Grid Computing, B. Wilkinson, 2004 6c.1

Globus

III - Information Services

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Resource Discovery

• Critical in a grid to be able to discovery what resources are available and what are the options.

• For compute resources, information can be hardware details and software details, and dynamically changing information such as load.

Grid Computing, B. Wilkinson, 2004 6c.3

Typical Details

• Compute resources:– CPU vendor, type, speed, cache sizes, ...– Memory type, size, speed, ...– Disk space …

• Network resources– Network bandwidth– Latency– Topology– Protocols, ...

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Compute Resource Software Details

• IP address

• Software available

• Operating System version number

• Resource manager, ...

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Static and Dynamic data

• Information is always subject to change and old.

• Some information changes naturally, such as load information.

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Centralized Information System

ClientsResources

Periodically update LDAP server information

Clients query for current information

LDAP Server

“push”

LDAP Lightweight Directory Access Protocol

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Disadvantages

• Does not scale well as number of resources grows

• Commercial LDAP services optimized for read operations, not good with frequent writes.

• System fails if LDAP server down

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Globus Grid Information ServiceMonitoring and Directory Service (MDS)

• Based upon LDAP.

• Originally called “Metacomputing Directory Service” - renamed

• MDS-2 uses a distributed organization.

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MDS-2

Consisting of two types of service:

• Grid Resource Information Service (GRIS)

• Grid Index Information Service (GIIS)

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Grid Resource Information Service (GRIS)

• Associated with each resource.

• Answers queries from client/user about the particular resource.

• Accesses an “information provider” deployed on that resource for requested information.

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Queries

• “White pages”– Resource information

• e.g. How much memory does machine have

• “Yellow” pages– Resource options

• e.g. Which queues allow large jobs.

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Grid Index Information Service (GIIS)

• A directory service that collects (‘pulls”) information for GRIS’s.

• A “caching” service.

• Provides indexing and searching functions.

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Overall StructureClients Resources

GIIS information as needed

Clients query resource GRIS directly for current information

GIIS

“pull”

GRIS

GRISClients makes indirect query to GIIS

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Scaling

• Can have multiple GIIS’s in various configurations

• Configuration can take into account virtual organizations

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Accessing Information

GT3 command:

grid-info-search

with various flags to specify host, port, etc.: -h MDS server

-p MDS port

-b Search start point

-T LDAP query time out

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Examplegrid-info-search -x -h hot.mcs.anl.gov -p 2135 -b

“Mds-Vo-name=local, o=Grid”

Produces:

dn: Mdss-Host-hn=hot.mcs.gove, Mds-Vo-name=local, o=grid

Mds-CPU-speedMhz: 866

Mds-Memory-Ram-Total-freeMB: 304

Mds-CPU-Free-5minX100: 134.

.

From “Grid Computing” by A. Abbas, page 204.

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LDAP Browser/Editor

• Java Commodity Grid (CoG) Kit has a LDAP Browser/Editor

Grid Computing, B. Wilkinson, 2004 6c.18From “Grid Computing” by A. Abbas, page 202.

LDAP Browser/Editor

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Security

• MDS 2.1 has PKI security for GSI mutual authentication

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LDAP Exercise

• Go to Globus subdirectory called ldap

• Follow instructions in README file

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Discovering Grid Services

• MDS, as described, is only for discovery hardware resources, not the actual grid services one might want.

• In a service oriented architecture, services are “published” in a registry so that they can be found.

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2. Find

3. Bind

1. Publish

Service-Oriented Architecture

Service requester

Service registry

Service provider

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UDDI(Universal Description, Discovery, and Integration)

• Web services often use UDDI registries.

• UDDI designed to support business services.

• Information can be classified as:– White pages -- company contact information, ...– Yellow pages -- Web service description– Green pages -- Technical information about Web

Service

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Web Services

From http://www.globus.org

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Accessing Grid Services

• GT 3 provides an “index service” (as a higher level service) to access service data provided with grid service.

• Service data can includes both hardware and software details of service.

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GT3 Index Service

From “Grid Computing” by J. Joseph and C. Fellenstein, page 340.

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Service Data

• Information about service provided in service data elements (SDEs) as part of the GWSDL file.

• The GWSDL file defines service interface (see assignment 2), and SDEs are added to this.

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Types of Service Data Elements

• State Information -- results, previous results, run time information, …

• Service Metadata -- system data, supported interfaces, cost of using service, ...

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Client Accessing Service Data

• Done through grid service methods.

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Changes to Grid service

• Done through “notification” mechanism whereby client subscribes to mechanism and is notified of changes.

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Derived from The Globus Toolkit 3 Programmer’s Tutorial” by Borja Sotomayor, 2004, page 65.

addListenerto subscribe

notifyChangewhen change occurs

deliverNotification to notify subscribers

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More Information

• “The Globus Toolkit 3 Programmer’s Tutorial” by Borja Sotomayor, 2004, Chapter 5 and Chapter 6.

http://www-unix.globus.org/toolkit/

Gives sample code.