A sunny evening last night for the latest Cambridge Search Meetup, which featured a couple of talks from Datastax on the highly scalable NoSQL database Apache Cassandra and how it is integrated with Apache Lucene/Solr. Jeremy Hanna started us off with a brief history of the Facebook-incubated Cassandra, which is a fully distributed, highly reliable system used by many including Netflix and Spotify with some customers running thousands of nodes in multiple data centres. Cassandra has its own SQL-like language, CQL3 and some basic collections such as Lists and Maps, but due to its fully distributed nature does lack some traditional features such as JOINs. Datastax themselves are now responsible for most of the ongoing work on Cassandra and offer the usual array of training, support, management services and tools. One common application mentioned was high speed and reliable recording of sensor data, increasingly important now with the rise of the Internet of Things.
After a short break for drinks and snacks (which this time were kindly sponsored by Datastax) Sergio Bossa told us how Solr is integrated with Cassandra, also running in a distributed fashion. Interestingly, this integration doesn’t use the same Zookeeper system as SolrCloud (the standard way to run clusters of Solr servers) but relies instead on Cassandra’s own internal scaling systems, passing data about using ‘gossip‘ between nodes. Zookeeper is not always the easiest thing to get running so an alternative is very interesting! Data can be added to the system over HTTP or the aforementioned CQL3 and after being entered into Cassandra’s tables is subsequently indexed by Solr. Queries can then be made over HTTP as usual. Some work is still necessary to prevent duplication of effort (at present one needs to create data structures in Cassandra and subsequently in Solr).
It was pleasing so see that so much care has been taken with this integration process and also that Datastax offer their Datastax Enterprise Search stack not only free for non-production use, but free to startups. Thanks to Jeremy, Sergio and all who came along and we’ll be back with another Search Meetup soon.