A Framework for the Smart Dynamic Selection of Web

							              Workshop on
 QoS 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.uniroma2.it             gaibisso@iasi.rm.cnr.it


      Marco Bianchi                    Flavio Lombardi
     bianchi@di.univaq.it             lombardi@di.uniroma1.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
                             
                QoS guaranteed approach
 Web Service Architecture Model



                                                                 Service
                                                                Description
                                              Service
                                              Registry




                 Find                                              Publish




                                                                                      Service
                   Service                                                Service
                  Requestor                                               Provider
                                                  Bind                                Service
                                                                                     Description

                                         Static          Dynamic
                                         Bind              Bind
Reference: Web Services Conceptual Architecture (WSCA 1.0) – IBM – 2001
A model for a simple scenario
                                                                        2
                                                       How can the Service Requestor
             1
                                                       choose the most “comfortable”
What happens in the Service
                                        Service        Service Instance?
Registry when a Service
Instance goes down?                    Requestor       Current discovery standards
                                                        (i.e. UDDI) don’t provide any
 Nothing. Current discovery                            non-operational information
 standards (i.e. UDDI)                                 about the run-time behavior
 could contain obsolete                                of Service Instances!
 reference to Services                  Service
                                                       How the research community
 Instances!                             Registry
                                                       is trying to fill this gap?
                                                       Using a declarative approach.



            Service                                           Service
           Instance   1                                      Instance   n




                                          …
                                 Service all implementing
                              the same interface (i.e. tModel)

     Service Provider     1                             Service Provider    n
 Web Services Technologies Relationships

                                         Monitoring in
                                         order to discover
                                         “best” Web
                                         Services
           Discovery           Monitoring




                                            Monitoring in
                                            order to
                                            “certificate”
                                            the declared
Integration of                              QoS
QoS declarations       QoS
in the discovery
process                            Monitoring in order to
                                   maintain the declared
                                   QoS
When ?




         Discovery                       Monitoring




Service Requestors:
   –do not intend to deal with of QoS aspects
Service Providers:
   –are not interested in building up a SW/HW required
   infrastructure
                             QoS
   –are interested in avoiding providing services of “bad” quality
Main goal of the framework



                             UDDI/WS
                              Client
            3
                                    1

                             Enhanced          Enhanced UDDI
                   2           UDDI            Registry still expose
                              Registry         a standard UDDI Interface!



    Web Service                 …                  Web Service
    Instance 1         CV1               CVn       Instance n


    Web Server 1                                   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                     Web Service
    Instance 1                      Instance n

   Enhanced UDDI                  Enhanced UDDI
     Monitoring                     Monitoring
      Agent 1          …             Agent n

    Web Server 1                   Web Server n


                                         …
                                         Vi-1=(x1,..xm)
                                         Vi =(x1,..xm)
                                         Vi+1=(x1,..xm)
                                         …
 Enhanced UDDI Registry Architecture



                    UDDI Registry


                                  Points of Access
                                     Evaluator



UDDI      Request                 UDDI Extension         Statistics
Client    Catcher                   Manager               Archive


                                      Agent
                                     Manager
           Enhanced
         UDDI Registry



                Enhanced UDDI                        Enhanced UDDI
                                          …
                Monitor Agent 1                      Monitor Agent n
Basic Scenario: Discovery Operation


       “Give me addresses associated to this tModel”    UDDI
                                                       Registry

                       Unordered list of addresses
    UDDI/WS
     Client
                                                       Enhanced
                                                         UDDI
      “Give me addresses associated to this tModel”
                                                        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            2          3
                     4


                  Web Service
                   Instance i

                 Enhanced UDDI
                 Monitor Agent i
                                          5

                  Web Server


                            Service
                          Administrator
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 (ECOWS04)