How to revome the prefix of nested json fields

Elastic Stack Logstash
#1

input:
{"cookies":{"mfov":"ZTE Q705U","sver":"5915","appid":"1","mfo":"ZTE","sysver":"4.2.2","plat":"1","sys":"android"}}
filter{
json {
source => ["message"]
}
}

how to remove prefix "cookie." of filed_name


i've tried
mutate {
rename => ["[cookies][mfo]","mfo"]
rename => ["[cookies][mfov]","mfov"]
rename => ["[cookies][plat]","plat"]
}
but there's only a few of entries affected

#2

Works fine with Logstash 2.3.2:

$ cat data 
{"cookies":{"mfov":"ZTE Q705U","sver":"5915","appid":"1","mfo":"ZTE","sysver":"4.2.2","plat":"1","sys":"android"}}
$ cat test.config 
input { stdin { codec => json } }
output { stdout { codec => rubydebug } }
filter {
  mutate {
    rename => ["[cookies][mfo]","mfo"]
    rename => ["[cookies][mfov]","mfov"]
    rename => ["[cookies][plat]","plat"]
  }
}
$ /opt/logstash/bin/logstash -f test.config < data             
Settings: Default pipeline workers: 8
Pipeline main started
{
       "cookies" => {
          "sver" => "5915",
         "appid" => "1",
        "sysver" => "4.2.2",
           "sys" => "android"
    },
      "@version" => "1",
    "@timestamp" => "2016-07-15T06:41:53.397Z",
          "host" => "lnxolofon",
           "mfo" => "ZTE",
          "mfov" => "ZTE Q705U",
          "plat" => "1"
}
Pipeline main has been shutdown
stopping pipeline {:id=>"main"}
#3

thanks, can i remove all prefix? there's so many nested field. it's hard to rename each field.

#4

You need to use a ruby filter for that. I'm pretty sure there are examples of that (or something very similar) in the archives here or on StackOverflow.

#5