title: Log4j2 custom fields Socket appender
body: <p>I'm currently sending information from my Java application to ELK using Log4j2 and socketAppender. I'd like to know if it's possible to add extra information to this message sent to ELK with things like, application name, original request, and stuff like that: </p>
  
  <p>My configuration right now looks like this: </p>
  
  <pre><code>Configuration:
    name: Remote
  
    Appenders:
      Console:
        name: Console
        target: SYSTEM_OUT
        PatternLayout:
          Pattern: "%d{yyyy-MM-dd HH:mm:ss} %-5p %c{10}:%L - %m%n"
      Socket:
        name: Elk
        port: 7000
        host: elk
        reconnectionDelayMillis: 10000
        SerializedLayout: []
  </code></pre>
  
  <p>Any clue or documentation about how to do it?</p>