we are in the process of preparation to upgrade Elasticsearch from version 2.1.1 to version 5.2.2. Our deployment is very simple which consists of only one Elasticsearch instance running on an active-standby cluster. There are no plugins installed. I have a couple of questions related to the upgrade:
- backward compatibility
We know that there is no backward compatibility between major releases of Elastic search as Lucene is changing the underlying data. What is the best practice to mitigate this issue in the case of a roll back?
- data migration or reindexing
Is my understanding correct that the upgrade from version 2.X to 5.X would be supported and the 5.X version would be able to read data from 2.X?
- configuration changes
I did not found any information regarding the configuration changes between Elasticsearch version 2.X and 5.X. Are there any changes needed prior to migration?
- environment changes
We run current 2.X with Java version jdk1.7.0_131, is it supported to run 5.X on the same version of Java ?