Solr, from the Apache Lucene project is an open source enterprise search platform which is written in Java. Its main features include hit highlighting, full-text search, faceted search, dynamic clustering, real-time indexing, database integration, rich document (e.g., Word, PDF) handling and NoSQLfeatures, providing index replication and distributed search. Solr is fault tolerant and highly scalable .No doubt it is the most popular enterprise search engine.
Solr runs as a standalone full-text search server within a servlet container like Jetty or Apache Tomcat and is written in Java. Solr employs the Lucene Java search library at its core for full-text indexing and search, and has JSON APIs and REST-like HTTP/XML which make it usable from most popular programming languages. The powerful external configuration of Solr enables it to be tailored to a number of applications without Java coding types and it has a plugin architecture for supporting more advanced customization.
Apache Solr and Apache Lucene are produced by the same Apache Software Foundation development team as the two projects were merged in 2010. Referring to the technology or products as Solr/Lucene or Lucene/Solr is common.
Solr was created in 2004 at CNET Networks by Yonik Seeley as an in-house project for adding search capability for the company website. Its main features are : Faceted navigation; Query language supports structured and textual search; Hit highlighting; Schema REST API and Schema-less mode; XML, JSON , PHP, Python, Ruby XSLT and custom Java binary output formats over HTTP; Replication to other Solr servers which enables scaling QPS and High availability; HTML administration interface; Search results clustering based on Carrot2; Distributed Search through Shading which allows scaling content volume; Caching -filters, queries and documents; Extensible through plugins; Embeddable in a Java Application; Geo-spatial search which includes multiple points per polygons and documents; Automated large clusters management through ZooKeeper; Field grouping and Collapsing; Auto-suggest.