Grid Computing & Web Services: A Natural Partnership

1. Grid Computing & Web Services:A Natural Partnership Dave Angulo Department of Computer Science The University of Chicago and Mathematics and Computer Science Division Argonne National Laboratory Ian Foster Mathematics and Computer Science Division Argonne National Laboratory and Department of Computer Science The University of Chicago Address at 2nd US-Hungarian Workshop on Cluster and Grid Computing, Budapest, Hungary, February 6, 2002

2. Partial Acknowledgements • Open Grid Services Architecture work is performed by • Ian Foster, Globus Co-PI @ Argonne/UofC • Carl Kesselman, Globus Co-PI @ USC/ISI • Steve Tuecke, Globus Toolkit Architect @ANL • Jeff Nick, Steve Graham, Jeff Frey @ IBM • Globus Toolkit R&D involves many fine scientists & engineers at ANL, USC/ISI, and elsewhere (see www.globus.org) • Strong collaborations with many outstanding EU, UK, US Grid projects • Support from DOE, NASA, NSF, Microsoft

3. Globus Toolkit: Evaluation (1) • Good technical solutions for key problems, e.g. • Authentication and authorization • Resource discovery and monitoring • Reliable remote service invocation • High-performance remote data access • This + good engineering is enabling progress • Good quality reference implementation, multi-language support, interfaces to many systems, large user base, industrial support • Growing community code base built on tools

4. Globus Toolkit: Evaluation (2) • Protocol deficiencies, e.g. • Heterogeneous basis: HTTP, LDAP, FTP • No standard means of error propagation • Significant missing functionality, e.g. • Databases, sensors, instruments • Programming tools: workflow, … • Virtualization of end systems (hosting envs.) • Little work on total system properties, e.g. • Dependability, end-to-end QoS, … • Reasoning about system properties

5. “Web Services” • Increasingly popular standards-based framework for accessing network applications • W3C standardization; Microsoft, IBM, Sun, others • WSDL: Web Services Description Language • Interface Definition Language for Web services • SOAP: Simple Object Access Protocol • XML-based RPC protocol; common WSDL target • WS-Inspection • Conventions for locating service descriptions • UDDI: Universal Desc., Discovery, & Integration • Directory for Web services

6. Transient Service Instances • “Web services” address discovery & invocation of persistent services • In Grids, must also support transient service instances, created/destroyed dynamically • E.g., to manage eBusiness workflow, video conference, or distributed data analysis • Significant implications for how services are managed, named, discovered, and used • In fact, much of our work is concerned with the management of service instances

7. Open Grid Services Architecture • Service orientation to virtualize resources • From Web services: • Standard interface definition mechanisms: multiple protocol bindings, multiple implementations, local/remote transparency • Building on Globus Toolkit: • The Grid service defines standard semantics for service interactions • Factory, registry, and mapper services • Reliable and secure transport • Multiple hosting targets: J2EE, .NET, “C”, etc.

8. OGSA Service Model • System comprises (a typically few) persistent services & (potentially many) transient services • All services adhere to specified Grid service interfaces and behaviors • Reliable invocation, lifetime management, discovery, authorization, notification, upgradeability, concurrency, manageability • Interfaces for managing Grid service instances • Factory, registry, mapper • Heavily leverage Globus Toolkit technology => Reliable secure mgmt of distributed state

9. The Grid Service • A (potentially transient) Web service with specified interfaces & behaviors, including • Creation (Factory) • Global naming (GSH) & references (GSR) • Lifetime management • Registration & Discovery • Authorization • Notification • Concurrency • Manageability

10. Factory • A Grid service with Factory interface can be requested to create a new Grid service instance • Reliable creation (once-and-only-once) • Create operation can be extended to accept Grid-service-specific creation parameters • Returns a Grid Service Handle (GSH) • A globally unique URL • Uniquely identifies the instance for all time • Based on name of a home mapper service

11. Mapper • A GSH is a stable name for a Grid service, but does not allow client to actually communicate with the Grid service • A Grid Service Reference (GSR) is a WSDL document that describes how to communicate with the Grid service • Contains protocol binding, network address, … • May expire (I.e. GSR information may change) • The Mapper interface allows a client to map from a GSH to a GSR • http get on GSH also returns a GSR

12. Lifetime Management • GS instances created by factory or manually; destroyed explicitly or via soft state • Negotiation of initial lifetime with Factory • SoftStateDestruction interface supports • GetTerminationTime message for inquiry • Notification interface also allows for lifetime notification • SetTerminationTime message for keepalive • Soft state lifetime management avoids • Explicit client teardown of complex state • Resource “leaks” in hosting environments • ExplicitDestruction interface also available

13. Discovery • A Grid service instance may maintain a set of service information • XML fragments encapsulated in standard <name, type, TTL-info> containers • Discovery interface allows clients to query the Grid service instance for this information • Query operation, plus supporting operations • Extensible query language support • See also Notification interfaces • Allows notification of service existence and about service information

14. Registry • The Registry interface may be used to discover a set of Grid service instances • Returns a WS-Inspection document containing the GSHs of a set of Grid services • Also returns policy associated with the set • Also available through Discovery interface • The RegistryManagement interface allows for soft-state registration of a Grid service • A set of Grid services can periodically register their GSHs into a registry service, to allow for discovery of services in that set

15. Authorization • Protocol binding handles authentication during invocation of Grid service operation • Gives service URI for authenticated subject • Grid service instance should apply authorization policy on all operations • May be site-, service-, instance-, etc., specific • OGSA defines standard interfaces for remote management of access control policy • OperationAuthorizationManagement • SubjectEquivalency

16. Notification Interfaces • NotificationSource for client subscription • One or more notification generators • Generates notification message of a specific type • Typed interest statements: E.g., Filters, topics, … • Supports messaging services, 3rd party filter services, … • Soft state subscription to a generator • NotificationSink for asynchronous delivery of notification messages • A wide variety of uses are possible • E.g. Dynamic discovery/registry services, monitoring, application error notification, …

17. Use of Web Services (1) • A Grid service interface is a WSDL portType • A Grid servicedefinition is a WSDL extension (serviceType) containing: • A set of one or more portTypes supported by the service • portType & serviceType compatibility statements, to support upgradability • For discovery of compatible services when interfaces are upgraded • Implementation version information

18. Use of Web Services (2) • A GSR is a WSDL document with extensions: • Extension to service element to reference serviceType • Service element extensions to carry the GSH, and the expiration time of the GSR • A GSH is an URL, with the following properties: • Globally unique for all time • http get on GSH + “.wsdl” returns GSR • Can derive GSH to Mapper from it • Registry returns WS-Inspection documents

19. (a) Simple Hosting Environment (b) Virtual Hosting Environment (c) Compound Services Registry Registry E2E Factory Factory E2E Reg Service Service Factory ... ... H2R H2R E2E H2R Factory Factory Mapper Mapper Mapper ... ... ... Service Service Service Service Service Service E2E S E2E S E2E S F F R R R R F F 1 2 M M M M F F S S S S S S S S S S S S Using OGSAto Construct Grid Environments In each case, Registry handle is effectively the unique name for the virtual organization.

20. OGSA and the Globus Toolkit • Technically, OGSA enables • Refactoring of protocols (GRAM, MDS-2, etc.)—while preserving all GT concepts/features! • Integration with hosting environments: simplifying components, distribution, etc. • Greatly expanded standard service set • Pragmatically, we are proceeding as follows • Develop open source OGSA implementation • Globus Toolkit 3.0; supports Globus Toolkit 2.0 APIs • Partnerships for service development • Also expect commercial value-adds

21. Globus Toolkit Refactoring • Grid Security Infrastructure (GSI) • Used in Grid service network protocol bindings • Meta Directory Service 2 (MDS-2) • Native part of each Grid service: • Discovery, Registry, RegistryManagement, Notification • Grid Resource Allocation & Mngt (GRAM) • Gatekeeper -> Factory for job mgr instances • GridFTP • Refactor control channel protocol • Other services refactored to used Grid services

22. Timeline • Summer 2002 – Alpha releases of high-level Grid Services • Late 2002, Early 2003 – Alpha release of new core Grid Services (MDS, GRAM, GridFTP)

23. Migration Paths • Globus ToolkitTM evolutionary in nature • Toolkit implementation may change • Underlying model of Grid Computing remains the same • Capabilities of future Toolkits will be superset of today’s Toolkit • New implementations integrate better with existing commodity technologies • In cases of radical departure from current implementations, migration paths will be provided • possibly maintain compatible APIs • possibly create gateways to today’s protocols

24. Summary:Evolution of Grid Technologies • Initial exploration (1996-1999; Globus 1.0) • Extensive appln experiments; core protocols • Data Grids (1999-??; Globus 2.0+) • Large-scale data management and analysis • Open Grid Services Architecture (2001-??, Globus 3.0) • Integration w/ Web services, hosting environments, resource virtualization • Databases, higher-level services • Radically scalable systems (2003-??) • Sensors, wireless, ubiquitous computing

25. Summary • The Grid problem: Resource sharing & coordinated problem solving in dynamic, multi-institutional virtual organizations • Grid architecture: Protocol, service definition for interoperability & resource sharing • Globus Toolkit a source of protocol and API definitions—and reference implementations • And many projects applying Grid concepts (& Globus technologies) to important problems • Open Grid Services Architecture represents (we hope!) next step in evolution

26. For More Information • The Globus Project™ • www.globus.org • Grid architecture • www.globus.org/research/papers/anatomy.pdf • Open Grid Services Architecture (soon) • www.globus.org/research/papers/ogsa.pdf • www.globus.org/research/papers/gsspec.pdf