Invalid JSON request bodies result in 500 response

[pugnascotia]

Elasticsearch version: v7.3.1
OS version: Linux 4.4.0-1098-aws
JVM: OpenJDK 1.8.0_201 / 25.201-b09

Current behaviour:

If I execute a search with an invalid JSON request body, e.g. missing a double-quote:

GET blogs/_search
{"query":{"match":{"title":{"query":"open source software,"minimum_should_match":2}}}}

Then ES rejects the query with a 500, which indicates a server-side problem.

Expected behaviour:

The server should respond with "400 Bad Request", to indicate a client problem.

Impact:

The 500 is problematic because it indicates to clients that they can retry the request, but of course it will always fail. See also #48308, which concerns the Bulk API.

[elasticmachine]

Pinging @elastic/es-core-infra (:Core/Infra/REST API)

[Mpdreamz]

Clients don't retry 500

See: https://www.elastic.co/guide/en/elasticsearch/client/net-api/current/fail-over.html

And

elasticsearch/client/test/src/main/java/org/elasticsearch/client/RestClientTestUtil.java

Line 39 in 237650e

private static List<Integer> ERROR_NO_RETRY_STATUS_CODES = Arrays.asList(400, 401, 403, 404, 405, 500);

Great fix though thanks @pugnascotia !

[jasontedor]

Some clients do, for example, Beats: https://github.com/elastic/beats/blob/ee5a4e73a98fbf63307cd5d7f6cfcf196bb15bd3/libbeat/outputs/elasticsearch/client.go#L522-L524