applications of soa and web services in grid computing
TRANSCRIPT
APPLICATIONS OF SOA AND WEB SERVICES IN GRID
COMPUTINGThanh H. Pham – Quynh Le
19 May 2010
2
31.900.000
3
• Service-oriented Architecture (SOA)1
• Web Services (WS)2
• Open Grid Service Architecture (OGSA)3
• Web Services Resource Framework (WSRF)4
Today’s Overview
4
Objectives
• SOA – An overview• WS & Related Technologies• OSGA & WSRF Overview• Applications of
SOA and WSin Grid Computing
5
SERVICE-ORIENTED ARCHITECTURE
6Image from Dr. Dang Tran Khanh slide
A Case Study
7
Key terms[1]
• An architecture:–Formal description of a system–Defines system purpose, functions–Defines system externally visible
properties, and interfaces.
[1] OGSA Glossary of Terms v1.0: http://www.gridforum.org/documents/GFD.44.pdf
8
Key terms (cont.)
• A service–Is a software component –Can be accessed via a network–Provides functionality to a requester
9
Key terms (cont.)• Service-oriented architecture refers to a
style of building reliable distributed systems that deliver functionality as loose coupling services
• Technically, then, the term SOA refers to the design of a system, not to its implementation
10
Services Characteristics
• May be individual useful, or can be integrated
• Communicate with clients by exchanging messages
• Can participate in a workflow
11
Services Characteristics (cont.)
• May be completely self-contained, or may depend on other services, resources
• Advertise details such as their capabilities, interfaces, policies, and supported communications protocols
• How’s about implementation details? Programing language, hosting platform…
12
Service interaction
13
A Real Life Example
14
Loose Coupling
• This term implies that the interacting software components minimize their in-built knowledge of each other
• They discover the information they need at the time they need it.
15
State and Statelessness
• Client can choose to go to any service that is capable of fulfilling its need: loose coupling
• Loose coupling vs. tight coupling
• Ex: A calculator service
16
Stateless vs. Stateful• Ex: a transaction that requires several steps
• The service retains some information (“state”) about each step
• This might result in a delay
17
Stateless Service Design• Service must hand back state information to
client
• Client must hand the state information to whichever service it selects to process the next step
• The selected service must be able to accept and handle the state information
18
A multi-step client/service interaction
19
WEB SERVICES
20
A Case Study
21
Step 1: A customer chooses to pay with a Credit Card.
22
Step 2: They enter shipping info on your site
23
Step 3: They enter their credit card details
24
Step 4: They review their payment info
25
Step 5: Their payment is processed.
26
Step 6: You get paid. (The fun part.)
27
1
2 3
As easy as
Right?
2828
What is Web Service?• Web Service Essential
Book: A web service is any
service that is available over the Internet, uses a standardized XML messaging system, and is not tied to any one operating system or programming language
XMLXML
Computer A:Language: Perl
OS: Windows 2000
Computer B:Language: Java
OS: Linux
A basic web service
2929
What is Web Service? (cont.)• W3C:
– A software system designed to support interoperable machine-to-machine interaction over a network
• W3schools.com:– Application components– Communicate using open protocols– Self-contained and self-describing– Can be used by other applications
30
Key specifications used by Web services
• XML: eXtensible Markup Language
• SOAP: Simple Object Access Protocol
• WSDL : Web Services Description Language
• UDDI: Universal Description Discovery and Integration
31
Key specifications used by Web services
• XML: eXtensible Markup Language
• SOAP: Simple Object Access Protocol
• WSDL : Web Services Description Language
• UDDI: Universal Description Discovery and Integration
3232
About…
• XML does not do anything• With XML, you invent your own tags• XML just plain text
<note> <to>Tove</to> <from>Jani</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body></note>
33
SOAP• Protocol for messaging and remote
procedure calling between distributed applications
• SOAP is for exchange information between applications
• SOAP is a format for sending messages
34
SOAP Message Structure
3535
A SOAP request• POST /InStock HTTP/1.1Host: www.example.orgContent-Type: application/soap+xml;
<?xml version="1.0"?><soap:Envelope><soap:Body xmlns:m="http://www.example.org/stock"> <m:GetStockPrice> <m:StockName>IBM</m:StockName> </m:GetStockPrice></soap:Body></soap:Envelope>
3636
The SOAP response• HTTP/1.1 200 OKContent-Type: application/soap+xml;
<?xml version="1.0"?><soap:Envelope><soap:Body xmlns:m="http://www.example.org/stock"> <m:GetStockPriceResponse>
<m:Price>34.5</m:Price> </m:GetStockPriceResponse></soap:Body></soap:Envelope>
37
WSDL
• Used to define Web Services and describe how to access them
• Describes location of the service, the function calls
39
SOA AND WEB SERVICES: STYLE VS. IMPLEMENTATION
40
SOA Is Not Web Services
• Service-orientation is an architectural style
• Web services are an implementation technology
• The two can be used together, and they frequently are, but they are not mutually dependent.
41
Demonstration
OPEN GRID SERVICE ARCHITECTURE (OGSA)
Abstract
• The Open Grid Services Architecture (OGSA), set to become the standard architecture for most grid applications, depends on Web Services as the underlying middleware.
• OGSA first spawned the Open Grid Services Infrastructure which, despite improving Web Services in several ways, failed to converge with existing Web Services standards.
• The Web Services Resource Framework (WSRF), introduced last January, improves on OGSI and will eventually replace it. The presentation will cover the evolution and current state of OGSA, OGSI, WSRF, and the next version of the Globus Toolkit (GT4), which will be the first implementation of the WSRF specification.
44
Building an Open Grid
OpenStandards
OpenSource
OpenInfrastructure
OpenGrid
45
Grids and Open StandardsIn
crea
sed
func
tiona
lity,
stan
dard
izatio
n
Time
Customsolutions
OGSA
GGF: OGSI, …(+ OASIS, W3C)
Multiple implementations,including Globus Toolkit
Web services
Globus Toolkit
Defacto standardsGGF: GridFTP, GSI
X.509,LDAP,FTP, …
App-specificServices
46
OGSA Overview (1/2)
• OGSA = Open Grid Services Architecture Open: communicated extensibility, vendor neutrality. Services: OGSA is based on SOA manifested in WS Architecture: well-defined set of basic interfaces… Grid Services = Grid + WS; service semantics
• aims to standardize the different services that are commonly found in a Grid application Job management, security, VO management, data
management, workflow, deployment, etc.
47
OGSA Overview (2/2)
• Addressing the challenges of integrating services across distributed, heterogeneous, dynamic VO formed from the disparate resources
• OGSA was introduced in “Physiology of the Grid” (I.Foster, C.Kesselman, J.Nick, y S.Tuecke)
• The actual standardization process is being carried out by the Global Grid Forum (GGF) http://www.ggf.org/
48
OGSA Evolution
Autonomy ofthe Grid
Physiology ofthe Grid
OGSA V1.0
OGSA Glossary
OGSAProfile
Basic ExecutionService
Naming
JSDL
Open GridServices
Infrastructure
Web ServicesResource
Framework
Web ServicesNotification
informational
Normative
49
What does OGSA define?
• “A set of core interfaces and behaviours that address key concerns in Grid systems.”– Each particular service can be accessed in the same fashion,
regardless of vendor, organization, internal implementation, etc.
• What underlies this?– How are the interfaces defined? – How does a client request a particular operation from a
service?
• OGSA relies on (&aims to improve) WS technologies– Broader context: Service-Oriented Architectures (SOA)– WS & GS
50
Web Services (1)
• A simple but powerful distributed system paradigm, that allows one to:– Describe a service (WSDL)– Invoke a service (SOAP)– Discover a service (various)
• What sets it apart?– Clean separation between interface (what the service does)
and implementation (how it does it)– Based on standard interoperable languages (XML)– Widespread use and abundant software available
• We can use web services to build SOAs, improving interoperability and reusability.
Web Services (2)
• Why are WS ideal for OGSA and for Grid systems?– Can easily cope with heterogeneous systems (different
programming languages, platforms, etc.)– Common interface language (WSDL) allows:
• Virtualization: from a pool of services (with the same interface) I can access any service in the same fashion regardless of vendor, platform, etc.
• Dynamic service indexing and discovery.• Dynamic access to services
51
Grid Services (1)
• Despite being the best option for OGSA, WSs still have important disadvantages:– Stateless (…)– Non-transient ('Persistent')– No supporting services (notifications, lifecycle
management, etc.)
• OGSA defines the concept of a Grid Service to overcome these limitations:– Grid Service = improved Web Service– Grid Services are compatible with WS– Note that Grids need access to stateful resource
52
Grid Services (2)• Grid services
– can maintain internal state for the lifetime of the service– can be created and destroyed dynamically (via a Factory)– have a globally unique name, the Grid service handle (GSH)– each instance has a set of service data elements (a
collection of XML elements)
• OGSA is based on Grid Services– Grid Services are specified in a separate spec spawned by OGSA: Open Grid Services Infrastructure (OGSI).– All the services in OGSA (Job management, security, etc.) will be based on (and implemented with) Grid Services
53
Grid Services (3)
54
55
OGSA Model: At a Glance
GT3 capabilities – e.g. GRMS, GridFTP, GRAM..
GT3 Security
Web services
OGSA – Grid Enabled Web Services
Other services – data services etc
56
The OGSA Platform
OGSI
TransportProtocolHosting EnvironmentHosting Environment
Host. Env. & Protocol Bindings
OGSA Platform services: registry,authorization, monitoring, data
access, etc., etc.
More specialized &domain-specific
services
Models for resources &
other entitiesO
therm
odels
Environment-specificprofiles
Domain-specificprofiles
OGSAPlatform
57
OGSI (1)
Web Service Interface (WSDL)
SOAPServer
Service Implementation
Web Services
A Grid ServiceGWSDL
Extends ..
58
OGSI (2)
Implementation
Hosting environment/runtime(“C”, J2EE, .NET, …)
Dataaccess
Grid ServiceHandle
Grid ServiceReference
handleresolution
Servicedata
element
Servicedata
element
GridService(required)
Introspection:• What port types?• What policy?• What state?
Client
Servicedata
element
Other standard interfaces:factory,
notification,collections
59
60
Globus Toolkit 3 (1)
• The Globus Toolkit is probably the best-known software package for Grid programming
• However, there seems to be an ongoing confusion regarding the relationship between GT3 and OGSA + OGSI...– GT3 == OGSA?– GT3 == OGSI?– Is GT3 a magical toolkit which will allow me to program
Grid systems out-of-the-box?
61
Globus Toolkit 3 (2)
• The Globus Toolkit 3 (GT3) is a complete implementation, in Java, of the OGSI spec
• Very important: GT3 isn't only an OGSI implementation.– Includes OGSA-defined services– Includes its own non-OGSA services (which have become
a de facto standard)– Also includes non-WS components (GT2.4)
62
GT3 Architecture
63
Non-GT3 services based on the GT3 architecture
Management of large volumes of data (Replica Management)
MMJFS, MDS, RFT
GSI (Grid Security Infrastructure), SSL, WS-Security, SOAP, ...
OGSI: Grid Services, Service Data, Notifications, Transient Services (Factory/Instance), Service Groups
OGSA, OGSI, and GT3(1)
64
OGSA, OGSI, and GT3 (2)
65
In standardization process (GGF)- VO management- Security- Job management- Data management- Workflow- etc.
Standardized (GGF) and implemented (GT3)
Standardized (W3C) and implemented (Apache Axis)
OGSA: summing up
• OGSA: standards-based Grid technology– From Web services: standard IDL, discovery, binding
independence, other desirable features– From Grid: naming, state, lifetime management, etc., etc.
66
WEB SERVICES RESOURCE FRAMEWORK (WSRF)
68
Grid and WS: Convergence?
• Despite being generally accepted as a good change within the Grid community, OGSI has not caught the eye of the Web Service community.– GGF had hoped that Web Services standards and OGSI
would converge, but that convergence is not happening.
Started far apart in apps & tech
OGSI
GT2GT1
HTTPWSDL,
WS-*
WSDL 2,
WSDM
Have beenconverging ?
OGSA Review
69
Web Services Messaging, Security, Etc.
Open Grid Services Infrastructure
Domain-Specific Services
Core Services
ProgramExecution Data Services
Sta
ndar
diza
tion
70
Three Major WS Concerns about OGSI
• “Dense specification”• “Does not work well with existing WS tooling”
– Extended WSDL & therefore not compatible with other Web service standards ..
– Grid services need to be stateful and dynamic– Therefore, WSDL had to be extended (how) to add state &
notification• Too “object oriented”
– Web Services are not supposed to be object-oriented, despite the fact that most Web Services are implemented using object-oriented languages. This specially refers to the fact that OGSI Services are stateful (Web Services are supposed to be stateless)
– Grid services extended Web services – means that Grid services are ON THEIR OWN…
WSRF (1)
• To achieve Web Service & Grid Service convergence, a new standard was announced during GlobusWORLD 2004 (January 2004)
• This new standard will supersede OGSI• WSRF – Web Services Resource Framework• OASIS, from 2006
71
WSRF (2)
72
• The definition of WSRF means that Grid and Web communities can move forward on a common base
WSRF (3)
73
•OGSA Services can be defined and implemented asWeb services instead of working w/ a diff “improved version” of WS
•OSGA can take advantage of other Web services standards
•OGSA can be implemented using standard Web services development tools
•Grid applications will NOT require special Web services infrastructure
• WSRF would be part of the WS standard, instead of being a “patch” over existing one (like OGSI)
WSRF (4)
74
Web Services Messaging, Security, Etc.
Open Grid Services Infrastructure
Domain-Specific Services
Core Services
ProgramExecution Data Services
Stan
dard
izatio
n
WS-Resource Framework
WSRF (5)• WS-Resource: Web Service + stateful resource
– Put state in the resource, not WS, each has a unique key– instruct the WS to use a particular resource, if we want a stateful
interaction with a WS– Pairing a WS with a resource is called a WS-Resource
• WS-Resource is a construct used to model stateful resources using WS architectural framework
• Unique (for the Web Service) - Has a distinguishable identity and lifetime
• Stateful - Maintains a specific state that can be materialized using XML
• May be accessed through one or more Web Services
75
Example of stateful Web services
76
Example of stateful Web services
77
Note: There are three resources, and the service interface is instructed to use Resource C
78
79
WSRF specification• WSRF is a collection of four different specifications
related to the management of WS-Resource1. WS-ResourceProperties – Supplies a set of interfaces
that will allow us to access, modify, and query resource properties
2. WS-ResourceLifetime: Resources have non-trivial life cycles. In other words, they are not static entity that is created when our server stops. Resources can be created and destroyed at anytime. The WS-ResourceLifetime supplies some basic mechanisms to manage lifecycle of resources.
80
WSRF specification (2)
• WSRF is a collection of four different specifications related to the management of WS-Resource3. WS-ServiceGroup – This is useful in managing groups of
WS or group of WS-Resources and performing operations such as “add new service to group”, “remove this service from group”, and (more importantly), “find a service in the group that meets the condition FOOBAR”, very basic but is the base of more powerful discovery services (such as GT4’s Index Service)
4. WS-BaseFaults – Aims to provide a standard way of representing faults when something goes wrong during WS service invocation
81
Related Specifications
1. WS-Notification – This is another collection of specification that, although not part of a WSRF, is closely related to it.
2. WS-Addressing: Provides mechanism for addressing WS. More versatile than URI. Can be used to address WS-Resource pair
82
83
Concerns Addressed
How WSRF deals with OGSI's problems:* “Dense specification” WSRF is divided in five documents plus a complementary
specification (WS-Notification) * “Doesn’t work well w/ existing WS tooling” WSRF harmonizes with WS: less aggressive use of XML
Schema, use of pure WSDL 1.1 for interface description (instead of GWSDL, a 'patched' version of WSDL fit for OGSI)
* “Too object oriented” WSRF makes an explicit distinction between the “service”
and the stateful “resources” acted upon by that service
Relation from WSRF to ...
84
• OGSA: WSRF mechanisms will enable OGSA• OGSI: WSRF restates OGSI concepts in WS terms
OGSI WSRF
Grid Service Reference (GSR) WS-Addressing Endpoint Reference
Grid Service Handle (GSH) WS-Addressing Endpoint Reference
HandleResolver portType WS-RenewableReferences
Service data elements (SDE) WS-ResourceProperties
GridService lifetime managementt
WS-ResourceLifeCycle
Notification portTypes WS-Notification
Factory portType Treated as a pattern
ServiceGroup portTypes WS-ServiceGroup
Base fault type WS-BaseFaults
WSRF and GT4
85
WSRF – summing up• Why is WSRF important?
– WSRF completes Grid/Web convergence
• How does WSRF relate to OGSI?– WSRF restates OGSI concepts in WS terms
• How does WSRF relate to OGSA?– WSRF mechanisms will enable OGSA
• Why is WSRF more likely to succeed? – Harmonizes with Web Services– Backed by IBM and HP
• First, full, free implementation: GT4– IBM will include support for WSRF in some of its tools.
• More WSRF details: – http://www.globus.org/wsrf
86
Summary
• “Grid Computing” is undergoing an intense standardization process.– OGSA: Still work-in-progress (some parts finished)– OGSI: Promising start, but didn't quite make it– WSRF: Will it achieve true Grid/Web convergence?
• Until OGSA is truly stable, the Globus Toolkit remains the de facto standard, and one of the most important pieces of software in Grid system development.
87
88
Resources[1] The Physiology of the Grid, Ian Foster, Carl Kesselman, Jeffrey M. Nick, Steven Tuecke, 2002[2] Towards a service-oriented Grid, Borja Sotomayor, University of Deusto, 2004[3] SOA, Web Service In Grid Computing, Phạm Hùng Tiến, Đặng Hoài Đức, K2008[4] Open Grid Services Architecture, Ian Foster, University of Chicago, 2003[5] WS-Resource Framework: Globus Alliance Perspectives, Ian Foster, University of Chicago, 2003[6] OGSA, WSRF, and the Foundations of Grid, David Snelling, Fujitsu Laboratories of Europe, 2005[7] Global Globus Forum http://www.globus.org[8] IBM: http://www.ibm.com/developerworks/library/ws-resource/
90
THANK YOU!
91
APPENDIX
WSRF 101: Stateful Resource• A Resource:
– A specific set of state data expressible as an XML document• This is not typically all of the resource’s state!
– Has a well-defined identity and lifecycle – Known to, and acted upon, by one or more Web services.
• Many Possible Instances– Files, Database tables, EJB Entities, XML documents, Compositions of
multiple data sources, Virtualized executions of applications, etc.• A WS-Resource has:
– Identity: Can be uniquely identified/referenced– Lifetime: Often created & destroyed by clients– State: Part of the state can be projected as XML– Type: Its Web service interface
92
Lifetime• Defines:
– Immediate, synchronous destruction operation– Time-based, scheduled destruction operation– “Soft-state” or “leased” lifetime management– Termination time not required to increase monotonically
• Resource properties:– CurrentTime: Can be used to determine clock skew– TerminationTime: Current scheduled termination time
• Notification of resource termination• Why:
– Define clear means by which resources can be destroyed– Allow the Grid to “Garbage Collect” itself automatically
93
Notification
• WS-Notification– Brings publish and subscribe messaging to Web services– Loosely coupled, asynchronous messaging in WSs– WS Notification composes with WSRF and other WSs
• Brokered notification– Support for intermediates, queuing, aggregation, distribution,
filtering, ...
• Topics and Topic Spaces– Define a mechanism to advertise topics for subscription.
• Use of WS-Notification in WS-RF– Receive notification changes to the Resource Properties
94
WSDL: Web Services Description Language
Define expected messages for a service, and their (input or output parameters)
An interface groups together a number of messages (operations)
Bind an Interface via a definition to a specific transport (e.g. HTTP) and messaging (e.g. SOAP) protocol
The network location where the service is implemented , e.g. http://localhost:8080
Web Services Server Applications• Web service – software that exposes a
set of operations• SOAP Engine – handle SOAP requests
and responses (Apache Axis)• Application Server – provides “living
space” for applications that must be accessed by different clients (Tomcat)
• HTTP server- also called a Web server, handles http messages
Borja Sotomayor , http://gdp.globus.org/gt4-tutorial/multiplehtml/ch01s02.html
Container
Let’s talk about state
• Plain Web services are stateless
Borja Sotomayor , http://gdp.globus.org/gt4-tutorial/multiplehtml/ch01s03.html
However, Many GridApplications Require State
Borja Sotomayor , http://gdp.globus.org/gt4-tutorial/multiplehtml/ch01s03.html
Keep the Web Serviceand the State Separate
• Instead of putting state in a Web service, we keep it in a resource
• Each resource has a unique key
Borja Sotomayor , http://gdp.globus.org/gt4-tutorial/multiplehtml/ch01s03.html
Web Service+
Resource=
WS-Resource
Address of a WS-resource is called an end-point reference
Resources Can Be Anything Stored
“Stateless” vs. “Stateful” Services
• Without state, how does client:– Determine what happened (success/failure)?– Find out how many files completed?– Receive updates when interesting events arise?– Terminate a request?
• Few useful services are truly “stateless”, but WS interfaces alone do not provide built-in support for state
Client
FileTransferService
move (A to B)move
GT3/GT4 Evolution
102
Although Grid services are implemented using WS technology, the following are the differences btw them
Grid services vs. Web Services
Web service• Addresses the issue of discovery and invocation of persistent services
•A WS is often presumed available if its corresponding WSDL file is accessible to its client
•WS typically outlive all their clients
Grid service• Addresses the issue of a virtual resource and its state management
•A grid is a dynamic environment hence, Grid services can be transient rather than persistent
•A Grid service can be dynamically created and destroyed.
104
OGSA Specs LandscapeSYSTEMSMANAGEMENT
UTILITYCOMPUTING
GRIDCOMPUTING
Core Services
Basic Profile WS-Addressing
Privacy
WSRF-RAP
WSDM
WS-Security
Naming
OGSA-EMSOGSA Self Mgmt
Others ...
GGF-UR Data Model
HTTP(S)/SOAP
Discovery
SAML/XACML
WSDL WSRF-RL
Trust
WS-DAI
VO Management
Information
Distributed query processing
ASP
Data CentreUse Cases &Applications Collaboration Multi MediaPersistent Archive
WSRF-RP
X.509
NotificationService Groups WS-I BP