BDII Notes

Introduction

The Berkeley Database Information Index (BDII) consists of two or more standard LDAP databases that are populated by an update process. Port forwarding is used to enable one database to serve data while the other is refreshing. The update process obtains LDIF from either doing an ldapsearch on LDAP URLs or by running a local script that generates LDIF. The LDIF is then inserted into the LDAP database. Options exist to update the the list of LDAP URLs from a web page and to use an LDIF file from a web page to modify the data before inserting it into the database. See Laurence Field's EGEE.BDII Page for more background.

It participates in the following

Components

The BDII service consists of

  • A set of LDAP servers
  • A web server providing the sites configuration

Data

Configuration

The BDII is configured from a web based configuration file. This is managed by grid-deployment.web.cern.ch (which is part of the webafs service).

Applications access the BDII using the environment variable LCG_GFAL_INFOSYS.

LCG_GFAL_INFOSYS=lcg-bdii.cern.ch:2170

The BDII consists of two separate services

  • Site BDII accesses the site information sources and presents them as a single directory to the global BDII
  • Global BDII provides a view for applications and users inside and outside CERN of the entire BDII tree.

Within the BDII, there are 3 LDAP servers with a port forwarded bdii-fwd which decides which one should be serving requests. The other LDAPs are in the upgrade cycle but at least one will respond to queries.

High Availability

If the BDII is down,

  • The status of the CERN site is not visible
  • No updates of the current status can be performed
  • No new jobs will be scheduled

If the BDII master is down,

* No site information can be added (new sites, clean old sites)

Each BDII is an independent service for its normal operations which permits a flexible failover using round robin DNS. A metric based on the number of active searches would allow some load balancing.

Edit drawing `HaDrawing1` (requires a Java 1.1 enabled browser) Edit drawing `HaDrawing1fail` (requires a Java 1.1 enabled browser)

In the event of failure of the master, the slave would take over the master functions. The copies will continue to serve data.

Equipment required

Assuming 1 master BDII and 2 round robin DBIIs along with 2 site BDIIs, the hardware required is

Component Number Purpose
Midrange Server 5 Masters and standby machines

Engineering required

Development Purpose
Start/Stop/Status procedure Scripts for operations
WebAFS page availability A sensor to monitor and report on the status of the grid-deployment.web.cern.ch page
Lemon BDII availability test A lemon aware sensor which can be used for reporting availability of the BDII service
Load Balanced Metric for lbclient Develop the BDII LB client metric calculation
Switch procedure Automatic switch from DBII master to slave changing web page, enabling the slave in its new master role
Capacity Metric Capacity metrics defined for
Number of requests/second

Questions

The following items require clarification to design the final solution.

Nr Description Status Open Date Who Log
1 What is the atlas-bdii closed 2005/09/15 Laurence Atlas BDII is a selected version
2 How does the global and site BDII interact closed 2005/09/15 Laurence Site is just CERN data view. Global groups sites together
-- TimBell - 20 Sep 2005
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Topic revision: r11 - 2006-11-28 - LaurenceField
 
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