WELCOME TO FRONTIER

The Frontier system distributes data from central databases to many clients around the world. The name comes from "N Tier" where N is any number and Tiers are layers of locations of distribution. For Large Hadron Collider (LHC) projects, the central database is located at Tier 0, which distributes data to to all the Tier 1, Tier 2, and Tier 3 sites around the world. Within each site the Frontier system also distributes the data to all the worker nodes (typically hundreds or thousands) that need to read the data. The protocol is http-based and uses a RESTful architecture which is excellent for caching and scales well. The Frontier system uses the standard web caching tool squid to cache the http objects at every site. It is ideal for applications where there are large numbers of widely distributed clients that read basically the same data at close to the same time, in much the same way that popular websites are read by many clients.
The Frontier system was developed for the CDF experiment at Fermilab and is heavily used there. Fermilab also adapted Frontier for the CMS experiment at the LHC at CERN and it is used to access "conditions data" (mainly detector calibrations and alignments) at all its sites worldwide. The ATLAS experiment at the LHC has also adopted Frontier to access conditions data at all its Tier 2 and Tier 3 sites. Even though this web site is hosted at CERN for convenience of the LHC projects, Frontier is maintained by Fermilab.

Source code and other project information for frontier client (implemented in C and C++) and frontier server (implemented as a java tomcat servlet) is freely available as open source, mostly under the Fermilab Fermitools license (a BSD license). Here are instructions for deploying squid for CMS and instructions for deploying squid for ATLAS. Here's a brief introduction to the CMS Frontier architecture.

These are the CMS Offline Frontier monitoring systems:

Overall status
Detailed statistics for central servers (awstats)
Graphed statistics for all worldwide squids (MRTG)
Graphed statistic summaries for major sites and tiers (MRTG)
Service Level Status of CERN central servers (SLS)
Service Level Status of CERN T0 squid servers (SLS)
Availability status at grid sites worldwide (SAM)
(select All Sites and tests CE-cms-frontier and CE-cms-squid and click Show Results)
Experimental detailed plots of CERN central servers: today, yesterday, all
MRTG plots are also accesible through this widget.

This is the CMS Online Frontier monitoring systems (awstats & MRTG)

These are the ATLAS Frontier monitoring systems:

Detailed statistics for central servers (awstats)
Graphed statistics for all worldwide squids (MRTG)
Service Level Status of ATLAS launchpad servers (SLS)
Site status of all worldwide squids (SSB)

For more information about Frontier visit the CMS DatabaseAccess TWiki page.
Here is a paper describing the use of Frontier in CMS , another paper describing its efficient cache consistency strategy , and a third paper describing RESTful protocols for High Energy Physics with Frontier as the main example.
There is an article about Frontier in International Science Grid This Week issue 173 of 5 May 2010.

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