UnexpectedElasticsearchClientException while logging with Nlog.Targets.ElasticSearch

NEST/Elasticsearch.Net version: 7.10.1

Elasticsearch version: 7.10

We get many exceptions in internal Nlog log with this stacktrace

2021-05-18 19:20:28.3081 Error ElasticSearch: Error while sending log messages Exception: Elasticsearch.Net.UnexpectedElasticsearchClientException: Method may only be called on a Type for which Type.IsGenericParameter is true.
 ---> System.InvalidOperationException: Method may only be called on a Type for which Type.IsGenericParameter is true.
   at System.RuntimeType.get_DeclaringMethod()
   at Serialize(Byte[][] , Object[] , JsonWriter& , RuntimeType , IJsonFormatterResolver )
   at Elasticsearch.Net.Utf8Json.Resolvers.DynamicMethodAnonymousFormatter`1.Serialize(JsonWriter& writer, T value, IJsonFormatterResolver formatterResolver)
   at Elasticsearch.Net.Utf8Json.Formatters.DynamicObjectTypeFallbackFormatter.Serialize(JsonWriter& writer, Object value, IJsonFormatterResolver formatterResolver)
   at Elasticsearch.Net.Utf8Json.Formatters.DictionaryFormatterBase`5.Serialize(JsonWriter& writer, TDictionary value, IJsonFormatterResolver formatterResolver)
   at Elasticsearch.Net.Utf8Json.Formatters.DynamicObjectTypeFallbackFormatter.Serialize(JsonWriter& writer, Object value, IJsonFormatterResolver formatterResolver)
   at Elasticsearch.Net.Utf8Json.JsonSerializer.SerializeUnsafe[T](T value, IJsonFormatterResolver resolver)
   at Elasticsearch.Net.Utf8Json.JsonSerializer.Serialize[T](Stream stream, T value, IJsonFormatterResolver resolver)
   at Elasticsearch.Net.LowLevelRequestResponseSerializer.Serialize[T](T data, Stream writableStream, SerializationFormatting formatting)
   at Elasticsearch.Net.DiagnosticsSerializerProxy.Serialize[T](T data, Stream stream, SerializationFormatting formatting)
   at Elasticsearch.Net.PostData`1.Write(Stream writableStream, IConnectionConfigurationValues settings)
   at Elasticsearch.Net.HttpConnection.SetContent(HttpRequestMessage message, RequestData requestData)
   at Elasticsearch.Net.HttpConnection.Request[TResponse](RequestData requestData)
   at Elasticsearch.Net.RequestPipeline.CallElasticsearch[TResponse](RequestData requestData)
   at Elasticsearch.Net.Transport`1.Request[TResponse](HttpMethod method, String path, PostData data, IRequestParameters requestParameters)
   --- End of inner exception stack trace ---
   at Elasticsearch.Net.Transport`1.Request[TResponse](HttpMethod method, String path, PostData data, IRequestParameters requestParameters)
   at Elasticsearch.Net.ElasticLowLevelClient.DoRequest[TResponse](HttpMethod method, String path, PostData data, IRequestParameters requestParameters)
   at Elasticsearch.Net.ElasticLowLevelClient.Bulk[TResponse](PostData body, BulkRequestParameters requestParameters)
   at NLog.Targets.ElasticSearch.ElasticSearchTarget.SendBatch(ICollection`1 logEvents)

Steps to reproduce:

1. Can’t reproduce since this only found on production with high logging volume

Expected behavior Proper client request processing More useful message to identify the cause of the problem

[stevejgordon]

@xumix and @snakefoot - FYI, 7.13.0 just shipped and includes this change.

[snakefoot]

@stevejgordon Thank you very much for adding the extra diagnostic details.