How to Add extra Data to Log Messages via a Processor

Version: 3.0
Edit this page

Warning: You are browsing the documentation for Symfony 3.0, which is no longer maintained.

Read the updated version of this page for Symfony 5.3 (the current stable version).

How to Add extra Data to Log Messages via a Processor

Monolog allows you to process the record before logging it to add some extra data. A processor can be applied for the whole handler stack or only for a specific handler.

A processor is simply a callable receiving the record as its first argument. Processors are configured using the monolog.processor DIC tag. See the reference about it.

Adding a Session/Request Token

Sometimes it is hard to tell which entries in the log belong to which session and/or request. The following example will add a unique token for each request using a processor.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
namespace AppBundle;

use Symfony\Component\HttpFoundation\Session\Session;

class SessionRequestProcessor
{
    private $session;
    private $token;

    public function __construct(Session $session)
    {
        $this->session = $session;
    }

    public function processRecord(array $record)
    {
        if (null === $this->token) {
            try {
                $this->token = substr($this->session->getId(), 0, 8);
            } catch (\RuntimeException $e) {
                $this->token = '????????';
            }
            $this->token .= '-' . substr(uniqid(), -8);
        }
        $record['extra']['token'] = $this->token;

        return $record;
    }
}
  • YAML
  • XML
  • PHP 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
# app/config/config.yml
services:
    monolog.formatter.session_request:
        class: Monolog\Formatter\LineFormatter
        arguments:
            - "[%%datetime%%] [%%extra.token%%] %%channel%%.%%level_name%%: %%message%% %%context%% %%extra%%\n"

    monolog.processor.session_request:
        class: AppBundle\SessionRequestProcessor
        arguments:  ['@session']
        tags:
            - { name: monolog.processor, method: processRecord }

monolog:
    handlers:
        main:
            type: stream
            path: '%kernel.logs_dir%/%kernel.environment%.log'
            level: debug
            formatter: monolog.formatter.session_request

Note

If you use several handlers, you can also register a processor at the handler level or at the channel level instead of registering it globally (see the following sections).

Registering Processors per Handler

You can register a processor per handler using the handler option of the monolog.processor tag:

  • YAML
  • XML
  • PHP 
1
2
3
4
5
6
7
# app/config/config.yml
services:
    monolog.processor.session_request:
        class: AppBundle\SessionRequestProcessor
        arguments:  ['@session']
        tags:
            - { name: monolog.processor, method: processRecord, handler: main }

Registering Processors per Channel

You can register a processor per channel using the channel option of the monolog.processor tag:

  • YAML
  • XML
  • PHP 
1
2
3
4
5
6
7
# app/config/config.yml
services:
    monolog.processor.session_request:
        class: AppBundle\SessionRequestProcessor
        arguments:  ['@session']
        tags:
            - { name: monolog.processor, method: processRecord, channel: main }
This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.