How to Configure Monolog to Email Errors

Monolog can be configured to send an email when an error occurs with an application. The configuration for this requires a few nested handlers in order to avoid receiving too many emails. This configuration looks complicated at first but each handler is fairly straight forward when it is broken down.

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        # app/config/config_prod.yml
monolog:
    handlers:
        mail:
            type:         fingers_crossed
            action_level: critical
            handler:      buffered
        buffered:
            type:    buffer
            handler: swift
        swift:
            type:       swift_mailer
            from_email: [email protected]
            to_email:   [email protected]
            # or list of recipients
            # to_email:   [[email protected], [email protected], ...]
            subject:    An Error Occurred!
            level:      debug
    

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        <!-- app/config/config_prod.xml -->
<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="mail"
            type="fingers_crossed"
            action-level="critical"
            handler="buffered"
        />
        <monolog:handler
            name="buffered"
            type="buffer"
            handler="swift"
        />
        <monolog:handler
            name="swift"
            type="swift_mailer"
            from-email="[email protected]"
            subject="An Error Occurred!"
            level="debug">

            <monolog:to-email>[email protected]</monolog:to-email>

            <!-- or multiple to-email elements -->
            <!--
            <monolog:to-email>[email protected]</monolog:to-email>
            <monolog:to-email>[email protected]</monolog:to-email>
            ...
            -->
        </monolog:handler>
    </monolog:config>
</container>
    

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        // app/config/config_prod.php
$container->loadFromExtension('monolog', array(
    'handlers' => array(
        'mail' => array(
            'type'         => 'fingers_crossed',
            'action_level' => 'critical',
            'handler'      => 'buffered',
        ),
        'buffered' => array(
            'type'    => 'buffer',
            'handler' => 'swift',
        ),
        'swift' => array(
            'type'       => 'swift_mailer',
            'from_email' => '[email protected]',
            'to_email'   => '[email protected]',
            // or a list of recipients
            // 'to_email'   => array('[email protected]', '[email protected]', ...),
            'subject'    => 'An Error Occurred!',
            'level'      => 'debug',
        ),
    ),
));
    

The mail handler is a fingers_crossed handler which means that it is only triggered when the action level, in this case critical is reached. It then logs everything including messages below the action level. The critical level is only triggered for 5xx HTTP code errors. The handler setting means that the output is then passed onto the buffered handler.

Tip

If you want both 400 level and 500 level errors to trigger an email, set the action_level to error instead of critical.

The buffered handler simply keeps all the messages for a request and then passes them onto the nested handler in one go. If you do not use this handler then each message will be emailed separately. This is then passed to the swift handler. This is the handler that actually deals with emailing you the error. The settings for this are straightforward, the to and from addresses and the subject.

You can combine these handlers with other handlers so that the errors still get logged on the server as well as the emails being sent:

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        # app/config/config_prod.yml
monolog:
    handlers:
        main:
            type:         fingers_crossed
            action_level: critical
            handler:      grouped
        grouped:
            type:    group
            members: [streamed, buffered]
        streamed:
            type:  stream
            path:  "%kernel.logs_dir%/%kernel.environment%.log"
            level: debug
        buffered:
            type:    buffer
            handler: swift
        swift:
            type:       swift_mailer
            from_email: [email protected]
            to_email:   [email protected]
            subject:    An Error Occurred!
            level:      debug
    

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        <!-- app/config/config_prod.xml -->
<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="fingers_crossed"
            action_level="critical"
            handler="grouped"
        />
        <monolog:handler
            name="grouped"
            type="group"
        >
            <member type="stream"/>
            <member type="buffered"/>
        </monolog:handler>
        <monolog:handler
            name="stream"
            path="%kernel.logs_dir%/%kernel.environment%.log"
            level="debug"
        />
        <monolog:handler
            name="buffered"
            type="buffer"
            handler="swift"
        />
        <monolog:handler
            name="swift"
            from-email="[email protected]"
            to-email="[email protected]"
            subject="An Error Occurred!"
            level="debug"
        />
    </monolog:config>
</container>
    

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        // app/config/config_prod.php
$container->loadFromExtension('monolog', array(
    'handlers' => array(
        'main' => array(
            'type'         => 'fingers_crossed',
            'action_level' => 'critical',
            'handler'      => 'grouped',
        ),
        'grouped' => array(
            'type'    => 'group',
            'members' => array('streamed', 'buffered'),
        ),
        'streamed'  => array(
            'type'  => 'stream',
            'path'  => '%kernel.logs_dir%/%kernel.environment%.log',
            'level' => 'debug',
        ),
        'buffered'    => array(
            'type'    => 'buffer',
            'handler' => 'swift',
        ),
        'swift' => array(
            'type'       => 'swift_mailer',
            'from_email' => '[email protected]',
            'to_email'   => '[email protected]',
            'subject'    => 'An Error Occurred!',
            'level'      => 'debug',
        ),
    ),
));
    

This uses the group handler to send the messages to the two group members, the buffered and the stream handlers. The messages will now be both written to the log file and emailed.

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