How to parse json in logstash /grok from a text fi

I have a logfile which looks like this ( simplified)

Logline sample

MyLine data={"firstname":"bob","lastname":"the builder"}

I'd like to extract the json contained in data and create two fields, one for firstname, one for last. However, the ouput i get is this:

{"message":"Line data={\"firstname\":\"bob\",\"lastname\":\"the builder\"}\r","@version":"1","@timestamp":"2015-11-26T11:38:56.700Z","host":"xxx","path":"C:/logstashold/bin/input.txt","MyWord":"Line","parsedJson":{"firstname":"bob","lastname":"the builder"}}

As you can see

..."parsedJson":{"firstname":"bob","lastname":"the builder"}}

That's not what I need, I need to create fields for firstname and lastname in kibana, but logstash isn't extracting the fields out with the json filter.

LogStash Config

input {
  file {
        path => "C:/logstashold/bin/input.txt"        
       }
}

filter {     

   grok {
            match => { "message" => "%{WORD:MyWord} data=%{GREEDYDATA:request}"}        
        }   

    json{
        source => "request"
        target => "parsedJson"
        remove_field=>["request"]
    }   
}   

output {  
    file{
        path => "C:/logstashold/bin/output.txt"
    }   
}

Any help greatly appreciated, I'm sure I'm missing out something simple

Thanks

After your json filter add another one called mutate in order to add the two fields that you would take from the parsedJson field.

filter {
  ...
  json {
     ...
  }
  mutate {
    add_field => {
      "firstname" => "%{[parsedJson][firstname]}"
      "lastname" => "%{[parsedJson][lastname]}"
    }
  }
}

For your sample log line above that would give:

{
       "message" => "MyLine data={\"firstname\":\"bob\",\"lastname\":\"the builder\"}",
      "@version" => "1",
    "@timestamp" => "2015-11-26T11:54:52.556Z",
          "host" => "iMac.local",
        "MyWord" => "MyLine",
    "parsedJson" => {
        "firstname" => "bob",
         "lastname" => "the builder"
    },
     "firstname" => "bob",
      "lastname" => "the builder"
}