title: Logstash optional fields in logfile
body: <p>I'm trying to parse a logfile using grok</p>
  
  <p>Each line of the logfile has fields separated by commas:</p>
  
  <pre><code>13,home,ABC,Get,,Private, Public,1.2.3 ecc...
  </code></pre>
  
  <p>I'm using match like this:
  <code>match =&gt; [ "message", "%{NUMBER:requestId},%{WORD:ServerHost},%{WORD:Service},</code>...</p>
  
  <p>My question is: Can I allow optional field?
  At times some of the fileds might be empty <code>,,</code></p>
  
  <p>Is there a pattern that matches a string like this <code>2.3.5</code> ?
  ( a kind of version number )</p>