in_monitor_agent returns wrong result

[repeatedly]

I tested in_monitor_agent with following configuration and got wrong result.

<source>
  @type monitor_agent
</source>
<source>
  @type forward
</source>
<match dummy>
  @type forward
  @id forward
  buffer_chunk_limit 30
  buffer_type file
  buffer_path /Users/repeatedly/tmp/fluentd/buffer/test
  <server>
    host 127.0.0.1
  </server>
</match>

v0.12.24

v0.12 returns correct result. buffer_queue_length is 1.

% ls buffer
test.dummy.b533f7cd1cef487ab.log  test.dummy.q533f7cd1ceaa1597.log

% curl http://localhost:24220/api/plugins.json
{"plugins":[{"plugin_id":"object:3fefc9d5d72c","plugin_category":"input","type":"monitor_agent","config":{"@type":"monitor_agent"},"output_plugin":false,"retry_count":null},{"plugin_id":"object:3fefc9d58150","plugin_category":"input","type":"forward","config":{"@type":"forward"},"output_plugin":false,"retry_count":null},{"plugin_id":"forward","plugin_category":"output","type":"forward","config":{"@type":"forward","@id":"forward","flush_interval":"10s","buffer_chunk_limit":"30","phi_failure_detector":"false","heartbeat_type":"none","buffer_type":"file","buffer_path":"/Users/repeatedly/tmp/fluentd/buffer/test","flush_at_shutdown":"true"},"output_plugin":true,"buffer_queue_length":1,"buffer_total_queued_size":40,"retry_count":0}]}

v0.14.0.rc.3

On the other hand, v0.14 retruns buffer_queue_length is 20 and there is no buffer_total_queued_size field. We should keep same result because many companies use in_monitor_agent to check buffer status.

% ls buffer/test/                             
buffer.b533f7d9364192049ec84fd70687246ca.log       buffer.q533f7d9363d704d4d13382bd5c03ae4a.log
buffer.b533f7d9364192049ec84fd70687246ca.log.meta  buffer.q533f7d9363d704d4d13382bd5c03ae4a.log.meta

% curl http://localhost:24220/api/plugins.json
{"plugins":[{"plugin_id":"object:3fd3c181f234","plugin_category":"input","type":"monitor_agent","config":{"@type":"monitor_agent"},"output_plugin":false,"retry_count":null},{"plugin_id":"object:3fd3c056cd1c","plugin_category":"input","type":"forward","config":{"@type":"forward"},"output_plugin":false,"retry_count":null},{"plugin_id":"forward","plugin_category":"unknown","type":"forward","config":{"@type":"forward","@id":"forward","flush_interval":"10s","buffer_chunk_limit":"30","phi_failure_detector":"false","heartbeat_type":"none","buffer_type":"file","buffer_path":"/Users/repeatedly/tmp/fluentd/buffer/test","flush_at_shutdown":"true"},"output_plugin":false,"buffer_queue_length":20,"retry_count":0}]}

[tagomoris]

I think we can update code of in_monitor_agent to return same result along with new buffer/output plugins, instead of modification of buffer/output side.
Built-in in_monitor_agent are used only with same version of Fluentd itself.