`parseEsResponse` cannot parse version conflict error response (OpenSearch 1.3)

[supersven]

Bloodhound version: 76a27a4
OpenSearch version: 1.3.19

Error:

EsProtocolException {
   esProtoExMessage = "Original error was: Non-200 status code Error parse failure was: Error in $: key \"error\" not found"
   , esProtoExResponse = "{\"took\":9,\"timed_out\":false,\"total\":3,\"updated\":1,\"deleted\":0,\"batches\":1,\"version_conflicts\":2,\"noops\":0,\"retries\":{\"bulk\":0,\"search\":0},\"throttled_millis\":0,\"requests_per_second\":-1.0,\"throttled_until_millis\":0,\"failures\":[{\"index\":\"directory_test\",\"type\":\"_doc\",\"id\":\"9fda4188-2afd-490d-8796-e023df61a4e9\",\"cause\":{\"type\":\"version_conflict_engine_exception\",\"reason\":\"[9fda4188-2afd-490d-8796-e023df61a4e9]: version conflict, required seqNo [11], primary term [1]. current document has seqNo [16] and primary term [1]\",\"index\":\"directory_test\",\"shard\":\"0\",\"index_uuid\":\"Y3RpVY_DQEW9ULn8oGulrg\"},\"status\":409},{\"index\":\"directory_test\",\"type\":\"_doc\",\"id\":\"d70b631d-966a-4951-a94c-35ddc210f28a\",\"cause\":{\"type\":\"version_conflict_engine_exception\",\"reason\":\"[d70b631d-966a-4951-a94c-35ddc210f28a]: version conflict, required seqNo [13], primary term [1]. current document has seqNo [15] and primary term [1]\",\"index\":\"directory_test\",\"shard\":\"0\",\"index_uuid\":\"Y3RpVY_DQEW9ULn8oGulrg\"},\"status\":409}]}"
}

[supersven]

To me it looks like the FromJSON EsError instance does not fit to the response.

instance FromJSON EsError where
  parseJSON (Object v) =
    EsError
      <$> v
        .:? "status"
      <*> (v .: "error" <|> (v .: "error" >>= (.: "reason")))
  parseJSON _ = empty

The implementation expects an error or error.reason field, while in the response there's an array (failures) with reasons.

Would it make sense to adjust the FromJSON EsError instance with one more alternative to match the response's structure?

[blackheaven]

Actually, at this point, ElasticSearch and OpenSearch are starting to diverge so much, I'm considering have their error types distinct.

[supersven]

diverge

@blackheaven Thanks a lot for looking into this!

I agree that in future separate types may make sense; especially, because the OpenSearch response carries more information than EsError.

However, I've created a quick-fix in #301 . It adjusts the FromJSON instance to map some information into an EsError.