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DIDA, a Distributed Discovery Architecture for Grid Environments

DIDA, a Distributed Discovery Architecture for Grid Environments. Carlos de Alfonso Miguel Caballer Vicente Hernández Universidad Politécnica de Valencia. Index. Index Background eGovernment framework Administration features The citizen in the administration Grid Technology

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DIDA, a Distributed Discovery Architecture for Grid Environments

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  1. DIDA, a Distributed Discovery Architecture for Grid Environments Carlos de Alfonso Miguel Caballer Vicente Hernández Universidad Politécnica de Valencia

  2. Index • Index • Background • eGovernment framework • Administration features • The citizen in the administration • Grid Technology • gCitizen project • Discovery Architecture • Service Naming • Service Discovery • Service Discovery in GT4 • Design of a Service Discovery System • DIDA • DIDA Architecture • Distributed Discovery Services • FADA Topology

  3. Background • Administration • Organized in different units and levels • State • Region • Local • … • Different specialised unit in each level. • Despite its heterogeneity the citizen should have a unique vision. • Should not have to know the internal operation complexity • Simple and effective interaction

  4. Background • The Citizen in the Administration • Citizen is the aggregation of information belonging to the administrative units. • This data dispersion produces some problems: • Not consolidated data • Different names for semantically equal data • etc.

  5. Background • Features of the information in the Administration • Geographically distributed • Different units located in different places. • Security • Only some people is allowed to read or modify the data. • Privacy • The information must be protected on access and transmission. • Ubiquitous access • Despite the geographical distributionthe access must be granted. • Interoperability • Among systems, for enabling the collaboration. • Scalability • The system must enable the addition of new components efficiently.

  6. Grid Technology • Grid Technology Provides some of the required features • Security, Transparency, Ubiquitous access, Scalability, … • GT4 implementation of the WSRF standard selected • Not all the needed functionality is provided • The service oriented programming model enables to develop some services over the middleware. • Log System • Service Discovery System • Distributed Authorisation • …

  7. gCitizen Project • Creation of a grid middleware for eGovernment. • Flexible and scalable prototype of a “grid citizen” • System integration project using grid technology. • Not invasive for the current systems.

  8. Discovery Architecture • Main issue: Discover services • System visibility • Any service should be “searchable” • Connectivity failure detection • Components • Service Naming • Identify the services in the system • Discovery System • Find the services using the naming defined

  9. Service Naming • WSRF uses URI as service identifier • Location dependent. • Redundancy • Not transparent • Changing the location of service implies a identifier change. • Not enable Mobility • Needed Features • Location independent • Show the hierarchy of the administration • Levels • Departments

  10. Service Naming • Design of a Service Naming system based on DNs • DNs are used to identify users and host in grid environments • Location independent • Service Mobility • A service can change its location maintaining the DN • Transparent Redundancy • Different physical services can have the same DN • Represented as a Resource Property • The hierarchy of the DN will place the service inside the context of the gCitizen system.

  11. Service Naming • Schema proposed: • Country Name (C) • Region Name (A) • State or Province Name (ST) • Locality (L) • Organization Name (O) • Organizational Unit Name (OU) * • Common Name (CN) • Example /C=ES/A=C. Valenciana/ST=Valencia/L=Valencia/O=Ayto. Valencia/OU=Informática/CN=Padrón

  12. Service Discovery in GT4 • Based on the use of Index Services • Services deployed that enable to index other services • Search by means of Resource Properties • Published in XML • Using XPath • Hierarchical structure • All the information only accessible on top level IS. • Not ubiquitous access • Central point of failure

  13. Design of a Service Discovery System • Objectives • Completely Distributed • Not use a central point of information • Ubiquitous access • Enable to access the information from different points. • Transparency • All the possible complexity of the system must be hided to the user. • Scalability • Enable to add components to the system easily • Fault tolerance • The failure of one component must not affect the whole system. • Detection of the failure of one component

  14. Distributed Discovery Architecture • Built up on the Globus Toolkit 4 Index Services • Services are indexed in the ISs • Every entity will have an IS • Use XPath as query language • Link the ISs to create a vision of a unique “Virtual Server” • Avoiding cascade node organizations

  15. DIDA Architecture • Use FADA to create the view of a virtual server. • Distributed directory of services • The ISs are registered into a set of FADA nodes. • FADA nodes distributed across the system. • Each FADA node know about its neighbours. • Fault tolerance

  16. FADA Network Topology • The FADA topology is “Scale-Free network” • Few highly connected hubs • Affect the whole system • Many nodes with few connections • Not affect whole system • Proposed a 2-Regular topology • 2 kind of links • Strong: create the 2-Regular graph. • FADA node know 2 neighbours • Weak: some additional links. • If one node fails the connectivity of the system is assured. • The fault of one component is detected

  17. Distributed Discovery Services • Entry points to the discovery system • Every entity has to deploy the DDS. • Ubiquitous access • All the users of the entity must know the location. • Implemented as WSRF services • Uses XPath as query language • Knows some FADA nodes • Transparency • The client query the service and get the results.

  18. Client DDS FADA Node 1 FADA Node n GT4 Node 1 GT4 Node m Service Search Request IndexServers Search Request Search for Registered IndexServers Search for Registered IndexServers Lost of Registered IndexServers Lost of Registered IndexServers in FADA network XPath Query Result Query XPath Query Result Query Send Results Distributed Discovery Services • UML Interaction Diagram of DDS

  19. Conclusions • eGovernment • New field for grid technology. • Grid as integration information system. • Used GT4 as WSRF implementation • Provides some interesting features, but have some lacks. • New service naming based on DN • Location independent • Discovery Service • Based on IS of GT4 Discovery Service • Linked using FADA network to create a “virtual server” • Totally distributed without a central point • Use a 2-Regular topology • More topologies must be studied • Cache of neighbour services

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