I am trying to reindex one index to a new index, while indexing on the source index is in progress, with the intention of switching over the application to use the new index. In other words, I want the switch-over to be as transparent as possible to clients of the application. At some point, the application will need to have downtime, to catch the last few objects that have been created, and that is fine, and that is not the question.
Is there anything to consider with regards to reindexing to a new destination index while indexing into the source index? This is in a ES cluster, it's not a single node. We are seeing some missed records and it could be an application problem, but maybe it's an ES issue.