How to Add extra Data to Log Messages via a Processor

Warning: You are browsing the documentation for Symfony 4.1, which is no longer maintained.

Read the updated version of this page for Symfony 6.2 (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 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 App\Logger;

use Symfony\Component\HttpFoundation\Session\SessionInterface;

class SessionRequestProcessor
{
    private $session;
    private $sessionId;

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

    public function __invoke(array $record)
    {
        if (!$this->session->isStarted()) {
            return $record;
        }

        if (!$this->sessionId) {
            $this->sessionId = substr($this->session->getId(), 0, 8) ?: '????????';
        }

        $record['extra']['token'] = $this->sessionId.'-'.substr(uniqid('', true), -8);

        return $record;
    }
}
    

Next, register your class as a service, as well as a formatter that uses the extra information:

YAML
XML
PHP

        1
2
3
4
5
6
7
8
9
10
        # config/services.yaml
services:
    monolog.formatter.session_request:
        class: Monolog\Formatter\LineFormatter
        arguments:
            - "[%%datetime%%] [%%extra.token%%] %%channel%%.%%level_name%%: %%message%% %%context%% %%extra%%\n"

    App\Logger\SessionRequestProcessor:
        tags:
            - { name: monolog.processor }
    

        1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
        <!-- config/services.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:monolog="http://symfony.com/schema/dic/monolog"
    xsi:schemaLocation="http://symfony.com/schema/dic/services
        http://symfony.com/schema/dic/services/services-1.0.xsd
        http://symfony.com/schema/dic/monolog
        http://symfony.com/schema/dic/monolog/monolog-1.0.xsd">

    <services>
        <service id="monolog.formatter.session_request"
            class="Monolog\Formatter\LineFormatter">

            <argument>[%%datetime%%] [%%extra.token%%] %%channel%%.%%level_name%%: %%message%% %%context%% %%extra%%&#xA;</argument>
        </service>

        <service id="App\Logger\SessionRequestProcessor">
            <tag name="monolog.processor" />
        </service>
    </services>
</container>
    

        1
2
3
4
5
6
7
8
9
10
11
        // config/services.php
use App\Logger\SessionRequestProcessor;
use Monolog\Formatter\LineFormatter;

$container
    ->register('monolog.formatter.session_request', LineFormatter::class)
    ->addArgument('[%%datetime%%] [%%extra.token%%] %%channel%%.%%level_name%%: %%message%% %%context%% %%extra%%\n');

$container
    ->register(SessionRequestProcessor::class)
    ->addTag('monolog.processor', ['method' => 'processRecord']);
    

Finally, set the formatter to be used on whatever handler you want:

YAML
XML
PHP

        1
2
3
4
5
6
7
8
        # config/packages/prod/monolog.yaml
monolog:
    handlers:
        main:
            type: stream
            path: '%kernel.logs_dir%/%kernel.environment%.log'
            level: debug
            formatter: monolog.formatter.session_request
    

        1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
        <!-- config/packages/prod/monolog.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:monolog="http://symfony.com/schema/dic/monolog"
    xsi:schemaLocation="http://symfony.com/schema/dic/services
        http://symfony.com/schema/dic/services/services-1.0.xsd
        http://symfony.com/schema/dic/monolog
        http://symfony.com/schema/dic/monolog/monolog-1.0.xsd">

    <monolog:config>
        <monolog:handler
            name="main"
            type="stream"
            path="%kernel.logs_dir%/%kernel.environment%.log"
            level="debug"
            formatter="monolog.formatter.session_request"
        />
    </monolog:config>
</container>
    

        1
2
3
4
5
6
7
8
9
10
11
        // config/packages/prod/monolog.php
$container->loadFromExtension('monolog', [
    'handlers' => [
        'main' => [
            'type'      => 'stream',
            'path'      => '%kernel.logs_dir%/%kernel.environment%.log',
            'level'     => 'debug',
            'formatter' => 'monolog.formatter.session_request',
        ],
    ],
]);
    

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
        # config/services.yaml
services:
    App\Logger\SessionRequestProcessor:
        tags:
            - { name: monolog.processor, handler: main }
    

        1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
        <!-- config/services.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:monolog="http://symfony.com/schema/dic/monolog"
    xsi:schemaLocation="http://symfony.com/schema/dic/services
        http://symfony.com/schema/dic/services/services-1.0.xsd
        http://symfony.com/schema/dic/monolog
        http://symfony.com/schema/dic/monolog/monolog-1.0.xsd">

    <services>
        <service id="App\Logger\SessionRequestProcessor">
            <tag name="monolog.processor" handler="main" />
        </service>
    </services>
</container>
    

        1
2
3
4
5
6
        // config/services.php

// ...
$container
    ->register(SessionRequestProcessor::class)
    ->addTag('monolog.processor', ['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
        # config/services.yaml
services:
    App\Logger\SessionRequestProcessor:
        tags:
            - { name: monolog.processor, channel: main }
    

        1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
        <!-- config/services.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:monolog="http://symfony.com/schema/dic/monolog"
    xsi:schemaLocation="http://symfony.com/schema/dic/services
        http://symfony.com/schema/dic/services/services-1.0.xsd
        http://symfony.com/schema/dic/monolog
        http://symfony.com/schema/dic/monolog/monolog-1.0.xsd">

    <services>
        <service id="App\Logger\SessionRequestProcessor">
            <tag name="monolog.processor" channel="main" />
        </service>
    </services>
</container>
    

        1
2
3
4
5
6
        // config/services.php

// ...
$container
    ->register(SessionRequestProcessor::class)
    ->addTag('monolog.processor', ['channel' => 'main']);
    

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.

Menu

How to Add extra Data to Log Messages via a Processor

How to Add extra Data to Log Messages via a Processor

Adding a Session/Request Token

Registering Processors per Handler

Registering Processors per Channel

What is Symfony?

Learn Symfony

Screencasts

Community

Blog

Services

Deployed on