In the last couple of weeks we've had an issue with web crawlers getting lost in facets, crawling literally millions of URLs in the faceted solr index. This is mainly a problem because some of them get quite expensive in terms of solr search (CPU and memory consumption of the solr component rises).
We've deployed the following fix:
#added to redirect long solr queries back to the homepage
RewriteEngine On
RewriteCond "%{QUERY_STRING}" "filter_3"
RewriteRule .
https://ir.wgtn.ac.nz/ [R]
The "filter_3' means that users and crawlers are allowed two facets deep before being redirected back to the homepage.
We're redirecting to our own homepage; others will probably want to redirect to their own homepages (and/or bot tarpits).
cheers
stuart