Upgrading to Elasticsearch 5.6.x
There are a number of template changes in Elasticsearch 5.6.x, most notably around string type handling, that may cause issues when upgrading.
For Elasticsearch 5.x, the existing indexes and templates need to upgraded. For more
information, see:
If you are upgrading from Elasticsearch 2.x to Elasticsearch 5.6.2, you will need to re-index.
