Hi, JanusGraph currently supports Thrift and CQL to communicate with Cassandra, but CQL not yet for OLAP jobs executed on Spark [1].
If you're not familiar with JanusGraph: JanusGraph[2] is a scalable graph database that uses different storage and index backends to store the data and support advanced index queries. Cassandra is one of these storage backends (and probably the most used one). So, I wanted to add support for a CQL Hadoop input format for JanusGraph which basically wraps the CQL input format included cassandra-all. Unfortunately, JanusGraph uses version 2.1.20 of that dependency which seems to still rely on Thrift, even for the CQL input format. That of course kind of defeats the purpose of implementing a CQL input format in JanusGraph that doesn't rely on Thrift any more. There were also some problems with the Hadoop input format in that version of cassandra-all and the version of the DataStax Cassandra driver JanusGraph is using. For these reasons, it seems necessary to update the cassandra-all dependency to major version 3 in JanusGraph. This comes with 2 new problems however: 1. There is no Hadoop input format any more for Thrift. It was removed in CASSANDRA-9353 [3]. So, JanusGraph probably has to copy the Thrift code from a pre-3 version of cassandra-all to continue supporting Thrift for some time until we can completely move to CQL. (There are other options, but this seems to be the best one for JanusGraph [4].) 2. The code changed a lot with major version 3 which is understandable of course, considering that the storage engine was largely rewritten. This however breaks a lot of code in the Thrift adapter of JanusGraph which needs to be updated accordingly. Now, why I'm writing all this? I hope that you can confirm whether my assertions / assumptions here are correct and whether this approach actually makes sense or whether you would suggest another way forward. Thanks, Florian [1]: https://github.com/JanusGraph/janusgraph/issues/985 [2]: http://janusgraph.org/ [3]: https://issues.apache.org/jira/browse/CASSANDRA-9353 [4]: https://groups.google.com/forum/#!topic/janusgraph-dev/7IU77lHwptw
