We have a site that's based on IndexTank, which has since been acquired by LinkedIn, and their service is scheduled to end by April. They recently release their software as open source, but its documentation is thin. https://github.com/linkedin/indextank-engine
I'd like to hear what others who used IndexTank are doing about replacing it, or if anyone is thinking of offering a hosted version of IndexTank open source. If so, there would definitely be a base of past customers ready to sign up.
I'm trying to get it running on a local instance of my site. I'm hoping that works out OK. I'll be testing that out in the next week or so. If that doesn't work, I'm going with Solr. If it does, then I'll go live with that.