title: need custom fields of log through grok filter in logstash
body: <p>I have logstash, kibana and elasticsearch installed on my system, with this filter configuration:</p>
  
  <pre><code>    filter{
  if [type] == "syslog" {
      grok {
        match =&gt; { "message" =&gt; "%{SYSLOGTIMESTAMP:syslog_timestamp} %{SYSLOGHOST:syslog_hostname} %{DATA:syslog_program}(?:\[%{POSINT:syslog_pid}\])?: %{GREEDYDATA:syslog_message}" }
        add_field =&gt; [ "received_at", "%{@timestamp}" ]
        add_field =&gt; [ "received_from", "%{host}" ]
      }
      mutate {
              add_field =&gt; {
                              "timestamp" =&gt; "%{TIME} %{MONTH} %{monthday}"
                           }
          }
  
      syslog_pri { }
      date {
        match =&gt; [ "syslog_timestamp", "MMM  d HH:mm:ss", "MMM dd HH:mm:ss" ]
      }
    }
  }
  </code></pre>
  
  <p>and receiving output on kibana as:
  <img src="https://i.stack.imgur.com/bY6EA.png" alt="Kibana output"></p>
  
  <p>but I need some fields which are as follows:
  @timestamp
  @version
  _id
  _index
  _type
  _file
  Log Level
  Host Name
  Host IP
  Process Name
  Response Time</p>
  
  <p>I tried adding Timestamp but its printing same string instead of dynamic result</p>
  
  <p><img src="https://i.stack.imgur.com/vhp6Q.png" alt="Kibana output"></p>