title: How do I parse a json-formatted log message in Logstash to get a certain key/value pair?
body: <p>I send json-formatted logs to my Logstash server. The log looks something like this (Note: The whole message is really on ONE line, but I show it in multi-line to ease reading)</p>
  
  <pre><code>2016-09-01T21:07:30.152Z 153.65.199.92 
  { 
    "type":"trm-system",
    "host":"susralcent09",
    "timestamp":"2016-09-01T17:17:35.018470-04:00",
    "@version":"1",
    "customer":"cf_cim",
    "role":"app_server",
    "sourcefile":"/usr/share/tomcat/dist/logs/trm-system.log",
    "message":"some message"
  }
  </code></pre>
  
  <p>What do I need to put in my Logstash configuration to get the "sourcefile" value, and ultimately get the filename, e.g., trm-system.log?</p>