Parser issue when loading similarity inside a PutIndexTemplateRequest

[garfberg]

Java API client version

8.2

Java version

12

Elasticsearch Version

8.2

Problem description

Hello,

Using the following index template:

PUT /_index_template/test_bm25
{
	"index_patterns" : ["test_bm25*"],
	"template" : {
		"settings": {
   			"index" : {
				"similarity": {
					"my_bm25": {
						"type": "BM25",
						"b": 0.0,
						"k1": 0.0
					}
				}
   			}
		}
	}
}

# PUT /_index_template/test_bm25
{
  "acknowledged" : true
}

GET /_index_template/test_bm25

# GET /_index_template/test_bm25
{
  "index_templates" : [
    {
      "name" : "test_bm25",
      "index_template" : {
        "index_patterns" : [
          "test_bm25*"
        ],
        "template" : {
          "settings" : {
            "index" : {
              "similarity" : {
                "my_bm25" : {
                  "type" : "BM25",
                  "b" : "0.0",
                  "k1" : "0.0"
                }
              }
            }
          }
        },
        "composed_of" : [ ]
      }
    }
  ]
}

The java client fails to parse as it looks like the json parser rules are not correct when defning a custom similarity.
Also tried to load it using withJson() with the same result (which makes sense).
See code below:

import java.io.FileInputStream;
import java.io.Reader;
import java.io.StringReader;

import co.elastic.clients.elasticsearch.indices.PutIndexTemplateRequest;
import co.elastic.clients.elasticsearch.indices.SettingsSimilarity;
import co.elastic.clients.elasticsearch.indices.SettingsSimilarityBm25;

public class ESClientTester {

	public static void main(String[] args) {
		try {
			
			PutIndexTemplateRequest req1 = new PutIndexTemplateRequest.Builder()
			.name("test_bm25")
			.indexPatterns("test_bm25")
			.template(template -> template
				.settings(settings -> settings
					.index(index -> index
						.similarity(similarity -> similarity
							// no custom name here allowed ?
							.bm25(bm25 -> bm25
								.b(0)   // type error: float value shall be allowed
								.k1(0.0)
							)
						)
					)
				)
			)
			.build();
			
			Reader queryJson = new StringReader(
				"{" +
					"\"index_patterns\" : [\"test_bm25\"]," +
					"\"template\" : {" +
						"\"settings\": {" +
					   		"\"index\" : {" +
								"\"similarity\": {" +
									"\"my_bm25\": {" +
										"\"type\": \"BM25\"," +
										"\"b\": 0.0," +
										"\"k1\": 0.0," +
										"\"discount_overlaps\": true" +
									"}" +
								"}" +
							"}" +
						"}" +
					"}" +
				"}"
			);

			PutIndexTemplateRequest req2 = new PutIndexTemplateRequest.Builder()
			.name("test_bm25")
			.withJson(queryJson)
			.build();
			
			System.out.println("ok");

		} catch (Exception ex) {
			ex.printStackTrace();
		}
	}
}

Exception: co.elastic.clients.json.JsonpMappingException: Error deserializing co.elastic.clients.elasticsearch.indices.SettingsSimilarity: Unknown field 'my_bm25' (JSON path: template.settings.index.similarity.my_bm25) (line no=1, column no=97, offset=96)

Best regards,
Alexis Berger

[swallez]

Thanks for reporting this. It's an issue in the API specification used to produce the Java code.

Once the API specification is fixed, the Java client code will be updated to resolve this issue.