  discovery
• Learning Plan agents to guide students and
  teachers

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What are System and Application Services?

• There are generic Grid system services security,
  collaboration, persistent storage, universal
  access
• OGSA (Open Grid Service Architecture) is
  implementing these as extended Web Services
• An Application Web Service is a capability used
  either by another service or by a user
• It has input and output ports data is from
  sensors or other services
• Consider Satellite-based Sensor Operations as a
  Web Service
• Satellite management (with a web front end)
• Each tracking station is a service
• Image Processing is a pipeline of filters which
  can be grouped into different services
• Data storage is an important system service
• Big services built hierarchically from basic
  services
• Portals are the user (web browser) interfaces to
  Web services

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Application Web Services

• Note Service model integrates sensors, sensor
  analysis, simulations and people
• An Application Web Service is a capability used
  either by another service or by a user
• It has input and output ports data is from
  users, sensors or other services
• Big services built hierarchically from basic
  services

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The Application Service Model

• As bandwidth of communication (between) services
  increases one can support smaller services
• A service is a component and is a replacement
  for a library in case where performance allows
• Services (components) are a sustainable model of
  software development each service has
  documented capability with standards compliant
  interfaces
• XML defines interfaces at several levels
• WSDL at Service interface level and XSIL or
  equivalent for scientific data format
• A service can be written as Perl, Python, Java
  Servlet, Enterprise JavaBean, CORBA (C or
  Fortran) Object
• Communication protocol can be RMI (Java), IIOP
  (CORBA) or SOAP (HTTP, XML)

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Application with W3C DOM Structure as a Web
Service
Data
Resource Facing Ports
Application as a Web service Application Model
Remaining W3C DOM Semantic Events
MVCM Model
Control
User FacingPorts
View
CControl
Events as Messages
Rendering as Messages
Application Viewand SelectedControl
V View
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7 Primitives in WSDL

• types which provides data type definitions used
  to describe the messages exchanged.
• message which represents an abstract definition
  of the data being transmitted. A message consists
  of logical parts, each of which is associated
  with a definition within some type system.
• operation an abstract description of an action
  supported by the service.
• portType which is a set of abstract operations.
  Each operation refers to an input message and
  output messages.
• binding which specifies concrete protocol and
  data format specifications for the operations and
  messages defined by a particular portType.
• port which specifies an address for a binding,
  thus defining a single communication endpoint.
• service which is used to aggregate a set of
  related ports

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(No Transcript)
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lt?xml version"1.0" encoding"UTF-8"?gt ltwsdldefin
itionsgt ltwsdlmessage name"execLocalCommandRes
ponse"gt ltwsdlmessage name"execLocalCommandReques
t"gt ltwsdlportType name"SJwsImp"gt ltwsdloperation
name"execLocalCommand" parameterOrder"in0"gt
ltwsdlinput message"implexecLocalCommandReque
st" name"execLocalCommandRequest"/gt
ltwsdloutput message"implexecLocalCommandRespons
e" name"execLocalCommandResponse"/gt
lt/wsdloperationgt lt/wsdlportTypegt ltwsdlbinding
name"SubmitjobSoapBinding" type"implSJwsImp"gt
ltwsdlsoapbinding style"rpc"
transport"http//schemas.xmlsoap.org/soap/http"/gt
ltwsdloperation name"execLocalCommand"gt
ltwsdlsoapoperation soapAction""/gt
ltwsdlinput name"execLocalCommandRequest"gt
ltwsdloutput name"execLocalCommandResponse"gt lt/ws
dloperationgt lt/wsdlbindinggt ltwsdlservice
name"SJwsImpService"gt ltwsdlport
binding"implSubmitjobSoapBinding"
name"Submitjob"gt lt/wsdlservicegt lt/wsdldefinit
ionsgt
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Discussion of 7 WSDL Primitives

• types specify data-structures which are
  equivalent to arguments of methods
• message specifies collections of types and is
  equivalent to set of arguments in a method call.
  Note that it is an abstract method in Java
  terminology
• operation is a a collection of input output and
  fault messages there are 4 types of operation
  one-way(service just receives a message),
  request-response(RPC), solicit-response,
  notification (services pushes out a message)
• portType represents a single channel that can
  support multiple operations. It is abstract as
  specified as a set of operations. It is
  equivalent to a interface or abstract class in
  Java
• binding tells you transport and message format
  for a porttype (which can have multiple bindings
  to reflect say performance-portability trades)
• port combines a binding and an endpoint network
  address (URL) and is like a class instance
• service consists of multiple ports and is
  equivalent to a program in Java

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OGSA OGSI Hosting Environments

• Start with Web Services in a hosting environment
• Add OGSI to get a Grid service and a component
  model
• Add OGSA to get Interoperable Grid correcting
  differences in base platform and adding key
  functionalities

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Functional Level above OGSA

• Systems Management and Automation
• Workload / Performance Management
• Security
• Availability / Service Management
• Logical Resource Management
• Clustering Services
• Connectivity Management
• Physical Resource Management
• Perhaps Data Access belongs here

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Two-level Programming I

• The paradigm implicitly assumes a two-level
  Programming Model
• We make a Service (same as a distributed object
  or computer program running on a remote
  computer) using conventional technologies
• C Java or Fortran Monte Carlo module
• Data streaming from a sensor or Satellite
• Specialized (JDBC) database access
• Such nuggets accept and produce data from users
  files and databases
• The Grid is built by coordinating such nuggets
  assuming we have solved problem of programming
  the nugget

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Two-level Programming II

• The Grid is discussing the linkage and
  distribution of the nuggets with the
  onlyaddition runtime interfaces to Grid as
  opposed to UNIX data streams
• Familiar from use of UNIX Shell, PERL or Python
  scripts to produce real applications from core
  programs
• Such interpretative environments are the single
  processor analog of Grid Programming
• Some projects like GrADS from Rice University are
  looking at integration between nugget levels but
  dominant effort looks at each level separately

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Why we can dream of using HTTP and that slow stuff

• We have at least three tiers in computing
  environment
• Client (user portal discussed Thursday)
• Middle Tier (Web Servers/brokers)
• Back end (databases, files, computers etc.)
• In Grid programming, we use HTTP (and used to use
  CORBA and Java RMI) in middle tier ONLY to
  manipulate a proxy for real job
• Proxy holds metadata
• Control communication in middle tier only uses
  metadata
• Real (data transfer) high performance
  communication in back end

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UserServices
GridComputingEnvironments
CoreGrid
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OGSA OGSI Hosting Environments

• Start with Web Services in a hosting environment
• Add OGSI to get a Grid service and a component
  model
• Add OGSA to get Interoperable Grid correcting
  differences in base platform and adding key
  functionalities

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PPPH Paradigms Protocols Platforms and Hosting II

• Self-describing programs/interfaces are key to
  scaling
• Minimize amount of work system has to do
• Hide as much as possible in services and
  applications
• Protocols describe (in principle at least)
  those rules that system obeys and uses to deliver
  information between services (processes)
• Interfaces tell the service what to do to
  interpret the results of communication
• HTTP is the dominant transport protocol of the
  Web
• HTML is the interface telling browser how to
  render
• But you can extend interface to allow PDF,
  multimedia, PowerPoint using helper
  applications which are (with more or less
  convenience) which are automatically downloaded
  if not already available
• Mime types essentially self-describe each
  interface

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Analogy with Web II

• HTTP and HTML are the analogies on the client
  side
• A Web Service generalizes a CGI Script on
  server side
• CGI is essentially a Distributed Object
  technology allowing server to access an arbitrary
  program labeled by a URL plus an ugly syntax to
  specify name and parameters of program to run
• Roughly WSDL (Web Service Description Language)
  is a better to specify program name and its
  parameters
• Web uses other protocols HTTPS for secure links
  and RTP etc. for multimedia (UDP) streams
• These again are required to integrate system
  codecs like MPEG are interfaces interpreted by
  client
• There are further protocols like H323 and SIP
  which will be placed (IMHO) by HTTP plus RTP etc.
  We should minimize number of protocols to get
  maintainable systems

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PPPH Paradigms Protocols Platforms and Hosting
III

• There are set of system capabilities which cannot
  be captured as standalone services and permeate
  Grid
• Meta-data rich Message-linked Web Services is
  permeating paradigm
• Component Model such as Enterprise JavaBean
  (EJB) or OGSI describes the formal structure of
  services EJB if used lives inside OGSI in our
  Grids
• Invocation Framework describes how you interact
  with system
• Security in fine grain fashion to provide
  selective authorization (Globus and EDG WP6)
• Policy context describes rules for this
  particular Grid
• Transport mechanisms abstract concepts like ports
  and Quality of Service
• Messaging abstracts destination and customization
  of content
• Network (monitoring, performance) EDG WP7
• Fabric (resources) EDG WP4

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Architecture in Pictures I
Invocation Framework
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Architecture in Pictures IIOGSA Interoperable
Grid
40
Architecture in Pictures IIIOGSA Federated Grid
Mediation Serviceconverting between OGSA and
native services
Mediation Service
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Virtualization

• The Grid could and sometimes does virtualize
  various concepts
• Location URI (Universal Resource Identifier)
  virtualizes URL
• Replica management (caching) virtualizes file
  location generalized by GriPhyn virtual data
  concept
• Protocol message transport and WSDL bindings
  virtualize transport protocol as a QoS request
• P2P or Publish-subscribe messaging virtualizes
  matching of source and destination services
• Semantic Grid virtualizes Knowledge as a
  meta-data query
• Brokering virtualizes resource allocation
• Virtualization implies references can be indirect

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IFS Interfaces and Functionality and Semantics I

• The Grid platform tries to minimize detail in
  protocols and maximize detail in interfaces to
  enhance scaling
• However rich meta-data and semantics are critical
  for correct and interesting operation
• Put as much semantic interpretation as you can
  into specific services
• Lack of Semantic interoperation is in fact main
  weakness of todays Grids and Web services
• Everything becomes a service (See example of
  education) whether system or application level
• There are some very important Global Services
• Discovery (look up) and Registration of service
  metadata
• Workflow
• MetaSchedulers

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IFS Interfaces and Functionality and Semantics II

• There are many other generally important services
• OGSA-DAI The Database Service
• Portal Service linked to by WSRP (Web services
  for Remote Portals)
• Notification of events
• Job submission
• Provenance interpret meta-data about history of
  data
• File Interfaces
• Sensor service satellites
• Visualization
• Basic brokering/scheduling

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Globus in a Nutshell from IPG

• GT2 (or Globus Toolkit 2) is original (non web
  service based) version which is basis of EDG
  (European Data Grid) work
• C programs and libraries
• See Chapter 5 of book with background in chapters
  2-4 and 37
• http//www.ipg.nasa.gov/ipgusers/globus/
• http//www.globusworld.org/globusworld_web/jw2_pro
  gram_tut.htm

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Globus GT2 from IPG

• The goal of the Globus GT2 is to provide
  dependable, consistent, pervasive access to
  high-end resources.
• This is original Grid start general recently to
  virtual organizations and data grids
• The Globus Project offers the most widely used
  computing grid middleware. The Globus Project is
  a joint effort of Argonne National Laboratory,
  the Informational Sciences Institute of the
  University of Southern California, in
  collaboration with numerous other organizations
  including  NCSA, NPACI, UCSD, and NASA. See
  http//www.globus.org/ for history, goals,
  release and usage notes, software distributions,
  and research papers.

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Globus GT2 II

• Grid Fabric Layer One The fabric of the Grid
  comprises the underlying systems, computers,
  operating systems, networks, storage systems, and
  routersthe building blocks.
• Grid Services Layer TwoGrid services integrate
  the components of the Grid fabric. Examples of
  the services that are provided by Globus Toolkit
  2
• GRAMThe Globus Resource Allocation Manager,
  GRAM, is a basic library service that provides
  capabilities to do remote-submission job start
  up. GRAM unites Grid machines, providing a common
  user interface so that you can submit a job to
  multiple machines on the Grid fabric. GRAM is a
  general, ubiquitous service, with specific
  application toolkit commands built on top of it
• MDSThe Monitoring and Discovery Service, also
  known as GIS, the Grid Information Service,
  provides information service. You query MDS to
  discover the properties of the machines,
  computers and networks that you want to use how
  many processors are available at this moment?
  What bandwidth is provided? Is the storage on
  tape or disk? Is the visualization device an
  immersive desk or CAVE? Using an LDAP
  (Lightweight Directory Access Protocol) server,
  MDS provides middleware information in a common
  interface to put a unifying picture on top of
  disparate equipment.
• Contd

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Globus GT2 III

• GSI gss-api library for adding authentication to
  a program. GSI provides programs, such as
  grid-proxy-init, to facilitate login to a variety
  of sites, while each site has its own flavor of
  security measures. That is, on the fabric layer,
  the various machines you want to use might be
  governed by disparate security policies GSI
  provides a means of simplifying multiple remote
  logins. The standard installation is based on a
  PKI security system the Kerberos installation of
  Globus is less standard. (Some installations with
  DoE and DoD insist on Kerberos)
• GridFTP A new (in Globus 2.0) protocol for file
  transfer over a grid. This is a Global Grid Forum
  standard
• GASS Globus Access to Secondary Storage, provides
  command-line tools and C APIs for remotely
  accessing data. GASS integrates GridFTP, HTTP,
  and local file I/O to enable secure transfers
  using any combination of these protocols..

48
Globus GT2 IV

• Application Toolkits Layer ThreeApplication
  toolkits use Grid Services to provide
  higher-level capabilities, often targeted to
  specific classes of application.
• For example, the Globus development team has
  created a set of Grid service tools and a
  toolkit of programs for running remotely
  distributed jobs. These include remote job
  submission commands ( globusrun,
  globus-job-submit, globus-job-run), built on top
  of the GRAM service, and MPICH-G2, a Grid-enabled
  implementation of the Message Passing Interface
  (MPI).
• A more modern interface is through CoG Kits
  (Commodity Grid) to different languages Perl
  Python Java see chapter 26 of Book
• The Java CoG kit provides a natural way to link
  GT2 to a Web service framework
• Globus Toolkit 3 (GT3) effectively integrated CoG
  Kit interface with core Globus by wrapping all
  Globus Services as Web services

49
Job Submission in Globus

• Very similar to UNIX Shell build Portal Web
  Interfaces to specific or general Shell commands.
  Some example commands
• globusrun Runs a single executable on a remote
  site with an RSL specification.
• globus-job-cancel Cancels a job previously
  started using globus-job-submit.
• globus-job-run Allows you to run a job at one or
  several remote resources. It translates the
  program arguments to an RSL request and uses
  globusrun to submit the job.
• globus-job-clean Kills the job if it is still
  running and cleans the information concerning the
  job.
• globus-job-status Display the status of the job.
  See also globus-get-output to check the standard
  output or standard error of your job.
• These are all controlled by metadata specified by
  the Globus Resource Specification Language (RSL)
  which provides a common language to describe jobs
  and the resources required to run them.
• http//www.globus.org/gram/gram_rsl_parameters.htm
  l
• The simplest RSL expression looks something like
  the following. (executable/bin/ls)

50
Virtual Data Toolkit VDT from GriPhyn

• http//www.lsc-group.phys.uwm.edu/vdt/
• Trillium (PPDG from DoE GriPhyn and iVDgL from
  NSF) is major US effort building Grid application
  software with a strong particle physics emphasis
• VDT is their major software release and its heart
  is Condor and GT2.
• There is some virtual data software as well but
  not clear if this is of interest in production
  use (interesting research area)
• Condor (Chapter 11 of Book) is powerful job
  scheduler for clusters and cycle scavenging
• It has a well developed interface (ClassAds) for
  defining requirements of jobs and matching to
  compute capabilities

51
OGSA/OGSI Top Level View
Chapters 7 to 9 of Book http//www.gridforum.org/M
eetings/ggf7/docs/default.htm http//www.globuswo
rld.org/globusworld_web/jw2_program_tut.htm

• OGSA is the set of core Grid services
• Stuff you cant live without
• If you built a Grid you would need to invent
  these things

52
OGSI Open Grid Service Interface

• http//www.gridforum.org/ogsi-wg
• It is a component model for web services.
• It defines a set of behavior patterns that each
  OGSI service must exhibit.
• Every Grid Service portType extends a common
  base type.
• Defines an introspection model for the service
• You can query it (in a standard way) to discover
• What methods/messages a port understands
• What other port types does the service provide?
• If the service is stateful what is the current
  state?
• A set of standard portTypes for
• Message subscription and notification
• Service collections
• Each service is identified by a URI called the
  Grid Service Handle
• GSHs are bound dynamically to Grid Services
  References (typically wsdl docs)
• A GSR may be transient. GSHs are fixed.
• Handle map services translate GSHs into GSRs.

53
OGSI and Stateful Services

• Sometimes you can send a message to a service,
  get a result and thats the end
• This is a statefree service
• However most non-trivial services need state to
  allow persistent asynchronous interactions
• OGSI is designed to support Stateful services
  through two mechanisms
• Information Port where you can query for SDE
  (Service Definition Elements)
• Factories that allow one to view a Service as a
  class (in an object-oriented language sense)
  and create separate instances for each Service
  invocation
• There are several interesting issues here
• Difference between Stateful interactions and
  Stateful services
• System or Service managed instances

54
Factories and OGSI

• Stateful interactions are typified by amazon.com
  where messages carry correlation information
  allowing multiple messages to be linked together
• Amazon preserves state in this fashion which is
  in fact preserved in its database permanently
• Stateful services have state that can be queried
  outside a particular interaction
• Also note difference between implicit and
  explicit factories
• Some claim that implicit factories scale as each
  service manages its own instances and so do not
  need to worry about registering instances and
  lifetime management
• See WS-Addressing from largely IBM and
  Microsofthttp//msdn.microsoft.com/webservices/de
  fault.aspx?pull/library/en-us/dnglobspec/html/ws-
  addressing.asp

Explicit Factory
Implicit Factory
55
Open Grid Service Architecture

• OGSA-WG chaired by
• Ian Foster, ANL and Univ. of Chicago
• Jeff Nick, IBM
• Dennis Gannon, IU
• Active Members from
• IBM, Fujitsu, NEC, SUN, Hitachi, Avaki
• Univ. of Mich, Chicago, Indiana (not much
  academic involvement)

56
OGSA Core Services I

• Registries, and namespace bindings
• Registry is a collection of services indexed by
  service metadata.
• find me a service with property X.
• Directory is a map from a namespace to GSHs.
• A namespace is a human understandable version of
  a Grid Handle
• Queues
• For building schedulers and resource brokers
• Jobs and other requests are in queues
• This is high-level messaging

57
Security

• Base this on Web Services Security
• Authentication
• 2-way. Who are you and who am I?
• Authorization
• What am I authorized to use/see/modify
• Accounting/Billing
• (not really security see monitoring)
• Privacy
• Group Access
• Easily create a group to share access to a
  virtual Grid.
• Very complex issues related to services and
  message delivery.

58
Common Resource Model

• Every resource on the grid that is manageable is
  represented by a service instance
• CRM is the Schema hierarchy that defines each
  resource (with its meta-data)
• Service for a resource presents its management
  interface to authorized parties.

59
Policy Management

• Policy management services
• Mechanism to publish policy and the services it
  applies to.
• Policy life-cycle mgmt.
• Policy languages exist for routing, security,
  resource use

60
Grid Service Orchestration

• Creating new services by composing other services
• Two types of Orchestration
• Composition in space
• One services is directly invoking another
• Composition in time
• Managing the workflow
• First do this.
• Then do this and that
• When that is done do this
• If something goes wrong do this
• And so on

61
Data Services

• Distributed Data Access
• Data Caching
• Data Replication Services
• Metadata Catalog Services
• Storage Services

62
Metering Resource Consumption

• At what granularity do services report resource
  consumption?
• How do they report it?
• How are services metered?

63
Transactions

• Two threads/workflows must synchronize and agree
  they have done so before moving on.
• Usually involves modification to two or more
  persistent states
• WS-transactions has been proposed.

64
Messaging, Events, Logging

• Messaging
• Delivery Model
• Queuing and Pub/Sub message delivery (not clear
  to me why these are different as
  publish/subscribe implemented as topic labeled
  queues)
• Events
• Time stamped messages
• Standard XML schemas
• Standard Logging
• MQSeries (IBM), JMS (Java Message Service) and
  NaradaBrokering (Indiana) provide this but most
  naturally at level of platform/hosting
  environment

65
Where should Messaging be?

• One can define messaging at the OGSA level above
  the hosting environment but that makes it
  difficult to virtualize messaging and support
  network performance
• Publish-subscribe or better queued messaging
  naturally supports optimized routing based on
  network performance
• One can naturally support collaborative Web
  services in same fashion in a way that it MUCH
  easier that GrooveNetworks and other
  collaborative environments (WebeX,
  Placeware(Microsoft)) do as long as every
  application is a Web service
• OGSA location of messages is fine for low volume
  logging or notification events
• Not good for events on video application where
  each frame is an update event

66
Application as a Web service
From Collaboration As a WS
Events
Rendering
From Master
Participating Client
67
Collaboration Shared Display

• Sharing can be done at any point on object or
  Web Service pipeline

SharedDisplay
Shared Web Service
Shared Export
Shared Event
Master
Event(Message)Service
Shared Display shares framebuffer with
eventscorresponding to changedpixels in master
client.
Object Display
As long as pipeline uses messages, easy tomake
collaborativeWindows framebuffers and in fact
most applications do NOT expose a message based
update interface
Object Display
68
Shared Input Port (Replicated WS) Collaboration
Collaboration as a WSSet up Session with XGSP
Master
Event(Message)Service
OtherParticipants
69
Shared Output Port Collaboration
Collaboration as a WSSet up Session with XGSP
Web Service Message Interceptor
Master
WS Display
WS Viewer
Text Chat Whiteboard Multiple masters
Event(Message)Service
OtherParticipants
WSDisplay
WS Viewer
70
NaradaBrokering

• Based on a network of cooperating broker nodes
• Cluster based architecture allows system to scale
  to arbitrary size
• Originally designed to provide uniform software
  multicast to support real-time collaboration
  linked to publish-subscribe for asynchronous
  systems.
• Now has four major core functions
• Message transport (based on performance
  measurement) in heterogeneous multi-link fashion
• General publish-subscribe including JMS JXTA
  and support for RTP-based audio/video
  conferencing
• Filtering for heterogeneous clients
• Federation of multiple instances of Grid services

71
Role of Event/Message Brokers

• We will use events and messages interchangeably
• An event is a time stamped message
• Our systems are built from clients, servers and
  event brokers
• These are logical functions a given computer
  can have one or more of these functions
• In P2P networks, computers typically
  multifunction in Grids one tends to have
  separate function computers
• Event Brokers just provide message/event
  services servers provide traditional distributed
  object services as Web services
• There are functionalities that only depend on
  event itself and perhaps the data format they do
  not depend on details of application and can be
  shared among several applications
• NaradaBrokering is designed to provide these
  functionalities
• MPI provided such functionalities for all
  parallel computing

72
Engineering Issues Addressedby Event / Messaging
Service

• Application level Quality of Service e.g.
  give audio highest priority
• Tunnel through firewalls proxies
• Filter messages to slow (collaborative/real-time)
  clients
• Choose Hardware or Software multicast
• Scaling of software multicast
• Efficient calculation of destinations and
  routes.
• Integrate synchronous and asynchronous
  collaboration with same messaging, control,
  archiving for all functions
• Transparently replace single server JMS systems
  with a distributed solution.
• Provides reliable inter-peer group messaging for
  JXTA
• Open Source (high quality) messaging

73
NaradaBrokering implements an Event Service

• Filter is mapping to PDA or slow communication
  channel (universal access) see our PDA adaptor
• Workflow implements message process
• Routing illustrated by JXTA and includes firewall
  
• Destination-Source matching illustrated by JMS
  using Publish-Subscribe mechanism
• These use Security model (being implemented)
  based on WS-Sec

74
Narada Broker Network
(P2P) Community
For message/events service
Broker
Broker
(P2P) Community
Resource
Broker
Hypercube topology for brokers? Tree for distance
education with teacher at root
Broker
Broker
(P2P) Community
Software multicast
Broker
(P2P) Community
75
NaradaBrokering Communication

• Applications interface to NaradaBrokering through
  UserChannels which NB constructs as a set of
  links between NB Broker waystations which may
  need to be dynamically instantiated
• UserChannels have publish/subscribe semantics
  with XML topics
• Links implement a single conventional data
  protocol.
• Interface to add new transport protocols within
  the Framework
• Administrative channel negotiates the best
  available communication protocol for each link
• Different links can have different underlying
  transport implementations
• Implementations in the current release include
  support for TCP,UDP, Multicast, SSL and RTP.
  HTTP, HTTPS support will be available in Feb 2003
  release.
• Supports communication through proxies such as
  iPlanet, Netscape and Apache.
• Supports communication through firewalls such as
  Microsoft ISA, Checkpoint.

76
Performance/Routing in Message-based Architecture
B2
B3

• In traveling from cities A to B (say 3 separate
  passengers), one chooses between and changes
  transport mechanism at waystations to optimize
  cost, time, comfort, scenic beauty
• Waystations are now NB brokers where one chooses
  transport protocol (individual or collective)
• Able to choose between car, type of car, plane,
  train etc
• Able to dynamically create waystations to cope
  with problems and acts as hubs for multicast
  messages
• Knows about traffic jams and can assign the HOV
  lane

77
Note on Optimization

• Note in parallel computing, couldnt do much
  dynamic optimization as aiming at microsecond
  latency
• Natural to use hardware routing
• In 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) due to routing,
  processing (in NB) or packet loss recovery is
  important property
• Grid needs and can tolerate significant dynamic
  optimization

78
Sender/receiver/broker - (Pentium-3, 1 GHz, 256
MB RAM). 100 Mbps LAN. JDK-1.3, Red Hat Linux 7.3
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82
Narada Performance Web Service

• Performance measurements are used by Links in
• Reconfiguring Connectivity between nodes
• Deciding underlying transport protocol
• Determining possible filtering
• Each node determines performance of links of
  which it is endpoint
• Individual node web services are aggregated as
  another Web Service

Probably should replace by a more sophisticated
measurement package

• Factors measured include
• Transit delays, bandwidth, Jitter, Receiving
  rates.
• Performance measurements are
• Spaced out at increasing intervals for healthy
  channels.
• Factors selectively measured for unhealthy
  channels.
• No repeated measurements of bandwidth for
  example.
• Injected into Narada network as XML events

Administrative Interface
83
The Overall Architecture

• The Grid is defined by a collection of
  distributed Services
• For many users the primary interaction with the
  Grid will be through a portal

Event and logging Services
The User
Application Factory Services
Messaging and group collaboration
Portal Server
Directory index Services
MyProxy Server
User's Persistent Context
Metadata Directory Service(s)
84
Application Portal in a Minute (box)

• Systems like Unicore, GPDK, Gridport (HotPage),
  Gateway, Legion provide Grid or GCE Shell
  interfaces to users (user portals)
• Run a job find its status manipulate files
• Basic UNIX Shell-like capabilities
• Application Portals (Problem Solving
  Environments) are often built on top of Shell
  Portals but this can be quite time confusing
• Application Portal Shell Portal Web Service
  Application (factory) Web service

85
Application Web service

• Application Web Service is ONLY metadata
• Application is NOT touched
• Application Web service defined by two sets of
  schema
• First set defines the abstract state of the
  application
• What are my options for invoking myapp?
• Dub these to be abstract descriptors
• Second set defines a specific instance of the
  application
• I want to use myapp with input1.dat on
  solar.uits.indiana.edu.
• Dub these to be instance descriptors.
• Each descriptor group consists of
• Application descriptor schema
• Host (resource) descriptor schema
• Execution environment (queue or shell) descriptor
  schema

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87
Web Services as a Portlet

• Each Web Service naturally has a user interface
  specified as just another port
• Customizable for universal access
• This gives each Web Service a Portlet view
  specified (in XML as always) by WSRP (Web
  services for Remote Portals)
• So component model for resources automatically
  gives a component model for user interfaces
• When you build your application, you define
  portletat same time

Application as a WSGeneral Application
PortsInterface with other WebServices
User Face ofWeb ServiceWSRP Ports define WS as
a Portlet
Web Services have other ports (Grid Service) to
be OGSI compliant
88
Online Knowledge Center built from Portlets
A set of UIComponents

• Web Services provide a component model for the
  middleware (see large common component
  architecture effort in Dept. of Energy)
• Should match each WSDL component with a
  corresponding user interface component
• Thus one must use a component model for the
  portal with again an XML specification (portalML)
  of portal component

89
HTML
Jetspeed Architecture
Turbine Servlet
JSP template
ECS Root to HTML
Screen Manager
PSML
ECS
PortletController
PortletController
ECS
ECS
ECS
PortletControl
ECS
ECS
ECS
ECS
ECS
Portlet
Portlet
Portlet
Portlet
Portlet
Portlets
HTML Local files
JSP or VM Local templates
WebPage Remote HTML
Portlets User implemented using Portal API
XML RSS, OCS, or other Local or remote
Data
90
Portlets and Portal Stacks

• User interfaces to Portal services (Code
  Submission, Job Monitoring, File Management for
  Host X) are all managed as portlets.
• Users, administrators can customize their portal
  interfaces to just precisely the services they
  want.

Aggregation Portals (Jetspeed)
User facing Web Service Ports
Message Security, Information Services
Application Grid Web Services
Core Grid Services
91
Jetspeed Computing Portal Choose Portlets
92
Choose Portlet Layout
Choose 1-column Layout
Original 2-column Layout
93
File management
Tabs indicate available portlet interfaces.
Lists user files on selected host,
noahsark. File operations include Upload,
download, Copy, rename, crossload
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Sample page with several portlets proxy
credential manager, submission, monitoring
96
Administer Grid Portal
Provide information about application and host
parameters
Select application to edit