Since its roots in the first Drupal 5 branch, the Apache Solr Search Integration module has had baked deep into its architecture the principle that it needs to support running searches and retrieving facets across multiple Drupal sites. One of our motivating use cases was our own home on the web, drupal.org.

With the reworking of the module in Drupal 7.x-1.x to support Facet API and entity indexing and the backport of those API changes to 6.x-3.x, we now have a solution that allows you to build a unified search that can access content across multiple Drupal 6 and Drupal 7 sites.

This session will cover the key principles behind the multi-site implementation, including a look at what search facets are different and why, meta data that's shared across sites, and how the Apache Solr Access module behaves in the context of multi-site content and its integration with the node access system.

Sites like *.drupal.org and *.acquia.com will be used as case studies to show how the modules work in practice.