Workshop on Qo. S in Geographically Distributed Systems 10 June, 2004 Rome A Framework for the Smart Dynamic Selection of Web Services Access Points Giorgio Gambosi Carlo Gaibisso gambosi@mat. uniroma 2. it gaibisso@iasi. rm. cnr. it Marco Bianchi Flavio Lombardi bianchi@di. univaq. it lombardi@di. uniroma 1. it
Goal of this presentation • To show a “in progress” research activity in the context of Web Service Technologies. • The focus of this activity is on the discovery of the “best” available Web Service Instance “Best effort” approach ¹ Qo. S guaranteed approach
Web Service Architecture Model Service Registry Service Description Publish Find Service Requestor Bind Static Bind Dynamic Bind Reference: Web Services Conceptual Architecture (WSCA 1. 0) – IBM – 2001 Service Provider Service Description
A model for a simple scenario 2 1 What happens in the Service Registry when a Service Instance goes down? Nothing. Current discovery standards (i. e. UDDI) could contain obsolete reference to Services Instances! Service Requestor Service Registry How can the Service Requestor choose the most “comfortable” Service Instance? Current discovery standards (i. e. UDDI) don’t provide any non-operational information about the run-time behavior of Service Instances! How the research community is trying to fill this gap? Using a declarative approach. Service Instance 1 n Service all implementing … the same interface (i. e. t. Model) Service Provider 1 Service Provider n
Web Services Technologies Relationships Monitoring in order to discover “best” Web Services Discovery Integration of Qo. S declarations in the discovery process Monitoring Qo. S Monitoring in order to “certificate” the declared Qo. S Monitoring in order to maintain the declared Qo. S
When ? Discovery Monitoring Service Requestors: –do not intend to deal with of Qo. S aspects Service Providers: –are not interested in building up a SW/HW required infrastructure Qo. S –are interested in avoiding providing services of “bad” quality
Main goal of the framework UDDI/WS Client 3 1 2 Web Service Instance 1 Web Server 1 Enhanced UDDI Registry still expose a standard UDDI Interface! Enhanced UDDI Registry CV 1 … CVn Web Service Instance n Web Server n
Roadmap First phase: a basic scenario • One Service Registry • Small set of Web Service Instances Second phase: more complex (and realistic) scenario • Several Service Registry • Large set of Web Services Instances • Authentication/Security • UDDI API extension … …
Basic Scenario: introducing monitoring Agent Enhanced UDDI Registry Web Service Instance 1 Web Service Instance n Enhanced UDDI Monitoring Agent 1 Enhanced UDDI Monitoring Agent n Web Server 1 … Web Server n … Vi-1=(x 1, . . xm) Vi+1=(x 1, . . xm) …
Enhanced UDDI Registry Architecture UDDI Registry Points of Access Evaluator UDDI Client Request Catcher Enhanced UDDI Registry Enhanced UDDI Monitor Agent 1 UDDI Extension Manager Statistics Archive Agent Manager … Enhanced UDDI Monitor Agent n
Basic Scenario: Discovery Operation “Give me addresses associated to this t. Model” UDDI/WS Client UDDI Registry Unordered list of addresses “Give me addresses associated to this t. Model” Enhanced UDDI Registry Ordered list of addresses • In order to fully exploit the advantages derived by the ordered list is it necessary to modify existing clients? No, if clients adopt the Invocation Pattern suggested by UDDI Technical Committee.
Basic Scenario: Publishing Operation Enhanced UDDI Registry 1 4 2 3 Web Service Instance i Enhanced UDDI Monitor Agent i Web Server Service Administrator 5
Prototype implementation details • Enhanced UDDI Monitoring Agent – Handlers for the AXIS Soap Engine – Monitored parameters: • Availability • Time of Completation • Throughtput • Enhanced UDDI Registry – JUDDI: an opensource Java implementation of the UDDI Specification
Concluding remarks • Presentation of a framework for the association of a dynamic convenience value to Web Service Instances implementing a “best effort” approach • More details in: M. Bianchi, C. Gaibisso, G. Gambosi, F. Lombardi “A Framework for the Smart Dynamic Selection of Web Service Access Points” Submitted to International Conference (ECOWS 04)
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