how to parse logs dynamically using logstash -

i logging logstash logs in following format:

timestamp  key=val key2=val2 ..<a list of key=val>.. [log-level] rest of message 

example:

17:21:20.470 pid=<0.20592.0> app=myapp  key1=val.1 key2=val/2 [info] message blabla 

i parse them format:

 {      "timestamp" => "17:21:20.470",      "pid" => "<0.20592.0>"      "app" => myapp      "key1" => "val.1"      "key2" => "val/2"      "level" => "info"      "message" => "my message blabla"    } 

note: key=val aren't known in advance, parse them dynamically

here configuration

input { stdin { } }    filter {  }  output { stdout { codec => rubydebug  }} 

what should filter be?