allow json target to be dynamic

[surlypants]

enable dynamic json target (eg, field value or tag name) a la

filter { json { target => "%{field}" } }

(http://discuss.elastic.co/t/json-target-based-field-value-or-tag/)

[prabhakarmanthena]

I tried the below workaround in the filter , I don't know weather it is right or wrong but itz perfectly worked for me.

filter {
    json{
    source => "json_message"
    target => "dynamic_json_field"
  }
  mutate {
    rename => { "dynamic_json_field" => "%{type}" }
  }
}

[wmalik]

@prabhakarmanthena Thanks, that worked.