1. gLite Information System overview
Africa Joint EUMEDGRID-Support/EPIKH School for Application Porting
Elisa Ingrà – Consortium GARR
Algiers, 4-16 July 2010

2. Outline
Motivation / Introduction Background GLUE Schema LDAP MDS Architecture Monitoring Information system in practice lcg-infosites lcg-info

3. Introduction

4. The power Grid paradigm
wind
coal
Electric
Power Grid
System
Users can access electrical power coming from different (and heterogeneous) sources
nuclear
hydroelectric

5. The computing Grid approach
System
Users can access storage and computing resources coming from different (and heterogeneous) sources
The resources shared within the Grid can be physical objects (CPUs, storage devices) or logical resources (computing queues, distributed file systems)

6. Information System What is? Why? How?
System to collect information on the state of resources
Why?
To discover resources of the grid and their nature
To have useful data in order to who is in charge of managing the workload to do it more efficiently.
To check for health status of resources.
How?
Monitoring state of resources locally and publishing fresh data on the information system.
Adopting a data model that MUST be well known to all components that want to access monitored information
Using different approaches that we are going to investigate in the next slides

7. The Info. system scope Discover new added resources
Make available updated information about the resources
Monitor resources load and status
How does it work?
Collecting information from the resources and publishing fresh data periodically.
Adopting a data model that MUST be well known to all Grid components.

8. How it is used and by whom?
Users
Retrieve information about resources:
Where can I run my job?
Where can I copy my files?
Which software packages are available on a given CE?
Site managers
Publish information about the resources and services they provide
Middleware
WMS: matching job requirements and allocating the resources
Monitoring Services: retrieving information about the status and availability of resources.

9. GLUE Schema LDAP MDS Architecture
Background
GLUE Schema LDAP MDS Architecture

10. GLUE Schema - Overview
Stands for “Grid Laboratory Uniform Environment”
Provides a standardized description of a Grid computing system
It is not tied to any particular implementation
The Grid components are represented as objects which have attributes and relations to other objects

11. GLUE Schema – Why we need it?
The Grid is a paradigm of distributed computing that enables the coordination of resources and services not subject to centralized control. These resources are geographically dispersed, span multiple trust domains and are heterogeneous.
Resources can be dynamically contributed by different owner institutions, so a precise and shared description of resources among information consumers and resource providers is necessary.
This description should also be common to different Grid infrastructures in order to contribute to the interoperability among them.

12. GLUE Schema – Core entities

13. GLUE Schema – Site properties
Site entity – Properties:
Property
Type
Description
UniqueID
string
Unique Identifier of the Site
Name
Human-readable name
Short description of this site
Contact
The main contact for the site. Syntax rule: "mailto:" followed by a list of addresses separated by a comma
UserSupportContact
addresses of the support service
SysAdminContact
addresses of the system administrator
SecurityContact
addresses of the security manager
Location
Geographical location of this site (e.g., city, state, country)
Latitude
real32
The position of a place north or south of the equator measured from -90º to 90º, with positive values going north and negative values going south
Longitude
The position of a place east or west of Greenwich, England measured from -180º to 180º with positive values going east and negative values going west
Web
uri
The URI identifying a web page with more information about this site
Sponsor
VO sponsoring the site; the syntax should allow the expression of the percentage of sponsorship
OtherInfo
This attribute is to be used to publish info that does not fit in any other attribute of the site entity

14. GLUE Schema – Service properties
Service entity – Properties:
Property
Type
Description
UniqueID
string
Unique Identifier of this service
Name
Human-friendly name
serviceType_t
The service type
Version
Version of the service: <major version number>.<minor version number>.<patch version number>
Endpoint
uri
Network endpoint for this service
Status
serviceStatus_t
Status of the service. String enumeration: OK, Warning, Critical, Unknown, Other
StatusInfo
Textual explanation for the status of the service
WSDL
URI of the WSDL describing the service
Semantics
URL of detailed description
StartTime
dateTime_xs_t
The timestamp related to last start time of this service
Owner
Owner of the service
AccessControlBase.Rule
ACL_t
Authorization rule for this entity

15. GLUE Schema – Cluster entity

16. GLUE Schema – CE entity

17. LDAP - Overview Stands for “Lightweight Directory Access Protocol”
It is a protocol that defines the method by which directory data is accessed
Optimized for reading, browsing and searching information (‘write-once-read-many-times’ service)
Data is represented as a hierarchy of objects (entities) forming a tree structure
Data Information Tree (DIT)

18. LDAP – Data Information Tree
Attribute Type String representation
Distinguished Name (DN)
Unique name (path) that unambiguously identifies a single entry
dc=grid (root of the DIT)
Attribute Type
String
domainComponent DC
CountryName C
OrganizationName O
OrganizationUnitName OU
CommonName CN
c= Brazil c=Italy c=Spain
o=INFN
ou=Catania ou=Roma
cn=Elisa Ingra
cn=Elisa Ingra,ou=Catania,o=INFN,c=Italy,dc=grid

19. LDAP – Data Information Tree
The tree hierarchy is described by textual files following the LDIF format (LDAP Data Interchange Files)
dn: dc=example,dc=root
dc: example
description: My company
objectClass: dcObject
objectClass: organization
o: Example, Inc.
## FIRST Level hierarchy - people
# this is an ENTRY sequence and is preceded by a BLANK line
dn: ou=people, dc=example,dc=root
ou: people
description: All people in organisation
objectClass: organizationalUnit
## SECOND Level hierarchy - people entries
dn: cn=Joe Schmo,ou=people,dc=example,dc=root
objectclass: inetOrgPerson
cn: Joe Schmo
sn: Schmo
uid: jschmo
mail:
ou: sales

20. LDAP – Referrals
An individual LDAP server might not store the entire DIT
Servers need to be linked together in order to form a distributed directory that contains the whole DIT
All client requests start at the global directory LDAP 1
LDAP 1 server
LDAP 2 server
LDAP 3 server
c=USA,dc=example
o=IBM,c=USA,dc=example
dc=example
referral
c= USA
o=CISCO o=IBM
ou=IT ou=Web
referral

21. MDS
gLite adopts the Globus Monitoring and Discovery Service (MDS) architecture as its Information System
It implements the GLUE Schema using OpenLDAP
Grid Resource Information Server (GRIS)
LDAP server at Grid Elements level
Local CEs and SEs run an Information Provider software, which collects info about the resource
Grid Index Information Server (or site BDII) (GIIS)
LDAP server at a site level
each Grid site to collect information by all GRISes present in that site
Berkeley Database Information Index (BDII)
Top level database
Store and publish data gathered from the site
Uses LDAP as protocol and GLUE Schema as data model

22. MDS - Architecture Site level BDII
Grid Index Information Server (GIIS)

23. MDS - Architecture
BDII consists of 2 servers: one contains a ready-only database and the other a write-only database
Every 2 minutes a cron-job runs a script and collects info from lower-level servers (GIIS)
Once updated, the 2 servers change roles

24. LDAP browser showing BDII info

25. lcg-infosites
In this section, two higher level tools will be presented: lcg-infosites and lcg-info. These tools should be enough for most common user needs and will usually avoid the necessity of raw LDAP queries.
The lcg-infosites command is actually just a perl script wrapping a series of LDAP commands and was developed to allow users to retrieve information on Grid resources for the most common cases

26. Praticals: lcg-infosites
USAGE: lcg-infosites --vo options -v --is
-h/--help: help option
--vo: VO name (mandatory)
--is: it's possible to specify a not default Top BDII
Some options:
se: The names of the SEs supported by the user's VO
ce: The information relative to number of CPUs, running jobs,etc.
rb: Names of the Rbs available for each VO
sitenames: Names of the LCG sites
tag: The names of the tags relative to the software installed in site is printed together with the corresponding CE
closeSE: The names of the CEs where the user's VO is allowed to run together with their corresponding closest SEs are provided

27. lcg-info
The lcg-info command can be used to list either CEs or the SEs that satisfy a given set of conditions on their attributes, and to print, for each of them, the values of a given set of attributes.
The information is taken from the BDII specified by the LCG GFAL INFOSYS environment variable or in the command line.

28. Praticals: lcg-info -h/--help: to see the help
USAGE: lcg-info [--list-ce | --list-se] [--query ] [--attrs ]
-h/--help: to see the help
–list-attrs: print the list of the possible attributes
--list-ce: lists the CEs which satisfy a query, or all the CEs if no query is given.
--list-se: lists the SEs which satisfy a query, or all the SEs if no query is given.
--bdii: allows to specify a BDII in the form <hostname>:<port>. If not given, the value of the environmental variable LCG_GFAL_INFOSYS is used. If that is not defined, the command returns an error.
--vo: restricts the output to CEs or SEs where the given VO is authorized.

29. References gLite documentation LDAP Concepts & Overview
LDAP Concepts & Overview
OpenLDAP community
GLUE Schema Specification version 1.3 Final
Lilongwe, EELA-2 Workshop,

30. export LCG_GFAL_INFOSYS=wms-01.eumedgrid.eu:2170
HANDS ON
Information System BDII (use eumed instead of gilda)
If will be necessary enter:
export LCG_GFAL_INFOSYS=wms-01.eumedgrid.eu:2170
Lilongwe, EELA-2 Workshop,