1. A. Cavalli - F. Semeria INFN Experience With Globus GIS 1 A. Cavalli - F. Semeria INFN First INFN Grid Workshop Catania, 9-11 April 2001 INFN Experience With Globus GIS

2. A. Cavalli - F. Semeria INFN Experience With Globus GIS 2 Introduction › In a distributed environment like a Grid, one of the primary needs is to collect and retrieve resource information. › Whithin the Globus model the Grid Information Service (GIS) is the way of making information available to Grid application.

3. A. Cavalli - F. Semeria INFN Experience With Globus GIS 3 The Globus GIS › Based on LDAP directory services. › A directory is similar to a database, but specialized in hierarchical information storage/retrieval.

4. A. Cavalli - F. Semeria INFN Experience With Globus GIS 4 Why LDAP? › PROs:  it is a standard way to describe and collect data.  it provides a distributed topological model for the data. › CONs:  directories are designed more for reading than for writing. Good for a DNS, but not for storing dynamic data like the CPU load of a machine.

5. A. Cavalli - F. Semeria INFN Experience With Globus GIS 5 Data & Schema Design › Define useful data to publish on GIS. › Manage in different ways dynamic & static data. › Take advantage of flexibility of LDAP objectclasses’ schema. › Complete the description of resources in Globus schema.

6. A. Cavalli - F. Semeria INFN Experience With Globus GIS 6 GIS=GRIS+GIIS Globus 1.1.3 implements the GIS by using two kinds of LDAP servers:  GRIS (Grid Resource Information Service) runs on each resource (machine). Its LDAP uses a shell backend to gather the resource configuration and status. It registers itself to a GIIS providing info about itself.  GIIS (Grid Index Information Service): LDAP server that runs on an organizational server that collects and caches information provided by GRIS’s registered under it.

7. A. Cavalli - F. Semeria INFN Experience With Globus GIS 7 Registration & Data Collecting › GRIS & GIIS send a registration (LDAP) to their upper Index Server every 5 mins. › When queried, a GIIS: scans regs kicks expired ones collect data from registered resources returns collected & valid cached data

8. A. Cavalli - F. Semeria INFN Experience With Globus GIS 8 Caching › Information are pulled by higher level GIISes from lower GIIS/GRIS resources upon a request. › Information are stored in cache for a period of time (TTL=Time To Live). › Higher the level of GIIS higher the TTL, lower the details. › Access control needed to let store only static data on higher levels.

9. A. Cavalli - F. Semeria INFN Experience With Globus GIS 9

10. 10 Extending the GRIS › The GRIS uses programs called information providers to collect information from the machine. › The requirements for an information provider are:  the program must emit LDIF objects to stdout  the object generated must respect the GLOBUS schema

11. A. Cavalli - F. Semeria INFN Experience With Globus GIS 11 Resource Discovery (proposal) 1. Top Level: get possible candidates using static data. 2. Mid Level: narrow the search on local Index Servers. 3. Resource Level: finalize the search using data available only at this level.

12. A. Cavalli - F. Semeria INFN Experience With Globus GIS 12 Performance › In the worst case the whole set of machines must be queried. › Some indexing techniques should be used to implement search space pruning (currently the GIIS backend always fetches data for every registered host). › Also a periodic information update mechanism can be investigated.

13. A. Cavalli - F. Semeria INFN Experience With Globus GIS 13 Fault Tolerance › Replication of Index Servers data must be implemented (for now at the root level with Netscape LDAP server). › Replica servers could be available through a DNS based mechanism.

14. A. Cavalli - F. Semeria INFN Experience With Globus GIS 14 Security and access policies › In the current implementation any machine can register itself to a GIIS › No access control when searching the GIIS. From any ldap client I can: ldapsearch –h mds.infn.it –p 389 –s sub –b “o=grid” “objectclass=*” and get all the information from the GIIS

15. A. Cavalli - F. Semeria INFN Experience With Globus GIS 15 INFN implementation › INFN has implemented a hierarchical structure of GIIS based on INFN departments (about 25). › Each GRIS registers itself to the site GIIS which in turn registers itself to the top level INFN GIIS.

16. A. Cavalli - F. Semeria INFN Experience With Globus GIS 16 Top level GIIS dc=infn,dc=it,o=grid GIIS Milano GRIS dc=mi,dc=infn,dc=it,o=grid GIIS Bologna GRIS dc=bo,dc=infn,dc=it,o=grid

17. A. Cavalli - F. Semeria INFN Experience With Globus GIS 17 MDS Browser http://bond.cnaf.infn.it/ cgi-bin/mdsbrowse1.pl

18. A. Cavalli - F. Semeria INFN Experience With Globus GIS 18 Experiments resources › Each GRIS can register itself to different GIIS’s. › This allows repartitioning of resources by experiment.

19. A. Cavalli - F. Semeria INFN Experience With Globus GIS 19 INFN GIIS “dc=infn, dc=it, o=Grid” MILANO GIIS “dc=mi, dc=infn…” BOLOGNA GIIS “dc=bo, dc=infn…” INFN CMS EXPERIMENT GIIS “dc=infn, dc=it, ou=cms, o=Grid” GRIS CERN CERN CMS EXPERIMENT GIIS “ou=cms, o=Grid” Experiment resources: topology

20. A. Cavalli - F. Semeria INFN Experience With Globus GIS 20 Some tests › We have tested the performance dependency from caching and cpu load. › Test have been made on WAN. › The same queries on a GIIS take: ~ 1 sec. when cache is on ~ 10 sec. or more when expired.

21. A. Cavalli - F. Semeria INFN Experience With Globus GIS 21 Some tests (2) › When a GRIS has a loaded CPU the response time from its own GIIS is much longer when the cache is expired (> 1 min. vs 1 sec.) › Also when a GIIS has a loaded CPU and the cache is not expired the response time is longer (6-7 sec.): it happens with GIIS also used for computation…

22. A. Cavalli - F. Semeria INFN Experience With Globus GIS 22 Some tests (3) We have also compared the Globus MDS with the OpenLDAP/LDBM server: with the same set of data, LDAP/LDBM response times are slower.

23. A. Cavalli - F. Semeria INFN Experience With Globus GIS 23 Conclusions › The Globus Information Service is based on a standard protocol (LDAP). › It provides flexibility and a potentially good distributed data model. › But...

24. A. Cavalli - F. Semeria INFN Experience With Globus GIS 24 Improvements & further studies have to be done mainly: › Performance: more efficient backend push/pull model › Security: authentication & ACLs › Data: more resource attributes & data typing › Topology: more flexible than the current hierarchical-geographical one