Apache Solr vs Carrot2: What are the differences?
What is Apache Solr? An open source search platform. It uses the tools you use to make application building a snap. It is built on the battle-tested Apache Zookeeper, it makes it easy to scale up and down.
What is Carrot2? An Open Source Search Results Clustering Engine. It organizes your search results into topics. With an instant overview of what's available, you will quickly find what you're looking for.
Apache Solr and Carrot2 can be categorized as "Search Engines" tools.
Carrot2 is an open source tool with 377 GitHub stars and 155 GitHub forks. Here's a link to Carrot2's open source repository on GitHub.