title: Getting logstash "fingerprint" filter to source every field
body: <p>I'm using the <code>fingerprint</code> filter in Logstash to create a <em>fingerprint</em> field that I set to <code>document_id</code> in the <code>elasticsearch</code> output.</p>
  
  <p>Configuration is as follows:</p>
  
  <pre><code>filter {
    fingerprint {
      method =&gt; "SHA1"
      key =&gt; "KEY"
    }
  }
  
  output {
    elasticsearch {
      host =&gt; localhost
      document_id =&gt; "%{fingerprint}"
    }
  }
  </code></pre>
  
  <p>This defaults to <code>source</code> being <em>message</em>, but how do I make it SHA1 the entire record and not just <em>message</em>?  Note, what fields a record has depends on the message.</p>