1. Information Services Claudio Cherubino INFN Catania Bologna
2-3 March 2006

2. 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
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3. Design of Information Systems
About Measures
Measures SHOULD be sensitive to the aim the users want to achieve.
Measures SHOULD be enough accurate to be considered valid.
Rate of taking measures MUST be adequate to be used.
About the gathering of Information
How and when collected info should be published?
Where should collected info be stored?
How long should this info be maintained in the storage?
Querying the Information System
Where should queries be sent to have a response?
What syntax and protocols have to be adopted to make queries?
What is the adopted data model to describe resources?
Security
Who is allowed to execute queries against the IS and what type of queries is he allowed to do?
Management of user rights and credentials.
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4. Adopted Information Systems
The BDII (Berkley DB Information Index)
has been adopted in LCG middleware as the Information System provider.
It is an evolution of the Globus Meta Directory System (MDS)
LCG-2 actually adopts BDII as Information System.
It is based on Lightweight Directory Access Protocol (LDAP) servers.
The Relational Grid Monitoring Architecture (R-GMA)
Is an implementation of the Grid Monitoring Architecture (GMA) standardized by the Global Grid Forum (GGF)
It is a relational implementation of the GMA
It is strongly Web Services Oriented
It will be adopted by next releases of the gLite middleware
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5. LCG Information System
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6. LCG Information System
LCG adopts a combination of solutions
Globus MDS
At the lowest level of the information system
To discover and monitor resources and publish information
Grid Information Security (GSI) credentials
Caching
BDII
At the highest level of the system
Because MDS had some troubles in terms of scalability
Used by the Resource Broker for the matchmaking process
Can be configured by each VO
Queries underlying systems periodically (2 minutes)
Hierarchical system
Information is collected on the leaves of a hierarchical tree and travels towards the root
Clients can query the hierarchical tree at every level
The higher the level against which queries are made, the older is the obtained information
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7. Collecting Information
Gathering of information at different levels
Lower level: Grid Resource Information Server (GRIS)
Collects information on the state of a given resource
One GRIS on top of each resource
A set of scripts and sensor that try to extract useful info on the resource
Medium level: Grid Index Information Server (GIIS)
Collects information on resources of a given site
One GIIS for each site
Higher level: BDII
Collects information on resources of a given VO
One BDII for each VO (suggested solution)
Way of collecting info
Pull model (higher level servers periodically query lower level servers)
LDAP query model
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8. Globus MDS (The past) Globus Meta Directory Server (MDS)
It is a hierarchical system
Based on LDAP servers
GRISes are leaves of the tree
GIISes are intermediate nodes of the tree
The user can query the system at every level
The higher the information is in the tree, the older it is
Grid Resource Information Service (GRIS)
One for each Grid Resource (CE or SE)
Collects info on that resource
Static or dynamic info
Adopts techniques to take measures (such as sensors)
Grid Index Information Service (GIIS)
One for each site
Collects info from above GRISes
Caches info according to its validity time
Queries above GRISes or GIISes whether needed
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9. BDII (the present) The Berkley Database Information Index (BDII)
Developed within the context of LCG project
Solves problems of instability of the MDS occurring when the number of sites grows too much
Stays on top of GIIS sites
One for each VO
Centralized system
Three levels of hierarchy
Accessed by the Workload Management System
Way of working
One GRIS for each resource
One GIIS for each site collecting info from below GRIS systems
One BDII for a given VO collecting information from below GIIS systems
Two LDAP servers, one for write access and one for read access
Every two minutes a cron-job runs a script and collects info from a list of GIIS sites
The list of GIIS is placed in the configuration file of the BDII
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10. R-GMA (the future) The Relational Grid Monitoring Architecture (R-GMA)
It is the relational implementation of GMA defined by the GGF
Adopts a database model with tables and relations between tables
Implements a virtual database
The user queries the R-GMA as he/she was querying to a classical database (SQL string)
Implements different type of queries
The information
Produced and accessed locally to its site
Always new
Can be collected by an entity (secondary producer) to be accessed faster
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11. GLUE Schema
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12. GLUE Schema Grid Laboratory Uniform Environment (GLUE) Schema
It is a data model to describe in a meaningful way information on grid resources (static and dynamic info)
As result of a collaboration between the EU-DataTAG and iVDGL projects
EGEE, NorduGrid, LCG and Grid3/OSG contributed to the definition of the schema
XML Schema
Now, GLUE Schema is being mapped to an XML representation
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13. Site Element
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14. Cluster Element
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15. Computing Element
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16. References LCG-2 User Guide R-GMA overview page. GLUE Schema
R-GMA overview page.
GLUE Schema
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17. Questions…
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