Breaking changes in 5.6

Starting from version 5.6.0 a new Java client has been released: the Java High Level REST Client. This official high-level client (named like this to differentiate it from the existing low-level client) for Elasticsearch can be used to execute search, index, delete, update and bulk operations using the same Core Java classes as the TransportClient uses.

This Java High Level REST Client is designed to replace the TransportClient in a near future.

The RPM and Debian packages now set the setgid flag on /etc/elasticsearch so that any files and subdirectories created under /etc/elasticsearch have the same ownership as /etc/elasticsearch (root:elasticsearch). This is used to ensure that files and subdirectories created under /etc/elasticsearch (e.g., a keystore) are readable by the elasticsearch user.

Previously when Elasticsearch was bound to localhost, Elasticsearch would bind to any address on the loopback device. This included link-local addresses on the loopback device such as fe80::1%lo0 on macOS. Starting in 5.6.6, Elasticsearch will now only bind to loopback addresses on the loopback device. Because of the previous behavior, Elasticsearch would skip the bootstrap checks if bound to a link-local address. Now that Elasticsearch no longer binds to such addresses when binding to localhost, the bootstrap checks now apply to link-local addresses.

Previously in Elasticsearch parent documents could be aggregated on or referenced in a script using _parent. Now in order to reference a parent document in an aggregation or script you must do _parent#my_parent as stated in the mapping a parent field documentation.