Logstash - Filters | Adglob Infosystem Pvt Ltd

In this guide we will discuss about Filters in Logstash. Logstash uses filters in the middle of the pipeline between input and output. The filters of Logstash measures manipulate and create events like Apache-Access. Many filter plugins used to manage the events in Logstash. Here, in an example of the Logstash Aggregate Filter, we are filtering the duration every SQL transaction in a database and computing the total time.

Installing the Aggregate Filter Plugin

Installing the Aggregate Filter Plugin using the Logstash-plugin utility. The Logstash-plugin is a batch file for windows in bin folder in Logstash.

>logstash-plugin install logstash-filter-aggregate

logstash.conf

In this configuration, you can see three ‘if’ statements for Initializing, Incrementing, and generating the total duration of transaction, i.e., the sql_duration. The aggregate plugin is used to add the sql_duration, present in every event of the input log.

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
      }
   }
}
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

As specified in the configuration file, the last ‘if’ statement where the logger is – TRANSACTION_END, which prints the total transaction time or sql_duration. This has been highlighted in yellow color in the output.log.

{
   "path":"C:/tpwork/logstash/bin/log/input.log","@timestamp": "2016-12-22T19:04:37.214Z",
   "loglevel":"INFO","logger":"TRANSACTION_START","@version": "1","host":"wcnlab-PC",
   "message":"8566 - TRANSACTION_START - start\r","tags":[]
}
{
   "duration":320,"path":"C:/tpwork/logstash/bin/log/input.log",
   "@timestamp":"2016-12-22T19:04:38.366Z","loglevel":"INFO","logger":"SQL",
   "@version":"1","host":"wcnlab-PC","label":"transaction1",
   "message":" INFO - 48566 - SQL - transaction1 - 320\r","taskid":"48566","tags":[]
}
{
   "duration":200,"path":"C:/tpwork/logstash/bin/log/input.log",
   "@timestamp":"2016-12-22T19:04:38.373Z","loglevel":"INFO","logger":"SQL",
   "@version":"1","host":"wcnlab-PC","label":"transaction1",
   "message":" INFO - 48566 - SQL - transaction1 - 200\r","taskid":"48566","tags":[]
}
{
   "sql_duration":520,"path":"C:/tpwork/logstash/bin/log/input.log",
   "@timestamp":"2016-12-22T19:04:38.380Z","loglevel":"INFO","logger":"TRANSACTION_END",
   "@version":"1","host":"wcnlab-PC","label":"end",
   "message":" INFO - 48566 - TRANSACTION_END - end\r","taskid":"48566","tags":[]
}

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