Not able to get plugin running

[dannylesnik]

Hello.
I followed your documentation, but I was not able to get this plugin running.
I believe I have configuration issue, bu I don't know what exectly.

I have a set of containers in docker swarm which send all data to fluentd container and I would like to grab all logs which tag starts from "ccms_".

I installed pugin in container using gem and I can see in log that actually plugin presents in fluentd.

This is my fluentd.conf file:

<source>
  @type forward
  @log_level debug
  port 24224
  bind 0.0.0.0
</source>
<match ccms_**>
  @type flatten_hash
  add_tag_prefix flattened.
  separator _
  flatten_array false
</match>
<match flattened.ccms_**>
  type "aws-elasticsearch-service"
  @log_level debug
  type_name "access_log"
  logstash_format true
  include_tag_key true
  tag_key "@log_name"
  flush_interval 10
  buffer_chunk_limit 4M
  buffer_queue_limit 256
  <endpoint>
    url https://xxx-ccms-kibana-xxxx.us-east-1.es.amazonaws.com
    region us-east-1
    assume_role_arn arn:aws:iam::xxxxxxxx:role/TMS_Standard_EC2
  </endpoint>
</match>

This is my json log example.

{
  "_index": "logstash-2019.03.21",
  "_type": "access_log",
  "_id": "E6uxn2kBys5QzvwH_Ii7",
  "_version": 1,
  "_score": null,
  "_source": {
    "container_id": "5d97e6299ef4ee8a7f589ca47d49b306db17229e82c4c58124d2beb7604d8c94",
    "container_name": "/ccms_write-service.3.xscsw6kiui3yaasa9h7hdei5l",
    "source": "stdout",
    "log": "{\"@timestamp\":\"2019-03-21T10:00:35.001+00:00\",\"message\":\"event [27760845] was successfully inserted to msg queue\",\"method\":\"com.tr.tms.ccms.write.WriteService$$anon$2\",\"threadname\":\"WriteService-blocking-code-dispatcher-2456\",\"level\":\"INFO\",\"level_value\":20000,\"prefix\":\"APP\"}",
    "@timestamp": "2019-03-21T10:00:35.000000000+00:00",
    "@log_name": "ccms_qa_write_service"
  },
  "fields": {
    "@timestamp": [
      "2019-03-21T10:00:35.000Z"
    ]
  },
  "sort": [
    1553162435000
  ]
}

When I use this configuration this code has not been flatten. Can you please help?