Update elastic search to the latest version
We are currently using Elastic Search with java bindings in 1.4.5 (PR for update to 1.7.6 is out). But currently the lastest version is 5.2 and they recommend REST bindings now.
It seems current opencast-elasticsearch integration is done using a java library/class, instead of REST API, which is the recommended way.
Furthermore, this implies our own maintenance and a harder to deploy an elasticsearch cluster.
We could locate (in source) where the embebed elastic is created, configured and deployed, and where indexes are uses, in order to change those to use a separate instance and his API.
IMHO the first easy step could be setting a separate "elasticsearch.url" property to reference the bundled ES instance.
Once done, migrating to a newer ES version or using an external instance would be another problem, and we could start dealing with it...otherwise it's a blocking item to clusterize admin.