How to read filebeat additional values from custom codec plugin?

Hi.

I am currently making Logstash Custom Plugin to analyze WAS logs.
I am making a Codec plugin to analyze the unstructured WAS log sent from remote Filebeat.
Filter plugin cannot be used because its stream disordered with multiple logstash workers.(Its very important part of the plugin)
Now, most of the plugin have been written and they are working well.
But the problem is I don't know how to read the additional values which is set on remote filebeat configuration, like processors/add_fields, add_tags, etc.. in side my codec plugin.
Any suggestions?