Unsupported methods on REST endpoints should respond with status code 405

[jasontedor]

Today, if a request is executed against an endpoint with a method in the request line that that endpoint does not support, Elasticsearch responds with a response like:

{
  "error" : {
    "root_cause" : [ {
      "type" : "illegal_argument_exception",
      "reason" : "No feature for name [_forcemerge]"
    } ],
    "type" : "illegal_argument_exception",
    "reason" : "No feature for name [_forcemerge]"
  },
  "status" : 400
}

This is confusing for users*, semantically wrong, and contrary to the HTTP spec. Instead, Elasticsearch should respond with HTTP status code 405 (Method Not Allowed) and include in the Allow header a list of methods that the endpoint does support.

*: Googling "no feature for name elasticsearch" just leads to pages describing issues when an index is missing.

[dakrone]

+1

[nik9000]

+1

[jbertouch]

@jasontedor Made a start on this, but it still needs unit tests. Are there existing http endpoint exception/http status code tests where new tests could be included? Had a quick look and couldn't find an appropriate home for them.

Also noticed that the RestController#executeHandler didn't have a complete implementation of the http OPTIONS method, so I cleaned it up. The prior code just returned 200 OK for all requests, and didn't included allowed methods for the endpoint as recommended in the spec.

[dakrone]

Are there existing http endpoint exception/http status code tests where new tests could be included? Had a quick look and couldn't find an appropriate home for them.

Usually this would go into the YAML REST tests, but for a special case like this you need a bit more powerful matching than that provides, so probably a test subclassing ESSingleNodeTestCase that uses java.net.URLConnection would work?

[jbertouch]

Thanks @dakrone