title: logstash output to kafka - topic data in message
body: <p>I want to create a conf file for logstash that loads data from a file and send it to kafka.</p>
  
  <p>the file is in json format and has the topicId in it.</p>
  
  <p>This is what I have so far..</p>
  
  <pre><code>input {
     file {
      path =&gt; "~/file1.json"
      start_position =&gt; "beginning"
      codec =&gt; "json"
    }
  }
  filter {
      json {
          source =&gt; message
      }
  }
  output {
    kafka { 
      bootstrap_servers =&gt; "localhost"
      codec =&gt; plain {
          format =&gt; "%{message}"
      }
      topic_id =&gt;  "???"
    }
  }
  </code></pre>
  
  <p>can this be done?</p>
  
  <p>Regards, 
  Ido</p>