isolated option has been removed. Each plugin will have its own classloader.

Site plugins have been removed. Site plugins should be reimplemented as Kibana plugins.

Multicast has been removed. Use unicast discovery, or one of the cloud discovery plugins.

Plugins implementing custom queries need to implement the fromXContent(QueryParseContext) method in their QueryParser subclass rather than parse. This method will take care of parsing the query from XContent format into an intermediate query representation that can be streamed between the nodes in binary format, effectively the query object used in the java api. Also, the query builder needs to be registered as a NamedWriteable. This is all done by implementing the SearchPlugin interface and overriding the getQueries method. The query object can then transform itself into a lucene query through the new toQuery(QueryShardContext) method, which returns a lucene query to be executed on the data node.

Similarly, plugins implementing custom score functions need to implement the fromXContent(QueryParseContext) method in their ScoreFunctionParser subclass rather than parse. This method will take care of parsing the function from XContent format into an intermediate function representation that can be streamed between the nodes in binary format, effectively the function object used in the java api. The function object can then transform itself into a lucene function through the new toFunction(QueryShardContext) method, which returns a lucene function to be executed on the data node.

Cloud AWS plugin has been split in two plugins:

Proxy settings for both plugins have been renamed:

Cloud Azure plugin has been split in three plugins:

If you were using the cloud-azure plugin for snapshot and restore, you had in elasticsearch.yml:

cloud:
    azure:
        storage:
            account: your_azure_storage_account
            key: your_azure_storage_key

You need to give a unique id to the storage details now as you can define multiple storage accounts:

cloud:
    azure:
        storage:
            my_account:
                account: your_azure_storage_account
                key: your_azure_storage_key

Cloud GCE plugin has been renamed to Discovery GCE plugin.

The Delete-By-Query plugin has been removed in favor of a new Delete By Query API implementation in core. It now supports throttling, retries and cancellation but no longer supports timeouts. Instead use the cancel API to cancel deletes that run too long.

Mapper attachments has been deprecated. Users should use now the ingest-attachment plugin.

Previously, Java system properties could be passed to the plugin command by passing -D style arguments directly to the plugin script. This is no longer permitted and such system properties must be passed via ES_JAVA_OPTS.

The ability to specify a custom plugins path via path.plugins has been removed.

Plugins that register custom scripts should implement ScriptPlugin and remove their onModule(ScriptModule) implementation.

Plugins that register custom analysis components should implement AnalysisPlugin and remove their onModule(AnalysisModule) implementation.

Plugins that register custom mappers should implement MapperPlugin and remove their onModule(IndicesModule) implementation.

Plugins that register custom actions should implement ActionPlugin and remove their onModule(ActionModule) implementation.

Plugins that register custom RestHandler`s should implement `ActionPlugin and remove their onModule(NetworkModule) implemnetation.

Plugins that register custom search time behavior (Query, Suggester, ScoreFunction, FetchSubPhase, Highlighter, etc) should implement SearchPlugin and remove their onModule(SearchModule) implementation.

The SearchParseElement interface has been removed. Custom search request sections can only be provided under the ext element. Plugins can plug in custom parsers for those additional sections by providing a SearchPlugin.SearchExtSpec, which consists of a SearchExtParser implementation that can parse`XContent` into a SearchExtBuilder implementation. The parsing happens now in the coordinating node. The result of parsing is serialized to the data nodes through transport layer together with the rest of the search request and stored in the search context for later retrieval.

ESIntegTestCase#pluginList has been removed. Use Arrays.asList instead. It isn’t needed now that all plugins require Java 1.8.

The metadata field _size is not accessible in aggregations, scripts and when sorting for indices created in 2.x. If these features are needed in your application it is required to reindex the data with Elasticsearch 5.x.