require_relative "lib/bootstrap/environment"
LogStash::Bundler.setup!({:without => [:build, :development]})
require "logstash-core"
require "logstash/environment"
require "logstash/plugin"

grok_class = LogStash::Plugin.lookup("filter", "grok")
grok = grok_class.new("match" => { "message" => [ "%{WORD:word}", "%{NUMBER:num}" ] })
grok.register
event = LogStash::Event.new("message" => "hey")
grok.filter(event)
puts event.to_hash

# /tmp/logstash-7.6.0
# ❯ bin/ruby script.rb 
# {"word"=>"hey", "@timestamp"=>2020-03-05T16:19:19.322Z, "@version"=>"1", "message"=>"hey"}