Listener after ES Node started

I write a Es plugin for scanning a file system.
If ES is starting, how can I check in my Plugin if the node is ready? If the Node started then my Plugin run a scheduler.
How can check in my Plugin if the Node is started ?

ES will mention if it loads the plugin during start, so check the logs.
Then it's entirely up to however you wrote the code as to what it will do.

You mean reading files off the FS? Why not just use Logstash with the file input?

Logstash can not Parse the File Data. And i thing with Logstash is it not possible to write the parsed file data to a custom Mapping.

You can definitely define your own mapping for LS to use!