title: Math functions in Logstash
body: <p>I am looking forward to use mathematical operations on the input received in Logstash, but unable to see any of such <strong>filter</strong>.</p>
  
  <p><strong>Input is as following:</strong></p>
  
  <pre><code>{
    "user_id": "User123",
    "date": "2016 Jun 26 12:00:12",
    "data": {
      "doc_name": "mydocs.xls",
      "doc_size": "8526587",
    }
  }
  </code></pre>
  
  <p><strong>The "doc_size" field will have bytes, I would like to add a new field say "doc_size_mb" which will contain the size in MB's.</strong> </p>
  
  <p>So I want a simple division operation here like: </p>
  
  <p>doc_size_mb = doc_size/(1024*1024)</p>
  
  <p>I could see a <a href="http://www.rubydoc.info/gems/logstash-filter-math/0.2/LogStash/Filters/Math" rel="noreferrer">link</a> which says Logstash has math filter, but this is not visible <a href="https://www.elastic.co/guide/en/logstash/current/filter-plugins.html" rel="noreferrer">here</a> .</p>