How to extract rows with logstash

Elastic Stack Logstash
10

ok good...many thanks for help
i have another problem

2017-07-13 13:32:32,562 | WARN  | ...other words.. {"request":{"cks":31155,"terminal"....}

I can extract a line where there is a WARM but I also want to extract and process the Json that is there after {"request":{"cks":31155,"terminal"........}
I'm trying with this conf.

filter {
grok {		 
	match => ["message", "(?<check>).*\| WARN  \|.*(?<check_json>){\"request\".*}"]
	break_on_match => true
	add_field => {"type" => "log_warn"}
    }
if !( "" in [check]){drop{}}

mutate {  remove_field => ["path","host","check"]
      add_tag => [ "WARNING" ]	}
	
	
if "_grokparsefailure" in [tags] {drop {}}	
else {
	json {
		source => "check_json"
	}}
}

what do you think?