Logstash Add field from grok filter

Question

Is it possible to match a message to a new field in logstash using grok and mutate?

Example log:

"<30>Dec 19 11:37:56 7f87c507df2a[20103]: [INFO] 2018-12-19 16:37:56 _internal (MainThread): 192.168.0.6 - - [19/Dec/2018 16:37:56] \"\u001b[37mGET / HTTP/1.1\u001b[0m\" 200 -\r"

I am trying to create a new key value where I match container_id to 7f87c507df2a.

filter {
  grok {
    match => [ "message", "%{SYSLOG5424PRI}%{NONNEGINT:ver} +(?:%{TIMESTAMP_ISO8601:ts}|-) +(?:%{HOSTNAME:service}|-) +(?:%{NOTSPACE:containerName}|-) +(?:%{NOTSPACE:proc}|-) +(?:%{WORD:msgid}|-) +(?:%{SYSLOG5424SD:sd}|-|) +%{GREEDYDATA:msg}" ]
  }
  mutate {
    add_field => { "container_id" => "%{containerName}"}
  }
}

The resulting logfile renders this, where the value of containerName isn't being referenced from grok, it is just a string literal:

"container_id": "%{containerName}" 

I am trying to have the conf create:

"container_id": "7f87c507df2a"

Obviously the value of containerName isn't being linked from grok. Is what I want to do even possible?

Answer 1

As explained in the comments, my grok pattern was incorrect. For anyone that may wander towards this post that needs help with grok go here to make building your pattern less time consuming.

Here was the working snapshot:

filter {
  grok {
    match => [ "message", "\A%{SYSLOG5424PRI}%{SYSLOGTIMESTAMP}%{SPACE}%{BASE16NUM:docker_id}%{SYSLOG5424SD}%{GREEDYDATA:python_log_message}" ]
    add_field => { "container_id" => "%{docker_id}" }    
  }  
}