Migrating to 8.5edit

This section discusses the changes that you need to be aware of when migrating your application to Elasticsearch 8.5.

See also What’s new in 8.5 and Release notes.

Coming in 8.5.0.

Breaking changesedit

The following changes in Elasticsearch 8.5 might affect your applications and prevent them from operating normally. Before upgrading to 8.5, review these changes and take the described steps to mitigate the impact.

REST API changesedit

The bulk API now rejects requests containing unrecognized actions

Requests to the bulk API comprise a sequence of items, each of which starts with a JSON object describing the item. This object includes the type of action to perform with the item which should be one of create, update, index, or delete. Earlier versions of Elasticsearch had a bug that caused them to ignore items with an unrecognized type, skipping the next line in the request, but this lenient behaviour meant that there is no way for the client to associate the items in the response with the items in the request, and in some cases it would cause the remainder of the request to be parsed incorrectly.

From version 8.5 onwards, requests to the bulk API must comprise only items with recognized types. Elasticsearch will reject requests containing any items with an unrecognized type with a 400 Bad Request error response.

We consider this change to be a bugfix but list it here as a breaking change since it may affect the behaviour of applications which rely on being able to send unrecognized actions to Elasticsearch.

Ensure your application only sends items with type create, update, index or delete to the bulk API.


The following functionality has been deprecated in Elasticsearch 8.5 and will be removed in a future version. While this won’t have an immediate impact on your applications, we strongly encourage you to take the described steps to update your code after upgrading to 8.5.

To find out if you are using any deprecated functionality, enable deprecation logging.

Plugin API deprecationsedit

Plugins that extend the NetworkPlugin interface are deprecated.


Plugins may override funcionality that controls how nodes connect with other nodes over TCP/IP. These plugins extend the NetworkPlugin interface. In the next major release, these plugins will fail to install.

Discontinue using any plugins which extend NetworkPlugin. You can see if any plugins use deprecated functionality by checking the Elasticsearch deprecation log.

Extending DiscoveryPlugin to override join validators or election strategies is deprecated

Plugins that extend DiscoveryPlugin may override getJoinValidator and getElectionStrategies. These methods are implementation details of the clustering mechanism within Elasticsearch. They should not be overriden. In the next major release, plugins overriding getJoinValidator or getElectionStrategies will fail to install.

Discontinue using any plugins that override getJoinValidator or getElectionStrategies in DiscoveryPlugin. You can see if any plugins use deprecated functionality by checking the Elasticsearch deprecation log.