Logstash - Transforming the Logs

Logstash offers various plugins to transform the parsed log. These plugins can Add, Delete, and Update fields in the logs for better understanding and querying in the output systems.

We are using the Mutate Plugin to add a field name user in every line of the input log.

Install the Mutate Filter Plugin

To install the mutate filter plugin; we can use the following command.

>Logstash-plugin install Logstash-filter-mutate

logstash.conf

In this config file, the Mutate Plugin is added after the Aggregate Plugin to add a new field.

input {
   file {
      path => "C:/tpwork/logstash/bin/log/input.log"
   }
} 
filter {
   grok {
      match => [ "message", "%{LOGLEVEL:loglevel} -
         %{NOTSPACE:taskid} - %{NOTSPACE:logger} -
         %{WORD:label}( - %{INT:duration:int})?" ]
   }
   if [logger] == "TRANSACTION_START" {
      aggregate {
         task_id => "%{taskid}"
         code => "map['sql_duration'] = 0"
         map_action => "create"
      }
   }
   if [logger] == "SQL" {
      aggregate {
         task_id => "%{taskid}"
         code => "map['sql_duration'] ||= 0 ; 
            map['sql_duration'] += event.get('duration')"
      }
   }
   if [logger] == "TRANSACTION_END" {
      aggregate {
         task_id => "%{taskid}"
         code => "event.set('sql_duration', map['sql_duration'])"
         end_of_task => true
         timeout => 120
      }
   }
   mutate {
      add_field => {"user" => "tutorialspoint.com"}
   }
}
output {
   file {
      path => "C:/tpwork/logstash/bin/log/output.log"
   }
}

Run Logstash

We can run Logstash by using the following command.

>logstash –f logstash.conf

input.log

The following code block shows the input log data.

INFO - 48566 - TRANSACTION_START - start
INFO - 48566 - SQL - transaction1 - 320
INFO - 48566 - SQL - transaction1 - 200
INFO - 48566 - TRANSACTION_END - end

output.log

You can see that there is a new field named “user” in the output events.

{
   "path":"C:/tpwork/logstash/bin/log/input.log",
   "@timestamp":"2016-12-25T19:55:37.383Z",
   "@version":"1",
   "host":"wcnlab-PC",
   "message":"NFO - 48566 - TRANSACTION_START - start\r",
   "user":"tutorialspoint.com","tags":["_grokparsefailure"]
}
{
   "duration":320,"path":"C:/tpwork/logstash/bin/log/input.log",
   "@timestamp":"2016-12-25T19:55:37.383Z","loglevel":"INFO","logger":"SQL",
   "@version":"1","host":"wcnlab-PC","label":"transaction1",
   "message":" INFO - 48566 - SQL - transaction1 - 320\r",
   "user":"tutorialspoint.com","taskid":"48566","tags":[]
}
{
   "duration":200,"path":"C:/tpwork/logstash/bin/log/input.log",
   "@timestamp":"2016-12-25T19:55:37.399Z","loglevel":"INFO",
   "logger":"SQL","@version":"1","host":"wcnlab-PC","label":"transaction1",
   "message":" INFO - 48566 - SQL - transaction1 - 200\r",
   "user":"tutorialspoint.com","taskid":"48566","tags":[]
}
{
   "sql_duration":520,"path":"C:/tpwork/logstash/bin/log/input.log",
   "@timestamp":"2016-12-25T19:55:37.399Z","loglevel":"INFO",
   "logger":"TRANSACTION_END","@version":"1","host":"wcnlab-PC","label":"end",
   "message":" INFO - 48566 - TRANSACTION_END - end\r",
   "user":"tutorialspoint.com","taskid":"48566","tags":[]
}