REST API changes

Previous versions of Elasticsearch ignored unrecognized URL query string parameters. This means that extraneous parameters or parameters containing typographical errors would be silently accepted by Elasticsearch. This is dangerous from an end-user perspective because it means a submitted request will silently execute not as intended. This leniency has been removed and Elasticsearch will now fail any request that contains unrecognized query string parameters.

When specifying an _id value longer than 512 bytes, the request will be rejected.

The deprecated /_optimize endpoint has been removed. The /_forcemerge endpoint should be used in lieu of optimize.

The GET HTTP verb for /_forcemerge is no longer supported, please use the POST HTTP verb.

It used to be possible to create an index by either calling PUT index_name or POST index_name. Only the former is now supported.

The endpoint for checking whether a type exists has been changed from {index}/{type} to {index}/_mapping/{type} in order to prepare for the removal of types when HEAD {index}/{id} will be used to check whether a document exists in an index. The old endpoint will keep working until 6.0.

The mem section contained only the total value, which was actually the memory available throughout all nodes in the cluster. The section contains now total, free, used, used_percent and free_percent.

The client, master_only, data_only and master_data fields have been removed in favor of master, data, ingest and coordinating_only. A node can contribute to multiple counts as it can have multiple roles. Every node is implicitly a coordinating node, so whenever a node has no explicit roles, it will be counted as coordinating only.

We now store allocation id’s of shards in the cluster state and use that to select primary shards instead of the version information.

Node roles are now returned in a specific section, called roles, as part of nodes stats and nodes info response. The new section is an array that holds all the different roles that each node fulfills. In case the array is returned empty, that means that the node is a coordinating only node.

Previously, JSON documents were allowed with unquoted field names, which isn’t strictly JSON and broke some Elasticsearch clients. If documents were already indexed with unquoted fields in a previous version of Elasticsearch, some operations may throw errors. To accompany this, a commented out JVM option has been added to the jvm.options file: -Delasticsearch.json.allow_unquoted_field_names.

Note that this option is provided solely for migration purposes and will be removed in Elasticsearch 6.0.0.

The filters and char_filters parameters have been renamed filter and char_filter. The token_filters parameter has been removed. Use filter instead.

The DELETE /_query endpoint provided by the Delete-By-Query plugin has been removed and replaced by the Delete By Query API.

The PUT /_scripts/{lang}/{id}/_create endpoint that previously allowed to create indexed scripts has been removed. Indexed scripts have been replaced by stored scripts.

The PUT /_search/template/{id}/_create endpoint that previously allowed to create indexed template has been removed. Indexed templates have been replaced by Pre-registered templates.

Some REST endpoints (e.g., cluster update index settings) supported detecting content in the Java properties format (line-delimited key=value pairs). This support has been removed.

The wait_for_relocating_shards parameter that used to take a number is now simply a boolean flag wait_for_no_relocating_shards, which if set to true, means the request will wait (up until the configured timeout) for the cluster to have no shard relocations before returning. Defaults to false, which means the operation will not wait.